This document describes how to generate a dynamic link library (DLL) using Simulink Coder (formerly Real-Time Workshop) and link it with MotionSolve to run a co-simulation.

Pre-requisites:

Check for supported versions of MATLAB and MSVS here:

Supported Versions - Third Party Software in the XML Format Reference Guide.

This example uses MATLAB R2011b with MSVS 2010.

Step 1: Prepare the MotionSolve Model

The MotionSolve model is set up to communicate with an external solver by using the modeling statements Control_PlantInput and Control_PlantOutput:

 

 <Control_PlantInput

    id                  = "30100100"

    num_element         = "2"

    variable_id_list    = "30100400, 30100500"

    sampling_period     = "0.01"

    offset_time         = "0.0"

    label               = "for controller 1"

    usrsub_param_string = "USER(987654321)"

    usrsub_dll_name     = "rtw_BusSuspension2PMIMODiscrete"

    usrsub_fnc_name     = "PINSUB"

    hold_order             = "2"

 />

 <Control_PlantOutput

    id                  = "30100200"

    num_element         = "2"

    variable_id_list    = "30100200, 30100300"

    sampling_period     = "0.01"

    offset_time         = "0.0"

    label               = "for controller 1"

    usrsub_param_string = "USER(987654321)"

    usrsub_dll_name     = "rtw_BusSuspension2PMIMODiscrete"

    usrsub_fnc_name     = "POUTSUB"

    hold_order             = "2"

 />

 <Control_PlantInput

    id                  = "30100300"

    num_element         = "2"

    variable_id_list    = "30100800, 30100900"

    sampling_period     = "0.01"

    offset_time         = "0.0"

    label               = "for controller 2"

    usrsub_param_string = "USER(987654321)"

    usrsub_dll_name     = "rtw_BusSuspension2PMIMODiscrete"

    usrsub_fnc_name     = "PINSUB"

    hold_order             = "2"

 />

 <Control_PlantOutput

    id                  = "30100400"

    num_element         = "2"

    variable_id_list    = "30100600, 30100700"

    sampling_period     = "0.01"

    offset_time         = "0.0"

    label               = "for controller 2"

    usrsub_param_string = "USER(987654321)"

    usrsub_dll_name     = "rtw_BusSuspension2PMIMODiscrete"

    usrsub_fnc_name     = "POUTSUB"

    hold_order             = "2"

 />

The key attributes of Control_PlantInput and Control_PlantOutput needed to link a Simulink Coder DLL are listed below.

In this case, this MotionSolve model has been prepared for you.  Copy the MotionSolve and Simulink models, rtw_BusSuspension2PMIMODiscrete.xml and rtw_BusSuspension2PMIMODiscrete.mdl, located in the motionsolve\cosimulation folder to your <working directory>.

Step 2: Preparing the Simulink Model – Generating Code

Before starting with the simulation, the Simulink model needs to be created and prepared to work with MotionSolve. After generating the contents of the Simulink model, MotionSolve requires the Simulink components Inport and Outport, which represent the interface to the MotionSolve model.  For example, like the following (blocks labeled below as In1, In2, Out1, Out2):

The order of these Inport's and Outport's must match the order of the Control_PlantOutput’s and Control_PlantInput's, respectively, in the MotionSolve model.

Simulink Coder does not allow using a variable-step integrator for the Generic Real-Time target that is required by MotionSolve to generate this code (more details on selecting the Generic Real-Time target later in this tutorial).  So, under the Solver option on the left, choose the Fixed-step solver, as shown below:

You should see messages that look similar to those below and end with:

### Successful completion of Real-Time Workshop build procedure for model: rtw_BusSuspension2PMIMODiscrete

…or similar.

Step 3: Modifying, Compiling and Linking the Code to Create the DLL

At this point, Simulink Coder has generated source code for the Simulink model, but this must be modified and recompiled to generate the DLL required by MotionSolve.  In the next steps, you will use a script to automatically compile and link this code and generate the Simulink Coder DLL that will be used in the MotionSolve model.

“ms_rtw_pre <mdl_name> <altair_root> <msvs_root> <win32|win64>”

where,

<mdl_name> is the name of the Simulink model (without the extension .mdl)

<altair_root> is the complete path to the root folder of the HyperWorks installation

<msvs_root> is the complete path to the root folder of the MSVS installation

<win32|win64> specify win32 or win64 depending on the required platform of the DLL

Notes:

set PATH = <MS_bin_path>;%PATH%

where <MS_bin_path> is the path to the MotionSolve binaries; for example, “C:\Program Files\Altair\13.0\hwsolvers\motionsolve\bin\win64”

An example of the above command for this model is:

ms_rtw_pre rtw_BusSuspension2PMIMODiscrete "C:\Program Files\Altair\13.0" "C:\Program Files (x86)\Microsoft Visual Studio 10.0" "win64"

Issuing the above command does the following:

You can confirm that this process has completed successfully by looking at the output in the command window.  On successful execution, you should see something like the following:

========== Build: 1 succeeded, 0 failed, 0 up-to-date, 0 skipped ==========

       1 file(s) copied.

** RTW dll is ready **

Step 4: Run a MotionSolve Model with The Generated DLL

At this point, you simply need to point MotionSolve to the Simulink library to complete the co-simulation.  By default, it assumes that it is in the same directory as the MotionSolve model.

The simulation should run quickly and you should review your results to confirm that the process worked as expected.

Appendix A

This section discusses the access functions CoSimAPI_SimulinkRTW_Update_U(api,model,input) and CoSimAPI_SimulinkRTW_Update_Y(api,model,output). These are added to the Simulink model source code in order to help perform the co-simulation via the DLL.

CoSimAPI_SimulinkRTW_Update_U(void *api, const RT_MODEL_x x_M, ExternalInputs_x &x_U)

This method updates the input data structure in the Simulink Coder generated code with the output from MotionSolve.

The first argument requests a pointer to the API ID.  The API ID is passed from the model XML in the line usrsub_param_string = "USER(987654320)".  The first parameter in the USER() string is always the ID of the API.  The MotionSolve API provides the method void * CoSimAPI_Get_API_Ptr(int api_id) to get the API pointer, where the api_id is the number specified in the XML file in the USER() string.

The second argument requests data structure x_M related to the generated Simulink Coder model information where ‘x’ is the name of the model.  The x_M data structure is inherent to the Simulink code.

The last argument requests input x_U where x_U is the data structure used by the Simulink Coder code to store the external inputs (see Appendix B).

CoSimAPI_SimulinkRTW_Update_Y(void *api, const RT_MODEL_x x_M, const ExternalOutputs_x x_y)

This method updates the input for the MotionSolve solver with output from the RTW generated code.

The first and second arguments are the same as described in the previous section.

The last argument requests RTW output x_Y which is deposited to MotionSolve for that current time step, where x_Y is the data structure used by the Simulink Coder code to store the external outputs (see Appendix B).

Appendix B

This section describes the data structure that Simulink Coder generated code uses for representing the external input/output ports.  In the following lines, the name of the model is assumed to be rtw_MS (rtw  = Real Time Workshop, former name of Simulink Coder).

Typically, the Simulink Coder generated code (SCGC) uses the following notations:

So for example, for a model with two Control_PlantInput (CPI) elements where the first has three channels and the second has two channels, the corresponding data structure in Simulink Coder code would be:

CPI #1: rtw_MS_U.In1[0], rtw_MS_U.In1[1] and rtw_MS_U.In1[2]

CPI #2: rtw_MS_U.In2[0] and rtw_MS_U.In2[1]

The same scheme is applicable for the data structure that handles Control_PlantOutput ports.

For example, if you name the first input to be myIn instead of In1, you need to make the following change to that function template:

   double *u_ptr = (double *)&u.myIn;

to replace the original code:

   double *u_ptr = (double *)&u.In1;