Home

Lab course automation technology Experiment No. 2 Real

1. 18 4 1 FIRED LEVEL RE a eo OE RE EEE 18 4 1 1 Communications link level eese nne enne 18 4 1 2 Communication command 1 19 4 1 3 Communication manager evel o seines 19 4 1 4 Module interface 19 4 2 PROCESS VARIABLE LEVEL ern rrr SPI TEID EIo ritos 19 4 2 1 Analog Interfages ose e kb 19 422 Dipifal interface 21 4 3 PROCESS CONTROL EBVEE lieet ae 22 4 4 GRAPHICAL USER INTERFACE een nennen rete 22 4 5 SCENARIO EXPERIMENT due diete pee Ee EA E En 22 4 5 1 Communication erstes sene eniin 23 5 2 Analog eier 23 Z3 zo dee eu E eee 24 ASA Analogoutpub SIGNALS o o eek 24 455 JIuwfal output re 24 45 6 Experiment control acsi REI IER Lea nu QUEE RES 24 5 JUSERMANUAL erecto eate eene epe va enlassesteressrafenosssnsenesanunseeensesnneee 24 5 1 POSSIBLE PROBLEMS DURING LAB EXPERIMENT ceeeeeeee eene nnn rnnt rere rennen 25 6 SAMPLE PROJECT AUTOMATION OF A BOTTLING PLANT 26 6 1 INTRODUCTION cess He T 26 6 2 ASSIGNMENT OE TASKS 2 a Rue 26 7 TASKS AN
2. range Output Voltage 0 10V DC The communication module EasyPortUSB also supports 16 digital inputs and outputs In the system following digital sensors are used Digital sensors Garc12 Output boolean true false B102 Flow rate sensor ID Flow Meter B102 Description This signal is used with a high speed counter for measuring the frequency 111 Float switch ID Float Switch S111 Description Maximum filling level of tank 101 Real time programming with Ada 17 112 Float switch ID Float Switch S112 Description Middle filling level of tank 102 B113 Capacitive proximity switch ID Proximity Switch Min Level B113 Description Minimum filling level of tank 101 The heater cannot be used from here B114 Capacitive proximity switch ID Proximity Switch Max Level B114 Description Maximum filling level of tank 101 Ball valve must be closed 115 Ball valve closed ID Ball Valve Closed S115 Description Ball valve is closed 5116 Ball valve opened ID Ball Valve Open S116 Description Ball valve is opened In addition the plant has four actuators Actuators Garc12 V102 Ball valve with pneumatic actuator ID Ball Valve V102 Typ Ball valve with pneumatic actuator Description The valve controls the flow rate from tank 102 into tank 10
3. 4 Heating Tank 101 Temperature Tank B104 108 Pressure_Tank_B103 Se v109 V104 V106 Proportional Valve V Fe 106 Flow_Meter_Pump_ B102 D gt P101 V105 Pump P101 Figure 9 P amp I diagram The components of the system which allow an interaction are now mentioned and described based on figure 9 The main components are the two large tanks tank 101 tank 102 which are connected to each other through various pipes Here several control loops can be activated and deactivated by manually opening or closing the ball valves Furthermore the model has several analog and digital sensors and some actuators The sensors provide all necessary information about the system and communicate via the communication module EasyPortUSB with the control program Since a USB connection can only transmit digital values the EasyPortUSB module transmits the analog measured values 0 to 10V in a 12 bit resolution i e discrete values from 0 to 4095 This information must then be converted into the right analog values by the software Here the EasyPort only serves as a transfer interface between the software and the system and assumes no technical control functions Only the sensor information from the system is being transferred to the software and the controlling commands are being passed to the actuators The plant has four analog sensors Analog sensors Garc12 B101 Level sensor tank 102 ID Sensor Level Tank B101 Sen
4. Author Chris Brand Main unit for experiment with Emergency use Emergency with StartingPosition use StartingPosition with TemperatureControl use TemperatureControl package body scenario experiment is type Controller Experiment Pointer is access Controller Experiment this procedure gets activated by pressing the button Panic Switch Real time programming with Ada 37 procedure Panic Switch Clicked Widget access Widget Record Class is begin Panic Switch true Set Markup Temperature Control L span weight light color red size xx large gt Stopped lt span gt Emergency PanicSwitch Create_Start Start_Created Running PreviousState_Running Panic_Switch_Hit end Panic_Switch_Clicked nn this procedure gets activated by pressing the button Starting Position procedure Starting_Position_Clicked Widget access Gtk_Widget_Record Class is begin Create_Start True end Starting_Position_Clicked this procedure gets activated by pressing the button Start Control procedure Start_Control_Clicked Widget access Gtk_Widget_Record Class is begin if not Task_Controller null then if Start_Created true then Set_Markup Temperature_Control_L lt span weight light xx large gt Running lt span gt mm mm color green size Running True PreviousState_Running True n end if end if end Start Control Clicked this procedure gets a
5. For functions the calculated expression must be given back to the origin of the call return Expression Real time programming with Ada 10 2 3 4 3 7 The raise statement With the raise statement you trigger the exception handling Ada provides a run time monitoring and triggers special predefined exceptions constraint error programm error 1 procedure Procedure name is etc even without the raise Exception name exception statement by the programmer RAERSREHES For example when divided begin b 0 Statement iu PEER Wa However the programmer when Expressionl gt raise Exception name may declare and define own when Expression2 gt raise constraint error exceptions and define how to d S en proceed when this exception exception occurs In addition he can 1 when Exception name also access the exceptions 13 ada text_io put_line item gt Exception already defined by Ada and when constraint error trigger those without having to implement them Exceptions are declared in the Figure 4 Basic structure of exception handling in a procedure declaration part and raised in the statement part If you want to call a particular statement with one exception you can use the exception handler for this purpose To describe this an exception part is inserted at the end of the statement part by using the keyword exception This part ends with the keyword end then Now you can specify what should be done when an exception
6. must then be fully described in the non visible part type X is range 10 10 With Ada the initiator decides which value range of an integer is used depending on the available hardware But at least the range from 32 768 to 32 767 16 bit Real time programming with Ada 8 2 3 3 Operators Similar to other programming languages in Ada there are different operators The most important are listed here TM potentiate E equality abs absolute value inequality not negation lt lt less than less than or equal multiplication gt gt greater greater than or equal division and conjunction addition or disjunction subtraction xor exclusive disjunction As another operator there has to be noted the binary operator amp which joins two strings one dimensional arrays 2 3 4 Commands in Ada In Ada three different commands are distinguished Agreement expression and statement In the following the three types are briefly described 2 3 4 1 Agreements Agreements declare variables or subroutines Basically you specify the name followed by the type and possibly a starting value X integer 17 Here the container value X was declared as a type integer with the initial value 17 2 3 4 2 Expressions Expressions calculate a value but it typically does not change content of containers Thus for example 10 X 4 is an expression that calculates a value bas
7. occurs To illustrate the impact of an exception we briefly assume that a procedure or similar is a framework If now an exception is raised in the code section of an inner frame the initiator goes from normal state into the state of emergency Here it jumps to the exception part of the inner frame and looks for the name of the raised exception If the right exception handler is found it executes its instructions then goes back to normal state and terminates the inner frame Now the outer frame is being continued at the point after the inner frame If there is no matching exception handler the initiator will remain in state of emergency and terminates the inner frame After that it triggers the same exception again in the outer frame and jumps into the exception part Now it looks for the appropriate exception handler again and proceeds analog to the inner frame Is there again no matching exception handler and there is no more additional outer frame the entire program will be aborted with an error message The basic structure of exception handling is shown in Figure 4 ada text io put line item end Procedure name 2 3 5 Program Units There are basically four different units in Ada Subroutines Tasks Reusable libraries packages Shared resources protected variable Program units are usually divided into a specification file file extension ads and an implementation file file extension adb The specification file must n
8. place within this period the task performs an alternative sequence of statements Another method to synchronize tasks is to use protected variables Even protected objects have a specification part and a body similar to a package The specification here consists of a visible and an invisible private part Here all variables must be declared as private So you have no way to access those variables from the outside and you need to use the procedures within the resource since only those have access rights to the variables If multiple tasks simultaneously access a protected object and try to read it this is possible without any problems Write access is allowed only in sequence and is monitored by the initiator 2 3 5 3 Reusable libraries packages Packages are used to group several subroutines but may also include types and objects It may be useful or necessary that parts of an existing program are being reused To ensure that this part is functional even without the rest of the program all necessary subroutines and agreements are combined into one package Such a package is then easy to integrate and also allows development of the program with several mutually independent programmers Packages even make it possible to use a variable that is needed in various subroutines to use as a global variable and to prevent the deletion by the subroutine after its execution variable remains exist with its value Such a package consists simil
9. served by the communications link level The main procedures are ReadMessage SendMessage and InitConnectPort e The procedure ReadMessage reads out the port and saves it in a string e The procedure SendMessage transmits the information to the serial port e The procedure nitConnectPort initializes and configures the port Real time programming with Ada 19 4 1 2 Communication command level This level describes the functions and procedures to communicate with the EasyPortUSB module Two types of procedures are basically used here One type reads the information from the module and the other transmits information to the module e The function Readl uses the special command to read the input and returns the decoded value from hex to decimal e The procedure WriteO writes the output in hexadecimal system Additional there is a procedure ConfigSetup e The procedure ConfigSetup reads the address of the EasyPort and checks the correctness of the answer To allow communication at first this message is sent to the EasyPort 4 1 3 Communication manager level The communication manager level provides the procedures to read the inputs from the EasyPort and pass the outputs to the EasyPort Three procedures are used therefor e The procedure nitCommunications creates a new object of type EasyPort and then enables communication with the EasyPort Only after this procedure has been called the communication with the EasyPort is possible This p
10. the value false as well as the variable Start Created Sequence If the initial position is not already established the loop StartingPosition is to be started First the inputs are updated and decoded If the level in tank 101 Low Level Tank 101 is too low the procedure FillingTank first opens the valve V102 and then codes and updates the outputs In the following loop FillingLoop only the inputs are updated and decoded followed by a short waiting interval of 200ms The loop FillingLoop should be left as soon as the sensor B113 is active After that the procedure StopFillingTank structurally identical to FillingTank must close the valve V102 Now the low level at the beginning has been corrected and the actual initial position can be prepared For this purpose at first it is ensured again by the procedure CreateStart that the valve V102 is closed Subsequently the proportional directional valve V106 is fully opened For this Real time programming with Ada 28 purpose at first the analog value must be set and then the valve V106 must be opened Only then the pump is turned on Finally the outputs should be coded and updated There now follows a loop StartingLoop which is constructed identically to the loop FillingLoop It should be left as soon as the level is below the sensor B113 In conclusion of loop StartingPosition the pump and then the proportional directional valve V106 nee
11. 09 Festo MPS PA Compact Workstation Festo Didactic http www festo didactic com de de lernsysteme prozessautomation regelungstechnik compact workstation mps pa compact workstation messen steuern und regeln auf kleinstem raum htm fbid ZGUuZGUuNTQOLJEZLjE4Ljg4Mi43NjQ3 2013 Garcia M Concept and realization of a process control for a bottling plant in Ada Masterarbeit IAS 2012 Gohner P Automatisierungstechnik I Vorlesungsskript Sommersemester 2010 IAS 2010 Grude U Einf hrung in Ada Ada95 Skript TFH Berlin http public tfh berlin de grude SkriptA da pdf 2001 Huber Steffen Die Programmiersprache Ada _ http www huber net de adagag htm 2001 IAS Versuch Nr 2 Echtzeitprogrammierung mit Ada95 Versuchsanleitung IAS 2007 Real time programming with Ada 34 Hile Dating ads Project Example program Dating Author Chris Brand Main unit of Example program Dating with Ada Text IO procedure Dating is task Eva is entry Request Gift string Task call with parameter called Gift of type string private entry Rendezvous Gift string private task call for other tasks not visible accessible end Eva task Dirk task Paul task John end Dating File Dating adb Project Example program Dating Author Chris Brand Main unit of Example program Dating with Ada Text IO procedure Dating is package TIO renames Ada Text IO TIO is used as an abbrev
12. 1 Control Digital signal to open or close the valve 101 Heater tank 101 ID Heating Tank 101 Typ Heater Description The heater heats the water in tank 101 if the fluid level is not too low Control Digital signal to turn the heater on and off P101 Pump ID Pump P101 Typ Pump Description The pump can be operated in a analog or digital mode Control Pump P101 Preset D A Selection signal between analog and digital mode Pump P101 In the digital operating mode the pump is turned on and off by this signal Pump P101 Analog In analog mode this signal controls the output level of the pump 106 Proportional valve ID Proportional Valve V106 Typ Electric valve Description This is an analog valve which controls the flow rate by the adjustable width of the Real time programming with Ada 18 valve opening However it can be fully opened and closed by a signal Control Proportional Valve V106 This signal opens and closes the valve completely Proportional Valve V106 Analog This signal controls the width of the valve opening in order to regulate the flow rate The relevant ball valves which can be opened and closed manually are labeled with Vxxx in Figure 9 This excludes V102 ball valve with pneumatic actuator V106 proportional valve and V111 not available 4 Structure of the existing Ada Process Controller The system i
13. D EXPERIMENTS 000000000000000000000000000000000002000000000000000000 see e eese tasa 29 7 1 INSTRUCTIONS FOR EXPERIMENTAL PROCEDURE eeeeen eee nnn rnnt treten nnn 29 7 2 INTRODUCTION TASKS Bn 30 7 3 IMPLEMENTATION OF THE STARTING POSITION AND EMERGENCY SWITCH FUNCTIONALITY 32 Real time programming with Ada 3 7 4 IMPLEMENTATION OF THE TEMPERATURE CONTROL eeeeen eene nnne rere rne nnn 32 Real time programming with Ada 4 1 Introduction This laboratory provides an introduction to the Ada programming language and the automation of a model bottling plant 11 Ways of real time data processing The Monitoring and management of technical equipment in the industry is one of the main topics and main task of automation technology Without the ability to control and automate complex technical processes our current life would not be possible to this extent especially in our way of consumption of goods What began with the invention of the first industrial fit steam engine by Thomas Newcomen in 1712 was continued in 1913 with the introduction of the first motorized assembly line by Henry Ford Of course nowadays a productions line not only consists of one assembly line but can consist of many machines with fast and precise movements that demand complex control requirements To be able to control and automate such a system various computer systems are used which must handle process data in r
14. The temperature control must be designed in accordance to figure 13 Experiment 3 Implement the designed automation program of the preparation task 6 Test your program with the help of the scenario Scenario experiment First create the starting position by activating the button Starting Position After the starting position is established you can trigger an error and start the temperature control by pressing the Start Control button Now wait at least two cycles and then press the Stop Control button Now the starting position should be restored Now check whether each of the emergency stop button and stop switch for each phase drain water heat water restore starting position yields the desired result Make a check list for the possible options to verify your results Note The checklist should represent a table with 2 rows and 3 columns It is then sufficient to confirm the result with a check Real time programming with Ada 33 8 Literature AXE12 Blie98 Fest Fest09 Fest13 Garc12 G hn10 Grud01 Hube01 IAS07 AXE Ada Reference Manual ISO IEC 8652 2012 E Language and Standard Libraries 3 Aufl AXE Consultans 2012 Blieberger J Rendezvous mit Ada Eine echtzeitige Ann herung TU Wien http www auto tuwien ac at blieb ADA Skriptum_TeX gesamt node9 html 1998 Festo MPS PA Datenbl tter Festo Didactic Festo Prozessautomation und Regelungstechnik Festo Didactic 20
15. Universit t Stuttgart Institut f r Automatisierungs und Softwaretechnik Prof Dr Ing M Weyrich Lab course automation technology Experiment No 2 Real time programming with Ada Experiment instructions Real time programming with Ada 2 Table of contents TABLE OF CONTENTS sssccecccckcesiscsccevssscoveseceseceuscecoeesescvecessecencoosessesecsasencostsdsesesbscaucosscseeseoses 2 T Code 4 1 1 WAYS OF REAL TIME DATA eee eene 4 1 2 CONTENT AND PURPOSE OF THIS EXPERIMENT eee eene eene rre retten 4 2 THE ADA PROGRAMMING LANGUAGE eee eese 4 2 1 ORIGIN AND HISTORICAL OVERVIEW te tete terere renun 4 2 2 ADVANTAGES OE ADA Restate Dem EA IE 5 2 3 STRUCTURE OF THE ADA PROGRAMMING LANGUAGE eee e e e emen nn nnnn n esses nsns esiste ise nsn 6 2 3 1 Formal structure of the programs na 6 2 32 D E 6 23 3 VOperalars DC D 8 2 3 4 Commands in ehem etes E esie te eese sinus 8 23 Program Unseren 10 SET UP OF THE MPS PA COMPACT WORKSTATION ee ee eee eere nouae 13 STRUCTURE OF THE EXISTING ADA PROCESS CONTROLLER
16. all numbers greater than zero and type natural for all numbers greater than or equal to zero Here a special feature of Ada is that you can specify your own value ranges In this case we speak of a subtype If for example you do not need the full range of an integer you can specify a smaller range of values To declare a value range of 0 to 10 you write subtype smaller range is integer range 0 10 If you want to calculate with multiple integers of different value ranges an automatic type conversion takes place If a suitable conversion cannot be preformed a constraint error is triggered Example X 5 has a value range of 0 10 and Y 10 has a value range of 0 20 Now if the expression X Y is calculated and written back to Y everything is fine Y 15 However if this expression is being calculated and written back to X a constraint error occurs because the range of values of X is not sufficient Should the value of a variable not be changeable you add a constant in front of the type e g number months constant integer 12 2 3 2 2 Real Numbers Real numbers can be specified in Ada as floating point fixed point or decimal numbers For floating point numbers the exact decimal places must be declared and you can also specify a range of values type length is digits 2 e g 10 55 type percent is digits 4 range 0 0 1 0 e g 0 3456 For fixed point numbers the difference between two successive values must be
17. and closes the valve completely Proportional Valve V106 Analog This signal controls the width of the valve opening in order to regulate the flow rate Maximaler Flow rate 10l min Wert Input Voltage 0 10V DC Connection Analog Output 2 Function Proportional Valve V106 Analog set Raw data percent 100 4 2 2 Digital interfaces The EasyPortUSB module supports 16 digital inputs and 16 digital outputs To accelerate the processing and read and write operations between the controller and the EasyPort all digital inputs and outputs are read at once in a 16 digit register For this purpose then only one command is required to read and write all inputs and outputs Real time programming with Ada 22 The following table shows the assignment of the sensors to the digital inputs Garc12 Input Sensor Function Description 0 B102 Flow Meter B102 This signal is used with a high speed counter for measuring the frequency 1 111 Float Switch S111 Maximum level of tank 101 2 112 Float Switch S112 Middle level of tank 102 3 B113 Proximity Switch Min Level B113 Minimum fill level of tank 101 From here neither the pump nor the heater can be used 4 B114 Proximity Switch Max Level B114 High level of tank 101 From here the ball valve must be closed 5 115 Ball Valve Closed S115 Ball valve is closed 6 5116 Ball Valve Open 116 Ball valve is opened The followin
18. ar to a subroutine of a specification part package specification package name is end name and an implementation part package body package body name is end name These units can also be translated separately The agreements which are described in the package body are not visible outside of the package A package is not executable alone For this purpose a subroutine is needed which calls the program units and variables from the package To this end however the package must be included first To do so you use the keyword with followed by the name of the package in the first line of the file If the keyword use with the package name is following all routines of the package are accessible without having to call them with packagename procedurename Set up of the MPS PA Compact Workstation Festo Didactic develops industry related education and training systems to meet the growing educational demands of the industry Since it is financially and technically often hardly possible to shut down industrial plants for education and training of the own employees models of these systems are needed to provide an understanding of the individual processes and dependencies These are developed and if necessary supervised by Festo Didactic One of these models the MPS PA Compact Workstation is shown in Figure 8 Real time programming with Ada 14 Figure 8 MPS PA Compact Workstation by Festo Didactic This workstation
19. ate is used Here one or more private entrences are included by private and task name b The Task Dirk performs first a delay statement 2s like the two other tasks Paul and John After that the task should either synchronize itself with Eva and in this case pass the parameter Gift which Flowers got assigned to or if task Eva is still not ready for synchronization after 10s Dirk should perform an alternative statement Here it is the output Dirk I do not want to wait any longer bye The tasks Paul and John do not perform an alternative statement block The assigned parameters are Paul Bread and butter John Boot polish Create the body of the tasks Dirk Paul and John in their prepared areas Note In the declaration part TIO is declared as an abbreviation for Ada Text IO and can be used analogously Example TIO Put Line Hallo c The body of the task Eva is now to be finally created Within a for loop the three synchronization requests should be processed After a delay instruction 1s was executed the task Eva should accept and process the synchronization requests In this case an if branch is used If the parameter Gift contains the string Flowers this task is passed to the private entrance requeue Entrancename with abort the addition with abort allows task Eva to terminate itself even if the synchronization is not happening This prevents a permanent waiting of task Eva a
20. ctivated by pressing the button Stop Control procedure Stop Control Clicked Widget access Gtk Widget Record Class is begin if not Task Controller null then Set Markup Temperature Control L span weight light color red size xx large gt Stopped lt span gt Running False if PreviousState_Running true and Panic_Switch_Hit false then Create_Start true mm end if end if end Stop_Control_Clicked task body Controller_Experiment is temperature used as set point with initial value 23 0 C possible range 20 0 C till 30 0 C Real time programming with Ada 38 SetPoint Temperature Float 23 0 begin P area P while Destroy false loop UpdateInputs Decode Inputs following if statements must not be modified by students since it is for safety of the plant if Pump P101 get true then Safety DigitalStartPump while Flow Meter Pump B102 get gt 0 40 and Panic Switch Hit false and Pump P101 get true loop UpdateInputs Decode Inputs delay 0 2 end loop Safety DigitalStopPump elsif Pump_P101_Preset_D_A get true then Pump Analog Value Float Get_Value Pump_P101_Analog_L Safety AnalogStartPump Pump Analog Value while Flow Meter Pump Bl02 get gt 0 40 and Panic Switch Hit false and Pump P101 Preset D A get true loop UpdateInputs Decode_Inputs delay 0 2 end loop Safety AnalogStopPump end if Real time programming with Ada 39 Star
21. ctor on the back of the PC has to get unplugged and re connected After that it should be possible to re establish a connection to the plant It should be noted that the USB port Port 4 is maintained 6 Sample project Automation of a bottling plant 6 1 Introduction The CEO of a chemical bottling company has the following problem Recent researches have shown that certain chemicals can be excreted if the temperature of the liquid is too low and the holding time in the filling tank is too long These chemicals settle in the tank and cause a reduction of the chemical concentration of the filled liquid on the one hand On the other hand a dangerously high concentration in the liquid can occur if the tank gets refilled and turbulences ensure that the deposit in the tank gets combined with the liquid again The filling process represents the end of the production line and the quality control takes place right before the filling tank Consequently there is no monitoring unit to check the chemical concentration of the liquid directly before bottling At a proper operation of the system the dwell time of the liquid in the filling tank is too short so that the described phenomenon will not take place However the duration increases in case of an error somewhere in the production line If the process has to be interrupted then the concentration of the liquid could change Since the purchasers of the liquids can accept almost no tolerance for concentrat
22. d to be turned off by the procedure StopStart And then the outputs need to be encoded and updated Finally the required variables need to be overwritten then Now the procedure StopStart is completed and the initial position is prepared Note that it must be able to bring the plant in a safe condition by pressing the emergency stop switch at all times Realization of the automation program For testing purposes the case of an error in chapter 6 1 should be triggered by the user using the button Start Control in the GUI Thereby the temperature control RunningLoop is activated but only if the starting position was created After triggering the error at first the inputs are updated and decoded Then the current level of tank 102 is read with the procedure StartSetLevel and the desired level 1 5 liters less is determined Thereafter the valve V102 is opened and the outputs encoded and updated The following loop LevelLoop is of the same structure as FillingLoop It is to be exited as soon as the desired level is reached Afterwards the valve V102 must be closed by means of the procedure StopSetLevel and the outputs must be encoded and updated After repeated updating and decoding of the inputs the set temperature for the temperature control is read with the command SetPoint_Temperature Float get_value Set_Point_Spinner With the procedure SetTemperature the current temperature is only read and assig
23. ded free of charge to all users 2 2 Advantages of Ada Nowadays Ada is widely used in security critical areas of real time reference for example in the military The reasons for this are plentiful On the one hand Ada was standardized very strictly and the entire standard has been available for free ever since in the so called Ada Language Reference Manual In addition all Ada compilers have to run through extensive tests and accomplish those correctly if they want to be officially validated This leads to a high portability on other systems The code is checked already at compile time to detect for example slips of the pen directly and to ensure the formal correctness This reduces considerable the effort of quality assurance In addition a run time check is performed so that an error is triggered when violations of predefined rules arise This feature of Ada is called the exception handling This allows to prescribe how the program should react in case of an error for example display a specific error code or to bring the plant to a safe state Besides this will make it much easier to localize the error Since Ada was developed for very large and complex systems with millions of lines of code this feature is also a guarantee that Ada is so widespread in safety critical task areas such as air traffic control weapon systems or in the aerospace Another advantage of Ada is the possibility to divide a software project in different modules T
24. e procedure Under is Here the procedure is a library subroutine and the begin procedure Under is in Main included and can only be Statement called within that procedure The fact should be noted that 5 end Under the lines 2 5 only generate the procedure Under and do begin not execute it In line 8 this procedure finally is executed Statement explicitly For this purpose it must be called with its name Under and terminated by a semicolon end Main When a subroutine is called it executes its instructions in order If the keyword return is used the subroutine is terminated at this point and it will jump back to the place from where the subroutine was called There are two different types of subroutines Procedures and functions The main difference is that a call of a procedure corresponds to a statement and returns no value e g put get etc In this case container values can be changed The call of a function corresponds to an expression and returns a value e g lt lt etc In this case values are calculated but no container values are changed Figure 5 Example of a subroutine 2 3 5 1 1 Procedure A procedure can contain any number of parameters in 3 different modes The basic structure is shown in Figure 6 A distinction is made here parameters which are transported from the calling point to the procedure keyword in or without keyword parameters which are transported
25. e This means that the valve V102 is closed and the liquid level of tank 101 is right below sensor B113 so B113 is off The button Panic Switch has the function of an emergency stop switch which is usually common for every system in the industry It is implemented in software and converts the system in any operating state to a safe state immediately This means that every actuator pump heater and valves is turned off After pressing the emergency switch though the further use of the system is possible without any restrictions In the middle you can set the desired temperature for the temperature control in a range between 20 C 30 C and the label underneath the caption Temperature Control gives colored feedback if the temperature control is active green Running or inactive red Stopped To be able to press the Start Control button at first it is necessary to establish the initial state otherwise the button is without function The Stop Control button interrupts the automation program in each phase and restores the initial state After pressing the Stop Control button though the further use of the system 1s possible without any restrictions 5 User manual Figure 11 shows the folder structure of the Ada Process Controller To create the executable exe file with the project file experiment gpr this structure must be maintained With the command gnatmake Pexperiment in the command prompt the code is c
26. e the execution of the experiment 2 The Ada programming language 2 1 Origin and historical overview Ada was developed in the 1970s At this time the U S Department of Defense DoD prompted an internal investigation and found out that more than 450 different programming Real time programming with Ada 5 languages have been used in their projects To reduce the enormous effort that was necessary to maintain the used software a task force was established The aim of this task force was to standardize and list the requirements of the DoD Despite the many programming languages available on the market none of them could meet the requirements in the area of maintenance training modularity and reuse After a global request of bids the concept of Jean Ichbiah language standard ANSI MIL STD 1815A 1983 was chosen and called Ada83 In the following years Ada has been revised expanded and standardized by the ANSI American National Standards Institute and the ISO International Organization for Standardization With the expansion of object oriented features Ada95 language standard ANSI ISO IEC 8652 1995 became the first standardized object oriented programming language In order to promote the rapid spread of the language the U S Departement of Defense directed till 1997 that in all software projects of the DoD at least 30 of the code had to be implemented in Ada In addition the GNAT compiler was funded by the U S Air Force and provi
27. eal time very often so that the system works properly To handle process data in real time there can be used various options The use of e Programmable logic controllers PLC e Hardware related microprocessors und controllers e High level programming in conjunction with a real time operating system on a PC e Programming using real time programming language e g Ada are approved methods The advantages of Ada for real time operation are for example parallel processing of tasks time controlled behavior and exclusive access to resources Thereby with Ada it is possible to perform real time programming directly without being dependent on interfaces of a real time operating system 1 2 Content and purpose of this experiment A typical task of an automation engineer is to develop a real time system This experiment serves to provide an insight into the programming of such real time systems using the Ada programming language For this purpose on the one hand a sample program has to be expanded and on the second hand there has to be realized an automation for a bottling plant Therefor a model of an industrial bottling plant from Festo Didactic is used the MPS PA Compact Workstation In order to ensure a rapid and successful experiment execution the experiment must be thoroughly prepared For that purpose the complete manual must be read including the appendix and the preparation tasks of Chapter 6 are to be processed in written form befor
28. ed on the content of the container X 2 3 4 3 Statements Unlike expressions statements can change the content of a container value and must be terminated by a semicolon This is most evident in the assignment statement X X Y 5 Here an expression is calculated and its result is written back into the container value X It should be noted that for example the screen and the keyboard are also count as container values and therefore input and output commands are statements as well In the following additional important statements are presented 2 3 4 3 1 The null statement The null statement is described by null and serves the purpose of doing nothing This is often useful as a placeholder for future functionalities au Zara T elsif Expression then 2 3 4 3 2 The if and case statement Statement The if and case statement is being used for selection Here the programmer has the possibility that a statement may not be executed end if With loops in contrast he can achieve that a statement is called 2 multiple times The basic structure is shown in Figure 1 when Valuel The if statement can also contain any number of elsif branches but must not have an else call necessarily 1 Statement2 In the case statement the expression must either belong to the type d Pen integer or enumeration In addition the value of the expression must ena case be known already at compile time not at run time Furtherm
29. ed to ensure proper operation This is for learning purposes to give you an understanding of modularity and parameter handling and exceptions in Ada Note that if you control actuators you must encode and update the outputs so that the commands are passed to the system You have to deal with the inputs similarly to obtain the current value update inputs and decode These methods are already available and can be used See appendix In Figures 12 and 13 the respective flow diagrams for the initial sate and the temperature control are shown Note The flow charts represent only the main functions and are not complete For detailed description of the individual parts of the program stick to chapter 6 2 Start Control SetStartLevel Starting position Y SetStopLevel Y Close Valve V102 Open Valve V102 Analog value V106 100 0 Open Valve V106 Close valve V102 Turn on Pump i P101 Read SetPoint Temperature es Set Current Temperature no v iperatu Turn off Pump less than yes Start Heating P101 etpoint no NEN NEN Stop Heating mperat re less than etpoint Close Valve V106 Start Created Position Figure 12 Flow diagram starting position Figure 13 Flow diagram temperature control 7 Tasks and experiments 7 1 Instructions for experimental procedu
30. es are required which are used as parameters plus one which is designated in the flowchart Note A total of 10 variables are required of which one is already in place Note the files available in the appendix Preparation task 4 Design the emergency stop switch according to chapter 6 For this purpose create the file Emergency adb Note the specification file Emergency ads available in the appendix Preparation task 5 Design the function Starting Position For this purpose create the file StartingPosition adb and the specific part in the scenario experiment adb Note the specification file StartingPosition ads available in the Appendix The starting position must be designed in accordance to figure 12 Experiment 2 Implement the designed program parts of the preparation tasks 3 5 First test the functionality of the emergency stop switch by opening the valve V102 and then press the emergency stop switch Now check that the correct starting position is produced by pressing the Starting Position button Now drain some water and test the emergency stop button while the starting position is creating for correct functionality 7 4 Implementation of the temperature control Preparation task 6 Design the control program temperature control from chapter 6 For this purpose create the file TemperatureControl adb the specific part in the scenario experiment adb Note the specification file TemperatureControl ads available in the Appendix
31. et is to be set to false The proportional valve Proportional Valve V106 must be closed gt The heater Heating Tank 101 must be switched off After pressing the emergency stop switch it should be possible to control the full system further Therefore all required variables must be meaningfully overwritten It is recommended that after the outputs are coded and updated to perform a delay statement 500ms and then to finish the statement block by overwriting the variable Panic Switch Hit V Realization of the initial state Since the Compact Workstation is a model first there needs to be a sensible initial state created to run the temperature control then For this the file StartingPosition adb must be implemented The corresponding specification file is located in the Appendix The starting position means that the valve V102 and the level of the water in tank 101 is just below the sensor B113 On the one hand it should be able for the user to activate it via the button Starting Position and on the other hand it should be activated automatically by the temperature control Before the initial position can be prepared first it needs to be checked whether there is too little liquid in the tank 101 at the beginning Only then can the loop Starting Position for the initial position begin If the level in tank 101 is below sensor B113 the variable Low Level Tank 101 is to be assigned true Otherwise the variable should get
32. from the procedure to the calling point keyword out and parameters which 1 procedure Name Parameterlname Typ Parameter2name Typ is are used for both ways 2 Agreements keyword in out begin An in parameter any 4 Statement expression is passed end from the calling point to the subroutine and is treated by that as a constant An out parameter name of a variable corresponds to an uninitialized variable and is written in the subroutine and then is passed to the calling point An in out parameter name of a variable behaves like an initialized variable So the subroutine gets a variable with an initial value It is allowed to read this variable overwrite it with a new value and then gives it back to the calling point Figure 6 Basic structure of a procedure with parameters Real time programming with Ada 12 2 3 5 1 2 Function A function can only have in parameters and must have at least one return statement Thereby the return value is specified which will be returned to the calling point by that function return sum 2 3 5 2 Tasks With tasks it is possible in Ada to work through command sequences not only sequentially but also parallel Fundamentally an Ada program is executed in one main task The programmer has the possibility to define more tasks which are then executed side by side and next to the main task A subroutine can be executed at the same time as part of different tasks Tasks are also separated
33. g table shows the assignment of the actuators to the digital outputs Garc12 Output Actuator Function Description 0 V102 Ball Valve V102 The ball valve with pneumatic actuator controls the flow from tank 102 into tank 101 1 E104 Heating Tank 101 Heating tank 101 2 P101 Pump P101 Preset D A Pump mode 0 Digital 1 2 Analog 3 P101 Pump 101 When digital pump mode is enabled this signal turns on the pump 4 V106 Proportional Valve V106 The proportional valve is controlled by this signal 0 turned off 1 turned on 4 3 Process control level The process control level controls the plant The main program is processed cyclically and repeated just like a PLC Programmable Logic Controller It includes the graphical interface to the user and provides functions to select different scenarios and to start and stop the system 4 4 Graphical User Interface The graphical interface to the user is realized via a GUI of the GTK library In this library all necessary elements are present to provide a functional interface that allows the user to efficiently access control and monitor the system 4 5 Scenario experiment To control the bottling plant and perform the experiment there must be Experiment Scenario selected on the top left button Select Scenario right after the execution of the exe file AdaController Real time programming with Ada 23 L Ada Experiment ADA Exper
34. his is one reason why very large and complex software projects are being realizable with Ada Furthermore the modularity simplifies the understanding of the program and minimizes the effort to expand it Through the use of libraries and thus the use of already established lines of code the expansion of programs is greatly simplified and accelerated The ability to manipulate individual bits and to program at register level makes Ada even interesting for the low level hardware programming Other advantages IAS07 e Support of methods of software engineering e Support for reusability e Event driven and concurrent programming e Use of a program library e Interface to peripheral software systems e Object orientation with dynamic polymorphism e Real time support after the British mathematician Ada Lovelace 1815 1852 Real time programming with Ada 6 e Optional automatic garbage collection e Parallel processing 2 3 Structure of the Ada programming language 2 3 1 Formal structure of the programs The character set of an Ada program consists of the 26 basic letters of the Latin alphabet in upper and lower case Although umlauts are possible it is strongly recommended to set those aside if you want to develop software with international use To the basic letters all digits from 0 to 9 space and the following characters are added Wet ON oun Fre Fa an 43 All lexical units consist of this character set There are identif
35. iation Useful for programs with many integrated libraries instead of use Body of task Eva task body Eva is begin delay 2 0 TIO Put Line Eva is waiting for requests end Eva Real time programming with Ada 35 begin delay 1 0 TIO Put Line Dirk Paul and John vie for the attention of Eva end dating File Emergency ads Project Temperature Control Author Chris Brand Unit of Panic Switch package Emergency is procedure PanicSwitch Create Start in out Boolean Start Created in out Boolean Running in out Boolean PreviousState Running in out Boolean Panic Switch Hit in out Boolean File StartingPosition ads Project Temperature Control Author Chris Brand Unit of Starting Position package StartingPosition is procedure FillingTank procedure StopFillingTank procedure CreateStart procedure StopStart Create Start in out Boolean Start Created in out Boolean end File TemperatureControl ads Project Temperature Control Author Chris Brand Real time programming with Ada 36 Unit of Temperature Control package TemperatureControl is procedure StartSetLevel Start Level Tank 101 in out Float Stop Level Tank 101 out Float procedure StopSetLevel procedure SetTemperature Current Temperature in out Float procedure StartHeating procedure StopHeating end Hile scenario experiment adb Project Experiment
36. iers reserved words numeric literals character literals string literals delimiters and comments A Space between two lexical items is ignored by Ada Identifiers for program components variables etc begin with a letter After that any number of letters digits and underscores can follow However underscores are not allowed to succeed and they cannot be at the end of the identifier In addition an identifier may go up to the end of line at the most For better readability identifiers are to be preferred which are as short and concise as possible Ada distinction is generally not case sensitive however identifiers should be written consistent over all parts of the program as otherwise the compiler could complain The following keywords are reserved in Ada and cannot be used as identifiers aa ea Cony EE Cex uuu Seay CER MEE E TREEIRENEERENSE RES Gears M M arr care EE E EE i abort begin i else goto i new i private reverse until abs elsif not procedure use abstract if null protected select accept case entry in separate when access constant exception is of raise subtype while aliased exit or with all declare limited others tagged delay for loop out task xor delta function rena
37. iment Select Scenario Connected Experiment Control Starting Position Set Point Temperature Panic Switch 4 Start Control Temperature Control Stop Control Analog Input Signals Sensor Level Tank B101 Flow Meter Pump B102 Pressure Tank B103 Temperature Tank B104 8 01 0 01 45 03 28 77 Digital Input Signals Float Switch S111 Float Switch 5112 Proximity Switch Min Level B113 ON ON OFF Serial Port Number Proximity Switch Max Level B114 Ball Valve Closed 5115 Ball Valve Open S116 ON OFF Analog Output Signals Pump P101 Analog Proportional Valve V106 Analog 1000 1000 Digital Output Signals Ball Valve V102 Heating Tank 101 Pump P101 Preset D A Pump P101 Proportional Valve V106 Valve V187 OFF OFF Figure 10 Graphical interface for the experiment The GUI of the experiment after a successful connection to the plant via the Connect button is shown in Figure 10 The graphical interface is divided into the following areas Communication control Experiment control Analog input signals Digital input signals Analog output signals Digital output signals 4 5 1 Communication control The Communication control is located on top under the heading ADA experiment It includes the button Select Scenario which allows selecting an available scenario As part of the Ada experiment here the scenario Scenario experiment has to be selected The button Connect connects the PC to the Com
38. ing with Ada 20 surface of the water Thus the filling level is determined Tank full 10V Tank empty OV measuring Distance 50 345mm range Output Voltage 10 OV DC Connection Analog Input 1 Function Sensor Level Tank B101 get Filling level 121 ae ee SAT 1095 raw data 50 4 2 1 2 Flow rate sensor Garc12 ID Flow_Meter_Pump_B102 Sensor type Flow rate sensor Description The sensor is located directly behind the pump and measures the water flow through the pipe measuring Flow rate 0 3 9 0l min range Output Frequency 40 1200Hz ID f U Sensor type Measuring transducer frequency to voltage Description The measuring transducer converts the frequency given by the flow rate sensor into a voltage signal measuring Frequency 0 1kHz range Output Voltage 0 10V DC Connection Analog Input 2 Function Flow Meter Pump B102 get l 10V Bu SEXE x PE T OE SOE L2kHz 4 2 1 3 Pressure sensor Garc12 ID Pressure Tank B103 Sensor type Pressure sensor Description The sensor measures the water pressure in the pipes which is generated by the pump and the proportional valve V106 The sensor is located behind the pump measuring Pressure 0 400mbar range Output Voltage 0 10V DC Connection Analog Inp
39. into specification part and body and must be specified A task that has been declared in the declaration section of a program unit is started just before the execution of the instructions in this program unit but only after all agreements have been processed 2 3 5 2 Delay statements In order that tasks do not directly run after calling a program there are the delay statements Firstly there is the delay statement which causes the task to be paused for the specified time in seconds delay 5 0 task is paused 5 seconds However it can only be guaranteed here that the task is stopped for this period Whether the task starts again immediately afterwards cannot be guaranteed because another task could be running at that time Secondly there is the delay until statement In contrast to the relative time specifyed by the delay statement the delay until statement provides an absolute time delay until time 2 3522 Synchronization of tasks In Ada there are several ways to synchronize tasks The rendezvous concept envisages that two or more tasks are synchronized at a time and in between they are running independently The faster task must then wait for the slower task when a synchronization should take place After synchronization the tasks run 2 task Paul task body Paul is mg begin further independently of each other again The basic 5 Sabine date structure of a rendezvous declaration is shown in Figure 7 end Paul Formally a task
40. ion variation and the T V discovered this problem at a routine check the CEO has to act fast Either an expensive monitoring system for the filling tank has to be installed which does not prepare the existing liquid in a case of an error or there has to be found another solution to keep the liquid at a certain temperature in the case of an error If this problem is not resolved in the shortest possible time the company is threatened by the closure of the plant with an unforeseeable financial damage To save time and money the CEO decides to use the alternative of a temperature control You now have the task as a software developer to implement this and other functions 6 2 Assignment of tasks Since there only exists an in hardware realized emergency stop switch for the plant you should first compose an emergency stop switch realized in software for the plant Since it is a model of the plant at the beginning there must be set a useful initial state to make the subsequent temperature control executable Moreover in order to avoid deposits of a liquid in tank 102 the fluid must be brought to a certain temperature and maintained For this purpose you should develop a temperature control Since it is not possible to integrate a heater in tank 102 the CEO decides to reactivate a unused tank with heater Fortunately the tanks have already been connected to each other by a piping system The CEO envisages the system in case of an error in the f
41. is a model of an industrial related bottling plant and is a learning system for a variety of regulation and control tasks It has four integrated control loops that can be operated individually by manually switching the ball valves This guarantees a very high complexity in the smallest space The level flow pressure and temperature control loop allow a wide ranging coverage of industrial automation tasks and the connection with various technologies such as pneumatic process actuators ensure a strong practical relevance The industry is using pneumatic actuators for valves more and more since they have clear advantages in terms of safety and energy efficiency The combination of various technologies in automation technology becomes more and more important The Compact Workstation provides tasks in the areas of Mechanics Process control Pneumatic Compressed air technology Sensors actuators PLC Closed loop control systems Closed loop control Fault finding The system combines pneumatic hydraulic and electrical components Figure 9 shows the P amp I diagram piping and instrumentation diagram of the bottling plant Real time programming with Ada 15 Sensor Level Tank B101 B101 Float Switch S Proximity Switch 112 115 Max Level B114 Tank 102 5 LSH o 4 B114 Float Switch Tank 101 d LSL Proximity_Switch_ B113 Min_Level_B113 en 103 104 r
42. mes terminate digits packages requeue then do generic pragma return type For numeric literals Ada granted some freedoms In this representation of integers for example underscores can be inserted to improve readability 1 500 000 or 1 5e6 correspond to the numerical value 1500000 Furthermore any number can be provided to a basis between 2 and 16 The numerical value 15 in decimal notation corresponds to the numerical value of 16 F in hexadecimal and to 21111 in binary notation As decimal separator Ada uses a point Character literals character may consist of any character and be enclosed by quotation marks String literals strings however may also consist of none character empty string and be enclosed by double quotes String Delimiter delimiter can be used individually or assembled compound delimiter and include the following characters lt gt amp The last thing to mention here are comments These are characterized by a double hyphen and go till the end of the line this would be a comment 2 3 2 Types With types the programmer has the opportunity to submit its own container values One type is for example the enumeration type month is January February December Real time programming with Ada 7 2 3 2 1 Integers For the representation of integers the type integer is used in Ada Furthermore there is the type of positive for
43. must have an input entry date and needs 7 task Sabine is to execute an accept statement accept date to confirm entry date that it is ready for the rendezvous The input must be called end Sabine by another task Sabine date to submit that it is available 10 task body Sabine is for a rendezvous as well Depending on which task is begin expressing their willingness for a rendezvous first it is 12 accept date do stopped until the other tasks agreed to it After that the instructions after the keyword do are being processed the tasks are synchronized at this time and then each task goes its own way again Just like the call of procedures may also the call of a Figure 7 Basic structure of the rendezvous include parameters in out in out and will xendezvous concept formally written analogues to procedures With the select statement selective synchronization this concept is further extended So that a task can have several inputs and select e g according to the FIFO method first in first out which rendezvous it agrees to Thereafter the task is then continued normally and the other rendezvous do not take place To ensure that multiple rendezvous can take place one after the other the select statements are often inside loops Another possibility is to let the 14 end date end Sabine Real time programming with Ada 13 task only wait a certain time for a rendezvous with a delay statement If the rendezvous does not take
44. nd therefore also of the complete program dating If the Parameter should not be Flowers a further delay statement 1s is executed followed by the output Eva Sorry but I don t like amp Gift amp Now follows another delay statement 1s and the output is Eva I made my decision Now the synchronization request which was diverted to the private entrance should in a subsequent select statement either be accepted and after a further delay 1s the output should be Eva Thank you for amp Gift amp Let s go or there will be a delay of 5s with the output Eva I should have made up my mind faster Create the body of task Eva Real time programming with Ada 32 Experiment 1 Complete the Ada program Dating of Preparation Task 2 and produce the output shown in Figure Eva is waiting for requests 14 Next change the delay Sorry but I don t like Bread and butter statement after the for Sorry but I don t like Boot polish loop from 1s to 10s in the I made my decision body of task Eva and run Thank you for Flowers Let s go the program again Give reasons for the result Figure 14 Output of the example program Dating 7 3 Implementation of the starting position and emergency switch functionality Preparation task 3 In order to use all functionalities several variables have to be declared List all required variables and set reasonable starting values if necessary Only those variabl
45. ned to the variable Current Temperature Now if the current temperature is lower than the set temperature the heating should be turned on by means of the procedure StartHeating with subsequent encoding and updating of the outputs The following loop TemperatureLoop is identical to the loop FillingLoop and should be exited once the desired temperature has been reached Now the heating must be turned off again with the procedure StopHeating structurally identical to StartHeating Before there will be a waiting interval of 1s now there should be the possibility to exit the loop RunningLoop with the buttons Stop Control or Panic Switch Do not forget that this must be possible at any time of the temperature control After waiting that one second the initial position should get restored and the loop RunningLoop should be exited Further notes The complete program of this experiment is running within a task in scenario_experiment adb All loops are to be implemented in this task See the corresponding excerpt in the Appendix The packages Emergency StartingPosition and TemperatureControl should only be used to control actuators and to overwrite variables so that the program remains clear in the scenario_experiment file Stick to the respective specification files concretely Here all required methods with parameters are described Also do not forget that all these parameters Real time programming with Ada 29 must be us
46. ollowing way The liquid which is stored in tank 102 has to be dumped gradually through valve V102 into the re activated tank 101 There the liquid has to be brought to a certain temperature Once the temperature has reached the setpoint the heater is switched off and the liquid gets pumped back into tank 102 This process should continue until the fault has been eliminated After that the initial state must be restored With that the control program is over The following requirements are placed on the automation e The emergency stop switch has to switch off all actuators at any time Real time programming with Ada 27 e Setpoint for the temperature of the liquid should be 23 e The automation needs to be terminated by the Stop Control button at any time e Once the error has been acknowledged stop button the starting position must be restored e The temperature control may only be started if the starting position was created Realization of the emergency stop switch To realize the emergency stop switch at first the file Emergency adb must be implemented The corresponding specification file is located in the Appendix The emergency stop switch should be realized as exception within the procedure PanicSwitch The emergency stop switch must convert the plant to a safe state at any time This means The temperature control must be stopped The valve Valve V102 must be closed The pump Pump P101 must be switched off The pump pres
47. ompiled and the executable file AdaController is created Real time programming with Ada 25 gt AdaController adb gt experiment gpr gt scenario_experiment adb P scenario_experiment ads puc e cool Layer m com_layer adb gt Emergency adb gt gui_module adb gt com_layer ads I Emergency ads gt gui_module ads gt link_layer adb gt StartingPosition adb gt main_gui adb gt link_layer ads gt StartingPosition ads gt main_gui ads gt mngr_layer adb gt TemperatureControl adb gt mngr_layer ads gt TemperatureControl ads gt module_interface adb x lib module_interface ads Figure 11 Folder structure of the Ada Process Controller 5 1 Possible problems during lab experiment Should you encounter the error message while compiling the source code that the output file could not be opened access denied then the process AdaController exe must be terminated in the Task Manager After that a compilation should be possible Should there be a program crash the AdaController can simply be restarted and re connected Then you can control the system again Real time programming with Ada 26 If it is not possible to make a successful connection to the plant then the USB conne
48. oop 1 Statement instead of ascending order default there is the keyword in reverse for Variable in reverse Variable type loop Loops can also be named by writing the Statement name with a colon before the loop block end loop This makes it possible that you always know exactly which loop is ending or being left even with nested loops Figure 2 shows the basic structure of the loops above Figure 2 Basic structure of loops 2 3 4 3 5 The block statement 1 Name declare The block statement is divided into a declaration part and a 2 Agreements statement part The basic structure is shown in figure 3 The begin declaration part is initiated by declare and ends with begin Statement where the statement part begins This is terminated by end The end Name block statement creates the container values declared in the declaration part and then executes the statements When exiting the block statement all container values created are getting cleared If not needed the declaration part can be omitted If you want to name the block you put the name followed by a colon either before declare with declarations or before begin without declarations Figure 3 Basic structure of the block statement 2 3 4 3 6 The return statement To exit subroutines and jump back to the origin of the call you use the return statement Within procedures you only use the keyword return with a final semicolon
49. ore a case _ Figure 1 Basic structure of if and case statement Real time programming with Ada 9 statement must be fully and clearly If completeness cannot be reached you have to use others as last entry 2 3 4 3 3 The exit statement To exit loops there is the unconditional and conditional exit statement exit exit when Expression On demand you can also specify the loop name after the key word exit exit loop name when If the exit statement is before any other statement in the loop it is a pre checking loop Is it behind all other statements in the loop it is a post checking loop 2 3 4 3 4 Loops Loops are divided into three different types There is a loop without iteration a while and a for loop Furthermore the loop without Loop name iteration is used to simulate loop types that do not actually exist in Ada e g 1 exit when Expression and post checking until loop While it is SERERE possible that a loop or while loop become end loop Loop name ar he an infinite loop this danger does not 5 while Expression loop appear with a for loop Statement For loops can run through the entire range of values of the variable type or only a limited range of values with the keyword end loop for Variable in Variable type loop Statement end loop range If it is necessary to run through the loop parameter in descending order for Variable in Variable type range Value range l
50. ot be present in order to compile an executable program But it is strongly recommended to use this useful feature of Ada for an easy understanding of programs In the specification file all necessary informations to call a program unit is stored name parameter parameter type parameter mode etc It should also include a comment to briefly describe what this program unit does Real time programming with Ada 11 exactly A specification is usually much clearer and easier to understand than a complex implementation In the implementation file first the specifications are repeated and thereafter the instructions are formulated 2 3 5 1 Subroutines Subroutines are statements or expressions which are combined in a block and assigned with a name This way you can use it multiple times without having to insert the code all over again In addition this simplifies the understanding and maintenance of the software as well as the readability Subroutines are divided into two parts At the beginning there is the declaration with the name parameters and if it is a function the return value is also defined The second part is the implementation of the instructions A distinction is made here on the one hand the library subroutines that can be called from anywhere and on the other hand the contained subroutines which can only be called within the unit in which they are described procedure Main is Figure 5 shows an example of a contained subroutin
51. pact Workstation and only then allows a communication with the system if a scenario was selected The black label Not Connected below the button changes into a green Connected if a successful connection has been made If a red Connection Error appears after pressing the button it was not possible to establish a successful connection to the plant To fix this error it should be enough to unplug the USB connector on the back of the PC and then re connect it Please make sure to use the right USB port on the back of the computer again 4 5 2 Analog input signals The box analog input signals shows the actual measurement value of the analog sensors Real time programming with Ada 24 4 5 3 Digital input signals The box digital input signals indicates the current state of the digital sensors 4 5 4 Analog output signals The box analog output signals allows the input of an analog value for controlling the analog actuators pump P101 and proportional valve V 106 4 5 5 Digital output signals The box digital output signals allows the point and click control of the digital actuators heating Heating Tank 101 as well as the turning on and off of the pump and the proportional valve Furthermore here can be switched between the analog and digital mode of the pump 4 5 6 Experiment control The upper box Experiment Control allows the control of the experiment The button Starting Position creates the desired initial stat
52. re The main purpose of this experiment is to implement the automation program which was described in Chapter 6 The hardwarenear control of the system has been already realized and is not part of the task of this experiment All program units that are used to obtain and process Real time programming with Ada 30 sensor data and to control actuators are already available and can be used These are attached in the appendix and must be worked through before experimental procedure It must not be converted any raw data The level sensor returns a value in liters The experiment is performed on the Compact Workstation presented in chapter 3 As a process computer there is a PC with Windows 8 provided For the Ada programming the program Notepad is used Please save all files you edit exclusively in your group folder The Windows command prompt is used to compile source code At the command prompt you must first navigate to drive C To do so type and press enter You may enter it by typing cmd in the search box of the Windows start menu To navigate in different folders in the command prompt the command cd is used cd foldername to navigate into the subfolder foldername in the current folder cd to navigate to the parent folder Now to compile a file use the command gnatmake programname for a single file the command gnatmake Pprojectname for a project To execute a program only the program name must be called from the command prompt in
53. rocedure also allows you to connect and communicate with multiple EasyPortUSB modules e The procedure UpdateInputs reads out all the inputs of all EasyPorts and stores them in the respective object e The procedure UpdateOutputs transmits all outputs to the EasyPort module 4 1 4 Module interface level The module interface level provides the functions and procedures which are necessary for the conversion of the inputs and outputs 4 2 Process variable level The process variable level is used to convert the raw data from the sensors into useful information and to encode the commands for the outputs and output them in the range of the EasyPort 4 2 1 Analog Interfaces The EasyPortUSB module supports four analog inputs and two analog outputs in a value range of either OV DC to 10V DC or 10V DC to 10 V DC For digital transmission of this information the EasyPort uses a range of values from 0 to 4095 discrete values this corresponds to a resolution of 12bit In this system always a value range of the sensors from OV DC to 10V DC is used The formulas for converting between the desired voltage and the raw data and vice versa are the following Garc12 ji _ raw data POMAS 085 voltage raw data 4095 4 2 1 1 Level sensor B101 Garc12 ID Sensor Level Tank B101 Sensor type Ultrasonic sensor Description The sensor is located at the top of tank 102 and measures the distance to the Real time programm
54. s based on the already existing Ada Process Controller which was created as part of the master thesis by Miguel Garcia The structure of the Ada controller is divided into three main planes This simplifies the handling with complex programs and clearly supports the easier understanding of the program The main planes are e Process control level This level is responsible for the graphical interface to the user and allows the starting and stopping of the system It is also used to monitor and control the system e Process variable level This level serves to encode and decode the commands for the EasyPortUSB module e Field level This level is used to communicate with the serial port 4 1 Field level The field level communicates with the EasyPortUSB module directly and assigns to it the values for the actuators from the control program It also reads out the sensor values which are received from the EasyPort module The field level is divided into four sub levels Communication manager Communication command Communications link Module interface 4 1 1 Communications link level This level provides the procedures which are used to open and close the signal port as well as to read write and configure it For this purpose the Serial_Communication library is used with the default data type Ada Streams Stream Element Array However this array has to be converted into a string to be processed by the control program This purpose is
55. sor type Ultrasonic sensor Description The sensor is located at the top of the tank 101 and measures the distance up to the water surface Thus the filling level is determined Tank full 10V tank empty OV measuring Distance 50 345mm range Output Voltage 10 OV DC Real time programming with Ada 16 B102 flow rate sensor ID Flow Meter Pump B102 Sensor type Flow rate sensor Description The sensor is located directly behind the pump and measures the water flow rate through the pipe measuring Flow rate 0 3 9 0l min range Output Frequency 40 1200Hz Flow rate sensor measuring transducer Frequency to Voltage ID f U Sensor type Measuring transducer frequency to voltage Description The measuring transducer converts the displayed frequency by the flow rate sensor into a voltage signal measuring Frequency 0 1kHz range Output Voltage 0 10V DC B103 Pressure sensor ID Pressure Tank B103 Sensor type Pressure sensor Description The sensor measures the water pressure in the pipes which is generated by the pump and the proportional valve V106 measuring Pressure 0 400mbar range Output Voltage 0 10V DC B104 PT100 Temperature sensor ID Temperature Tank B104 Sensor type Temperature sensor Description The sensor measures the water temperature in tank 101 measuring Temperature 0 100 C
56. specified Analogous to floating point numbers it is optionally also possible to specify a range of values type length is delta 0 01 To conclude there is the possibility to declare real numbers as decimal numbers Here both the difference and the decimal places need to be indicated type temperature is delta 0 01 digits 2 2 3 2 3 Arrays When declaring arrays you have the possibility to determine the exact bounds of the array constrained array or leave them open unconstrained array type Eight Bit is array 0 7 of boolean constrained array type Vector is array integer of positive unconstrained array In the definition of constrained arrays you do not need to specify the boundaries Byte Eight Bit But in case of a unconstraint array you have to specify the boundaries Square Matrix 1 5 1 5 In order to access a single element of an array you use parentheses Byte 3 Square 2 4 In addition you can also cut out slices a selected range from an array and receive a new array Byte 3 6 2 3 2 4 Private abstract types To protect specific components of an object from possibly accidental change Ada is providing the private types type day is private Those must be declared twice in the package specification First it must be described incompletely in the public block before the keyword private Le you declare for example that a variable is private type X is private Secondly this type
57. t by restarting the main program But often a multiple execution of a task during a program is needed What option is available to execute a task several times Give an example of such a task body Real time programming with Ada 31 Preparation task 2 Cyclic task programs and parameter passing Automation technology often requires the use of cyclic processes e g sampling control Additionally it is often necessary that parameters are passed between task programs to read for example sensor data once and further process somewhere else The following example program Dating illustrates the operation of parameter passing and synchronization between tasks using the rendezvous concept In addition to the main program four additional tasks are implemented Eva Dirk Paul and John Dirk Paul and John send Eva a rendezvous request named Request and pass it a parameter of type String called Gift Eva now checks whether the Gift is Flowers and refers this task on its own private entrance Rendezvous Is it not Flowers Eva then dispenses that she does not like the Gift a The Task Eva therefore has two entrences public entrence Request and a private entrance Rendezvous Both entrences accept a parameter called Gift of type String Now create the specification of the task Eva and the other required tasks Note the specification file Dating ads available in the appendix Note To implement a private entrance the keyword priv
58. tPosition Code Outputs UpdateOutputs delay 0 2 end loop end of process control end of programming area for experiment P area V Task Controller null exception when others gt P area V Set Markup Connect Status span weight light gt Error Connection lt span gt Task_Controller null end Controller_Experiment nm nm color red size xx nm large procedure Destroy_Scenario is begin Ball Valve V102 set false Pump P101 set false Pump P101 Preset D A set false Proportional Valve V106 set false Heating Tank 101 set false Destroy True Protect variable P area P Code Outputs UpdateOutputs P area V end Destroy Scenario end scenario experiment
59. the specific folder To ensure that the experiment can be usefully and quickly processed the instructions must be read completely and the following tasks are to be processed in writing prior the experiment In addition results have to be recorded during the experiment Notes about the plant The valve V105 must be closed at any time To be able to perform the experiment properly please ensure the following before the experiment and fill out the checklist Valve V101 is closed Valve V103 is closed Valve V104 is closed Valve V105 is closed Valve V107 is opened Valve V108 is opened Valve V110 is opened Valve V112 is closed 7 2 Introduction tasks Preparation task 1 Expiration of task programs a Once all the agreements of a program have been processed all tasks which are declared within it and the main task are started the main program itself is executed as atask as well Then all tasks are running in any order independently from each other This order can happen to be the same with a renewed program execution or may not be Now however a particular sequence is often required What possibilities does the programmer have with Ada to keep a specific order and how can he prevent an uncontrolled start of the task at startup Give an example of a task agreement and a task body b As soon as a task has completed its instruction part it is terminated It is now no longer possible to call this task excep
60. ut 4 Function Pressure Tank B103 get rss Pressure raw data sas 10V 4 2 1 4 Temperature sensor Garc12 ID Temperature Tank B104 Real time programming with Ada 21 Sensor type Temperature sensor Description The sensor measures the water temperature in tank 101 measuring Temperature 0 100 C range Output Voltage 0 10V DC Connection Analog Input 3 Function Temperature Tank B104 get m i jus 10V 100 C emperatuer raw aata 5 10V 4 2 1 5 Pump Garc12 ID Pump P101 Type Pump Description The pump can be operated in an analog or digital mode Steuerung Pump P101 Preset D A Selection signal between analog and digital mode Pump P101 In digital mode of operation the pump is turned on and off by this signal Pump P101 Analog In analog mode this signal controls the output level of the pump Maximale Flow rate 10l min Leistung Input Voltage 0 10V DC Connection Analog Output 1 Function Pump P101 Analog set d 4095 Raw data percent 100 4 2 1 6 Proportional valve Garc12 ID Proportional Valve V106 Type Electric valve Description This is an analog valve which controls the flow rate by the variable width of the valve opening However it can be fully opened and closed by a signal Steuerung Proportional Valve V106 This signal opens

Lab course automation technology Experiment No. 2 Real

Contents

Download Pdf Manuals

Related Search

Related Contents