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PROGRAMMABLE CONTROLLERS

1. positioning modules and others less frequently used co processor modules stepper motor control modules etc Modular programmable controllers can be expanded by remote racks bases connected to the main rack base by a network connection Expansion capabilities of modular controllers and the maximum number of inputs and outputs are bigger than in case of compact controllers Producers of programmable controllers usually have and offer whole series of controllers sometimes they name them families of controllers For particular models of programmable controllers that belong to the same series it is characteristic that u the same or similar technical solutions in particular controllers and their modules construction have been used NIE E Ireneusz Moso Programmable Controllers usually controllers from the same series are programmed with the use of the same programming software programming package u very often application programs written for one programmable controller from a series can be used either directly or after a small adaptation or just only a new compilation in another controller from the series Below there are examples of series of programmable controllers that have been or had been produced in the last twenty years Simatic S5 and S7 series of programmable controllers are typical examples of programmable controllers series and replacement in production of the older series S5 by the new ser
2. Liczniki CTU Licznik zliczajacy impulsy z generatora Kasuj BOOL Zmienna kasujaca licznik po doliczeniu do 100 impulsow END_YAR Pozwolenie II Stop Pozwolenie Liczniki Pozwolenie CTU OUT cu T 50ms TIMELOW Kasuj RESET LI Liczba T 50ms TIMEHIGH 100 PY mmontillib b_Commomstandard lib ONLNE OV READ easy Soft CoDeSys pierwszy pro proces3 FB CFC ile Edit Project Insert Extras Online Window Help SBER o FUNCTION_BLOCK proces3 O002 VAR_INPUT Stop2 BOOL Up BOOL 0005 Down BOOL Lannglchin sao Generator impul LE gt ONLNE OV READ 3 Start Gm Program w XSoft Fig 4 8 An example of a POU written in the CFC language 55x lt Ireneusz Moso Programmable Controllers 4 5 Standard functions and function blocks In the International Standard IEC 61131 3 there is a number of standard functions declared All these functions are divided into seven groups 41 16 Type conversion functions u Numerical functions Bit string functions u Selection and comparison functions Character string functions Functions of time and data types Functions of enumerated data types All function blocks that are mentioned in the International Standard IEC 61131 3 are divided into four groups 41 16 Bistable elements
3. phases of the program cycle as shown in figure 2 2 Execution of the Operating application system program functions Fig 2 2 Simplified diagram of a programmable controller operation without using the process image memory In this case every time when an operand of the instruction is an input variable its state is read from the controller s input hardware input analogously every time when an operand of the instruction is an output variable its state is changed in the controller s output hardware output An example of programmable controllers that work in such a way are PCD series controllers produced by SAIA Operation without using the process image memory is their typical operation Their outputs are updated at the point of time during the application 16 Ireneusz Moso Programmable Controllers program execution when they are operands of the currently executed instructions Writing programs for PCD series controllers it is necessary to take into consideration that parts of the application program can be executed for different states for each particular input variable In some applications this necessity could be a disadvantage On the other hand updating outputs during execution of the program is an advantage because the control system reaction is faster If the user of the PCD series controllers wants to work with a process image memory such a memory area have to be programmed by him Despite the fact that m
4. 2 3 5 have been used to prepare examples and some software features that are included into the materials Additionally because the basic source of information about programmable controllers their hardware and software is the International Standard IEC 61131 which is also the European Standard EN 61131 as well as Polish Standard PN EN 61131 selected information from the standard has been included into this materials Paragraphs and sentences that have been taken directly from the standard are written in blue instead of using parenthesis Part 2 of these materials is written in Polish to give students from the speciality Information technologies in electrical engineering an opportunity to learn terminology related to programmable controllers and control systems with programmable controllers in both languages English and Polish In the second part such problems as structuring of user programs control of sequential processes and networking programmable controllers are presented In the list of references the list is common for both parts of the materials not only references quoted in this materials have been included there are also other references that can be helpful in understanding lectures tutorials and laboratory tasks Ireneusz Moso Programmable Controllers Contents Syllabus and learning outcomes of the course Programmable Controllers 6 1 Programmable Controllers Basics aaa GO sess OFOP ia ka 7
5. Edge detection elements u Counters Timers Functions and function blocks belonging to the listed above groups are not discussed in these materials because there is a detailed description of all these functions and function blocks in the standard IEC 61131 3 Description of these functions and function blocks can be also found in some references for example in 16 In these materials only some important remarks have been made Manufacturers of programmable controllers usually provide quite a lot of diverse functions and function blocks more than those described in the standard IEC 61131 3 This is so because their programming packages have been evolving during past years and contain functions and function blocks which have been developed before the International Standard IEC 61131 have been established The use of such functions and function blocks should not be recommended if analogous IEC functions and function blocks exist but is fully acceptable if these functions and function blocks are somehow unique for example because they can implement specific programmable controllers hardware features The prototypes of IEC and manufacturer functions and function blocks often have generic data types ANY associated with their inputs and outputs Generic data types cannot be used for declaration of user function blocks Overloaded data types of this kind are only 56 Ireneusz Moso Programmable Controllers possible with i
6. Programmable Controllers Looking at this example it can be concluded that despite different names of the program cycle phases in figure 3 2 they are very similar to those at the simplified diagram shown in figure 1 2 reading inputs is named input processing execution of the user programme is named arithmetic processing of the program writing outputs is named output processing and finally forced setting resetting and peripheral processing are the operating system tasks 3 3 Third example Koyo DL series Third example refers to DL205 and DL405 modular programmable controllers produced by Koyo Company These programmable controllers CPU has two operating modes that allow different types of operations These modes are Program Mode and Run Mode The program cycle for these controllers is shown in figure 3 3 Read Inputs Read Inputs from Specialty I O Service Peripherials Force I O CPU Bus Communication Update Clock Special Relays Solve the Application Program Write Outputs Write Outputs to Specialty I O Diagnostics Fig 3 3 The program cycle for Koyo DL series programmable controllers 27 Ireneusz Moso Programmable Controllers The CPU operating system activities during particular phases of the program cycle are as follows Read Inputs The CPU reads the status of all input modules present in the local CPU base and local expansion bases The status of each input is stored in the proce
7. 1 1 What is a programmable controller ssssessesssssssssssrrrreersrrrrssererrerereeess 7 1 2 Basic structure of a programmable controller 1 2 0 0 cece eee eee eee ee ene eee eens 8 1 3 General principle of operation i5ccs0sgescng cveas ee deeesy ares Met ook Mess o hanes ois 9 1 4 Types and series of programmable controllers cece cee ee ence aaa aaa awa 12 2 Principle of Operation in Details cat ol RO O al PO bO 15 2 1 Cyclical and periodic operation La AAAA PA AJ OE 15 2 2 Operation with or without process image memory ssssssessrrrecrrerrererrreeeere 15 2 3 Control system and programmable controller response time 1 22 19 3 Examples of the Program Cycle Descriptions euea cece aaa aaa aaa aaa aaa ii es 24 3 1 First example Moeller PS4 series ue eeik EO AO EPL AE AEC 0 24 3 2 Second example Hitachi E series wasi Ai A LILA 25 3 3 Third example Koyo DL series ue a WA AW 27 3 4 Fourth example GE Fanuc 90 30 series did EO ad zada 30 4 Programming of Programmable Controllers ssssssssseeresssesssererrrrererereseerreere 34 4 1 Programming model according to IEC 61131 3 osssscccccssesesessrerrrersrrrssesee 34 4 2 Data types and variables 4 44 45 A OO O O W O W AGA cts 37 4 3 Program organization units asy KO OE 44 4 4 Programming languages a oi O o saber ee kd O aa 46 4 5 Standard functions and function blocks meeea aaa aaa aaa ene tees
8. An example of a POU written in the ST language with the use of Easy Soft CoDeSys programming package is shown in figure 4 4 XSoft WCKFO5x1 pro OBL_UCIAG FB ST File Edit Project Insert Extras Online Window Help aau E lS ejE z gt EB 0001 FUNCTION_BLOCK OBL_UCIAG POUs a H GENERATOR FB 0003 EN BOOL YVejscie Enable E OBL_UCIAG FB ZU UINT Zadana wartosc uciagu 0005 Hf PLC_PRG PRG wyjscie Enable Output Zadana wartosc uciagu w procentach Maksymalna zadana wartosc uciagu w procentach Minimalna zadana wartosc uciagu w procentach 0004 IF ZUP 100 THEN ZUP 100 END_IF O007 IF ZUP 7 lt 20 THEN WMIN 139 OOO8 ELSE WMIN ZUP 7 Fig 4 4 An example of a POU written in the ST language Function Block Diagram FBD The Function Block Diagram is a graphically oriented programming language It works with a list of networks Each network contains a structure which represents either a logical or arithmetic expression the call of a function block a jump or a return instruction An example of a network written in the FBD language with the use of Sucosoft S40 programming package is shown in figure 4 5 Ladder Diagram LD The Ladder Diagram is a graphically oriented programming language which resembles the structure of an electric circuit A program written in the LD language consists of a series of networks A network is limited on the l
9. C Loading libran ommomUtil lib NDARD LIB XSoft Cwiczenia_05_11_2009x pro PLC_PRG PRG LD Gi POUs af PLC_PAG PRG Awaria_czujnika BOOL Licznik CTUD Gent BLINK Gen2 BLINK Impulsy_1 BOOL Impulsy_2 BOOL Alarm BOOL Pom BOOL TRUE Wpisz BOOL Wartosc UINT 204 Cisnienie_x1 UINT Cisnienie_X2 UINT X BOOL ADD EN Wartosc 526 Wartosc Loading library C Loading libran lt mmon Fil alleriLib_ e Lib Fig 4 10 Conditional execution of the function ADD 589s ONLINE OV READ Ireneusz Moso Programmable Controllers Creation and usage of user POUs in application programs especially user function blocks has many advantages helps in structuring application programs important application program quality features verifiability modifiability and reusability are improved creation of application programs can be less time consuming as function blocks can be declared and used many times it is possible to create user function blocks that refer to specific hardware features u once user function blocks has been thoroughly tested it is then easier to test and start up application programs Usage of user function blocks helps in structuring application programs because its structure becomes more clear Part of the application program complexity is covered by user function block bodies This in t
10. The attribute RETAIN is written behind the keyword VAR or VAR_GLOBAL after a space Remark In some programmable controllers non retentive variables are called volatile and retentive variables are called non volatile CONSTANT The attribute CONSTANT is used to declare a local or global variable if its value cannot be PCE Ireneusz Moso Programmable Controllers changed The attribute CONSTANT is written behind the keyword VAR or VAR_GLOBAL after a space Additionally there are two other attributes that refer to BOOL data type and can only be used as input variables VAR_INPUT for user function blocks These are R EDGE rising edge and F_EDGE falling edge The user function block input declared as R_TRIG or F_TRIG is high for one program cycle if the variable associated to its input changes its value from low to high for R_TRIG declaration or from high to low for F_TRIG declaration If the user function block is not executed every cycle the user function block input will remain high until the next execution of this user function block 4 3 Program organization units There are three Program Organisation Units that have been distinguished in the programming model u F Functions u FB Function Blocks P Programs A function procedure is a program organization unit which when executed yields exactly one data element and possibly additional output variables which may be multi valued for exampl
11. controller in which the first three modules are digital input modules with 16 digital inputs each this is the first input in the third module 38 Ireneusz Moso Programmable Controllers 11 2 3 1 7 if this digital input variable refers to PS4 series compact programmable controller with EM4 network stations and LE4 local expansion modules this is the seventh digital input in the first byte in the third module in the second network station in the first communication line In this case the physical hierarchy is controller network station module input byte single digital input If the hierarchy is logical it is usually with no relation to the physical structure of the programmable controllers inputs outputs memory For directly represented variables their memory location is always known Depending on the variable it can be stored in the controller s memory or in the communication buffer network variables It should be remembered that digital input and output variables are stored in the process image memory The available addresses depend on the programmable controllers hardware The following symbols can be used to specify a variable length Symbol Meaning Length Examples X or none Bit 1 bit 10 0 0 0 3 M0 0 0 1 7 B Byte 8 bits 1B0 0 0 0 MBO 0 0 1 W Word 16 bits 1WO 0 0 0 MW0O 0 0 2 D Double word 32 bits 1D0 0 0 0 MDO 0 0 8 Remark Examples s
12. rq By 14 28 Fig 4 12 Usage of the function block input variable as a program variable that do not need to be declared Another example of a user function block created with the use of Easy Soft CoDeSys programming package is shown in figure 4 13 This is the user function block OBL_UCIAG which has been declared with the name ZAD_UCIAG It has one input of UINT data type and three outputs of UINT data type Additionally it has an EN input BOOL type and an ENO output BOOL type but these input and output are not used in the program The OBL_UCIAG function block has been programmed in the ST language and the body of this user function block has been shown in figure 4 4 In the declaration section declaration of some variables can be seen It is worth to mention that apart from symbolically represented variables FST_SCAN and ALWAYS_ON which are declared with an initial value TRUE other variables are directly represented 61 Ireneusz Moso Programmable Controllers variables the keyword with the variables addresses Comments in have been associated to all variables shown in figure u XSoft WCKFO5x1 pro PLC_PRG PRG LD File Edit Project Insert Extras Online Window Help ale SELES ZIBIAA A 700 alan fr 7 H_AUTO AT QX2 4 BOOL Lampka praca automatyczna H_AWARIA AT QX2 5 BOOL Lampka awaria sterowania GENERATOR FB WENT_HAM AT X2 6 BOOL Zalaczony we
13. 1 They have fixed 12 Ireneusz Moso Programmable Controllers number of inputs and outputs of particular types This does not mean that they cannot be expanded They can often be expanded up to hundreds or even thousands inputs and outputs For example Moeller PS4 201 MM1 programmable controllers have 8 digital inputs 6 digital outputs 2 analog inputs and 1 analog outputs After connecting to PS4 201 MM1 maximum possible number of local expansion modules LE4 and also maximum number of remote modules EM4 using only the controller s build in network interface RS485 with Suconet K protocol the total number of digital inputs and outputs in such a system would be 1006 Modular programmable controllers do not have fixed hardware architecture as compact controllers They consist of a rack or base and some number of modules Modules are mounted in the rack or fixed on the base The number of modules and their types depend on the application Some parts and modules are obligatory other modules can be chosen or not Apart from the rack base power supply module and of course central processing CPU module other modules are optional These optional modules can be digital input modules digital output modules digital input output modules analog input modules analog output modules analog input output modules analog modules for temperature measurements u communication modules high speed counter modules
14. 16 89A 168AB 16 BC 16 CD 16 DE 16 EF Tablica_2 ARRAY 1 3 1 4 OF UINT 1 2 3 4 5 6 7 8 9 10 11 12 Zdarzenie STRUCT Kod FSINT Data_i Czas DATE_AND_TIME Wartose_1 INT Wartosc_2 INT Wartosc_3 INT END_STRUCT END_TYPE T Fig 4 2 Declaration of derived data types examples Declaration of a sub range data type restricted value range The use of derived data types enables the user to restrict the value range for the used data type If values beyond the value range are assigned the limit value next to it will be entered automatically This rule applies also to initial values Declaration of a variable Temperatura_C of integer data type with restricted value range from 0 to 100 with the initial value 25 and declaration of a variable Temperatura_F of unsigned integer data type with restricted value range from 32 to 212 and the initial value 77 are shown in figure 4 2 as examples S Ireneusz Moso Programmable Controllers Declaration of a data type as array Various data elements of the same type can be combined into an array which can consist of elementary or derived data types This data type is declared with the keyword ARRAY and the definition of the number of array elements and their data type Array variables may be assigned with a direct address which is an address of the first element of the array Declaration of the array Tablica_1 as a vector of 6 variables of byte data
15. bases Forced outputs that are not used in the programme are also sent and corresponding outputs continue to be turned on until their forcing will be released Write Outputs to Specialty I O After updating the outputs in the local and expansion bases the CPU sends the output information that is required by any specialty modules which are installed In this phase of the cycle also the information from the process output image register that is intended for the Remote I O racks is updated Diagnostics During this part of the cycle the CPU performs all system diagnostics and other tasks such as calculating the scan time updating special relays and resetting the watchdog timer There are many various error conditions that are automatically detected One of the most important CPU activities during this phase of the cycle is the scan time calculation and the watchdog timer control The watchdog timer stores the maximum time allowed to solve the application programme and complete a cycle If this time is exceeded the CPU will enter the Program Mode and will turn off all outputs The default value for the DL405 CPU set from the factory is 200 ms It is possible to view the minimum maximum and current scan time An error is automatically signalised Looking at this example it can be concluded that despite different names of the program cycle phases in figure 3 3 they are very similar to those at the simplified diagram shown in figure 1 2 read
16. execution execution execution execution Reading Writing inputs outputs Operating system Field input functions Input signal state a mj o Fig 2 7 Detection of very short input signals in TSX07 programmable controllers As far as methods of shortening of the I O response time are concerned it can be concluded again that apart from common methods specific technical solutions applied in programmable controllers of particular producers can be found in their technical documentations es Ireneusz Moso Programmable Controllers 3 Examples of the Program Cycle Description 3 1 First example Moeller PS4 series First example refers to PS4 series compact programmable controllers produced by Moeller Company These programmable controllers can be in three different operating states Run Ready and Not Ready Only when the controller is in Run state it executes the user program The program cycle for these programmable controllers is shown in figure 3 1 Operating system Writing outputs Reading inputs Execution of the user program Fig 3 1 The program cycle for Moeller PS4 series programmable controllers The CPU operating system activities during particular phases of the working cycle are as follows Reading inputs Before the user program execution begins during the reading inputs phase of the cycle the CPU reads simultaneously the states of all inputs and stores these values in the input ima
17. name XControl 14 Ireneusz Moso Programmable Controllers 2 Principle of Operation in Details 2 1 Cyclical and periodic operation As it was mentioned earlier standard operation of a programmable controller is cyclical processing of the program cycle In this case program cycles are performed one by one without any delay or it can be said as quickly as possible for the particular controller But cyclical is not the only possible way of operation programmable controllers operation can be also periodic In such a case each next program cycle starts after a constant period of time this time is counted from the beginning of the previous program cycle If for periodic operation execution of the application program is shorter than the time set for periodic operation the operating system waits until the set time for periodic operation has elapsed and only then starts the next program cycle While waiting for the set time of period to elapse the CPU is not idle it performs operating system functions For example if the cycle time equals 5 ms while the set time for periodic operation is 50 ms the operating system waits 45 ms before the next program cycle is started In case of a single control task execution in a programmable controller there is not a big difference between cyclical and periodic operation provided that the time set for periodic operation is reasonably short taking into account time constants of the cont
18. operator the signal processing function and the machine process Programming debugging testing and documentation functions These functions provide for application programme generation and loading monitoring testing and debugging as well as for application programme documentation and archiving Power supply functions The power supply functions provide for the conversion and isolation of the PLC system power from the mains supply Characteristics of the CPU function The capabilities of the programmable controllers are determined by programmable functions which for ease of use are subdivided into application oriented groups a logic control logic timers counters signal data processing mathematical functions data handling analogue data processing interfacing functions input output other systems HMI printers mass memory 67 Ireneusz Moso Programmable Controllers u execution control system configuration Operating system The operating system function is responsible for the management of internal PLC system interdependent functions configuration control memory management application programme execution management communication with peripherals and with the interface functions to sensors and actuators etc After a power down or a distortion the PLC system can restart in three different ways Cold restart Restart of the PLC system and its application programme after all dynamic data
19. signal state in the process output image memory In Moeller PS4 compact programmable controllers direct access to inputs and outputs is possible using special addressing However direct access to inputs and outputs is possible only to inputs and outputs of the controller itself direct access is not possible to inputs and outputs of local expansion modules and remote expansion modules connected to the controller Direct access is possible for single inputs single outputs input bytes and output bytes for bigger controllers like for example PS4 341 MMI also for input words and output words For example standard addressing when the process image memory is used is IBO 0 0 0 for the input byte and QB0 0 0 0 for the output byte direct addressing the process image memory is not used is IP0 0 0 0 for the input byte and QB0 0 0 0 for the output byte Single inputs and outputs can also be accessed as it was mentioned earlier for example IPO 0 0 0 5 means direct reading of the 5 th input in the 0 input byte whereas QPO 0 0 0 3 means direct writing to the 3 rd output in the 0 output byte For programmable controllers from the series PS4 150 and PS4 200 direct reading of inputs and writing outputs during execution of the application program do not change states of the corresponding inputs and outputs in the process image memory In contrast to behaviour of these controllers the process image of the PS4 300 series controllers is updated immed
20. type and initial values written in hex format data delimited on the left by 16 and declaration of the two dimensional array Tablica_2 of 12 variables three rows and four columns of unsigned integer data type with initial values are shown in figure 4 2 as examples Declaration of a data type as structure Several data elements of different data types can be grouped together into a single structure A structure may consist of elementary or derived data types A structure is declared with the keywords STRUCT END_STRUCT and a list of the structure elements specifying their data types A structured data type is an aggregate data type which has been declared using a STRUCT or FUNCTION_BLOCK declaration An aggregate is a structured collection of data objects forming a data type Declaration of a structure is shown in figure 4 2 as an example Zdarzenie is a structure comprising 5 variables of different data types Kod is of unsigned short integer data type Data_i_czas is of DATE_AND_TIME type whereas Wartosc_1 Wartosc_2 and Wartosc_3 are of integer data type The declaration of local and global variables can be supplemented with the following attributes qualifiers RETAIN and CONSTANT RETAIN The attribute RETAIN is used to declare a retentive local or global variable Retentive means that with a warm start the variable declared as retentive keeps the last valid value it had before the stop
21. variables such as I O image internal registers timers counters etc and programme contexts are reset to a predetermined state A cold restart may be automatic for example after a power failure a loss of information in the dynamic portion s of the memory ies etc or manual for example push button reset etc Warm restart Restart after a power failure with a user programmed predetermined set of remnant data and a system predetermined application programme context A warm restart is identified by a status flag or equivalent means made available to the application programme indicating that the power failure shut down of the PLC system was detected in the run mode Hot restart Restart after power failure that occurs within the process dependent maximum time allowed for the PLC system to recover as if there had been no power failure AII I O information and other dynamic data as well as the application programme context are restored or unchanged Hot restart capability requires a separately powered real time clock or timer to determine elapsed time since the power failure was detected and a user accessible means to programme the process dependent maximum time allowed Memory for application data storage Application programme storage The application programme storage provides for memory locations to store a series of instructions whose periodic or event driven execution determines the progression of the 68 Ire
22. with the use of Sucosoft S40 programming package for control of a specific hardware element is shown in figure 4 11 This is a user function block named IZM_1T to control a circuit breaker of IZM type This function block has 4 digital inputs 2 time inputs and 6 digital outputs As it can be seen in the declaration 59 Ireneusz Moso Programmable Controllers section this function block has been used in the program several times with the following names CB_TR1 CB_TR12 CB_TR2 CB_TR3 CB_TR4 Each time different variables have been associated with its inputs and outputs POU Editor PROG_BC1 PROGRAM J Z File Edit Insert View Options Windows Help ea ea 3 NE JE i pje EJ rs w Type Initial value Attribute Address Comment Obs ta CB TR lt i gt AT IZM_1T WCB_TR1 NHI_NC CBTR1_Z WAR_ZAL CBTRL_W WAR_WYL NIE_ZAL AUTO_PN1 Kasowanie NIE_WYL T 1500ms Czas_ 01 NIE_PRZEL T 500ms Czas_10 TRWA_PRZE Help via key F1 PS4 300 INS 05632 3 Start Navigator BCITY1 POU Editor PROG_ Fig 4 11 User function block IZM_1T for control of the ICM circuit breaker An interesting function block declaration feature is that after declaring a function block its inputs and outputs can be used in the program without any additional declaration Even if there are no variables associated with some inputs and outputs of the function block that does not mean that these inputs and outputs are no
23. 11 low Instructions of the ST language are listed below 41 16 Elementary statements Value assignment Syntax Data element Expression Empty statement Example a single semicolon can be used as an empty statement 49 Ireneusz Moso Programmable Controllers Branching within a POU Conditional statement Syntax IF Expression THEN StatementSequence END_IF Single alternative statement Syntax IF Expression THAN StatementSequence1 ELSE StatementSequence2 END_IF Multiple alternative statement Syntax IF Expressioni THEN StatementSequence1 ELSIF Expression2 THEN StatementSequence2 ELSIF Expression3 THEN StatementSequence3 ELSE StatementSequenceN END_IF Multiple selection CASE statement Syntax CASE Expression OF ValueList1 StatementSequence1 ValueList2 StatementSequence2 ELSE StatementSequenceN END_CASE WHILE loop Syntax WHILE Expression DO StatementSequence END_WHILE REPEAT loop Syntax REPEAT StatementSequence UNTIL Expression END_REPEAT FOR loop Syntax FOR LoopVariable ExpressionlnitialValue TO ExpressionEndValue BY StepWidth DO StatementSequence END_FOR Loop exit Syntax EXIT Branching within the application POU exit Syntax RETURN Call of a function block with assignment of inputs and outputs Remark Function calls are not separate statements but expressions therefore they can only be used within expressions 50 Ireneusz Moso Programmable Controllers
24. 4 Mikulczy ski T Samsonowicz Z Analiza wybranych metod modelowania i programowania dyskretnych proces w produkcyjnych PAK Nr 3 1995 Mikulczy ski T Samsonowicz Z Automatyzacja dyskretnych proces w produkcyjnych WNT Warszawa 1997 Moson I Karkosi ski D Programowalne sterowniki logiczne w dydaktyce Zastosowanie komputer w w dydaktyce 94 Cykl seminari w zorganizowanych przez PTETiS Oddzia w Gda sku Zesz Nauk Wydz Elektrycznego Politechniki Gda skiej Nr 6 1994 s 89 94 Moso I Sterowniki programowalne PS4 w zdecentralizowanych systemach sterowania Elektroinstalator Automatyka 1996 Nr 11 s 27 30 Moson I Karkosi ski D Program sterowania diagnozowania stanu technicznego 1 monitorowania parametr w pracy linii technologicznej okleinowania p yt meblowych Opis algorytmu 1998 15 s 2 rys 3 tabl bibliogr 6 poz maszyn Ee Ireneusz Moso Programmable Controllers 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Moso I J zyk GRAFCET a weryfikacja algorytm w i program w sterowania Materia y Seminarium Naukowo Techniczne Zastosowanie nowoczesnej aparatury Schneider Electric w urz dzeniach i instalacjach elektroenergetycznych niskiego napi cia Gda sk 9 czerwiec 1999 s 4 14 Moson I Wybrane aspekty wprowadzenia do dydaktyki przedmiotu Sterowniki Programowalne Zastosowanie komputer w w dydaktyce 99 IX cykl semina
25. 987 Brock S Muszy ski R Urba ski K Zawirski K Sterowniki Programowalne Wydawnictwo Politechniki Pozna skiej Pozna 2000 Broel Plater B Uk ady wykorzystuj ce sterowniki PLC Projektowanie algorytm w sterowania Wydawnictwa Naukowe PWN Warszawa 2010 Cena G Valenzano A Vitturi S Hybrid Wired Wireless Networks for Real Time Communications IEEE Industrial Electronics Vol 2 Nr 1 2008 pp 8 20 DL405 User Manual 2nd Edition Direct Logic Koyo PLC Direct M Jnc 1995 Dirnfeldner M Automation with Programmable Controllers An Introduction for Beginners LS 27 064 GB Klockner Moeller 12 88 Flaga S Programowanie sterownik w PLC w j zyku drabinkowym Wydawnictwo BTC Legionowo 2010 Gom ka W Realizacja algorytm w sterowania sekwencyjnego za pomoc sieci dzia a GRAFCET PAK 1990 Nr 7 s 136 141 Hitachi Programmable Controller E Series Operation Manual No NJI 008A Kaminski K Programowanie sterownika S7 Norkom Gdansk 2000 Kaminski K Programowanie w Step 7 MicroWin Wydawnictwo GRYF Gdansk 2006 Kaminski K Podstawy sterowania z PLC Wydawnictwo GRYF Gdansk 2009 Kasprzyk J Programowanie sterownik w przemys owych WNT Warszawa 2006 Kie tyka L Stoi ski D Fengler W F Wykorzystywanie sieci Petriego do sterowania procesami sekwencyjnymi Prace IX Sympozjum SPD 9 Symulacja proces w dynamicznych Polana Chocho owska 10 14 czerwiec 1996 s 125 129 Konen P L Leu
26. KAPITA LUDZKI Bam NARODOWA STRATEGIA SPOJNOSCI FUNDUSZ SPOLECZNY Politechnika Gdanska Wydzia Elektrotechniki i Automatyki PROGRAMMABLE CONTROLLERS Part 1 Ireneusz Moso Gda sk 2010 Publikacja jest dystrybuowana bezp atnie Materia zosta przygotowany w zwi zku z realizacj projektu pt Zamawianie kszta cenia na kierunkach technicznych matematycznych i przyrodniczych pilota wsp finansowanego ze rodk w Unii Europejskiej w ramach Europejskiego Funduszu Spo ecznego Nr umowy 46 DSW 4 1 2 2008 zadanie 018240 w okresie od 21 08 2008 15 03 2012 Ireneusz Moso Programmable Controllers Materia y pomocnicze do przedmiotu Sterowniki programowalne prowadzonego w j zyku angielskim w semestrze zimowym w roku akademickim 2010 2011 dla V semestru specjalno ci zamawianej Technologie informatyczne w elektrotechnice na studiach pierwszego stopnia na kierunku Elektrotechnika Ireneusz Moso Programmable Controllers Preface Complex automation in all branches of industry is one of the dominating tendencies in technical development nowadays Programmable controllers are among the most important devices implementation of which makes possible this complex automation For the first time programmable controllers were designed produced and implemented in control systems of production lines in General Motors automotive plants over forty years ago At that time they were named programmable
27. LC system according to the needs of the machine process and also for later expansion up to the maximum configuration The input output system may be located in close proximity to the signal processing function or may be mounted close to the sensors and actuators of the machine process remotely from the signal processing function Characteristics of the communication function The communication function represents the communication aspects of a programmable controller It serves the programme and data exchange between the programmable controller and external devices or other programmable controllers or any devices in an automated system It provides functions such as device verification data acquisition alarm reporting programme execution and I O control application programme transfer and connection management to the signal processing unit of the PLC from or to an external device The communication function is generally accomplished by serial data transmission over local area networks or point to point links Characteristics of the human machine interface HMI function The HMI function has two purposes To provide the operator with the information necessary for monitoring the operation of the machine process u To allow the operator to interact with the PLC system and its application programme in order to make decisions and adjustments beyond their individual user scope 70 Ireneusz Moso Programmable Controllers Ch
28. Other operating modes include stop with I O disabled mode and stop with I O enabled mode In the latter two modes the logic program is not executed Each of the listed modes is controlled by external events and application configuration settings The programmable controller makes the decision regarding its operating mode at the start of every sweep The CPU operating system activities during particular phases of the program cycle for standard program sweep are as follows Housekeeping During this phase of the sweep cycle all of the tasks necessary to prepare for the start of the sweep are performed Among the most important tasks are calculation of the sweep time determination of an operating mode of the next sweep updating fault reference tables updating timer values and reset of the watchdog timer If the controller is in constant sweep mode the sweep is delayed until the required sweep time elapses If the required time has already elapsed the system variable meaning oversweep is set and the sweep continuous without any delay Data input During this phase of the sweep all input modules are scanned and the obtained data are stored in discrete inputs memory I or analog inputs memory AI accordingly Any data received from Genius communication modules are stored in the part of memory for global data G If the CPU is in the stop with I O disabled mode the input scan is skipped Program execution The application
29. PC with programming software Sucosoft S40 or a hand held programmer during on line operation with the programmer connected Looking at the program cycle for Moeller PS4 series programmable controllers it can be concluded that it comprises the same phases as the diagram in figure 1 2 The names of the cycle phases are almost the same and the only difference is its circular form 3 2 Second example Hitachi E series Second example refers to E series compact programmable controllers produced by Hitachi Company The E series programmable controllers have different number of digital inputs outputs 20 28 40 64 are locally expandable by additional 64 inputs outputs and can have relay or transistor outputs There are three modes of operation for these controllers PROG programming mode TEST test mode and RUN operation mode The program cycle for these controllers is shown in figure 3 2 The CPU operating system activities during particular phases of the program cycle are as follows Input processing During this phase the ON OFF status of the external inputs is taken into the data RAM of the E series For each input its status in the data RAM remains unchanged even if the ON OFF status of any external input changes during the arithmetic processing of the program The status change will be taken into the data RAM when input processing is made for the next 25 Ireneusz Moso Programmable Controllers sc
30. Programmable Controllers access then the response time is shorter whereas if after the instruction with direct access then it does not influence the response time Instructions with direct access are always effective and make the response time shorter if used in special function blocks For example in Moeller PS4 series controllers there are three so called alarm function blocks These are CounterAlarm EdgeAlarm and TimerAlarm The first one is associated with the high speed counter input the second one with the interrupt input and the third one with internal time interrupts Direct access to inputs and outputs if used in these function blocks are always effective and the response is always fast If for example the interrupt input with the address 10 0 0 0 1 in PS4 201 MM1 programmable controller with the function block EdgeAlarm is used outputs with addresses QP will update the controller s output signals at the point in time they are used in this function block FB The I O response time for this case is shown on the time diagram presented in figure 2 5 Program cycle Program cycle Mag ig L I Program Program Program execution execution execution Writing Reading i inputs outputs II I Il I I I II tot it I I l FB Il II execution R II I I I tot IL I SEK IIli I l IL I tot Field input EE E Fig 2 5 The I O response time when using the EdgeAlarm function block 22 Iren
31. SE then the signal is not passed on through this contact 5 Ireneusz Moso Programmable Controllers POU Editor Example1 PROGRAM EJ File Edit Insert View Options Windows Help EBEIEE ACEEJ CJ i 0 0 Io First input I0 0 0 0 Second input I0 0 0 0 Third input I0 0 0 0 Forth input I0 0 0 0 Fifth input Q0 0 0 0 Output nr O 0001 Label El An example with digital variables Var_I1 Var _I3 Var_I4 i w Var_I5 Rim Fig 4 6 An example of a network written in the LD language A contact can be negated negated contact is represented by the slash in the contact symbol If the value of the variable associated with the negated contact is FALSE then the signal is passed on through this contact If opposite i e the value of the variable associated with the negated contact is TRUE then the signal is not passed on through this contact Contacts can be connected in parallel then one of the parallel branches must transmit the signal so that the parallel branch transmits the signal or contacts can be connected in series then all contacts must transmit the signal This therefore corresponds to electric circuits parallel and series circuit Coils On the right hand side of a network in LD there can be any number of so called coils coils are represented by parenthesis They can only be in parallel A coil transmits the signal is energized if the signal in the network has been passed on to th
32. TUTORIALS Number systems used in programmable controllers Data types and functions of their conversion Creation of control algorithms graphical elements of the algorithms Programming software Easy Soft CoDeSys Creation of control programs in IL LD FBD ST CFC languages and their debugging with the use of program simulator virtual controller Creation of visualisation applications Programming of control of sequential processes in SFC language LABORATORY Programming software Sucosoft S40 structure configuring control systems editing debugging testing and documenting programs Program for a conveyor control I and IL Conversion functions and arithmetic operators Counting events and compiler options Creation of the user function block Modifying programs and changing variable values in On line mode Programming PS4 200 and PS4 150 series controllers in the network master active slave Learning outcomes Student describes types and structures of programmable controllers Explains principle of programmable controller operation and principle of execution of the user program Student selects programmable controllers for specific applications Analyses requirements of control tasks and creates control algorithms Writes debugs and tests programs of low and middle complexity for control of different control objects Creates user functions and function blocks Creates simple visualisation applications Ireneusz Moso Programma
33. ajority of programmable controllers use the process image memory it is usually possible to read input signal states directly and to write output signal states directly This is called direct access and this is necessary when signal states have to be processed immediately in the control program The purpose of direct access to inputs and outputs is to shorten a control system reaction time Following are some examples of direct access to inputs and outputs in programmable controllers from different manufacturers In Siemens S5 115U modular programmable controllers digital module signal states are stored in two memory areas the second one is a process image memory It is possible to set parameters of this controller changing one bit in the system data word SD120 that it will not use the process image memory In this case exchange of information with digital modules takes place directly In GE Fanuc 90 30 series programmable controllers a special function block Do I O DO_IO can be used to read selected input signal states directly or to write selected output signal states directly This function block is used during execution of the program cycle Depending on the function block parameters the input signal states that have been read using this function block either modify the input signal states that had been read at the beginning of the program cycle process image or are written to a different memory area for example markers area Similarly progr
34. aken into account during the current program cycle The advantage of such a way of operation is that for a single cycle the whole program will be executed for the same states for each input signal and even if a change of an input signal occur this will not influence corresponding state in the process input image memory until next reading of inputs in the next cycle Execution of the application program Typically the application program is executed cyclically The processor reads the application program memory locations one after another from the beginning to the end of the program This does not mean that in each cycle every instruction every rung is being processed Some parts of the program can be omitted if their execution is conditional Conditional execution of some program parts can depend on states of the controlled process or just on the program realization of the control algorithm The program performs all necessary logic and arithmetic operations on the data Every time when an operand of the instruction is an input variable its state is read from the process input image memory The same rule applies to output variables Every time when an operand of the instruction is an output variable its state is changed in the process output image 10 Ireneusz Moso Programmable Controllers memory During a single program cycle the state of an output variable can be changed many times but the valid state of this variable at the en
35. ammable controllers outputs can be updated during the program cycle with signal states taken either from the process output image or from a specified memory area for example markers area If necessary this function block can be used many times in a program cycle In Koyo DL405 modular controller in order to shorten the programmable controller reaction so called immediate inputs and outputs that are special Boolean instructions can be used This immediate instructions are used to read directly input states and write directly signal states to outputs during execution of the application program The immediate oy be ae Ireneusz Moso Programmable Controllers instructions take longer time to execute the program execution is interrupted while the CPU reads or writes signal states from a digital module Immediate input and immediate output instructions in a different way influence signal states that are stored in the process image memory Although an immediate input instruction reads the most current status of the input signal it only uses the result to solve that one instruction It does not update the process input image memory Therefore any regular not immediate instructions that follow will still use the input states not updated from the process input image The immediate output instruction writes the current status of the output signal to the corresponding output in a digital output module and simultaneously updates this output
36. an To be sure that the change of the input signal status will be taken into the data RAM the pulse width should exceed one scan time 1 scan time sl eee IP Input Processing AP Arithmetic processing of the program F S R Forced Setting Resetting PP Peripherial Processing OP Output Processing Fig 3 2 The program cycle for Hitachi E series programmable controllers Arithmetic processing of the program A written program is arithmetically processed starting from the first step according to the commands of the program The arithmetic processing causes the contents of external outputs and internal outputs i e markers and registers to be changed from time to time in the data RAM Forced setting resetting During operation of the programmable controller forced setting will be made after completion of all operations of the program Once this function is activated the power failure protected internal outputs timers and counters in the data RAM can be set or reset Peripheral processing In case the ON OFF status of input output or the current value of timer counter are monitored via the programmer the content of the data RAM is displayed during the peripheral processing phase Output processing During this phase of the scan the ON OFF status of each external output in the data RAM is sent out to the external output terminal driving the output relays 26 Ireneusz Moso
37. an be represented in a subset of the above listed languages Writing the application programme Generating the application programme The application programme may be entered via alphanumeric or symbolic keyboards and when menu driven displays are or a graphical programme entry is used via cursor keys joystick mouse etc All programme and data entries are generally checked for validity and 71 Ireneusz Moso Programmable Controllers internal consistency in such a way that the entry of incorrect programmes and data is minimized Displaying the application programme During application programme generation all instructions are displayed immediately statement by statement or segment by segment in the case of a monitor or other large display In addition the complete programme can generally be printed If alternative representation of programming language elements is available than the display representation is generally user selectable Automated system start up Loading the application programme The generated programme resides either in the memory of the programmable controller or in the memory of the PADT The latter requires a programme transfer via down loaded or memory cartridge insertion into the programmable controller before start up Accessing the memory During start up or trouble shooting operations the application programme and application data storage are accessed by the PADT as well by the processing
38. aracteristics of the programming debugging monitoring testing and documentation functions These functions are implemented as either an integral or an independent part of a programmable controller and provide for code generation and storage of the application programme and application data in the programmable controller memory ies as well as retrieving such programmes and data from memory ies Language For the programming of the application there is a set of languages defined in IEC 61131 3 Textual languages Instruction list IL language A textual programming language using instructions for representing the application programme for a PLC system Structured text ST language A textual programming language using assignment sub programme control selection and iteration statements to represent the application programme for a PLC system Graphical languages Function block diagram FBD language A graphical programming language using function block diagrams for representing the application programme for a PLC system Ladder diagram LD language A graphical programming language using ladder diagrams for representing the application programme for a PLC system Sequential function chart SFC A graphical and textual notation for the use of steps and transitions to represent the structure of a program organisation unit program or function block for a PLC system The transition conditions and the step action c
39. are said to be pluggable when they may be plugged or unplugged at any time into their associated interface without any risk to the operators and the application In all other cases PADT are said to be fixed Remote input output station RIOS Manufacturer s catalogued part of a PLC system including input and or interfaces allowed to operate only under the hierarchy of the main processing unit CPU for UO multiplexing demultiplexing and data pre processing post processing The RIOS is the only permitted limited autonomous operation for example under emergency conditions such as 65 Ireneusz Moso Programmable Controllers breakdown of the communication link to the CPU or of the CPU itself or when maintenance and trouble shooting operations are to be performed FUNCTIONAL CHARACTERISTICS Basic functional structure of a programmable controller system The general structure with main functional components in a programmable controller system is presented in figure 5 1 These functions communicate with each other and with the signals of the machine process to be controlled Other systems functions functions DATA STORAGE HUMAN MACHIME INTERFACE OPERATOR COMMUNICATION functions ACE PROGRAMMING DEBUGGING APPLICATION TESTING programmer functions SIGNAL PROCESSING furictions OPERATING SYSTEM functions a APPLICATION APPLICATION ains PROGRAMME PROGRAMME supply STORAGE INTERFACE functions to sensors and a
40. arting from its basics and end with its detailed analysis Any time it was appropriate necessary comparisons in relation to various programmable controllers have been made and discussed A special effort have been made to present all material step by step in a well organised manner especially Chapter 4 about programming In the last chapter in this part of materials selected information from the International Standard IEC 61131 is presented It should help to get acquainted with programmable controllers and programmable controller based control systems basics as well as with programmable controllers nomenclature These materials are auxiliary materials for students to better understand the course Programmable controllers Completion of this course should give them a good basis to start their engineering activities in the field of programmable controllers applications 75 Ireneusz Moso Programmable Controllers References 10 11 12 13 14 15 16 17 18 Automation Systems and Drives Main Catalogue 2001 2002 Moeller GmbH Bonn 01 2001 HPL0213 2001 2002GB Automation systems Main Catalogue 2004 2005 Moeller GmbH Bonn HPL0213 2004 2005GB INT MM We 10 04 Bauernfeind D Dung O Skupin J CM4 505 GS1 AS Interface Master Gateway for Suconet K Actuator Sensor Interface Moeller GmbH Bonn AWB 27 1271 GB 09 96 Berger H Automatyzacja za pomoc sterownika SIMATIC S5 115U SIEMENS AG Erlangen 1
41. ble Controllers 1 Programmable Controller Basics 1 1 What is a programmable controller In brief it can be said that a programmable controller is a programmable electronic device used in control systems More precise explanation is published in the International Standard IEC 61131 1 40 see also Chapter 5 of this materials The definition in the standard says that a programmable controller is a digitally operating electronic system designed for use in an industrial environment which uses a programmable memory for the internal storage of user oriented instructions for implementing specific functions such as logic sequencing timing counting and arithmetic to control through digital or analogue inputs and outputs various types of machines or processes It also says that the programmable controller and its associated peripherals are designed so that they can be easily integrated into an industrial control system and easily used in all their intended functions The definition especially when reading it fast may seem not very clear but is precise and refers to all programmable controllers from the first programmable controller to the newest controllers that are produced currently It should be mentioned that the definition is general as it obviously should be and it doesn t mention that a programmable controller is a microprocessor based electronic system This is so because first programmable controllers were developed produced and i
42. ce as required They are placed exactly as in the IL language between parenthesis with asterisks An expression is not an independent statement but a construction which after its evaluation returns a result a value for further processing in the statement An expression consists of one or several operands that are linked together by means of operators An operand can be a constant a variable a function call or another expression The evaluation of an expression takes place by means of processing the operators according to certain binding rules The operator with the strongest binding is processed first then the operator with the next strongest binding etc until all operators have been processed Operators with equal binding strength are processed from the left hand side to the right hand side 48 Ireneusz Moso Programmable Controllers Operators that can be used in ST language are shown in table 4 3 41 16 Table 4 2 Operators in the ST language Operation Symbol Binding strength Parenthesization 1 high Function call Name 2 Two s complement 3 Two s complement used twice 3 One s complement NOT 3 Exponentiation Gy 4 Multiplication i 5 Division 5 Modulo MOD 5 Addition 6 Subtraction 6 Comparison gt gt lt lt 7 Equality 8 Inequality lt gt 8 Logic AND AND w 9 Logic EXCLUSIVE OR XOR 10 Logic OR OR
43. chs K Networking Programmable Controllers An Introduction for Beginners G 27 2100 GB Klockner Moeller 5 90 76 Ireneusz Moso Programmable Controllers 19 20 21 22 23 24 25 26 2T 28 29 30 31 32 33 Kr l A Moczko Kr l J S5 S7 Windows Programowanie i symulacja sterownik w PLC firmy SIEMENS Wydawnictwo Nakom Pozna 2000 Kwa niewski J Programowalne sterowniki przemys owe w systemach sterowania J Kwa niewski amp Fundacja Dobrej Ksi ki Krak w 1999 Kwa niewski J Sterowniki PLC w praktyce in ynierskiej Wydawnictwo BTC Legionowo 2008 Kwa niewski J Programowalny sterownik SIMATIC S7 300 w praktyce in ynierskiej Wydawnictwo BTC Legionowo 2009 Legierski T Kasprzyk J Hajda J Wyrwa J Programowanie sterownik w PLC Wydawnictwo Pracowni Komputerowej Jacka Skalmierskiego Gliwice 1998 Liider A Lorentz K IAONA Handbook Industrial Ethernet IAONA e V Magdeburg 2005 Maczy ski A Sterowniki programowalne PLC Budowa systemu i podstawy programowania Astor Sp z 0 0 Krak w 2002 Menden R Petrick B Manual Structuring of User Programs Klockner Moeller Bonn 5 91 AWB 27 101 1 GB Mikulczy ski T Samsonowicz Z Synteza sekwencyjnych uk ad w sterowania zautomatyzowanych proces w technologicznych PAK Nr 7 1994 Mikulczy ski T Samsonowicz Z O syntezie sekwencyjnych uk ad w sterowania ZPT PAK Nr 10 199
44. cking programme sequences for example step by step operations variations of programme cycle time halt commands simulation of interface functions for example forcing of I Os of information exchanged between tasks or modules internal to the PLC system Modifying the application programme Functions for modification provide for changing adjusting and correcting application programmes Typical functions are search replace insert delete and add they apply to characters instructions programme modules etc Documentation A documentation package should be provided to fully describe the PLC system and the application The documentation package may consist of u description of the hardware configuration with project dependent notations application programme documentation consisting of programme listing with possible mnemonics for signals and data processed cross reference tables for all data processed I Os internal functions such as internal stored data timers counters etc comments description of modifications maintenance manual Application programme archiving For rapid repair and to minimize down time the user may want to store the application programme in non volatile media such as flash PC cards EEPROM EPROM discs etc Such a record needs to be updated after every programme modification so that the programme executed in the PLC system and the archived programme remain the same Characte
45. contacts and coils function blocks can also be entered in an LD network In the network they must have an input and an output with Boolean variables and can be used at the same places as contacts that is on the left hand side of the LD network In some LD editors however function blocks can be entered in a POU only as separate rungs in the ladder Only single variables can be associated with their inputs and outputs If a value of an input variable depends on a complex condition this should be evaluated in a separate rung Such an example is shown and discussed in chapter 4 6 An example of a network in the LD language with the use of Easy Soft CoDeSys programming package with two function blocks connected in parallel a signal generator and an up counter is shown in figure 4 7 Continuous Function Chart CFC The Continuous Function Chart editor does not operate like Function Block Diagram with networks but rather with elements that can be placed quite freely in different positions This allows for example feedback connections An example of a POU written in the CFC language with the use of Easy Soft CoDeSys programming package is shown in figure 4 8 54 Ireneusz Moso Programmable Controllers XSoft Nowy1 pro PLC_PRG PRG LD File Edit Project Insert Extras Online Window Help alaju Helea o ee o001 PROGRAM PLC_PRG 3 POUs VAR i pA PLC_PRG PRG Gent BLINK Generator impulsow o czestotliwosci 10 Hz
46. ctions and function blocks are shown comparatively in table 4 1 Declaration of a function block is called its instantiation Each instantiation means that a copy of the function block with a new name has been created The name of a function block assigned to it during creation is called the instance name During function block declaration a part of the programmable controller s memory is reserved to store all internal variables of this function block These internal variables can be either allocated dynamically in the controller s memory or it is necessary to know how many registers are needed to store all internal variables and point out the address of the first register n consecutive registers are used to store the function block internal data Table 4 1 Differences between Functions and Function blocks Functions Function blocks Functions are not declared Function blocks need to be declared Each function block can be used many times but each time it need to be declared with a different name Each function can be used many times Function can have many inputs but only one output Function block can have many inputs and many outputs Function has not internal variables Function block has internal variables Function is a static language element that means that each time for the same combination of values of input signals the value of the output signal is always the same Function bloc
47. ctuators blachine Process Fig 5 1 Basic functional structure of a PLC system Signal processing functions The CPU function consists of the application programme storage the operating system and 66 Ireneusz Moso Programmable Controllers the execution of the application programme functions The CPU processes signals obtained from sensors as well as internal data storage and generates signals to actuators as well as internal data storage in accordance with the application programme Interface function to sensors and actuators The interface function to sensors and actuators converts the input signals and or data obtained from the machine process to appropriate signal levels for processing u the output signals and or data from the signal processing function to appropriate signal levels to drive actuators and or displays The input output signals to the interface functions may be coming from special modules which pre process external sensor signals according to the defined functions contained in the special modules themselves Examples of such special modules include PID module fuzzy control module high speed counter module motion modules and others Communication function The communication function provides data exchange with other systems third party devices such as other PLC systems robot controllers computers etc Human machine interface HMI function The HMI function provides for interaction between the
48. d of the program cycle is the last state of this variable written to the process output image memory In short it can be said that during execution of the application program the programmable controller s processor operates on images of physical hardware inputs and outputs stored in the process image memory Writing outputs After execution of the application program states of output variables from the process output image memory are simultaneously written to the controller s physical hardware outputs Thus all hardware outputs are updated simultaneously once in a cycle at the end of the program cycle Operating system functions All operating system functions can be divided into two groups The first group is performed before execution of the application program begins in a cycle or just after the end of execution of the application program in a cycle Such functions are for example the watchdog timer resetting and diagnostic functions The second one is a group of functions that are performed simultaneously with the execution of the application program They are event driven functions because they are called up by various operating system interrupts These interrupts make possible that several functions run virtually simultaneously Functions belonging to this group are for example monitoring the cycle time watch dog monitoring the power supply processing the basic cycle pulses communicating with a programming device us
49. defines basic terms general rules programming model communication model as well as basic types and data structures In IEC 61131 3 the elements of programmable controller programming languages are classified as follows Data types u Variables Program Organization Units POUs Functions Function Blocks ce Ireneusz Moso Programmable Controllers Programs Configuration elements Global variables Resources Tasks Access paths Sequential Function Chart elements The software model from the standard is shown in figure 4 1 Definitions and explanations to the software model elements are as follows A configuration is a language element which corresponds to a programmable controller system as defined in IEC 61131 1 A resource corresponds to a signal processing function and its man machine interface and sensor and actuator interface functions if any as defined in IEC 61131 1 A configuration contains one or more resources each of which contains one or more programs executed under the control of zero or more tasks A program may contain zero or more function blocks or other language elements as defined in this part Configurations and resources can be started and stopped via the operator interface programming testing and monitoring or operating system functions defined in IEC 61131 1 The starting of a configuration shall cause the initialization of it
50. e an array or structure and whose invocation can be used in textual languages as an operand in an expression A function block type is a programmable controller programming language element consisting of 1 the definition of a data structure partitioned into input output and internal variables and 2 a set of operations to be performed upon the elements of the data structure when an instance of the function block type is invoked An input variable input is a variable which is used to supply an argument to a program organisation unit An output variable output is a variable which is used to return result s of the evaluation of a POU An argument is synonymous with input variable output variable or in out variable An instance is an individual named copy of the data structure associated with a function block type or a program type which persist from one invocation of the associated invocation to the next 44 Ireneusz Moso Programmable Controllers An instance name is an identifier associated with a specific instance An instantiation is the creation of an instance Before the standard IEC 61131 had been created such program organisation units as functions and function blocks were usually called sub programs Sub programs could be called from programs or other sub programs nested calls According to the standard there are some clear distinctions between functions and function blocks Differences between fun
51. e entry line on the left of the coil Then the Boolean value of the variable associated with this coil takes the value TRUE Otherwise the Boolean value of the variable associated with this coil is FALSE 53 lt Ireneusz Moso Programmable Controllers Coils can also be negated negated coil is represented by the slash in the coil symbol A negated coil is energized if the signal in the network has not been passed on to the entry line of the coil the variable associated with this coil is then TRUE Otherwise the negated coil is not energised and the variable associated with this coil is FALSE Set Reset coils Coils can also be defined as set or reset coils A set coil can be recognized by the S in the coil symbol A reset coil can be recognized by R in the coil symbol Boolean variables are associated with set and reset coils In a POU the same Boolean variable is associated with at least one set coil and with at least one reset coil A set coil never writes over the value TRUE of the associated Boolean variable That is if the variable was once set at TRUE then it remains so A reset coil never writes over the value FALSE of the associated Boolean variable If the variable has been once set on FALSE then it remains so Therefore it is rather pointless to have a Boolean variable associated with either only a set coil set coils or only a reset coil reset coils Function blocks in the LD network Apart from
52. e Controllers Response time Input delay Program cycle time Output delay The I O response time is the longest when the input signal state change takes place just after the reading inputs phase of the program cycle The I O response time for this case is shown on the time diagram presented in figure 2 4 Program cycle Program cycle j Program Program Program Program execution execution execution execution BE Writing I I i inputs I Outputs Field input l I O response time Fig 2 4 The I O response time worse case In the second case the I O response time equals approximately Response time Input delay 2 x Program cycle time Output delay Taking into account that input delay and output delay are usually substantially shorter than the program cycle time it can be concluded that the maximum response time is approximately twice the program cycle time In many applications even the maximum I O response time is such that the timing analysis is in fact not relevant However some applications do require extremely fast responses In such cases direct access to controller s inputs and outputs can be used Using direct access with Boolean instructions during execution of the application program not always is effective and shortens the response time It depends on the point in time when the change of the input signal took place if before the instruction with direct ox Ireneusz Moso
53. e may also be considered for special applications Design testing and maintenance of the application programme The application programme is a key component of the overall automated system Most programmable controllers provide enough computing power to permit implementation of diagnostic functions in addition to the minimum control function Machine process behaviour modelling and subsequent identification of faulty conditions should be considered Adequate testing of the application programme is mandatory Every modification implies proper design and testing so that the overall availability and reliability are not impaired The programme documentation shall be maintained and annotated accordingly Installation and service conditions PLC systems are typically of rugged design and intended for general purpose service However as for any equipment the more stressing the service conditions the worse is the reliability and benefit in this area may be expected when permitted service conditions are better than the normal service conditions specified in IEC 61131 2 Some applications may require consideration of special packaging cooling electrical noise protection etc for reliable operation 74 Ireneusz Moso Programmable Controllers Conclusion In Part 1 of these materials information about programmable controllers their principle of operation and programming is presented It was intended to start presentation of each problem st
54. e placed in the CPU base The CPU performs both read and write requests Update Clock Special Relays During this phase of the cycle special memory locations that hold the Clock and the Calendar i e the Real Time Clock RTC information are updated on every cycle This information can be used therefore in the application programme There are also several different Special Relays such as diagnostic relays etc that are also updated during this phase of the cycle 28 Ireneusz Moso Programmable Controllers Solve the Application Program The CPU evaluates each instruction in the application programme during this phase of the cycle The instructions define the relationship between the input conditions and the desired output response The CPU uses the process output image register to store the status of the desired action of the outputs The actual outputs are updated during the Write Outputs phase of the cycle If the CPU have obtained and stored forcing information when it serviced peripheral devices the process output image register also contains this information but if an output point was used in the application programme the results of the programme solution will overwrite any forcing information that was stored Write Outputs After solving the application programme the CPU sends current output states of the process output image register to the output modules located in the local CPU base or the local expansion
55. e use of parity checking self testing diagnostics etc are addressed Refer to IEC 60364 or applicable national local regulations for electrical installation and guidelines This Part of IEC 61131 gives the definitions of terms used in this standard It identifies the principal functional characteristics of programmable controller systems Two other parts are indispensable for the application of the IEC 61131 1 part of the standard TEC 61131 2 Programmable controllers Part 2 Equipment requirements and tests TEC 61131 3 2003 Programmable controllers Part 3 Programming languages For the purposes of the first part of the standard the following terms and definitions apply Application programme or user programme Logical assembly of all the programming language elements and constructs necessary for the intended signal processing required for the control of a machine or process by a PLC system Automated system Control system beyond the scope of IEC 61131 in which PLC systems are incorporated by or for the user but which also contains other components including their application programs 64 Ireneusz Moso Programmable Controllers Field device Catalogued part to provide input and or output interfaces or to provide data pre processing post processing to the programmable controller system A remote field device may operate autonomously from the programmable controller system It can be connected to the progra
56. ee eneenaeenes 56 4 6 User functions and function blocks asd aoi dO AO OWE EWA O EG Oak 57 5 International Standard IEC 61131 Selected Information scessescccccrsreresereree 63 CO CIUSI zd OWO WE EO INE EEC RE OE EW 75 E NC W AO A OKA ou E A E E E KA EA 76 Ireneusz Moso Programmable Controllers Syllabus and learning outcomes of the course Programmable controllers Syllabus LECTURE Programmable controllers in control systems Types structure and principle of operation Execution of the user program Process image memory Hardware characteristics Interaction with a controlled process Digital analogue and special input output circuits Fundamentals of programming PN EN 61131 3 standard Programming model Programming languages Data types and declaration of variables Addressing Program organization units programs functions and function blocks Creation of user functions and function blocks Structuring of user programs Factors of a program quality Networking programmable controllers Network structures Communication interfaces and transmission media Methods of media access control Communication protocols Suconet K Modbus RTU Profibus DP AS i Industrial Ethernet protocols Modbus TCP Powerlink Profinet Design of programmable controllers based control systems Selection of a programmable controller depending on an application Realization of a human machine interface HMI SCADA programs
57. eft hand side and on the right hand side by vertical lines In the middle there is a circuit diagram made up of contacts coils and connecting lines 51 Ireneusz Moso Programmable Controllers POU Editor Example1 PROGRAM Ep File Edit Insert View Options Windows Help lees e fala eE Ly i Comment I0 0 0 0 1 First input I0 0 0 0 Second input I0 0 0 0 Third input I0 0 0 0 Forth input I0 0 0 0 Fifth input 00 0 0 0 Output nr 0 0001 Label El An example with diqital variables Fig 4 5 An example of a network written in the FBD language The left vertical line can be treated as a power supply line usually 24 V DC in a control electric circuit whereas the right vertical line can be treated as a 0 V line Networks are analysed in a similar way as electric circuits whether they pass signal current from the left hand side to the right hand side or not An example of a network written in the LD language with the use of Sucosoft S40 programming package is shown in figure 4 6 Contacts Each network on the left hand side consists of a number of contacts contacts are represented by two parallel lines A Boolean variable is associated with each contact The value of a Boolean variable can be TRUE or FALSE If the value of the variable associated with the contact is TRUE then the signal is passed on through this contact If opposite i e the value of the variable associated with the contact is FAL
58. emory capacity depending on the amount and format of data stored Execution of the application programme An application programme may consist of a number of tasks The execution of each task is accomplished sequentially one programmable function at a time until the end of the task The initiation of a task periodically or upon the detection of an event interrupt condition is under the control of the operating system Characteristics of the interface function to sensors and actuators Types of input output signals Status information and data from the machine process are conveyed to the I O system of the programmable controller by binary digital incremental or analogue signals Conversely 69 Ireneusz Moso Programmable Controllers decisions and results determined by the processing function are conveyed to the machine process by use of appropriate binary digital incremental or analogue signals The large variety of sensors and actuators used requires accommodating a wide range of input and output signals Characteristics of the input output system Various methods of signal processing conversion an isolation are used in input output systems The behaviour and performance of the PLC system depend on the static dynamic evaluation of the signal detection of events storing non storing procedures opto isolation etc Input output systems in general display a modular functionality which allows for configuration of the P
59. eration For both direct and symbolic variable representation an initial value can be assigned to the variable An initial value is the value assigned to a variable at system start up If an initial value is not assigned during declaration of a variable the variable will be assigned its default value at the programmable controller start up The default value depends on the data type of the variable For variables of ANY_BIT ANY_NUM and TIME data types their default initial value is zero For variables of STRING data type their default initial value is empty string For variables of ANY_DATE data types their default initial value depends on the manufacturer There are different types of variables The types of all variables are defined in the declaration section of a program organisation unit Variable types are identified with keywords Variables of the same type are stored in the declaration block A declaration block starts with a keyword that depends on the variable type and ends with a keyword that depends on the variable type VAR END_VAR Local variables are declared in this declaration block They are valid only within the POU where they were declared VAR_GLOBAL END_VAR Global variables are declared in this declaration block A variable is declared as a global variable if it is to be used in a program and in POUs which can be called by this program A global variable called up in a program is known within this pro
60. eusz Moso Programmable Controllers The EdgeAlarm function block can be called in the program as a result of the input signal rising edge in the controller s interrupt input or as a result of the input signal falling edge There is one more problem concerning digital input signals that has not been discussed yet In the preceding analysis of programmable controllers input signals it was always assumed however never underlined that the duration of an input signal is longer than the program cycle time Such signals can always be detected because for at least one reading inputs phase of the cycle their state is high The situation is different in case of signals which duration is shorter than the program cycle time They are detected in a stochastic manner if it happens that they exist during the reading inputs phase of the program cycle they are detected if opposite they are not detected However there are programmable controllers that have inputs on which such short signals are always detected in a fully deterministic way For example Telemecanique TSX07 compact programmable controller has inputs from which short changes of input signal states shorter than one program cycle and existing between consecutive reading inputs phases can be stored and will have the high state during the next program cycle The time diagram of the described case is shown in figure 2 7 Program cycle Program cycle Program Program Program Program
61. ge register as high H or low L for digital signals The status image of all inputs remains constant for a whole program cycle Changes in status of the inputs which can take place within processing of the program are therefore ignored by the controller Execution of the user program During this phase of the program cycle the user program is executed Each instruction of the program is distinguished by its memory location number the address The program counter has to select these addresses step by step It starts from the zero address and ends on the address with the instruction of the end of the program During execution of the user program SIE Ireneusz Moso Programmable Controllers every time when an input is the operand of an instruction its status is read from the input image register The output results of the program sequences are stored temporarily in the output image register Writing outputs At this phase writing outputs of the program cycle after executing the whole user program states of the outputs from the output image register are allocated together simultaneously to the controller physical outputs Operating system During this phase of the program cycle the controller s operating system activities are carried out These system activities are independent of current program processing For example signal transfer between the programmable controller and a programmer The programmer can be a
62. gram and within the POUs that are called up by this program The variable must be declared with the same identifier name as external variable in all invoked POUs in which it is used VAR_EXTERNAL END_VAR 40 Ireneusz Moso Programmable Controllers External variables are declared in this declaration block If a global variable is used within a function block it must be declared there as external variable with the same identifier name VAR_INPUT END_VAR Input variables are declared in this declaration block A variable is declared as an input variable if it is to be read only within a function or within a function block or if it is to be used for transferring parameters in a function or a function block This variable value cannot then be changed in this POU VAR_OUTPUT END_VAR Output variables are declared in this declaration block Output variables are used as outputs in function blocks VAR_IN_OUT END_VAR Input output variables are declared in this declaration block An input output variable is read processed and output under the same name by the function block in which it is used Since operations on an input output variable have direct effect on its value this variable cannot be of a type that does not permit write operations for example variables with the attribute CONSTANT TYPE END_TYPE Derived data types are declared in this declaration block Declaration of various variable type
63. he program for example global variables or for the topology for example communication functions CONFIGURATION RESOURCE TASK PROGRAM PROGRAM GLOBAL AND DIRECTLY REPRESENTED VARIABLES Vv ACCESS PATHS Communication function Execution control path uM gt of gt Variable access paths FB 5 Function block Variable Fig 4 1 Software model 36 Ireneusz Moso Programmable Controllers Communication functions are also described in IEC 61131 3 while describing the communication model In the communication model the ways that values of variables can be communicated among software elements are presented Data exchange between program elements in programmable controller systems can take place between u elements of a single program for example between function blocks with the use of input and output variables programs within a single configuration for example with the use of global variables different configurations for example using declared access paths or with the use of communication functions Communication functions are executed by communication function blocks and can perform data exchange not only between different configurations topologies but also within a single configuration or even within a single program 4 2 Data types and variables A number of elementary pre defined data types are recognized by the s
64. hown in the table are input and memory addresses used in PS4 series programmable controllers Double word applies only to PS416 modular programmable controller Apart from direct representation of variables there is also symbolic representation of variables Symbolic representation means the use of identifiers to name variables An identifier is a string of letters digits and underline characters which shall begin with a letter or underline character The case of letters shall not be significant in identifiers the underline characters positions in identifiers are significant Identifiers are usually called variable names In contrast to directly represented variables there is automatic memory allocation of symbolic variables 30 Ireneusz Moso Programmable Controllers Symbolic names usually are but do not have to be assigned to directly represented variables In this case symbolic names not assigned the operands are addressed with their physical addresses starting with the character In the declaration the keyword AT is entered before the physical address separated by a space However even with directly represented variables the use of symbolic names is recommended because this enables faster modifications in POUs while programming debugging testing and starting up programs An operand is a language element on which an operation is performed An operator is a symbol that represents the action to be performed in an op
65. iately during execution of the application program Almost all considerations so far about usage of the process image memory referred to digital binary inputs and outputs For majority of programmable controllers using process image memory for digital inputs and outputs is a standard The situation is different as far as other types of inputs and outputs are concerned Some programmable controllers do not use the process image memory for analog inputs and outputs 18 Ireneusz Moso Programmable Controllers For example in Siemens S5 115U modular programmable controller analog module signal states are not written to the process image memory They are read in or transferred to an analog output module directly As far as usage of process input image in programmable controllers is concerned it can be concluded that majority of programmable controllers as a standard solution use the process input image On the other hand programmable controllers enable usage of direct access to their inputs and outputs However technical solutions of how this can be achieved are quite different for programmable controllers of different producers Sometimes they can be different even for different programmable controllers of the same producer Therefore detailed study of technical documentation of a particular programmable controller should always be recommended 2 3 Control system and programmable controller response time The control system respon
66. ies S7 In the older series Simatic S5 there are two compact mini programmable controllers S5 90U and S5 95U one failsafe mini programmable controller S5 95F one modular mini programmable controller S5 100U and three modular programmable controllers S5 115U S5 135U and S5 155U all of them with various CPU modules In the new series Simatic S7 there are in general three programmable controllers S7 200 S7 300 and S7 400 each of them with a wide variety if CPU modules Another example are Moeller earlier Klockner Moeller programmable controllers In the last twenty years there were two changes in produced series of controllers from the PS3 series with PS3 PS306 compact programmable controllers and PS316 PS32 modular programmable controllers to the PS4 series with PS 100 PS 150 PS 200 PS 300 compact programmable controllers PS 400 compact fuzzy logic programmable controller and PS416 modular programmable controller and recently to XC series XC100 and XC200 modular programmable controllers with various CPUs available Currently only some of programmable controllers from the PS4 series are produced PS4 141 MM1 PS4 151 MM1 PS4 201 MM1 PS4 271 MM1 PS4 341 MM1 and all controllers from the series XC Additionally there are produced Easy Control EC4P programmable controllers and XV operator panels with touch screen and integrated programmable controllers The latter ones and controllers from XC series are under the common
67. ing and debugging tools PADTs humane aioe Ireneusz Moso Programmable Controllers machine interfaces HMIs etc which have as their intended use the control and command of machines and industrial processes PLCs and their associated peripherals are intended to be used in an industrial environment and may be provided as open or enclosed equipment If a PLC or its associated peripherals are intended for use in other environments than the specific requirements standards and installation practices for those other environments must be additionally applied to the PLC and its associated peripherals The functionality of a programmable controller can be performed as well on a specific hardware and software platform as on a general purpose computer or a personal computer with industrial environment features This standard applies to any products performing the function of PLCs and or their associated peripherals This standard does not deal with the functional safety or other aspects of the overall automated system PLCs their application programme and their associated peripherals are considered as components of a control system Since PLCs are component devices safety considerations for the overall automated system including installation and application are beyond the scope of this Part However PLC safety as related to electric shock and fire hazards electrical interference immunity and error detecting of the PLC system operation such as th
68. ing inputs is named read inputs and read inputs from specialty I O 90 Ireneusz Moso Programmable Controllers execution of the user programme is named solve the application program writing outputs is named write outputs and write outputs to specialty I O and finally service peripherals and force I O CPU bus communication update clock and special relays diagnostics are all the operating system tasks 3 4 Fourth example GE Fanuc 90 30 series The forth example refers among others to 90 30 series and VersaMax programmable controllers produced by GE Fanuc Company In documentations of these controllers the sequence of operations necessary to execute a program one time is called a sweep The sweep includes obtaining data from input devices executing the logic program sending data to output devices performing internal housekeeping diagnostics servicing the programmer and servicing other communications The program cycle the sweep is shown in figure 3 4 START OF SWEEP HOUSEKEEPING PROGRAM EXECUTION DATA OUTPUT PROGRAMMER SERVICE SYSTEM COMMUNICATIONS DIAGNOSTICS Fig 3 4 The program cycle the sweep for 90 30 series programmable controllers 30 Ireneusz Moso Programmable Controllers Programmable controllers of this series normally operate in standard program sweep mode They can also operate in constant sweep mode In both listed above modes the controller executes the logic program
69. ing on the type of operation one or more operands separated by commas In front of the first instruction in a program sequence there can be a label followed by a colon A POU written in the IL language can have also comments Comments are placed between parenthesis with asterisks for example This is a comment Operators and modifiers that can be used in IL language are shown in table 4 2 X X In the table CR means current result and this is the value which is stored in the accumulator N means Boolean negation of the operand modifier means that the result of consecutive operators until the operator is met is an operand C means condition whereas CN means negation of the condition for example JMPC means jump conditional JMPCN means jump conditional not ES1 is the label name NFB1 is the function block name 46 Ireneusz Moso Programmable Controllers Table 4 2 Operators and modifiers in the IL language Operator Modifiers Operand Description LD N gt Operand is loaded into the accumulator CR ST N s CR is stored as the operand value S BOOL Set if CR 1 then the operand is TRUE R BOOL Reset if CR 1 then the operand is FALSE AND N N BOOL Boolean AND CR and operand OR N G N BOOL Boolean OR CR and operand XOR N N BOOL Boolean XOR CR and operand ADD Addition CR and operand SUB K Subtrac
70. k is a dynamic language element that means that for the same combination of values of input signals the values of the output signals can be different Although a function can have only one output the output variable can consist of many elements as for example an array type variable 45 Ireneusz Moso Programmable Controllers 4 4 Programming languages There are two groups of programming languages defined in the standard textual and graphical Textual languages u IL Instruction List u ST Structured Text Graphical languages LD Ladder Diagram FBD Function Block Diagram In the IEC 61131 3 standard a method of creation of a program structure as a Sequential Function Chart SFC is also presented The SFC enables description of sequential control tasks by means of graphs consisting of steps and transitions between these steps Transitions and actions that are associated with the particular steps are programmed in one of the programming languages Sequential control is presented in Part 2 of this materials An additional programming language available in some programming packages is Continuous Function Chart CFC This is also a graphical language Instruction List IL The Instruction List language looks like and is similar to an assembler language The IL language consists of a series of instructions Each instruction begins in a new line and contains an operator and depend
71. logic controllers Today s programmable controllers are not only logic as they were while used for the first time Enormous changes in information technology have influenced and caused such changes in programmable controllers technology that increased controllers potential of signal processing enabled easier programming improved controllers reliability and network functions have been developed Therefore the number of programmable controllers implemented in industry increases constantly Concurrently there is a rising demand for engineers prepared for designing programming starting up and supervising control systems with programmable controllers The above listed trends clearly show that Programmable controllers is a subject that engineering students have to be taught during their first level of study B Sc One of the groups of engineering students for whom at least basic knowledge of programmable controllers is vital in their future professional activity are electrical engineering students The basic knowledge that electrical engineering students are expected to acquire comprises not only programming aspects the ability of writing testing and commissioning control programs but also a variety of technical aspects including mainly systems design and development networking structuring of user programs etc Moreover as far as complex automation with networking from a shop floor to the management level is concerned a more sy
72. logic execution starts immediately after the data input phase of the sweep Solving the program logic provides a new set of output signals which are stored in discrete outputs memory Q or analog outputs memory AQ accordingly In some CPU models there are logic co processors the logic co processor executes the Boolean instructions In such a case the time needed to solve the application program is shortened Data output During this phase of the sweep following the program execution outputs are updated according to data from discrete outputs memory Q and analog outputs memory AQ Global data G are sent to Genius communication modules This phase continues until all outputs in output modules are updated If the CPU is in the stop with I O disabled mode the 2G Ireneusz Moso Programmable Controllers output scan is skipped Programmer service This phase of the sweep is performed if a programmer is connected to the programmable controller The programmer is either a PC with a programming package VersaPro or Logicmaster or the Hand Held Programmer however usage of the latter is very rare nowadays During this phase of the sweep the CPU executes the programmer communication window The programmer can communicate with the CPU or with intelligent option modules In the default limited window mode the CPU performs one operation for the programmer each sweep If the programmer makes a request that requires more than 6 ms to pr
73. mmable controller using a field bus Ladder diagram or relay ladder diagram One or more networks of contacts coils graphically represented functions function blocks data elements labels and connective elements delimited on the left and optionally on the right by power rails Programmable logic controller PLC Digitally operating electronic system designed for use in an industrial environment which uses a programmable memory for the internal storage of user oriented instructions for implementing specific functions such as logic sequencing timing counting and arithmetic to control through digital or analogue inputs and outputs various types of machines or processes Both the PLC and its associated peripherals are designed so that they can be easily integrated into an industrial control system and easily used in all their intended functions Programmable controller system or PLC system User build configuration consisting of a programmable controller and associated peripherals that is necessary for the intended automated system It consists of units interconnected by cables or plug in connections for permanent installation and by cables or other means for portable and transportable peripherals Programming and debugging tool PADT Catalogued peripheral to assist in programming testing commissioning and troubleshooting the PLC system application programme documentation and storage and possibly to be used as HMIs PADTs
74. mplemented some years before the first microprocessors were produced and implemented in electronic systems In practice not definition from the standard but another definition referring to the performed functions and tasks can better explain what a programmable controller is According to definition of the authors of the references 16 23 programmable controllers are industrial computers which under the control of the real time operating system u with the use of input modules acquire results of measurements from digital and analog sensors and measurement devices u using acquired data from the controlled process or machine execute user programs that comprise coded data processing and control algorithms in accordance to results of user programs execution generate control signals and with the use of output modules send them to actuators and additionally are able to transmit data with the use of interfaces and communication modules perform hardware and software diagnostic functions 7 Ireneusz Moso Programmable Controllers As mentioned in the standard although for Programmable Controllers the abbreviation PC should be used this abbreviation could lead to confusion because PC is commonly used as abbreviation for Personal Computer Therefore for programmable controllers the abbreviation PLC Programmable Logic Controllers is used instead Historically this is the first abbreviation used because first programmable controller
75. mples of derived data type with their characteristic are shown later in the current chapter Variables provide a means of identifying data objects whose content may change for example data associated with the inputs outputs or memory of the programmable controller A variable can be declared to be one of the elementary types or one of the derived types Declaration is the mechanism for establishing the definition of a language element A declaration normally involves attaching an identifier to the language element and allocating attributes such as data types and algorithms to it All variables can be divided into u directly represented variables symbolic variables Direct_representation is a means of representing a variable in a programmable controller program from which a manufacturer specified correspondence to a physical or logical location may be determined directly The manufacturer shall specify the correspondence between the direct representation of a variable and the physical or logical location of the addressed item in memory input or output When a direct representation is extended with additional integer field separated by periods it shall be interpreted as a hierarchical physical or logical address with the leftmost field representing the highest level of the hierarchy with successively lower levels appearing to the right For example 10033 if this digital input variable refers to 90 30 series modular programmable
76. n order to learn the whole material Readers should refer to the standard itself or to one of the references 16 23 in which the content of the standard is presented more widely The third part of the standard is tightly connected to the first part of the standard in which definitions are established and characteristics of programmable controllers and programmable controller systems are presented Therefore a lot of information all necessary as the selected information from IEC 61131 1 is placed in the last chapter of this materials All definitions and programmable controllers characteristics to which there are references in the programming model are in this last chapter In this materials the main stress is put on these elements of the programming model according to IEC 61131 3 that have been implemented and are used in programming packages Sucosoft S40 and Easy Soft CoDeSys that are used during tutorials and in the laboratory Presentation of other elements of the programming model for example tasks access paths is less detailed 4 1 Programming model according to IEC 61131 3 The third part of IEC 61131 specifies syntax and semantics of programming languages for programmable controllers Syntax describes language elements and the way they can be used whereas semantics their meaning Semantics is the relationship between the symbolic elements of a programming language and their meaning interpretation and use The standard
77. neusz Moso Programmable Controllers machine or the process The application programme storage may also provide for memory locations to store initial values for application programme data Application data storage The application data storage provides for memory locations to store I O image table and data for example set values for timers counters alarm conditions parameters and recipes for the machine or the process required during the execution of the application programme Memory type memory capacity memory utilisation Various types of memory are in use read write RAM read only ROM programmable read only PROM reprogrammable read only EPROM UV PROM EEPROM Memory retention at power failure is achieved by a proper selection of the memory type where applicable for example EPROM EEPROM or the use of memory back up for volatile memories for example a battery Memory capacity relates to the number of memory locations in Kbytes which are seserved to store both the application programme and the application data Memory capacity measurements are capacity in the minimum useful configuration u size s for expansion increments u capacity ies at maximal configuration s Each programmable function used by the application programme occupies memory locations The number of locations required generally depends on the programmable functions and the type of programmable controller Application data storage requires m
78. nput and output parameters of IEC or manufacturer functions and function blocks In graphical languages POUs functions and function blocks can have an additional input EN and an additional output ENO The EN input and the ENO output are always of the BOOL type The EN meaning is the POU with EN input is evaluated if the EN input has the value TRUE The ENO meaning is after correct evaluation of the POU with EN input the ENO output has the value TRUE Otherwise the output has the value FALSE These special inputs and outputs are used to control the application program execution An example how the EN input of the function can be used or not in a program to control the program execution is shown in figures 4 9 and 4 10 The intention was to add the value 526 to the variable Wartosc only once in the first program cycle after the programmable controller has been switched on In the first program part of which is shown in figure 4 9 this was realized in the following way There is a Boolean variable Pom declared with an initial value TRUE In the first program cycle the condition for the conditional jump to the label skok is therefore not fulfilled The next rung with the ADD function is executed any time the function ADD is executed the value on the EN input is TRUE and 526 is added to the variable Wartosc In the next rung the Boolean variable Pom is reset by itself In the following program cycles until the va
79. ntylator ukladu hamowania OBL_UCIAG FB REZ_WYAT 0X2 7 BOOL Wyiscie rezerwowe PLC_PRG PRG A Z_PREDKAT lvy4 UINT Zadajnik predkosci od 0 do 10V 5 Z_UCIAGAT IW6 UINT Zadajnik uciagu od 0 do 10v MOMENT AT 1IWY8 UINT Biezaca wartosc momentu od 0 do 10V z wyjscia AM OMEGA AT IvV 10 UINT Biezaca wartosc predkosci obrotowej od 0 do 10v z wyjscia AMI PREDKOSC AT Q V4 UINT Zadawana wartosc predkosci obrotowej na falownik od 0 do 10 REZ_ANALOG AT QVV6 UINT Rezerwa wyjscia analogowego FST_SCAN BOOL TRUE Pierwszy cykl obiegu programu ALW_ON BOOL TRUE Zawsze wartosc TRUE Zakaz BOOL Brak pozwolenia manetka wychylona Timer_4 We_Timer_4 TON We_Timer_4 IN D Qa FR T 1000ms 4PT ET ZAD_UCIAG OBL_UCIAG EN ENO _UCIAG zZU ZUP Z_UCIAG_P WMAX UCIAG_MAX WMMIN UCIAG_MIN CKFOSx1 pr Fig 4 13 An example of a user function block Basing on the above shown examples it can be definitely concluded that usage of user function blocks helps to structure and reduces the complexity of application programs 62 Ireneusz Moso Programmable Controllers 5 International Standard IEC 61131 Selected Information International Standard IEC 61131 consists of the following parts under the general title Programmable controllers Part 1 General information Part 2 Equipment requirements and tes
80. ocess for some CPU models 8 ms the request processing is spread out over several sweeps lengthening each of these sweeps by no more than 6 or 8 ms System communications In this phase of the sweep communication requests from intelligent option modules are processed Communication with intelligent option modules is performed in the order of appearing requests but according to the rule communication with one intelligent option module in a sweep In the default run to completion mode the length of the system communications window is limited to 50 ms If an intelligent option module makes a request that requires more than 50 ms to process the request is spread out over multiple sweeps lengthening each of these sweeps by no more than 50 ms Diagnostics Diagnostics is made as a checksum calculation performed on the user program at the end of every sweep The number of words to be checked can be specified by the user from 0 to 32 If the calculated checksum does not match the reference checksum the system variable meaning the program checksum failure is set This causes a fault entry to be inserted into the programmable controller fault table and the controller mode to be changed to stop The default number of words for checksum calculation is 8 In the standard program sweep each sweep executes as quickly as possible with a varying duration of a sweep An alternative to this is a constant sweep mode in this mode duration
81. of each sweep is the same A value from 5 to 200 ms for some CPU models up to 500 ms can be set for the constant sweep timer Constant sweep mode is used if it is necessary to update input and output variables at a constant frequency as required in many control algorithms Constant sweep mode is also used to ensure that a certain amount of time elapses between outputs update in current sweep Laos Ireneusz Moso Programmable Controllers and reading inputs in the next sweep this time delay is necessary to be sure that particular input signals have changed their states after the output signals that influence these input signals had been changed Looking at this example it can be concluded that despite small differences in names of the program cycle phases in figure 3 4 they are very similar to those at the simplified diagram shown in figure 1 2 reading inputs is named data input execution of the user programme has almost exactly the same name program execution writing outputs is named data output and finally housekeeping programmer service system communications and diagnostics are all the operating system tasks 33 Ireneusz Moso Programmable Controllers 4 Programming of Programmable Controllers In this chapter basic information about programming programmable controllers is presented This chapter is based on the third part of IEC 61131 and covers main terms and ideas presented with more details during lectures I
82. ogramowalne PLC Wydawnictwo COSiW SEP Warszawa 2003 Sa at R Korpysz K Obstawski P Wst p do programowania sterownik w PLC Wydawnictwo Komunikacji i czno ci Warszawa 2010 Schunemann U Programming PLCs with an Object Oriented Approach ATP International Automation Technology In Practice Nr 2 2007 pp 59 63 Seta Z Wprowadzenie do zagadnien sterowania wykorzystanie programowalnych sterownik w logicznych PLC Wydawnictwo NIKOM Warszawa 2002 78 Ireneusz Moso Programmable Controllers 48 49 50 51 52 53 Simatic S5 115U Programmable Controller Manual Siemens AG 1991 EWA 4NEB 811 6130 02a Sta czak W Przemys owe sieci lokalne Sieciowe systemy komunikacyjne integruj ce automatyzacj wytwarzania Podr czniki Nr 6 PIAP Warszawa 1998 Sterownik VersaMax Podr cznik u ytkownika Astor Sp z 0 0 Krak w 1999 Tassin A Structured Programming and Utilities for the Series PCD User s Guide SAIA AG 1992 Edition 26 732 E4 06 94 Trybus L Regulatory wielofunkcyjne WNT Warszawa 1992 Volberg J Actuator Sensor Interface Networking I O on the fieldbus Klockner Moeller Bonn 1996 79
83. ollers construction maximum number of inputs and outputs the scale of applications in which controllers can be implemented are these factors depending on which the classification can be made Taking into account programmable controllers construction they can be divided into compact controllers u modular controllers Taking into account maximum number of inputs and outputs programmable controllers can be divided into small with a few dozen inputs and outputs medium size up to several hundreds of inputs and outputs big over one thousand inputs and outputs Taking into account the scale of applications programmable controllers can be divided into controllers used in small application tasks usually control of an individual machine or a small technological process controllers used in medium size application tasks usually control of several machines in a production line technological processes in different branches of industry controllers used in large and complex automation tasks usually complex production and technological processes in some branches of industry chemical petrochemical pharmaceutical etc Only the first classification is based on a clearly technical factor The other two classifications are rather relative and subjective Compact programmable controllers in their single enclosure have all necessary systems to perform all programmable controller functions figure 5
84. ri w zorganizowanych przez PTETiS Oddzia w Gda sku Zesz Nauk Wydz Elektrotechniki i Automatyki Politechniki Gda skiej Nr13 1999 s 101 106 Moso I Sterowniki programowalne strukturyzacja program w sterowania Zastosowanie komputer w w nauce i technice 2001 XI cykl seminari w zorganizowanych przez PTETiS Oddzia w Gda sku Zesz Nauk Wydz Elektrotechniki i Automatyki Politechniki Gda skiej Nr 17 2001 s 145 152 Moso I ukowski K Symulator Sym PS4 sterownika programowalnego PS4 201 MMI Zastosowanie komputer w w nauce i technice 2002 XII cykl seminari w zorganizowanych przez PTETiS Oddzia w Gda sku Zesz Nauk Wydz Elektrotechniki i Automatyki Politechniki Gda skiej Nr 18 2002 s 125 130 Moson I Control systems with programmable controllers teaching aspects IX Konferencja Naukowo Techniczna Zastosowania Komputer w w Elektrotechnice ZKwE 2004 Pozna Kiekrz 19 21 kwietnia 2004 s 621 624 Or owski H Komputerowe uk ady automatyki WNT Warszawa 1987 PN EN 61131 1 2004 Sterowniki programowalne Cz 1 Postanowienia og lne PN EN 61131 3 2004 Sterowniki programowalne Cz 3 J zyki programowania Practical Aspects of Industrial Control Technology Telemecanique Technical Collection Editions CITEF 1994 Roersch P LE4 505 BS1 AS I Network Module Hardware and Engineering Moeller GmbH Bonn AWB 27 1314 GB 02 98 Ruda A Olesi ski R Sterowniki Pr
85. riable Pom will remain FALSE the jump condition will be fulfilled and the rung with the ADD function will be skipped In the second program part of which is shown in figure 4 10 this was realized with the use of EN input There is also a Boolean variable Pom declared with an initial value TRUE In the first program cycle when the value of the Boolean variable Pom is TRUE the ADD function is executed because the value on the EN input is TRUE and 526 is added to the variable Wartosc In the next rung the Boolean variable Pom is reset by itself In the following program cycles until the variable Pom will remain FALSE the ADD function will not be executed 4 6 User functions and function blocks Apart from IEC and manufacturer functions and function blocks also user functions and user function blocks can be used in application programs User POUs functions and function blocks are created using appropriate to particular programmable controllers programming packages 57 XSoft Cwiczenia_05_11_2009 pro PLC_PRG PRG LD File Edit Project Insert Extras Online Window Help Ireneusz Moso Programmable Controllers alae xejeialuj o Gi POUs ar PLC_PAG PRG 0013 Impulsy_2 BOOL Alarm BOOL Pom BOOL TRUE Wpisz BOOL Wartosc UINT 204 Cisnienie_x1 UINT Cisnienie_X2 UINT X BOOL ND_VAR ADD EN Wartosc 526 Wartosc Loading library
86. ristics of the power supply functions The power supply functions generate voltages necessary to operate the PLC system and generally also provide control signals for proper ON OFF synchronization of the equipment Various power supplies may be available depending on supply voltages power consumption parallel connection requirements for uninterruptible operation etc aero ee Ireneusz Moso Programmable Controllers AVAILABILITY AND RELIABILITY Every automated system requires a certain level of availability and reliability of its control system It is the user s responsibility to ensure that the architecture of the overall automated system the characteristics of the PLC system and its application programme will jointly satisfy the intended application requirements Architecture of the automated system Techniques such as redundancy fault tolerance and automatic error checking as well as machine process diagnostic functions can provide enhancements in the area of availability of the automated system Architecture of the programmable controller system A modular construction in conjunction with suitable internal self tests allowing rapid fault identification may provide enhancements in the area of maintainability of the PLC system and therefore of the availability of the automated system Techniques such as redundancy and fault tolerance of the availability of the automated system Techniques such as redundancy and fault toleranc
87. rolled process The situation is different if it is possible to program and execute in a programmable controller more than one control task Lets assume that there are for example two control tasks One to control a fast process with a short time constants the other one to control a slow process with long time constants In such a case there would be advantageous to configure execution of the latter control task as periodic with the set time of period significantly longer for example n times longer than the time of execution of the former control task that has been configured as cyclical Control signals of the faster process would be updated then approximately n times more frequently than control signals of the slower process 2 2 Operation with or without process image memory Typically programmable controllers operate with the use of the process image memory However the operation without using the process image memory is also possible If as shown in figure 2 1 phases Reading inputs and Writing outputs are excluded from 15 Ireneusz Moso Programmable Controllers Da Execution of the Operating application system program functions Fig 2 1 Excluding Reading inputs and Writing outputs in the simplified diagram the program cycle the controller operates without using the process image memory In such a case the simplified diagram of a programmable controller operation consists only of two
88. roller s output circuit but is not just a sum of the listed factors because the I O response time depends also on the point in the program cycle when the field input changes states In practice the delay of the controller s input circuit is longer than the delay of the controller s output circuit The delay of the controller s input circuit can be relatively big in comparison to the program cycle time if the function of the input circuit is also hardware filtering of input signals The delay of the controller s output circuit is often negligible in comparison to the program cycle time Two cases should be analysed when the input signal state changes just before the reading inputs phase of the program cycle the best case and when the input signal state changes just after the reading inputs phase of the program cycle the worst case The I O response time is the shortest when the input signal state change takes place just before the reading inputs phase of the program cycle The I O response time for this case is shown on the time diagram presented in figure 2 3 Program cycle Program cycle j l I Program Program Program Program execution execution execution execution Operating system Field input functions Input joffion delay I O response time Fig 2 3 The I O response time better case In the first case the I O response time equals approximately 20 Ireneusz Moso Programmabl
89. s and the range of their usage Keywords beginning of the declaration block VAR P F FB TYPE P F FB locally within the POU VAR_GLOBAL P VAR_EXTERNAL FB VAR_INPUT gt F FB VAR_OUTPUT FB VAR_IN_OUT FB Keyword end of the declaration block END_VAR or END_TYPE where P means program F means function FB means function block 4 Ireneusz Moso Programmable Controllers Derived data types with examples Declaration of a data type as enumeration The declaration of an enumerated data type defines a list of identifiers whose values may contain a data element In order to declare the enumerated data type the variable list is entered in parenthesis with individual elements separated with a comma An initialisation value can be assigned to a variable of this data type If an initialization value has not been assigned during declaration the variable will be assigned the value of the first element in the enumeration list at the controller start up Declaration of a variable SYGNALIZACJA of a data type as enumeration with the initial value Zolte is shown in figure 4 2 as an example POU Editor Test2 PROGRAM EJ File Edit Insert View Options Windows Help Cees Joe se eal JEJ Co ie EJ kd bebe EE TYPE SYGNALIZACJA Czerwone Zolte Zielonej Zolte Temperatura_C INT 0 100 25 Temperatura _ F UINT 32 212 77 Tablica _1 ARRAY O 5 OF BYTE
90. s global variables according followed by the starting of all the resources in the configuration The starting of a resource shall cause the initialization of all the variables in the resource followed by the enabling of all the tasks in the resource The stopping of a resource shall cause the disabling of all its tasks while the stopping of a configuration shall cause the stopping of all its resources A task is an execution control element providing for periodic or triggered execution of a group of associated POUs The standard describes also mechanisms for the control of tasks and mechanisms for the starting and stopping of configurations and resources via communication functions Yet for majority of programmable controllers and programmable controller systems not all language elements that are present in the programming model have been implemented in operating systems of controllers and their programming packages Still the most common situation for programmable controllers working in different control systems is that the controller performs one application program and there is only one resource in the 35 Ireneusz Moso Programmable Controllers configuration which is usually not explicitly declared For programmable controllers that are used during tutorials and in the laboratory instead of configurations topologies of control systems are being created Other language elements of the programming model are created either for t
91. s were using and processing only logic binary signals Despite the fact that currently programmable controllers operate not only on logic signals the abbreviation PLC is well recognized and still in common use in the automation industry and in the literature in technical books journals documentations etc In resent years however one more abbreviation PAC have become popular this abbreviation stands for Programmable Automation Controller In the year 2002 the company National Instruments started to use this name for their programmable controllers Very quickly also many other companies followed and named their new programmable controllers as programmable automation controllers for example GE Fanuc and other companies The intention of this change from PLC to PAC was to underline their increased functionality and processing capabilities PLC and PAC are not the only abbreviations that mean programmable controllers Some companies use other names for their programmable controllers For example the Austrian company B amp R their programmable controllers names Programmable Computer Controller abbreviation PCC whereas the Swiss company SAIA their programmable controllers names Programmable Control Device abbreviation PCD 1 2 Basic structure of a programmable controller The basic functional structure of a programmable controller system is presented in the standard and in these materials is shown in figure 5 1 in the 5 th chap
92. se time is the period between the occurrence of an event and the reaction of the control system to this event The programmable controller response time is the period between the change of a signal state in the controller s input and the change of a signal state on the controller s output The latter response time is of course shorter than the former one The difference is the sum of the following u time necessary for a sensor output signal change u time needed to transfer this signal to the controller s input u time needed to transfer controller s output signal to an actuator u time necessary for an actuator for its reaction The first time is not negligible because it is the response time of a sensor for example an inductive proximity switch The second and the third time are negligible in case of standard wiring of the control system but they are not negligible in case of usage of a bus system for sensors and actuators for example AS interface The forth time is also not negligible because it is the response time for an actuator for example a contactor The sum of these times does not depend on the programmable controllers What should be analysed in this chapter is the programmable controller response time This response time often called the I O response time depends on 19 Ireneusz Moso Programmable Controllers u the delay of the controller s input circuit the program cycle time u the delay of the cont
93. so called a process image register 1 3 General principle of operation The principle of operation of a programmable controller can be explained using a simplified diagram shown in figure 1 2 and analysed together with the simplified hardware block diagram shown in figure 1 1 The simplified diagram of a programmable controller operation consists of four blocks which names refer to their functions u reading inputs u execution of the application user program writing outputs operating system functions The three blocks on the left hand side in figure 1 2 refer to certain phases of the program cycle and are essential for explanation of the programmable controller operation Reading inputs At the beginning of each cycle the processor reads the signal states of all inputs and stores them in the process input image memory After reading states of the input signals do not change during the current cycle 9 Ireneusz Moso Programmable Controllers Reading inputs Execution of the Operating application system program functions Writing outputs Fig 1 2 Simplified diagram of a programmable controller operation If during execution of the application program an operand is the input signal its state is read from the process input image not from the controller s physical hardware input Therefore even if during program execution there will be a change in the state of the input signal this will not be t
94. ss input image register Read Inputs from Specialty I O After the CPU reads the inputs from the input modules it reads ant input point data from the specialty modules that are installed such as High Speed Counter HSC modules etc In this phase of the cycle also the input status from Remote I O are read Service Peripherals and Force I O After the CPU reads the inputs from the Specialty I O modules it reads any attached peripheral devices This is primarily a communication service for a programming device to see if any input or output status needs to be modified Or the programmer may be requesting a Run Time Edit or a change to Program Mode The CPU also gets any output forcing information during this phase One of the most popular requests is forcing an input on even though it is really off This allows the programmer to change the point status that was stored in the process image register This value will be valid until the process image register location is written to during the Read Inputs phase of the next cycle This forced value is used in solving the application programme but only during the current cycle In the next cycle if there is no another request for a force the process input image register maintains the status obtained during the reading of the inputs CPU Bus Communication During this phase of the cycle the CPU communicates with intelligent modules like for example Data Communication Modules that must b
95. stem approach to programmable controllers and their use is necessary Such an approach has been offered to students that study speciality Information technologies in electrical engineering in the Electrical engineering field of study The course Programmable controllers according to the Study programme for full time students in the field of Electrical engineering is an obligatory course and is taught during the 5 th semester 3 rd year of study The course comprises 30 hours of lectures 15 hours of tutorials and 15 hours of laboratory works during the semester two hours of lectures one hour of tutorials and one hour of laboratory per week The course Programmable controllers can be characterised by its syllabus and expected learning outcomes There are 5 ECTS credit points allocated to this course Ireneusz Moso Programmable Controllers In the academic year 2010 2011 for the speciality Information technologies in electrical engineering the course is taught in English to help these students to improve their communication skills in English to prepare them to international exchange of students and possible future professional work in an international team These materials Part 1 written in English comprise basic information about programmable controllers and their programming according to the syllabus of the course Two programming software packages Sucosoft S40 ver 4 24 and Easy Soft CoDeSys ver
96. t used in the program For example even if there is no variable on the WAR_ZAL function block input it is used in the program This is shown in figure 4 12 In the lower rung shown in the figure there is an output variable coil with the name CB_TR1 WAR_ZAL The first part of this name refers to the function block CB_TRI whereas the second part of the name means the particular input of this function block which is WAR_ZAL Such usage of inputs and outputs of function blocks can limit the number of auxiliary variables that need to be declared in the program or other POU This is also a proof 60 Ireneusz Moso Programmable Controllers that during declaration of a function block a part of the programmable controller s memory is reserved to store the function block input output and internal variables POU Editor PROG_BC1 PROGRAM J Z File Edit Insert View Options Windows Help fea Eas onl eE i Initial value Attribute Address Comment Stany zasilania i wylacznikow przy ktorych ma nastapic zalaczenie CB TR1 WSD_TR1x1 WSD_TR2x1 uli WCB_TR12 2 2 PWP_G PWP_GEN PWP_B2 Z_CB_TRL I i i O a H WSD_TR1x1 U13 WCB_TR2 2 HR gt WCB_TR2 WCB_TR12 Kontrola warunkow umozliwiajacych zalaczenie CB TR1 CB_TR1 WA Z_CB_TR1 TRIP_N1 AUTO N1 R_ZAL m Help via key F1 PS4 300 INS 00413 7 Start Navigator BCITY1 POU Editor PROG PL mm gt
97. tandard Additionally generic data types are defined for use in the definition of overloaded functions and a mechanism for the user or manufacturer to specify additional data types derived data types are also defined A data type is a set of values together with a set of permitted operations A generic data type is a data type which represents more than one type of data Overloaded with respect to an operation or function capable of operating on data of different types Certain data types can be grouped together to form generic data types Generic data types are identified by the prefix ANY Generic data types and their hierarchy ANY gt 1 ANY_BIT BOOL BYTE WORD DWORD 2 ANY_NUM gt 2a ANY_INT SINT INT DINT USINT UINT UDINT gt 2b ANY_REAL REAL LREAL 3 ANY_DATE DATE TIME_OF_DAY DATE_AND_TIME gt 4 TIME 5 STRING gt 6 Derived data types 37 Ireneusz Moso Programmable Controllers Among other groups of data types there is also a group of derived data types Derived data types are special manufacturer or user defined data types derived from elementary data types and which have been assigned a new name They are declared with the keywords TYPE END_TYPE and can thus be used with the new names in variable declarations Derived data types can be divided into Enumerated data type Sub range data type Array data type Structured data type Exa
98. ter However such a detailed description of a programmable controller functions and hardware is not necessary in this chapter to explain the principle of operation of a programmable controller A simplified hardware block diagram shown in figure 1 1 should be helpful instead This hardware block diagram consists of three blocks inputs meaning input circuits CPU Central Processing Unit in which a processor microprocessor and a memory are the most important parts to understand the programmable controller principle of operation outputs meaning output circuits Ireneusz Moso Programmable Controllers Processor CPU Outputs Memory Fig 1 1 Simplified hardware block diagram of a programmable controller Input and output circuits are the programmable controller s interfaces through which it is connected to the controlled object usually either a machine or machines in a production line center or a technology process Each programmable controller has an internal memory which is a RAM memory that is used to store the application program and data A part of the data memory is a process image memory The process image memory consists of two parts One part is a process input image memory to store states of input signals during the program cycle The other part is a process output image memory to store states of output signals during the program cycle Sometimes the process image memory is al
99. tion CR and operand MUL ii Multiplication CR and operand DIV Division CR and operand GT gt Greater Than comparison CR gt operand GE Greater than or Equal comparison CR gt operand LT Less Than comparison CR lt operand LE Less than or Equal comparison CR lt operand EQ Equal comparison CR operand NE Not Equal comparison CR lt gt operand JMP C CN ES1 Jump to the label ES1 CAL C CN NFB1 Call FB with the name NFB1 RET C CN Return from F or FB Delimiter of the modifier An example of a program sequence written in the IL language with the use of Sucosoft S40 programming package is shown in figure 4 3 47 Ireneusz Moso Programmable Controllers POU Editor Example1 PROGRAM P Fie Edit Insert View Options Windows Help eB EJ d ki EE comment First input second input Third input Forth input Fifth input Output nr 0 Var_I1 Var_I2 Var_I3 Var_I4 Var_I5 var_O Fig 4 3 An example of a program sequence written in IL language Structured Text ST The Structured Text language is similar to high level languages The instruction section of a POU written in the ST language consists of at least one ST statement or a sequence of statements Each statement must be terminated with a semicolon This separator allows a statement to cover several lines and several statements can be written on the same line Comments can be positioned at any pla
100. ts Part 3 Programming languages Part 4 User guidelines Part 5 Communications Part 6 Reserved Part 7 Fuzzy control programming Part 8 Guidelines for the application and implementation of programming languages for programmable controllers The purposes of this standard are Part 1 establishes the definitions and identifies the principal characteristics relevant to the selection and application of programmable controllers and their associated peripherals Part 2 specifies equipment requirements and related tests for programmable controllers PLC and their associated peripherals Part 3 defines for each of the most commonly used programming languages major fields of application syntactic and semantic rules simple but complete basic sets of programming elements applicable tests and means by which manufacturers may expand or adapt those basic sets to their own programmable controller implementations Part 4 gives general overview information and application guidelines of the standard for the PLC end user Part 5 defines the communication between programmable controllers and other electronic systems Part 6 is reserved Part 7 defines the programming language for fuzzy control Part 8 gives guidelines for the application and implementation of the programming languages defined in Part 3 The first part of the standard IEC 61131 1 applies to programmable controllers PLC and their associated peripherals such as programm
101. ually a personal computer with programming software or a hand held programmer however it is used very rarely nowadays As far as operating system functions are concerned it should be mentioned that apart from functions performed in every program cycle programmable controllers perform also operating system functions when the controllers are switched on or off Functions that are performed after switching on the controller are for example self test when starting initialisation of the CPU determining the start up behaviour restart conditions copying retentive data from the backup memory in controllers with EEPROM into the working memory A function that is performed after switching off the controller is for example backup of the retentive data into the backup memory EEPROM 11 Ireneusz Moso Programmable Controllers The above listed functions are performed only once before the first reading inputs phase of the cycle but they are not shown in figure 1 2 as being of a minor importance to understand general principle of programmable controllers operation Typical execution of the application program in programmable controllers is cyclical what means that program cycles are performed one by one without any delay between them 1 4 Types and series of programmable controllers Different divisions of programmable controllers into groups can be made depending on what factor will be taken into account Usually programmable contr
102. unit to allow programme monitoring modification and correction This may be done on line i e while the PLC system is controlling the machine process Adapting the programmable controller system Typical functions for adapting the PLC system to the machine process to be controlled are u test functions which check the sensors and actuators connected to the PLC systems for example forcing the outputs of the PLC system u test functions which check the operation of the programme sequence for example setting the flags and forcing the inputs setting or resetting of variables for example timers counters etc Indicating the automated system status The ability to provide information about the machine process and the internal status of the PLC system and of its application programme facilitates the start up and debugging of a PLC application Typical means are status indication for inputs outputs indication recording of status changes of external signals and internal data u scan time execution time monitoring u real time visualization of programme execution and data processing u fuse short circuit protection status indicators 72 Ireneusz Moso Programmable Controllers Testing the application programme Test functions support the user during writing debugging and checking the application programme Typical test functions are checking the status of inputs outputs internal functions timers counters che
103. urn positively influences many important application program quality features verifiability modifiability and reusability It is easier to analyse such a structured program and make changes if necessary during the control system life time A user function block once created can be declared with different names and used in an application program many times Therefore repeated section of a program can be programmed as a user function block and used many times Moreover even if there are no repeated sections in a program and a user function block will be created it can be used in other programs In such a way a programmer can create its own library of user function blocks to save time in writing other application programs in future The use of tested user function blocks helps in testing an starting up application programs If there are errors in a program it is easier to find them debugging the program because the programmer can be quite sure that they are not inside its user function blocks The other important difference between IEC or manufacturer function blocks and user function blocks is the fact that user function blocks can refer to specific features of the sensors actuators and other automation equipment that operates in a programmable controller based control system Unlike standard function blocks user function blocks can be created as specific hardware functions oriented function blocks Such a user function block created

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