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The Design of a Simulator for the Automation Industry - IEA

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1. Sim CollectionOfBodies Item body 233 S etConfig 0 78 0 12 0 142 0 0 0 True Sim CollectionOfBodies Item body 234 S etConfig 0 78 0 065 0 142 0 0 0 True Sim CollectionOfBodies Item body 235 S etConfig 0 78 0 01 0 142 0 0 0 True Sim CollectionOfBodies Item body 236 S etConfig 0 78 0 045 0 142 0 0 0 True Sim CollectionOfBodies Item body 237 S etConfig 0 78 0 1 0 142 0 0 0 True End Sub 49 9 Module Simulation WM3 This module contains the code which transfers signals from to WM3 and is called once during every simulation cycle Private load_new_package_on_conveyor As Integer Private load_new_package_on_conveyor_memory As Integer Sub Scan Sim As Simulation_Main Copy values from FX to WM3 FX OUT SW MOTOR SPEED Read 2 WM3 IN SW MOTOR OUT SW MOTOR SPEED Value FX OUT LW MOTOR SPEED Read 2 WM3 IN LW MOTOR SPEED Setint FX OUT LW MOTOR SPEED Value FX OUT CONVEYOR SPEED Read 2 WM3 IN CONVEYOR OUT CONVEYOR SPEED Value load new package on conveyor 0 Forl 0702 FX OUT SW HOLD CONTAINER I R ead 2 WM3 IN SW HOLD CONTAINER I Setlnt FX OUT SW HOLD CONTAINER I Value load new package on conveyor new package on conveyor FX OUT SW HOLD CONTAINER I Value Next 0709 FX OUT LW_HOLD_CONTAINER I Read 2 WM3 IN LW HOLD CONTAINER
2. pu A SR EEA 37 sam kani aigua e aoe eode t va 37 Form Simulation Vie Wis ut Dui etie a SEO 38 Class Simulation 41 Class Input Controller 2 2 at e eai Qe E eee 43 5 Dt cer 44 v NNI OT e adiit 45 Module Simulation FX Connection nennen 46 Module Simulation WM3 Connection 48 Module Simulation_FX_To_WM 3 50 Module Simulation WM3 To FX uQ a santan 51 Controller code Ten Bb ted ds 53 meto eed Me Su does tetas G 57 Preface Finally this work has been completed and I want to thank all people involved during this project both at Tetra Pak R amp D in Lund and Department of Industrial Electrical Engineering and Automation at LTH I would like to tank Bo Hellberg and Lennart Christensson at Tetra Pak for their help during my time at Tetra Pak A special thanks for their encouragement and patience goes to Istvan Ulvros Tetra Pak and professor Gustaf Olsson Finally I would like to thank my girlfrien
3. 10 M4sual Basic VB Sa Sa anan uapa a dec t e 11 Use of communication mechanism n nunana 12 12 FrameworX built in OPC server its OLE Automation interface 12 Working Models OLE Automation interface 14 Simulator sa 16 Description of the simulator s satu ad qu sas ur ade 16 Code design in Visual Basic e eee ie eri en ER INPS isan 18 Simulation Mam Class a e ee e deti A a aa 19 Compotiellt Classes p etu eoo Rede er ead edits dut 22 Simulation module Siana testet e rs EH 23 Arrangement in FrameworX and Working Model eee 25 Test Model zna au unas 28 Description of thednodel 2552 a n ee ad Be eae ai ae 28 E 31 TPheconirollepua sa E UN 32 Concl stiOlls caecis 35 eedem aste ie ree ated 35 Possible improvements naa EQUES AUN SIR HIR sedate ENTER ARES AN babe bad niue 35 Future s n au testo M usadas o dU Veo iate 36
4. CStr I EMERGENCY DROP FX LW Group ClientHandle SetFX IN LW ARM AT INPUT I FX LW lItems Addltem LW ARM CStr I IN ARM AT INPUT FX LW Group ClientHandle Next End With End Sub 47 8 Module Simulation Connection This module connects every signal that is used between WM3 and the simulator core The name of the object in the WM3 model is used to connect Public CONVEYOR SPEED As New Input Controller Public OUT CONVEYOR END 5 As New Sensor Public WM3 CONVEYOR Package List 4 As String Public WM3 IN LOAD NEW PACKAGE ON CONVEYOR As New Input Controller Public IN SW MOTOR SPEED As New Input Controller Public OUT SW ARM AT INPUT 3 As New Sensor Public OUT SW ARM OUTPUT 3 As New Sensor Public OUT SW EMERGENCY RELEASE 3 As New Sensor Public IN SW HOLD CONTAINER 3 As New Input Controller Public IN LW MOTOR SPEED As New Input Controller Public WM3 OUT LW ARM AT INPUT 10 As New Sensor Public OUT LW ARM AT OUTPUT 10 As New Sensor Public WM3 IN LW HOLD CONTAINER 10 As New Input Controller Sub Setup Sim As Simulation Main Connects all signal and sets them to initial value WM3 CONVEYOR SPEED Init Sim Conveyor Motor 240 WM3 LOAD NEW PACKAGE CONVEYOR Init Sim input 244 WM3 OUT CONVEYOR END 0 Init Sim body 239 body 233 WM3 OUT CONVEYOR END 1 InitSim body 239 body 234 WM3 OUT CONVEYOR END
5. FX IN LW RECEIVER READY 6 Caption IN LW RECEIVER READY 6 Value FX IN LW RECEIVER READY 7 Caption IN LW RECEIVER READY 7 Value FX IN LW RECEIVER READY 8 Caption FX IN LW RECEIVER READY 8 Value 9 2 3 4 5 6 7 8 FX IN LW RECEIVER READY 9 Caption FX IN LW RECEIVER READY 9 Value 39 The sensor which signals if there is a package ready the small wheel FX IN LW CONTAINER READY 0 FX_IN LW CONTAINER READY FX IN LW CONTAINER READY 1 FX IN LW CONTAINER READY FX IN LW CONTAINER READY 2 Caption FX IN LW CONTAINER READY FX IN LW CONTAINER READY 3 Caption IN LW CONTAINER READY FX IN LW CONTAINER READY 4 Caption IN LW CONTAINER READY FX IN LW CONTAINER READY 5 Caption IN LW CONTAINER READY FX IN LW CONTAINER READY 6 Caption IN LW CONTAINER READY FX IN LW CONTAINER READY 7 Caption FX IN LW CONTAINER READY FX IN LW CONTAINER READY 8 Caption IN LW CONTAINER READY FX IN LW CONTAINER READY 9 Caption FX IN LW CONTAINER READY 0 Value 1 Value 2 Value 3 Value 4 Value 5 Value 6 Value 1 Value 8 Value 9 Value pe M MR RED MM tC ODER et The sensor which signals if the arm is in position to grab a package at the large wheel FX IN LW ARM AT INPUT 0 IN LW ARM AT INPUT 0 Value FX IN LW ARM AT INPUT l Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 2 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 3 Caption FX IN
6. SetSim Control Group Groups Add Sim Control Group Sim Control Group UpdateRate 250 Sim Control Group IsActive True Sim Control Group IsSubscribed True SetSim Control Items 2 Sim Control Group OP Cltems SetSim Control 2 Sim Control Items Addltem sCommand Sim Control Group ClientHandle SetPLC Ready 5 Control Items Addltem P LC Ready Main Group ClientHandle Set Main Group 5 Control Group OP Cltems Set Main Control Start Main Group Items Addltem Main Control S witchO utput 0 Main Group ClientHandle Set Main Control Stop Main Group Items Addltem Main Control SwitchO utput 1 Main Group ClientHandle Set Main Control Reset Main Group Items Addltem Main Control S witchOutput 2 Main Group ClientHandle PLC Ready Read 2 While Not PLC Ready Value 1 PLC Ready Read 2 Wend End Sub 20 The most important signal for the simulator is the Command signal in the PLC which allows us to control the simulator by starting stopping and do a single scan in the controller The object corresponding to Command is named Sim_Control in VB There is an other signal in this group PLC_Ready that is used in the beginning to check if the controller is up and running As soon as all five signals are registered the event driven method Sim Control Group DataChange is called when anyone of those signals changes its value So to start the simulation we just have to push the start button in FX Public Sub Sim
7. where we want to pass information between the programs several times during runtime So instead of running each program completely we run them a little bit at a time and in between information are shared So the main idea behind the simulator is that the available time in the computer is divided in small fractions and that each simulation program is running in parallel Between the time periods the third program executes and transfers parameters between the programs Though it is interesting to know how a computer handles several programs at the same time we should not concern us anymore about that Instead we will look how the different programs work together and thereby understand more about the simulation method At first we will look at them as we would like to do in a simulation Let us start with the simulator Before the VB script can be executed we must start WM3 and FX View and load the simulation model into the environment After that we start the VB script and we are then ready to run the simulation from FX View Initialize simulation Setup connections Control simulation WMGD application creates WM3D objects in VB Continue FX Control OPC register variables in OPC Read from OPC Step one frame Read from Run one scan Write to WM3D In WM3d WM3D in FX Control Control simulation Hold Continue Quit End simulation Figure 4 1 The simulator structure 16 When the VB script is started it begins with initialising t
8. 1 Total structure The simulator consists of a soft PLC communication link and a mechanical simulation program The control program resides inside the PLC and it communicates with OPC OLE Automations for Process Control trough an OPC server The soft PLC used is FX Control from FrameworX GE Fanuc and from now on called FX But the simulator is not bound to FX and it can be replaced by any other soft PLC that uses OPC to communicate But FX has an advantage in having a built in OPC server and all communication between FX and the OPC server 15 handled automatically by FX Therefore when referring to FX the OPC server is included FX WM3 Figure 2 1 The model consist of three parts To the left The soft PLC and an OPC server from now on called FX Middle Visual Basic and both API referred as VB To the right Working model 3D shorten toWM3 The communication link consists of two OLE Automation interfaces refereed as API and the simulator core written in Visual Basic hereafter named VB The main task for the communication link is to transfer and translate signals from FX to the mechanical simulation program but it also contains functions such as starting and stopping the simulator Finally it also has a monitoring function which allows us to se how the signals change during a simulation One API is providing VB with an interface to communicate between OPC and VB Through the interface object is created and connected
9. 2 Init Sim body 239 body 235 WM3 OUT CONVEYOR END 3 Init Sim body 239 body 236 WM3 OUT CONVEYOR END 4 Init Sim body 239 body 237 WM3 IN SW MOTOR SPEED InitSim SW Motor 45 WM3 OUT SW ARM AT INPUT 0 Init Sim body 46 body 10 WM3 OUT SW ARM AT INPUT 1 Init Sim body 48 body 10 WM3 OUT SW ARM AT INPUT 2 Init Sim body 50 body 10 WM3 OUT SW ARM AT OUTPUT 0 Init Sim body 59 body 12 WM3 OUT SW ARM AT OUTPUT 1 Init Sim body 61 body 12 WM3 OUT SW ARM AT OUTPUT 2 Init Sim body 63 body 12 WM3 OUT SW EMERGENCY RELEASE 0 Init Sim body 59 body 274 WM3 OUT SW EMERGENCY RELEASE 1 Init Sim body 61 body 274 WM3 OUT SW EMERGENCY RELEASE 2 Init Sim body 63 body 274 48 WM3 IN SW HOLD CONTAINER 0 Init Sim input 246 WM3 IN SW HOLD CONTAINER 1 Init Sim input 248 WM3 IN SW HOLD CONTAINER 2 Init Sim input 250 WM3 IN LW MOTOR SPEED Init Sim LW Motor 47 WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT WM3 OUT LW ARM AT INPUT Init Sim body 80 body 11 Init Sim body 82 body 11 Init Sim body 84 body 11 Init Sim body 86 body 11 Init Sim body 88 body 11 Init Sim body 90 body 11 Init Sim body 9
10. ARM D IN RECEIVER READY SW ARMI 0 S4 SW ARM 0 53 34 c of Off SW ARM 0 53 Off SW ARM DO IN EMERGENCY DROP SW ARM O S4 35 Off Off SW ARM 0 53 ARM 0 OUT HOLD CONTAINER Off Y T Rung 32 through 35 is the ladder code corresponding to the grip arm discussed in chapter 5 3 and described in fig 5 5 as a state diagram Rung 36 through 79 contains the remaining 12 grip arms 55 ARM S IN ARM AT INPUT LW ARM 9 IN CONTAINER READY ARM 9 52 LW ARM 9 S1 80 c j Of LW ARM 8 S1 ARM 9 OUT HOLD CONTAINER Off LW ARM 9 S1 LW ARM SIN ARM AT OUTPUT LWi ARM 8 S4 LW ARM 9 52 81 e LW ARM 9 52 LW_ARMI9 S2 LW_ARMI 9JIN_RECEIVER_READY LW_ARM 9 54 LW_ARMI9 S3 82 4 o Off LW ARM 9 53 LW ARM 9 IN EMERGENCY DROP ARM 9 S4 83 Off Off ARM 9 53 ARM S OUT HOLD CONTAINER Off 84 ACT END Run Machine 85 ACT START Start Machine MOV 86 24 OUT OUT_LW_MOTOR_SPEED 2 lN OUT OUT SW MOTOR SPEED MOV TIN OUT OUT CONVEYOR SPEED 87 ACT END Start Machine 88 ACT START Stop Machine MOV 88 TIN OUT OUT LW MOTOR SPEED 1 lN OUT OUT SW MOTOR SPEED MOV OUT OUT CONVEYOR SPEED 90 ACT END Stop Machine 56 References Reports Nor n Adam 2000 Simulating logical function
11. Control Group DataChange If Main Control Start Then Call OneScan End If If Main Control Restart Then Call Reset End If End Sub Now we have reached the core in the simulator the One Scan method If we compare the code with figure 4 1 we recognise that the four boxes in the middle row corresponds to the five lines in the method The remaining two lines are updating the VB form so every signal can be monitored This is done every time signals are parsed from FX or WM3D Public Sub OneScan Simulation Fx To WM3 Scan Me Call Simulation Veiw Update Frame Frame 1 Doc RunTo Frame Simulation WM3 To FX Scan Me Call Simulation Veiw Update Sim Control Write 8 End Sub OneScan begins with passing all signals from the controller to WM3D Then one frame is executed in WM3D During that time period the VB script is halted and will resume first when WM3D is done Next signals are transferred to the controller and finally one scan are executed in the PLC Now VB is idle and waits for something to happen And as soon the PLC has done one scan the Command will be set to 0 and the Sim Control Group DataChange method is activated and another cycle is started 21 4 2 3 55 5 There two things user of the simulator has to do in VB to be able to run a simulation One of them is creating component classes and the other is connecting them to the simulator When we want to design a new class corresponding to a r
12. I Setint FX OUT LW HOLD CONTAINER I Value Next If Not Hold Conveyor Then Ifload new package on conveyor memory load new package on conveyor Then WM3 IN LOAD NEW PACKAGE ON CONVEYOR Setlnt 1 Else WM3 IN LOAD NEW PACKAGE ON CONVEYOR Setlnt 0 End If load new package on conveyor memory new package on conveyor End If End Sub 50 A10 Module Simulation WM3 FX This module contains the code which transfers signals from WM3 to FX and is called once during every simulation cycle Public conveyor end As Boolean Sub Scan Sim As Simulation Main Copy valus from WM3 to FX conveyor end False Z0To4 conveyor end conveyor end OrWM3 OUT CONVEYOR END I CheckP ower Next FX IN SW CONTAINER READY 0 Write conveyor end FX IN SW CONTAINER READY 1 Write conveyor end FX IN SW CONTAINER READY 2 Write conveyor end FX IN SW ARM AT INPUT 0 Write WM3 OUT SW ARM AT INPUT 0 CheckPower FX IN SW ARM AT INPUT 1 Write WM3 OUT SW ARM AT INPUT 1 CheckPower FX IN SW ARM AT INPUT 2 Write WM3 OUT SW ARM AT INPUT 2 CheckPower FX IN SW ARM AT OUTPUT 0 Write OUT SW ARM OUTPUT 0 CheckPowert FX IN SW ARM AT OUTPUT 1 Write OUT SW ARM AT OUTPUT 1 CheckPowert FX IN SW ARM AT OUTPUT 2 Write OUT SW ARM AT OUTPUT 2 CheckPowert FX IN SW EMERGENCY RELEASE 0 Write WM3 OUT SW EMERGENCY RELEASE 0 CheckP ower FX IN SW EMERGENCY RELEASE 1 Write OUT SW EMERGEN
13. LW ARM AT INPUT FX IN LW ARM AT INPUT 4 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 5 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 6 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 7 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 8 Caption FX IN LW ARM AT INPUT FX IN LW ARM AT INPUT 9 Caption FX IN LW ARM AT INPUT The sensor which signals if the package is in position to be released FX IN LW ARM AT OUTPUT O Caption IN LW ARM AT OUTPUT 0 FX IN LW ARM AT OUTPUT IN LW ARM AT OUTPUT 1 FX IN LW AR M AT OUTPUT 2 Caption FX IN LW AR M AT OUTPUT 2 FX IN LW ARM AT OUTPUT 3 Caption IN LW ARM AT OUTPUT 3 FX IN LW ARM AT OUTPUT 4 Caption FX_IN LW ARM AT OUTPUT 4 FX IN LW ARM AT OUTPUT 5 Caption FX_IN LW ARM AT OUTPUT 5 FX IN LW ARM AT OUTPUT IN LW ARM AT OUTPUT 6 FX IN LW ARM AT OUTPUT IN LW ARM AT OUTPUT 7 FX IN LW ARM AT OUTPUT 8 Caption FX_IN LW ARM AT OUTPUT 8 FX IN LW ARM AT OUTPUT 9 Caption FX_IN LW ARM AT OUTPUT 9 End Sub 40 Value Value Value Value Value Value Value Value Value 1 2 3 4 5 6 7 8 9 Value Value Value Value Value Value Value Value Value Value pas occ ee Mees dic et ee ac Class Simulation_Main This object contains the simulator core When the object Is created the Init method should be called to initialise the simulator Public App As Wm3d A
14. S1 First there needs to be a container in position to be picked up Second the arm needs to be at the right place If both these criteria s are met the container is picked up i e the output signal to the arm is set on and the arm should grab the container Next we wait for a signal that we are in position to deliver the container and that takes us to state 52 Finally we wait for a signal from the receiver which takes us to 53 and then directly back to S4 If something goes wrong there is emergency drop signal that will take us back to S4 and the container is dropped immediately Since the container is transferred between the small and the large wheel these must be synchronised They must have the same lead time and the grip arms must be in correct position for at transfer to occur For that matter there is a subroutine Motor_Setup which will set the wheel in right position This is done by running each motor at a lower speed until they reach a senor When both wheels signals that they are in right position both motors will continue in full speed 34 6 Conclusions 6 1 Result There three major results to point out from this thesis First of course most important is that the idea behind the simulator structure works It was possible to connect these two programs with help of a third tool and let the simulator work in accurate time The real drawback was that it is far from real time simulation Second point is t
15. can retrieve a single value that we can parse along to the controller This is how it is implemented in Simulation WM3 To Public conveyor end As Boolean Sub Scan Sim As Simulation Main conveyor end False Forl 0 To4 conveyor end conveyor end Or WM3 OUT CONVEYOR END I CheckPowert Next FX IN SW CONTAINER READY 0 Write conveyor end We can see that the same naming conventions apply except that is substituted against WM3_ One other major difference is that the object in this case Sensor has methods which is called instead of the set statement Once again it depend on how the component is designed In this case we start by calling the init method which basically connects the object to an object in WM3D The last two modules are called during runtime One of them contains the code that transfers the signal value from FX to WM3 The other module is taking care of the signals in the opposite direction from WM3D to FX They both contain a method named Scan which is called once in each simulation cycle 4 2 5 Arrangement in FrameworX and Working Model In this section we will take a closer look at some special arrangement that must be done in FX and WM3D in order to make the simulator to work First of all we must make sure of that both programs have the same simulation speed i e the frame rate in WM3D and the scan rate in FX This could and should be done from the Sim Objects sim init method However for some unknown r
16. component to the model Of course they have to be connected to the model but we don t have to do any modifications in the simulation core which is one of the goals of the thesis 18 closer look at the components object reveals that they have two types of methods in common initialisations methods and runtime methods The initialisations methods are responsible for connecting registering and settings of a specific component These methods are executed in the beginning of each simulation and may also be called when a simulation is reset The runtime methods are used during a simulation and their task is to read or write signals between FX and WMsBD They are normally called once each scan during the simulation We will discuss these classes in more detail in 4 2 2 4 2 2 Simulation Main class The simulator core consists of one class Simulation Main and four modules The class itself controls and runs the simulation The modules contain all information about all used signals between FX and WM3D The reason we use four modules is that then we don t need to change anything in the class when we are creating a new simulation model Everything that belongs to the model itself is controlled from the four modules The main program in this model is actually very small and simple Most of the simulators functionality lies in the Sim object that is an instance of class Simulatin Main When we start the VB program a form is activated and this form crea
17. have different geometrical and physical properties and they can also have initial speed and acceleration Movements are described by functions and tables and of course the impact the environment consisting of all other bodies There are also some defined objects such as motors springs and pistons that can be used to create more dynamic models Momentum and forces can be applied anywhere and can be used as initial conditions Other greater feature is that it is possible to import models form other CAD tools and convert them into WM3 models se Working Model Motion DemoSimulator1 WM3 Seen through 5 Eile Edit View Insert World Object Tools Window 81x Ose s o o4 6 SQN SB HS kb GDS 9 e ITI DETE e EJ 5 5 DemoSimulator1 E body 46 body body body body body body j body body body body body body f 0 1225 gt coord 5 Ground gt coord 4 on body 1 a E F B QE 1343 s Draws a Restraint Last computed motion frame 2685 Figure 2 3 Screenshot of WM3 Several properties can be controlled during the simulation through inputs It is actually this feature that makes it possible to control the model from an outside source i e a controller WM3 has a very simple script language which mainly consists of the if function mathematical function and some signal generators But together with i
18. is the name of the server started by FX Control The third row in the code below creates an OPC Groups object Each signal in the server must belong to a group The advantage with groups is that you can create an event to each group that will fire as soon as one of the signals in the group changes its value This is a very useful way to notify the client that something has happened among all the signals in a specific group The 12 object OPC_Groups handles all groups created program before we do anything group must be created SetOPC_Server New OPCServer OPC_Server Connect fxControl OP CServer 1 SetOPC Groups Server OPCGroups Set myGroup OPC_Groups Add myGroup After the group two properties are added IsActive and IsSubscribed must be set to true in order to acquire data from the OPC server continuously Before we can register the signals we have another level of object in the OPC server to handle OPCItems is an object that keeps a collection of items together inside a specific group myGroup IsActive True myGroup IsS ubscribed True Set myltems myGroup OP Cltems Set myCommand myltems Addltem Command roup ClientHandle Then finally the signal is added to the OPCItems object Here it is important that the signal name is spelled exactly as in the server i e case sensitive Otherwise a signal is registered in the server but if there is no corresponding signal name in the ser
19. primary information trial and error had to be used a lot during the work When documentation then was available is become easier and the communication was improved quite fast Then it was possible to focus on building a few objects and test model so it became possible to demonstrate the simulator function It finally worked 1 3 1 Results The main goal was to build a complete simulator and that goal was achieved However to build a complete machine part as intended failed But the principles are shown in the small test model and it is only a question of available time to build a more complex test model 1 3 2 Report outline The report is divided into three parts The first part describes briefly the software used and the communication protocols This is done in Chapters 2 and 3 The second part Chapters 4 and 5 deals with simulation methods and test model Finally the last chapter summarises the result of the work To fully understand how this simulation works the reader should have some knowledge about object orientated programming in Visual Basic Those just interested in the simulation method may look directly at Chapter 5 During second part will be some written code among the text This code is taken from final code created in Visual Basic But some details are left out and sometimes there is no real code Just some text notes However the complete code is printed in appendices A2 10 2 Simulation environment 2
20. the wheels never occurs Instead we will be able to see that the IN SW EMERGENCY RELEASE signal works as it should 31 5 3 The controller The control program in the simulation is quite simple and its main purpose is to show that it is possible to control a model in WM3 All development of the controller program is done in FX The program is built in ladder and SFC and the full program can be found in Appendix 11 To be able to understand the simulation better a brief explanation of how it works comes next Foren nt Main_Control SwitchOutput 0 Program_Star Skip_Setup SwitchOutput 0 Skip_Setup SwitchOutput 1 Main Control SwitchOutput 1 Motor Setup Ready Main Control SwitchOutput 1 Main Control SwitchOutput 1 Main Control SwitchOutput 2 Main Control Switch utput 0 Program Start Run Fig 5 4 The controller described in SFC First we have the SFC which shows the different states that the machine can be in There are 5 different states in the chart and almost all transitions are controlled from the main menu in FX View When the controller is started we start in the state named Program Init where the initialisation takes place Before we explain the flow further a few words about how the SFC chart works are in order The dark grey boxes are the different states in the flow Each state has a name and those boxes with rounded corners with the same name as a state mean that the flow will jump to tha
21. to transfer control signals in both directions during one cycle In the model we begin each cycle by reading the current controller value in the OPC server They are then transferred to WM3D which then executes one simulation frame Next we read the out signals from WM3D and write them to the OPC server Finally we execute one scan in the controller The question that should be raised after this is how we can assure that only one scan is executed in the controller and how do we know when it is done The answer is that the controller is equipped with a command option which aloud us to run only on scan in the controller and then freeze it After this scan it also changes a value of one of its internal variables command This variable is accessible throughout the OPC server and connected to a VB variable during connection connection phase When the controller executes VB is idle and is waiting for an event from the OPC server This event is trigged each time the controller changes the value of command To summarise the controller is signalling when one scan is done and VB will continue to execute Actually we have the same problem for WM3D but it is solved much easier and was discussed in 3 3 17 4 2 Code design Visual Basic The simulator consists of several different components but the main functionality lies in the VB script Therefore we will take a closer look at the structure and code in VB The complete code 15 in Appendix A2 1
22. way to do a short cut Finally there is a transition condition Motor Setup ready which isn t controlled from FX View Instead this signals becomes true when Motor Setup is done Now lets get back to the flow As mentioned before there a five states in the machine and all of them have at least one subroutine linked to them To simplify it even further we say that the Initialisation Motor Setup Start Machine and Stop Machine subroutines are so easy that they don t need any further explanation The only thing they do is to change some variables value and this can be seen in the ladder code in Appendix A11 Instead we will concentrate on the Run Machine subroutine In section 5 1 the model was described and there we saw that the machine consists of 13 grippers placed around the wheels When we run the machine each arm has it own piece of ladder code and they all run independently of each other Each piece is encapsulated into an object and the Run Machine therefore consists of 13 objects of the same type Instead of printing the ladder code here lets look at the functionality through an equivalent state diagram shown in fig 5 5 IN ARM AT INPUT andIN CONTAINER READY IN EMERDGENCY DROP IN ARM AT OUTPUT IN EMERDGENCY DROP IN RECEIVER READY STATE OUT HOLD CONTAINER Fig 5 5 An equivalent state diagram over the grip arm 33 There 4 states in the diagram and it starts in 54 There are two requirements to meet to move to
23. 0 As Public FX IN LW RECEIVER READY 10 As OPCItem Public FX IN LW CONTAINER READY 10 As OPCItem Public FX IN LW ARM AT OUTPUT 10 As OPCItem Public IN LW EMERGENCY RELEASE 10 As Public FX IN LW ARM AT INPUT 10 As OPCItem Sub Reset Sim As Simulation Main Resets all signal to initial value FX OUT CONVEYOR SPEED Write 0 FX OUT SW MOTOR SPEED Write 0 Forl Z0To2 FX OUT SW HOLD CONTAINER I Write 0 FX IN SW RECEIVER READY I Write 0 FX IN SW CONTAINER READY I Write 0 FX IN SW ARM AT OUTPUT Write 0 FX IN SW EMERGENCY RELEASE Write 0 FX IN SW ARM AT INPUT I Write 0 Next FX OUT LW MOTOR SPEED Write 0 0709 FX OUT LW HOLD CONTAINER I Write 0 FX IN LW RECEIVER READY I Write 0 FX IN LW CONTAINER READY I Write 0 FX IN LW ARM AT OUTPUT I Write 0 FX IN LW EMERGENCY RELEASE I Write 0 FX IN LW ARM AT INPUT I Write 0 46 Next End Sub Sub Setup Sim As Simulation_Main Connects all signal and sets them to initial value With Sim SetFX Conveyor Group OPC_Groups Add Conveyor SetFX Conveyor Items Conveyor Group OP Cltems SetFX OUT CONVEYOR SPEED Conveyor Items Addltem OUT CONVEYOR SPEED FX Conveyor Group ClientHandle SetFX SW Group Groups Add Small Wheel SetFX SW Items SW Group OPCltems SetFX OUT SW MOTOR SPEED FX_SW_ltems Addltem OUT SW MOTOR SPEED FX SW Group ClientHandle Forl 0702 SetFX OUT SW HOLD CONTAI
24. 0 but some extracts are shown below to make it easier to understand the design and functionality In previous chapters we have talked about objects and how we need to create them to be able to run the simulation But before we can create them they must be designed and programmed in VB We also need to know which objects are needed and how they work together which also be seen in figure 4 2 Form Class Simulation_View Simulation_Main UserForm Activate Init Update Setup Connection Distortion Click OneScan Called Quit Button Click UserForm by FZ CloseSim Sim_Control_Group_DataChange Setup Connection Reset Module Simulation FX Connections Simulation FX To Setup Scan Reset Module Module Simulation WM3 Connections Simulation WM3 To FX Setup Scan All but Init Class Class rm Input Controller Init Init CheckPower Start CheckPulse Hold SetInt Figure 4 2 Form class and module dependency in the simulator In our model we use one class for the simulation core and three classes represent different real components in the machine Of course a machine normally contains more than three components but for now three is sufficient To be able to simulate a more realistic machine more objects need to be designed The design of each such object totally depends on how the object is supposed to work and how accurate the model would be However it is really easy to add a new class i e a new
25. 2 body 11 Init Sim body 94 body 11 Init Sim body 96 body 11 Init Sim body 98 body 11 Mu cr de rr Nae 0 1 2 3 4 5 6 7 8 9 eee yee WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT WM3 OUT LW ARM AT OUTPUT 0 Init Sim body 80 body 275 1 Init Sim body 82 body 275 2 Init Sim body 84 body 275 3 Init Sim body 86 body 275 4 Init Sim body 88 body 275 5 Init Sim body 90 body 275 6 Init Sim body 92 body 275 1 Init Sim body 94 body 275 8 Init Sim body 96 body 275 9 Init Sim body 98 body 275 DE EE oe WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER WM3 IN LW HOLD CONTAINER 0 Init Sim input 251 1 Init Sim input 253 2 Init Sim input 255 3 Init Sim input 257 4 Init Sim input 259 5 Init Sim input 261 6 Init Sim input 263 Sim input 265 8 Init Sim input 267 9 Init Sim input 269
26. 2 ACT END Reset Rung 13 through 20 are identical as rung 12 except for the index 53 23 START Motor_Setup 24 DIN OUT OUT CONVEYOR SPEED 0 LVW_ARM 4 IN_ARM_AT_INPUT LYW_ARM 9 IN_ARM_AT_INPUT LVW_ARM 3 IN_ARM_AT_INPUT LYW_ARM 8 IN_ARM_AT_INPUT LVW_ARM 2 IN_ARM_AT_INPUT LVW_ARM IN_ARM_AT_INPUT LVWW_ARM 1 IN_ARM_AT_INPUT LVW_ARM 6 IN_ARM_AT_INPUT LVW_ARM O0 IN_ARM_AT_INPUT LVV_ARM 5 IN_ARM_AT_INPUT LW_S2 LW 51 25 v vk rt ki YU Of Off Off Off Off Off Off Off Off Off Off Off LW 51 Off LW 1 ARM O IN ARM AT INPUT 52 25 Off Off LY ARM 1 IN ARM AT INPUT ON OUT OUT MOTOR SPEED Off 0 Lw_ARMIS IN_ARM_AT_INPUT Off 952 Off S8 ARM 1 IN ARM AT INPUT SW ARM O0 IN ARM AT INPUT SW ARM 2 IN ARM AT INPUT Sw 52 SW 51 27 Of Off Off Off Sw 81 Off SW 81 SW ARM O0 IN ARM AT INPUT 28 Off Off S ARM 1 IN ARM AT INPUT Off OHN OUT OUT Sw MOTOR SPEED S8 ARM 2 IN ARM AT INPUT Sw 52 Off Sw 82 52 Motor Setup Ready 29 l gt Off Off 30 ACT END Motor Setup 54 31 START Run Machine SY ARM O IN ARM AT INPUT SW ARMID IN CONTAINER READY SW ARM 0 82 Sw ARM O S1 32 Off SW ARM D S1 SW ARM 0 OUT HOLD CONTAINER Off Off SW ARM D S1 SW ARM OLIN ARM AT OUTPUT SW 01 54 SW ARM 0 52 33 I Off SW ARM 0 52 Off SW ARM D S2 SW
27. CODEN LUTEDX TEIE 5160 1 62 2002 The Design of a Simulator for the Automation Industry Jan Olof Sivtoft Department of Industrial Electrical Engineering and Automation Lund University 5 4 2 D T d D ul i E 7 5 5 d IEX LUND INSTITUTE OF TECHNOLOGY 4 Tetra Pak Lund University The design of a simulator for the automation industry Maj 2002 Jan Olof Sivtoft E94 Handledare Tetra Pak Istvan Ulvros Handledare IEA Gustaf Olsson Abstract The development of new technologies forces the industry to develop new products cheaper and faster Every advance has it own opportunity window and if you are too late a lot of money and time are wasted In the automation industry the product development process can last over a year and therefore several project are running side by side but only a few will survive to the end Tetra Pak R amp D in Lund has studied this problem during the past few years and their aim is to find out if there is a possibility to use some kind of simulator instead of expensive test machines This master thesis is one step in that direction and its main goal is to construct as simulation environment consisting a soft PLC and a mechanical visualization program The main problem is how these two programs should communicate during a simulation The PLC will control the model built in the visualization program and react from signals produced from the mode
28. CY RELEASE 1 CheckP ower FX IN SW EMERGENCY RELEASE 2 Write OUT SW EMERGENCY RELEASE 2 CheckP ower SW receiver ready False Forl Z0To9 Sw receiver ready sw receiver ready Or WM3 OUT LW ARM AT INPUT I CheckP ower Next FX IN SW RECEIVER READY 0 Write sw receiver ready FX IN SW RECEIVER READY 1 Write sw receiver ready FX IN SW RECEIVER READY 2 Write sw receiver ready lw container ready False For 0To2 Iw container ready container ready OUT SW ARM AT OUTPUTI J CheckPower And FX OUT SW HOLD CONTAINER Value Next If NotFail Container Ready Then lw container ready False End If 51 ForK 0 T09 FX_IN_LW_CONTAINER_READY K Write lw container ready FX IN LW ARM AT OUTPUT K Write OUT LW ARM AT OUTPUT K CheckP ower FX IN LW EMERGENCY RELEASE K Write 0 FX IN LW ARM AT INPUT K Write OUT LW ARM AT INPUT K CheckPower FX IN LW RECEIVER READY K Write 1 Next End Sub 52 11 Controller ladder code The ladder code for the controller 1 START 2 3 END Off 4 ACT START Initialization 5 8 ACT END Initialization 4llN OUT sCommand 7T ACT START Reset PLC Ready DJIN OUT OUT CONVEYOR SPEED SW ARM 0 DOUT HOLD CONTAINER Off SW ARM 1 OUT HOLD CONTAINER Off SwW_ARM 2 OUT_HOLD_CONTAINER Off LA ARM 0 DOUT HOLD CONTAINER M Off ARM 8 OUT HOLD CONTAINER 21 Off 2
29. Control Group UpdateRate 250 Sim Control Group IsActive True Sim Control Group IsS ubscribed True SetSim Control Items Sim Control Group OPCltems SetSim Control Sim Control Items Addltem Command Sim Control Group ClientHandle SetPLC Ready 5 Control Items Addltem PLC Ready Sim Control Group ClientHandle SetMain Group Items Sim Control Group OP Cltems SetMain Control Start Main Group Items Addltem Main Control S witchOutput 0 Sim Control Group ClientHandle SetMain Control Stop Main Group Items Addltem Main Control S witchOutput 1 Sim Control Group ClientHandle SetMain Control Restart Main Group Items Addltem Main Control S witchO utput 2 Sim Control Group ClientHandle PLC Ready Read 2 While Not PLC Ready Value 1 PLC Ready Read 2 Wend End Sub Public Sub Sim Control Group DataChange ByVal TransactionID As Long ByVal Numltems As Long ClientHandles As Long ItemValues As Variant Qualities As Long TimeStamps As Date II An event which is trigged from fx when one scan is done If Main Control Start Then Call OneScan End If If Main Control Restart Then Call Reset End If End Sub Public Sub CloseSim Close down connections OPC Server Disconnect End Sub 42 4 Class Input Controller A simple discrete controller with two predefined values but also has a method to set any discrete value Private WmObjectlnput As Wm3d Input Public Sub Init Sim As Simulation Main InputOb
30. EED Value FX OUT CONVEYOR SPEED Caption CStr FX OUT CONVEYOR SPEED Value The out signal the griparm FX OUT LW HOLD CONTAINER 0 OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 1 Caption OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 2 Caption FX OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 3 Caption OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 4 OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 5 Caption ZFX OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 6 Caption OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 7 Caption ZFX OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 8 Caption OUT LW HOLD CONTAINER FX OUT LW HOLD CONTAINER 9 Caption OUT LW HOLD CONTAINER Value Value Value Value Value Value Value Value Value Value ond Elle rm Ear Qusa es ee Aes 0 1 2 3 4 5 6 7 8 9 See ROM ON The sensor which signals if there is an arm on the small wheel in position to deliver a package FX_IN_LW_RECEIVER_READY_0 Caption FX_IN_LW_RECEIVER_READY 0 Value FX IN LW RECEIVER READY 1 Caption FX_IN_LW_RECEIVER_READY 1 Value FX IN LW RECEIVER READY 2 Caption FX IN LW RECEIVER READY 2 Value FX IN LW RECEIVER READY 3 Caption FX IN LW RECEIVER READY 3 Value FX IN LW RECEIVER READY 4 Caption IN LW RECEIVER READY 4 Value FX IN LW RECEIVER READY 5 Caption FX IN LW RECEIVER READY 5 Value
31. NER I SW Items Addltem SW ARM CStr I JOUT HOLD CONTAINER FX SW Group ClientHandle SetFX IN SW RECEIVER READY I FX SW lItems Addltem SW ARM 4 CStr I RECEIVER READY FX SW Group ClientHandle SetFX IN SW CONTAINER READY I SW Items Addltem SW ARM CStr I CONTAINER READY FX SW Group ClientHandle SetFX IN SW ARM AT OUTPUT I zFX SW Items Addltem SW ARM 4 CStr I ARM AT OUTPUT FX SW Group ClientHandle SetFX IN SW EMERGENCY RELEASE I FX SW Items Addltem SW ARM CStr I EMERGENCY DROP FX SW Group ClientHandle SetFX IN SW ARM AT INPUT I SW Items Addltem SW ARM CStril ARM AT INPUT FX SW Group ClientHandle Next SetFX LW Group Groups Add Large Wheel SetFX LW Items LW Group OPCltems SetFX OUT LW MOTOR SPEED LW ltems Addltem OUT LW MOTOR SPEED FX LW Group ClientHandle Forl Z0To9 SetFX OUT LW HOLD CONTAINER I LW Items Addltem LW ARM CStr I OUT HOLD CONTAINER FX LW Group ClientHandle SetFX IN LW RECEIVER READY FX LW Items Addltem LW ARM CStr I IN RECEIVER READY FX LW Group ClientHandle SetFX IN LW CONTAINER READY I LW ltems Addltem LW ARM CStr I CONTAINER READY FX LW Group ClientHandle SetFX IN LW ARM AT OUTPUT I LW Items Addltem LW ARM CStr I IN ARM AT OUTPUT FX LW Group ClientHandle SetFX IN LW EMERGENCY RELEASE I FX_LW_ltems Addltem LW_ARM
32. and clients The server is connected to a controller and provides data to the system throughout clients on their request Since the server simply is a program it can run in parallel on the same computer as the controller The clients are data consumers but they can also send information to the server typically trough a HMI to control a process There are two ways a client can get information from the server The easiest but an inefficient way is polling The client asks the server and will receive an answer directly But the client doesn t know when a value has changed so it has to ask repeatedly Another way is to let the server notify the client when a value has changed Then the client can respond by acquiring the value form the server or by reading all values of interest at the moment 3 2 FrameworX built in OPC server and its OLE Automation interface As mentioned earlier FX has a built in OPC server The advantage of this is that every signal defined in the controller is registered in the server directly The only thing VB needs to know is the name of the server and some additional information if they are located on different machines Lets take a closer look how we connect the OPC server from VB Of course the API must be installed and registered in VB before any of the code below will work First an object that will handle the OPC server at the client is created It is then connected to the OPC server named fxControl OPCServer 1 which
33. are of interest but they all work in a similar way so there is no need to go deeper into that Now let s go back to the Doc object In order to control the simulation there is a method RunTo FrameNumber which is very helpful when simulating Upon calling the method the simulation will start and continue until it reaches the frame number During this time VB is halted and will resume first when WM3 is done The frame number is kept by the Doc object so in order to make a good simulation you increase the frame number by one each simulation cycle and the precision in the simulation is mainly determined by the frame rate i e frames per second 14 15 4 Simulator design 4 1 Description of the simulator To begin with we have two industrial programs running on the same computer and using the same resource the CPU A third program is also executing in the same environment and is responsible for synchronising information between the programs When we are simulating we need to calculate how it would be in a real machine and extract information from those calculations and pass the information between the two programs If we knew from the beginning what we want to do and have all the inputs ready then it would be best to run and complete the first program The information could them be passed to the second program and after it is completed we would have the result of the simulation But this is not sufficient for simulations in the automation industry
34. at the beginning of the conveyor and is transported along the line until it reaches the end of the conveyor Here we need some kind of sensor 1 telling the controller that a package is ready for the small wheel The wheels are running at continually speed so we need a second sensor 2 to tell when the grip arms are in position to pick up the package When the controller receives the signal it responds with a signal to the grip arm to grab the package Actually it is the grip arm that sends a signal when it has reached the sensor and this is how the controller knows which grip arm should grab the package The package then moves along the small wheel until it reaches the transfer point to the large wheel Here the controller receives another signal 3 which means that the package is in position to be released to the large wheel In the same way the large wheel has a sensor 4 at each grip arm The controller then responds with one signal to the grip arm at each wheel so the transfer of the package could be complete Now the package will move almost 28 one turn at large wheel before the grip arm receives a signal 5 to release the package and it will disappear 29 Figure 5 2 A closer look over the sensors placement In a perfect machine there wouldn t be any problem with delays or lost signals Or the wheels would always be synchronised But what happens if a signal is lost In a real machine there could very well be some proble
35. between FX and VB signals controlling the simulation come from FX and are transferred to mechanical simulation except from a few simulator signals The other API is providing VB with an interface to the mechanical simulation program Through these interface signals is collected from the mechanical model and transferred to FX Of course the interface also provides the model with signals sent from FX Finally the mechanical simulation program is built to visualise the machine movements This simulator is using Working Model 3D Motion from MSC Working Knowledge This program will be referred to as WM3 from now on WM3 has a large number of possibilities to build advanced models but our model is very simple and its main purpose is to show the idea behind the simulator 2 2 Components mentioned previous sections totally six components simulator They be divided into three parts according to fig 2 1 The part consist of and OPC server as shown in the left box in the figure Below in this chapter there 15 an overview of FX and the server is discussed in chapter 3 The VB part or the core of the simulator consists of all written code in VB Both API are imported and used in the code so they are treated as a one in VB The middle box contains both API and VB Both API will be described a bit further in chapter three and below a very brief overview to VB The third part con
36. c Engineers Object Linking and Embedding OLE for Process Control Programmable Logic Controller Sequential Flow Chart Visual Basic Working Model 3D 37 2 Form Simulation_View This form contains the monitor and is also the starting application in Visual Basic When the form is activated the simulation core is started Each time here is a transport of value the Update method is called Beside the quit button which ends the application there is a distortion button that removes a signal to simulate a failure Public Sim As New Simulation_Main Private Main_Control As Boolean Private Sub Distortion Click Toggles distortions Sim Interference Distortion Value End Sub Private Sub Quit Button Click Ends application Sim CloseS im SetSim Nothing End Sub Private Sub UserForm Activate Executed on activation Sim Init Sim Setup Connections Sim Sim Control Write 8 End Sub Public Sub Update Updates monitor values 1 The sensor at the conveyors end IN CONVEYOR END Caption conveyor_end The out signal the griparm FX OUT SW HOLD CONTAINER 0 ZFX OUT SW HOLD CONTAINER 0 Value FX OUT SW HOLD CONTAINER 1 Caption ZFX OUT SW HOLD CONTAINER 1 Value FX OUT SW HOLD CONTAINER 2 Caption FX OUT SW HOLD CONTAINER 2 Value The sensor which signals if there is a package ready on the conveyor FX IN SW CONTAINER READY 0 ZFX IN SW CONTAINER READY 0 Value FX IN SW CONTAINER READY 1 Captio
37. d Tove who has been supporting me all along this work 1 Introduction 1 1 Why building software simulator In the automation industry it usually takes a long time to develop new machines There are many steps in a development cycle that all costs a lot of money If the development time could be shortened the costs would be reduced Far from every machine design idea leads to a complete machine If an idea could be rejected earlier it would save unnecessary development costs In at least one stage during the development cycle it is necessary to build a test machine This test machine is expensive and without any doubt there must be corrections made of this machine several times due to incomplete design If the number of errors could be reduced before starting using the real machine it will reduce the development time spare parts and of course the costs So there are several reasons why a research and development department would like to build a simulator instead of a real machine in the early stages of a development cycle In a simulator we can build a model of the machine and we can test it without breaking anything It is much easier to do changes in the simulator than in the real machine By using a simulator the control program could be tested several times long before it is first tested on the real machine we see there are many reasons to build a simulator It helps to shorten development time reduce cost due to errors and
38. e developments When we have a stable and functional simulation core there are several possible expanding tools to consider Below there is a list with several different tools with a brief explanation They are not ordered in any particular way Graphical construction tool This would make the simulator much more user friendly and easier to build the model and understand the simulation Libraries with objects Each new object constructed in the simulator should be added in the library structure in order to build up a powerful toolbox Report generator If we want to run longer simulations we must have a tool that can summarize the simulation Finally a quick look in the systems performance monitor at the particular computer we used reveals that it is WM3 that consumes around 75 of the CPU capacity during a simulation So in order to have a good simulator WM3 must be improved quite a bit One way could be to use two computers and separate WM3 from the rest But this is a hardware issue and as mention before changing the hardware can increase the simulation speed enormous 36 1 CAD CPU DCOM FX GUI HMI IEEE OLE OPC PLC SFC VB WM3 Nomenclature Application Programming Interface Computer Aided Design Central Processing Unit Distributed Component Object Model FX Control Graphical User Interface Human Machine Interface Input Output Institution of Electrical and Electroni
39. eal component there are several things to look at First of all we want the object to act as a real one but on the other hand it must be reasonably easy to use Depending of the type of simulation there is a trade off between accuracy and speed If we want better performance of the object it usually takes more time to calculate the simulated parameters of the component and vice verse However in our model we already has a program WM3D taking care of the mechanical simulation What we have to do is extracting information from the model in WM3D and translate it to useful signals in FX control Some properties are easy to gain others take some calculations to obtain Fortunately the API to WM3D gives us several ways to extract information which isn t supported by the internal script language in WM3D Exploring all possibilities using script and API together would probably give us quite good objects but that is not one of the main goals of this thesis Therefore only three components are modelled and in a quick and dirty fashion way The most important has been to show that a controller can control WM3D during runtime There are three classes each one representing one type of component in the simulation model These are Sensor Arm and InputController They all have one method init in common This method is called during Set up and is responsible for connecting a VB variable to WM3D During the simulation each component has its own methods dep
40. eason this hasn t been implemented in the simulator and instead it has been done manually It should be quite easy to implement and in a full working simulator this must be done If we look at it in the quick and dirty way we begin with setting the scan rate variable It should be set to a value no less than 50 ms even if the PLC is capable of handling scan rates down to 10 ms Instead the limit is based on WM3D capacity and therefore 50 ms are recommended as a minimum value In the model have chosen 250 ms to avoid a slow simulation Scan rate in FX corresponds to frame rate in WM3D but instead of assigning the time interval between each scan we assign the number of calculated frames per second A scan rate of 50 ms corresponds to a frame rate of 20 frames per second Even if it quite easy to calculate this value it should be done during the execution of sim init to avoid any miss configuration 25 Besides actually building model WM3D we do some settings to improve simulator speed One way is to remove unnecessary calculations among some graphical objects For example we can turn off collision detection for those objects that can never be in contact with each other There are several other possibilities to improve the simulation but then one really has to know how WM3D works in detail to take advantage of those methods In FX or more precisely in the controller there is one signal in the program that belongs to the simu
41. ending on its functionality Next we will discuss each component in brief Sensor component A sensor can be one many different types optic heat pressure etc Depending of the model different sensors will be implemented The sensor modulated in our model is a contact sensor which gives a true value when something is in contact with the sensor otherwise false There are 34 sensor objects that together act as 28 sensors in the model The idea behind each sensor is when two objects are in contact with each other a signal should be set to true Now how do we detect this If we look at WM3D one way would be to calculate the distance between specific points in each object When the distance is smaller than a certain value the objects are in contact with each other If the objects are symmetrical it would in general be fairly easy to make the detection But if they were not we would have to a bit more complex algorithm which would take some CPU time to execute and thereby slowing the simulation down and also increase the time to build the model Instead of doing all this by ourselves we use a method for body objects in the API for WM3D This method IsInterfering reveals if two specific objects are in contact In WM3D the sensor consists of one single body The size and position of the body depends on the specific model Unfortunately this method has two bodies as input parameters and therefore we must test every pair of bodies that are of intere
42. hat if both programs would have used the same communication system 1 OPC we would have had a much simpler and better core Instead of a lot of connection modules we could connect the signals directly to each other and the core should only contain the timing mechanism and the monitor But this is something the industry can work by pushing the software manufacturers to supply them with better tools Originally WM3 wasn t designed to handle external signals during simulation and therefore there was no need for the manufacturer to integrate any common communication interface like OPC but now there is a reason Third point is about designing the model and core code as efficient as possible Even if we will get faster computers they cannot make up for everything We need to think carefully how the logic should be structured in the simulator and how the code can be optimised independently of where it is located i e in the core or in Working Model If the script language in WM3 would have been a bit more powerful we could have smoother calculations and the core wouldn t have to do anything else besides controlling the flow Then we may ask ourselves if WM3 is the best program for this purpose 6 2 Possible improvements Besides changing the hardware which can improve the simulation speed there are a few things to do to the simulator in general First all signals are hard coded into the four VB modules which takes some time and is incon
43. it to a signal in the OPC server This is done in the same way as we introduced the PLC_Ready signal earlier All signals are declared as Public and there is a naming convention which states that every object related to the OPC server should begin with If it is a signal all the following letters are written in upper case otherwise they are written in lower cases but the first letter in each word is still in upper case If it were an input to the OPC server the letters IN will be added to the object name and of course the name of an output object would be FX OUT When Set up is called the signal is registered in the OPC Server and ready to be used In the code it would look something like this Public FX Test Group As OPCGroup Public FX Test Items As 0P Cltems Public FX IN TESTSIGNAL As OPCltem Sub Setup Sim As Simulation Main SetFX Test Group Sim OPC_Groups Add Test_ Group Name SetFX Test Items FX Test Group OPCltems SetFX IN TESTSIGNAL FX Test Items Addltem OPC SIGNAL FX Test Group ClientHandle End Sub It is important to notice that the OPC SIGNAL NAME must be written exactly i e case sensitive as in the controller Otherwise it will not be found in the server The other method reset is much simpler because the only task it has is to reset the value to the initial values of the component The other module Simulation WM3 Connections is a bit more complicated Of course we have to declare the ob
44. ject but we also might have to declare some extra variables to support depending how the component is designed One example is when we use the sensor component Besides the sensor object we need a variable to store the result of an OR function between a group of sensor The reason behind this is the implementation of the sensor As discussed in the previous section the ChechPower function works between two bodies If we want a sensor to react upon more bodies we must test each pair An other way to deal with this could be done with an alternative implementation of the Sensor component Instead of one trigger body we could have entered several bodies but the work of the computer would remain the same Let s see how the sensor placed at the end of the conveyor is modulated First a look at Simulation WM3 Connection Public WM3 OUT CONVEYOR END 5 As New Sensor Sub Setup Sim As Simulation Main WM3 OUT CONVEYOR ENDY 0 Init Sim body 239 body 233 WM3 OUT CONVEYOR END 1 Init Sim body 239 body 234 WM3 OUT CONVEYOR END 2 Init Sim body 239 body 235 WM3 OUT CONVEYOR END 3 Init Sim body 239 body 236 WM3 OUT CONVEYOR END 4 Init Sim body 239 body 237 24 each container body 233 237 acting as sensor will react upon contact with body 239 with is the real sensor But we want the sensor the give us a signal when any of the containers are in contact with the sensor So by using the OR function we
45. jectName As String Initialise the object Set CollectionOflnputs Sim CollectionOflnputs Set WmObjectinput CollectionOflnputs Item InputO bjectN ame WmoObjectinput InputValue 0 End Sub Public Sub Start Sets the controller to one WmoObjectinput InputValue 1 Sub Public Sub Hold reset value to zero WmoObjectinput InputValue 0 End Sub Public Sub Setlnt x Sets any diskrete value WmoObjectinput InputValue x End Sub 43 5 Class Arm A simpler two level switch that uses reversed logic Private WmObjectlnput As Wmdd Input Public IsActive As Boolean Public Sub Init Sim As Simulation Main WmObjectName As String Initialse the object Set WmObjectinput Sim CollectionOflnputs Item WmO bjectName WmoObjectinput InputValue 1 IsActive False Sub Public Sub Drop switch off WmoObjectinput InputValue 1 IsActive False End Sub Public Sub Grip Turn the switch on WmoObjectinput InputValue 0 IsActive True End Sub 44 6 Class Sensor A simple sensor which gives a signal if two object is interfering with each other Private SensorObjectBody As Wm3d Boay Private TriggerObjectBody As Wm3d Body Private CollectionOfBodies As Bodies Private SensorMemory As Boolean Public Sub Init Sim As Simulation_Main SensorObjectName As String TriggerObjectName As String II Initialise the object Set CollectionOfBodies Sim CollectionOfB odies Set SensorO bjec
46. l Therefore a simulation core has been designed and one possible solution to the communication problem is explained The core is developed in Visual Basic and a test model is a common part taken from any ordinary filling machine Finally the controller program is designed in ladder code Contents 1 1 1 2 1 3 1 31 1 3 2 2 1 2 2 2 2 1 2 2 2 22 3 3 1 3 2 3 3 4 1 4 2 4 2 2 4 23 4 2 4 4 2 5 5 1 5 2 5 3 6 1 6 2 6 3 Al A2 A3 A4 A5 6 7 8 9 10 Preface eRe BAR a REIS SY PEGE M AS RR OE EC t EE Ae 3 Introd ction oio oce ett b ERR P S epe OS aie 5 Why building software simulator cin tds ORI NEED RU QUE 5 OF the thesits RD me Dini DU 5 Limitationsand methods Na a SSS aaa Sup 0 ua E 6 Results aaa to SL QA E m as 6 Report o tline vsa 6 Simulation ERI HAN RR UNS dud 8 ebrei ua EFRON EN S REOR USER 8 EITM TS His sabes Sas em ama pa u awa Dama E E A od E 9 sas nent te asi 9 Working
47. lator The signal PLC_Ready was described in section 4 2 1 and its main purpose it to tell VB that the controller is up and running and ready to start There will be a closer look at this in chapter 5 when the ladder code is examined in more detail 26 27 5 Test Model 5 1 Description of the model In the previous chapters we have focused on the simulator but we also need something to simulate For that reason a simple test model the machine has been designed fig 5 1 The main purpose 15 to show how the signals from FX can control the machine in WM3D and of course the other way around In brief the machine consists of two wheels one conveyor and a number of grip arm stations symmetric placed around the wheels edge This could very well be a part taken from a filling machine form the packaging industry There is one small wheel with 3 arms and a larger wheel with 10 arms Figure 5 1 A simple graphical overview over the test model A package is first transported on the conveyor and then picked up by a grip arm on the small wheel After three quarter of a turn it is released to the larger wheel which controls the package for almost one turn before the grip arm drops the package and it disappears The conveyor and the small wheel act as a synchronisation module to the large wheel which will fill and close the package If we look at one package and describe what the machine is supposed to do we have the following A package arrives
48. m bodies and to set new values to inputs Lets take a closer look how we acquire a reference to a specific body object The first step is to get references to every body form the Doc object Then we must know the name of the body in WM3 Here are two possibilities first we can use WM3 predefined name fore each body which is body index where index corresponds to the order the bodies where created in WM3 Second we can give each object in WM3 a name and use that name to find it from VB Set CollectionOfBodies Doc Bodies Set myBody CollectionO fBodies Item myName In the code above myBody now contains a reference to a specific object named myName in WM3 There is no need to go into each detail of each property but a body object has 4 methods and 6 properties Two of these methods are GetConfig and SetConfig which can be used to change the three dimensional configuration of the body object However one of the properties is of great importance to the simulator This is the IsInterferingWith property that returns true or false if the body is interfering with any other body i e this property alone acts as a sensor Unfortunately this property requires a name of an other body to check if they are interfering This means that one has to loop through every body of interest before one knows the answer But the great benefit is that there is no need to calculate any geometry to reveal the answer Besides bodies there are motors inputs and outputs that
49. ms between the two grip arms attached to the two wheels The controller program will not release the package from the small wheel if the signal from the receiving grip arm is lost Instead it will keep the package and continue What will happen then The package will continue and eventually crash into the waiting package on the conveyor Of course this is not acceptable Instead a sensor 6 a bit further on the turn will sense the package and an emergency drop will be performed To test this during simulation there is a button in the monitor window which removes a signal from the controller so the package will continue In same way the grip arm on the large wheel would sense that there is no package in the grip and the controller program should prevent any filling or other activities round the large wheel when there is no package in place In the model there is no action around the large wheel so the controller program doesn t bother about that but there is a release sensor 5 just before the grip arm is going to get new package from the small wheel 30 5 2 monitor watch the simulation there is a simple monitoring tool It was the last thing implemented in the simulator and in a quick and dirty way However it fulfills its purpose even if it could be improved a lot As we can se in fig 5 2 there is a window placed besides the FX view so we can se all signal changes but still be able to control the simulator The monitor is
50. n ZFX IN SW CONTAINER READY 1 Value FX IN SW CONTAINER READY 2 Caption ZFX IN SW CONTAINER READY 2 Value The sensor which signals if the arm is in position to grab a package at the small wheel FX IN SW ARM AT INPUT 0 ZFX IN SW ARM AT INPUT 0 Value FX IN SW ARM AT INPUT 1 Caption ZFX IN SW ARM AT INPUT 1 Value FX IN SW ARM AT INPUT 2 Caption FX IN SW ARM AT INPUT 2 Value 38 The sensor which signals if the package is in position to be released to the large wheel FX IN SW ARM AT OUTPUT O Caption SW ARM AT OUTPUT 0 Value FX IN SW ARM AT OUTPUT 1 Caption IN SW ARM AT OUTPUT 1 Value FX IN SW ARM AT OUTPUT 2 Caption FX IN SW ARM AT OUTPUT 2 Value 1 The sensor which signals if there is an arm on the large wheel in position to receive a package FX IN SW RECEIVER READY O Caption ZFX IN SW RECEIVER READY 0 Value FX IN SW RECEIVER READY 1 Caption ZFX IN SW RECEIVER READY 1 Value FX IN SW RECEIVER READY 2 Caption ZFX IN SW RECEIVER READY 2 Value 1 The sensor which signals if the package isn t released in a normal way FX IN SW EMERGENCY RELEASE 0 IN SW EMERGENCY RELEASE 0 Value FX IN SW EMERGENCY RELEASE 1 Caption IN SW EMERGENCY RELEASE 1 Value FX IN SW EMERGENCY RELEASE 2 Caption FX SW EMERGENCY RELEASE 2 Value Motor and conveyor speed controls FX OUT SW MOTOR SPEED Caption 2CSt FX OUT SW MOTOR SPEED Value FX OUT LW MOTOR SPEED Caption CSt FX OUT LW MOTOR SP
51. nputs it is quite simple to control properties during the simulation of the model 10 It is also possible to collect information from the model or as we see it signals that be sent to the controller This is done by using an output that is an object that calculates a value during each frame using information from the model properties together with the script language Here the signal generator functions that can extend a signals duration are especially helpful But even if outputs give us a way to get a certain information from the model they are not used in the simulator The reason is that it is easier to directly use the API and acquire the information from the model Visualisation of the model is very powerful It is possible to look at the model from anywhere and zooming down to small details When a simulation is performed it remains in the memory until a new simulation is done or if it is deleted Rerunning the simulation will increase the visualisation speed and it can be done from any angle and zooming Finally it is possible to export a simulation as a video clip that can be shown in other tools However one major feature is missing in WM3 which was a part of is predecessor Working Model 2D Instead of giving a value to the side of a cube and the let other bodies refer to that side it must be set to a numerical value This makes it very time consuming to edit fundamental body values in a model and the whole model must be revisi
52. ns textboxes and lists and so on in order to communicate with the program Besides this there are several APIs that can be added to the VB environment that can be used to create objects to control other applications without implementing that object We just create an instance of the object and it is ready to use 11 3 Use of communication mechanism 3 1 What is OPC OPC stands for OLE for Process Control and it is a standard protocol to transmit data and I O signals between programs running within the Windows environment OPC is built upon two of Microsoft s technologies OLE and DCOM and it s also designed and optimised for industrial applications It is developed by a non profit organisation the OPC Foundation which provides free specifications for developers The main reason behind OPC was to create a protocol which allows different automation applications to work together independent of any manufacture specifications There are many benefits both for consumers and manufactures The consumers are no longer limited to one manufacturer and the system they provide The consumer can freely change the controller and choose one that suits his needs without changing the whole system The manufacturers only have to provide one communication interface and therefore their development process will be shortened Thus they can concentrate on the application and compete with their products in a larger market OPC uses the concept of servers
53. ore should not have to be changed when a new object is added 1 3 Limitations and methods The simulator was limited to two programs available in the commercial market one being the controller and the other the simulation of the machine The two programs are FrameworX from GE Fanuc which is soft PLC and Working Model 3D Motion from MSC Working Knowledge WM3 which is a mechanical motion simulation software As the work went along it turned out to be difficult to establish communication between the programs The main reason of this was that in the early stages in my work FrameworX was only available in a beta version without proper manuals Especially the OLE Automations for Process Control OPC documentation was missing which made it very difficult to connect the two programs together Another problem was that the final version of Working Model 3D was delivered very late during the limited thesis working time Therefore the work had to be focused on the minor problems and there were no time left in the end to build a complete machine simulator as intended The thesis is limited to establish communication between the programs control the data flow between them and build a small demonstration model to show how the simulator is supposed to work In the beginning of the work time had to be spent to learn and understand the basics around FrameworX and Working Model 3D Internet was used to find information about OPC Missing lot of
54. ports A 141 gt For Help press F1 405 LOCAL Stop Machine B amp Logging Groups OPC Client PLC Access Drivers 5 amp SFCI 4 Iff Cinnlamaental Files Stan fy DemoSimulatort Fra S Working Model Motion U 2 Exploring C Snap32 MAB 00 35 Figure 2 2 Screenshot of FX control In the very early stage of the thesis the graphical tool was explored to reveal if it could be used as a visualisation tool of the machine But then the model would only consist of a schematic model and most important only in two dimensions Also add some advanced algebra to solve all mechanical properties and it would be a thesis of it own Actually there two different programs that can be executed FX control FX view The differences between them are that FX control contains the development environment and FX View consists only of the HMI and the executing controller It is said before that there is a built in OPC server to FX actually there are two of them one each to FX control and FX view Every time any of those programs is started the corresponding OPC server is also started 2 2 2 Working Model 3D WM3 is a 3 dimensional simulation program for mechanical models in motion It s a pure simulator tool where the model of the real machine is simulated The model is build by many different bodies and constraints with different degrees of freedom Each body can
55. pplication Public Doc As Wm3d Document Public CollectionOfBodies As Bodies Public CollectionOflnputs As Inputs Public Frame As Integer Public OPC Server As OPCServer Public OPC Groups As OPCGroups Public WithEvents Sim Control Group As OPCGroup Public Sim Control Items As OPCltems Public Sim Control As Public Main Control Start As OPCltem Public Main Control Stop As Public Main Control Restart As OPCItem Public PLC Ready As Public Sub Setup Connections Handles initial signals connections Simulation WM3 Connections Setup Me Simulation FX Connections Setup Me Simulation FX Connections Reset Me End Sub Public Sub Reset Resets the simulation Simulation FX Connections Reset Me Frame 0 Doc GoTo 0 Doc RunTo 1 Doc EraseHistory End Sub Public Sub OneScan Performs one simulation cycle Simulation Fx To WM3 Scan Me Call Simulation Veiw Update Frame Frame 1 Doc RunTo Frame Simulation WM3 To FX Scan Me Call Simulation Veiw Update Sim Control Write 8 End Sub 41 Public Sub Init Initialise the simulation core Set App GetObject WM3D Application Set Doc App ActiveDocument Doc Reset App Activate Set CollectionOfBodies Doc Bodies Set CollectionO flnputs Doc Inputs Set OPC_Server New OPCServer OPC_Server Connect fxControl OP CServer 1 Set OPC Groups Server OP CGroups SetSim Control Group Groups Add Sim Control Group Sim
56. s in a filling machine master thesis at Tetra Pak R amp D AB and Dept of Industrial Electrical Engineering and Automation Lund University Books Olsson Gustaf and Gianguido Piani 1998 Computer Systems for Automation and Control Prentice Hall New Jersey USA Olsson Gustaf 2002 Industrial Automation A system approach Department of Industrial Electrical Engineering and Automation Lund Institute of Technology Sweden Manuals OPC Foundation 1999 OPC Data Access Automation Specification version 2 02 Working Model 3D Automation Programming Guide MSC Working Model User manual version 5 0 FrameworX Beta 3 Package Online manual Internet resources http www gefanuc com totalcontrol products oas frameworx_home frameworx_home html http www opcfoundation org http www workingmodel com 57
57. sists only of WM3 that also will be discussed later in this chapter 2 2 4 FrameworX FX FX is a soft PLC which integrates development and execution of a controller It also provides a graphical tool to build a HMI that can monitor the process The program supports tools such as Ladder and SFC according to IEEE 1131 It also has a tool chest where many predefined objects are stored Most of them has a graphical interface and can be used when building a HMI 1 5 1 FrameworX Target Ladder Program File Edit Search View Insert Data Controller Tools Window Help 8 x xx Program Description double click to edit a xi Targetl m Alarm G B H A Advanced Math TR Coni I O Divers 1 START 5 6 AlenBradey RID Factory Web e 39 a i Graphical Panels 8 asic AA Bit Shift Rotate B Bitwise Logic H A 8 Hone PLC Ready amp C Col Tools 2 H Comparison Ladder_Program Off t Contacts Labels Conversion Subroutines a Copy S A Actions 3 END ff Counters Initialization a DeviceNet Motor_Setup Increment Decrement Reset 4 ACT START Initialization E e InterBus S Run_Machine H A Process Control H A Program Flow H A Sequencer MOV H E Timers OUT Command 0 x Logged in with no server ERROR Auditing is disabled Tei Build Import Se Re
58. spare parts and makes it easier to do changes and so on But why don t we do this every time we want to build a machine One answer to that question is that there is no software available designed for this purpose So in this thesis I will try to design a simple simulator out of known software and make it work 1 2 Goals of the thesis The main goal was to make a simulator and to simulate a part taken from a filling machine The simulator must handle signals both ways between itself and a controller The simulator must also contain some kind of visualisation and this is done by some software supplied with graphical tools This means that the visualiser must allow to be controlled from outside and be able to send signals back when some certain criteria are met To achieve this there were a few other minor problems that had to be solved first Programs use different ways of communication with other programs Therefore a communication link between them must be designed The programs can t work together in real time since they are located on the same computer The time must be divided between them and this must be controlled in some way An object must be constructed to simulate different parts of a real machine How these objects are designed depends on several things but the most important thing is that we must be able to reuse all objects and that there must not be any limitations to add new objects to the model In other words the simulation c
59. st If any pair is true the sensor should be set to true otherwise false But this method is much easier to use than calculate the distance 22 The sensor object has three methods init and CheckPower CheckPulse difference between the last two ones is that CheckPulse only is set to true during the first executed frame when the two objects are in contact CheckPower remains true during the whole time while the objects are in contact The init method is used during connection and contains the sensor body and the trigger body During the simulation CheckPower and CheckPulse are called every time signals are parsed from WM3D to FX Input Controller component The Input Controller component is a simple object It passes an integer value to an input object in WMGD that could be used in many ways I our model an input controls the speed of a motor The motor has three levels 0 2 that mean stop half and full speed To set the value a method setInt is implemented and the value from is parsed to the input object Besides this method Input Controller has three more init start and hold Start and Hold actually sets the value 1 and O Init is used during setup and it has one parameter a WM3D input object Arm component Finally the Arm component which basically is the same as an Input Controller but it only has two levels So it is fair to say that it is more like a binary controller and that properly would be a better name But it
60. t state The remaining light grey boxes have a link to a yellow box which contain the name of those actions or subroutines that are executed when we are in a certain state Before each name there is a letter N or P The label P means that the subroutine is executed only at the first scan after it enters a state This is useful for initialisations of variables The N label means that the subroutines are executed 32 every scan until it leaves the state Each subroutine is written in ladder and these are found in Appendix Between states there is a condition to fulfil before a transition is made In this flow a transition takes place when the variables value is true or if it is an integer greater than zero In the chart we can se that there are three variables which control the transitions in the chart Main_Control is an object in FX View that controls the simulation status The user of the simulator can start stop and reset the simulator from FX view This corresponds to three Boolean attributes to Main Control where SwitchOutput 0 is the start button and SwitchOutput 1 is the stop button and finally SwitchOutput 2 is the reset button A second object in FX View Skip set up is controlling weather we should skip the initialisation sequence Motor Setup when running the test model The actual reason for this control is that it takes several seconds to go though this sequence and to save some time during every test this was an easy
61. tB ody CollectionOfBodies ltem S ensorO bjectName Set TriggerO bjectBody CollectionO fBodies Item TriggerO bjectN ame End Sub Public Function CheckP ower Checks if the two object are interfering CheckSensor SensorObjectBody IsInterferingW ith TriggerO bjectB ody True CheckP ower CheckSensor End Function Public Function CheckP ulse Checks only for the first scan they interfere CheckSensor SensorObjectBody IsInterferingW ith T riggerO bjectB ody True TempMemory CheckS ensor CheckSensor Not SensorMemory And CheckS ensor SensorMemory TempMemory CheckPulse CheckSensor End Function 45 A7 Module Simulation FX Connection This module connects every signal that is used between FX and the simulator core The names in the OPC server are case sensitive Public FX Conveyor Group As OPCGroup Public FX Conveyor Items As OPCItems Public FX OUT CONVEYOR SPEED As Public FX SW Group As OPCGroup Public FX SW Items As OPCltems Public FX OUT SW MOTOR SPEED As Public FX OUT SW HOLD CONTAINER 3 As Public IN SW RECEIVER READY 3 As Public IN SW CONTAINER READY 3 As OPCItem Public FX IN SW ARM AT OUTPUT 3 As OPCitem Public FX IN SW EMERGENCY RELEASE 3 As OPCItem Public FX IN SW ARM AT INPUT 3 As Public EX LW Group As New OPCGroup Public FX LW Items As OPCItems Public FX OUT LW MOTOR SPEED As OPCltem Public OUT LW HOLD CONTAINER 1
62. ted The same problem occurs when objects are placed in the model Fore example if two objects should be three radiuses apart it would be very helpful to use the first objects reference point and then add three radiuses for the second one One other thing to understand is that WM3 is not currently powerful enough to perform real time simulation even if it is working stand alone Of course this is also a hardware issue and therefore there are a great possibilities to improve performance in the future 2 2 3 Visual Basic VB The simulator core is written in Microsoft Visual Basic 6 as a part of Microsoft Excel tool The core serves as a glue between WM3 and FX taking care of timing issues and signal handling but also has a simple monitor window where the user can follow the signal flow between FX and WM3 VB is an object orientated language with 15 focused on the user and his interaction with the program In an application it is the user who controls the flow by actions throw the GUI normally by the mouse or keyboard VB contains classes which has methods and properties that can perform operations and set attributes in the object VB works with three components class modules classes modules and forms Each class contains information about an object and its methods and properties The modules contain a set of procedures that should be executed each time they are called Finally the forms represent the visible part in VB We can create butto
63. tes the Sim object It also throws an event that executes the UserForm Activate method Private Sub UserForm Activate Sim Init Sim Sim Setup Connections Sim Sim Control W rite 8 End Sub The Sim object must first be initiated i e create all object used by the simulator such as the OPC server object WM3D application object and connect main control signals Next all signals used by the model must be attended This means that every signal defined in the Simulation FX Connections and Simulation WM3 Connections modules are created initiated and registered Finally signal is sent to the PLC which to run one scan Besides this the form is drawn on the screen The form is monitoring all signals connected between FX During each cycle every signal is updated and this is a very helpful tool when we want to study the simulators behaviour The buttons to control the model are created in FX but they are also connected to the Sim object through the OPC Server The buttons Start Stop and Reset controls the PLC and the program that lies inside Each one of these buttons is throwing an event when they are pushed causing VB to start stop or restart the simulation As mentioned above Sim is the core of the simulator and therefore we will take a closer look at is Sim Init method There are five main tasks for Sim Init to do First import and create an object App that corresponds to the WM3D model WM3D must be running and the acti
64. uses reversed logic which means that set is zero instead of one and vice verse Besides init it has two other methods named Grip zero and Drop one which makes it easier to use the component because one does not have to bother about the reversed logic 4 2 4 Simulation modules Besides the main class we have four modules that are strongly connected and works together with the main class Two of them Simulation Connections and Simulation Connections handle the initialisations of the signals and they are called once in each simulation The other two Simulation Fx To and Simulation To Fx are called once each scan during runtime and transfer the signals between the programs They all have in common that the builder of the simulation model must edit these modules For each signal or group of signals depending on design in the simulation model the builder must program the four modules according to their use The Connections modules contain two methods connection and reset Set up is called when Sim Setup Connection is called in the beginning of the simulator execution Connection is responsible for connecting a signal between FX and WM3D This means create an object corresponding to a signal in the OPC server and register it And of course create an object corresponding to a component in WM3D and initiate it 23 If we start looking at Simulation_FX_Connections the builder must declare the object and connect
65. ve document 15 the simulation model which is reset 19 Public Sub Init Set App GetObject WM3D Application Set Doc App ActiveDocument Doc Reset App Activate After that an object OPC Server as discussed in chapter 3 2 is created that will handle the OPC server Set OPC Server New OPCServer Server Connect IxControl O P CServer 1 SetOPC Groups Server OP CGroups Third a number of signals are registered in the OPC server that will handle the start and stop of the simulation For this reason a group Sim Control Group is added to the OPC groups object It is also a good idea to set some properties for the group Most important are the IsActive and IsSubscribed properties as mentioned in 3 2 A third property UpdateRate is also set This controls the rate at which an event from the group may be fired This rate should match the general frame rate for the simulator Next we create an OPCItems to hold the individual signals within the group Since we only have five signals we could manage with one group but I have chosen to create two groups One contains the PLC control buttons i e start stop and restart signals and the other one contains simulator signals After this is done we are ready to register the items or signals to the OPC server So by adding them to the Main Group Items object we create a VB object at the same time The only requirement is the name of the corresponding signal in FX control
66. venient It should at least be reduced to one module Instead each object should have some more method that takes care of all initialisation and connection in a more automatic way The core should be replaced by stand alone program perhaps written in Java or C This should provide a faster transmission between FX WM3 One problem here is that there is no API for C or Java available but since there is a VB API it shouldn t be any problem to generate one for C We could also improve the simulation of failure by adding a property to each signal This property could contain the fail rate of the signal The rate could determine how often a signal change would be lost or randomly changed 35 There some overall simulation properties like frame rate scan rate that should be controlled from the simulation main instead of changing them separately inside FX and WM3 A great improvement would be a connection tool where we could map signals from FX to WM3 and vice verse There is some kind of support for this through the VB API between OPC and VB but between the VB and WM3 it must be implemented from scratch To achieve this in a simple way all logic that is performed in VB to support WM3 should be moved to WM3 The drawback here is that WM3 script language is limited as mentioned in 2 2 2 but newer versions might provide better functions and a deeper insight into what can be done with the script may overcome this 6 3 Futur
67. ver no error is reported Now we can use the signal in our program and we can read and write to the signal Writing to the signal is simple We use the method write and the value is written to the OPC server Of course a value must be of correct type i e Boolean integer char but otherwise it s easy myCommand Write set Value myCommand Read k k myCommand Value Reading a value is done in two steps When the read method is called it collects the value from the OPC server and stores it in the object in a property named value After that the value is accessed by calling the property The value will remain the same until the read method is called again 13 3 3 Working Models Automation interface In this section we will take a closer look at WM3 and the API we are using to communicate between WM3 Before we can read or write to WM3 we must create an object in VB so we can accesses its properties Following code does this Set App GetObject WM3D Application Set Doc App ActiveDocument The App object contains a reference to the WMG program and the Doc object contains a reference to the model in WM3 The Doc object is our link to the model and through this we can access almost everything in the model We can control the whole simulation or the colour of any body in the model But to do this we must create a link to each specific object we want to control In the simulator we are most interested to get values fro
68. wo objects which is the WM3D application and the other is the OPC server in FX These object are necessary because they contain the simulation variables that must be transferred between the programs to make the simulation work The WM3D application object contains the whole model and every object can be manipulated from the VB script However most of the manipulation is done during the second stage set up connections before the actual simulation begins During simulation the only external changes in the model are changing colours at some objects i e turning their visibility on or off But to be able to read some values from the applications object we must create a corresponding object in VB Of course we must send control signals inputs to the simulation but those signals should not be treated as a part of the model If we look at the OPC Server we have a similar problem But instead of creating a corresponding object in VB we only have to register a variable in the OPC Server and connect it to the corresponding variable in the controller So before the actual simulation can start we must initialise all objects and register all variables that we need for the simulator to work This is also done in the VB script in two separate modules which are executed in the set up connection phase Now we are ready to run the simulation Each cycle in the simulator consists of one scan in the controller and one frame calculation in WM3D We also have
69. written in VB and is updated each time signals are transferred in any direction A minor error in the monitor is that there is a mix of Booleans and integers but they really mean the same false means zero and true means one As mentioned earlier signals labelled OUT_ is signals from FX and signals labelled IN_ are signals to FX or as it says in the monitor from WM3 SW means the small wheel and LW the large wheel There are three arms on the small wheel implying that there are three columns after the signals name and ten arms around the large wheel fxView Runtime Simulation Signals from FX Control Insert Project Name H 9 OUT_SW_MOTOR_SPEED OUT_LW_MOTOR_SPEED OUT CONVEYOR SPEED 1 Home OUT SW HOLD CONTAINER 110 OUT LW HOLD CONTAINER 0001100000 2 z Signals from Working Model CONVEYOR END True IM Sw CONTAIMER READY True True True IN Sw ARM AT INPLIT False False False IN SW ARM AT OUTPUT False False False 1 IN_SW_RECEIVER_READY False False False IN SW EMERGENCY RELEASE False False False IN LW CONTAINER READY 0000000000 Distortion ARM AT INPUT FFFFFFFFFFale LW ARM AT OUTPUT FFFFFFITFFFale IN LW RECEIVER READY 1111111111 IN LW EMERGENCY RELEASE 0000000000 Fig 5 3 FX view and the monitor side by side Besides monitoring all signals we can also put in some failure in the simulation When active we are overriding the IN LW CONTAINER READY signal and the transfer between

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