Modelica modbus communication

Question

I need to create a hardware-in-the-loop test setup. I will be using Modelica (Dymola) to do a real time simulation of a system. Dymola should send/receive data to/from some hardware and where the received data will be input to the model. I am trying to communicate with Modbus over a serial connection. The hardware is a PLC-like device so this seems like the preferred method.

I do not have the hardware yet, so I am testing with an Arduino Uno. I have installed a Modbus-slave library from here on the Arduino, and tested it with it with an Modbus tester.

I cannot figure out how to communicate with Dymola. I have tried the Modelica_DeviceDrivers library and was able to send or receive (not both together) data from the arduino but not by the Modbus protocol. My question is if there is any modelica library for modbus communication or any other way to accomplish this from Dymola/modelica?

score 1 · Answer 1 · answered Jun 28 '15 at 21:36

1

The free ModelPlug library will connect SystemModeler (and potentially Dymola too) to an Arduino board for I/O. You can download it here: http://www.wolfram.com/system-modeler/libraries/model-plug/

answered Jun 28 '15 at 21:36

jrhodin

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I have actually tried with the ModelPlug library, but it doesnt seem to work with Dymola. – Martin Frølich Olesen Jun 29 '15 at 06:47
Furthermore, my main issue is about the ModBus communication in Dymola. The Arduino is just for testing. – Martin Frølich Olesen Jun 29 '15 at 06:49
You could also export an FMU from SystemModeler that has the communication with the Arduino (via the ModelPlug library) and then use that FMU in the other tool. – jrhodin Jul 01 '15 at 16:14

score 1 · Answer 2 · answered Jun 29 '15 at 20:28

If you want to write your own drivers, you could go to the Resources\Include folder under Modleica_Device_Drivers library, there is a bunch of c header files, and they are very good examples of how to write your own driver. If you can write it in the way that it could be compatible with Modleica_Device_Drivers "package", then it will be quite easy to assemble/disassemble your data messages.

If you just want something quick, you can write a C function and reference it in Dymola.

Both methods may require when(sample(...)) clauses in order to sync your sim time with real time. But this means event generation, tho it is a time event, but for big models with a lot of states, it may slow down your simulation.

I would prefer to create several inputs and outputs around the model, then export the Dymola model as a C or FMU model, I'll write another communication program to control the data flow.

I haven't thought about using a FMU, but it sounds like the way to go. I have no C-coding experience, so I would prefer Python. Can I do real time simulation with PyFMI? Or is that a totally new question:-) — Martin Frølich Olesen, Jun 30 '15 at 20:04

Modelica modbus communication

2 Answers2