Continuously Update MATLAB Variable and Use in Simulink

I was trying to use Simulink Desktop Real-Time in order to implement a real-time communication simulation with ModBus Protocol, where I send data (a request) from qModMaster (a tool, which imitates Master PC) to MATLAB using tcpserver. Then I instantly assign the data to a variable {var_name} and use the variable in Simulink in combination with Real-Time Sync Block. However, when a simulation starts, it takes the initial value of the {var_name}, and when I send another data(request), the {var_name} updates in the base workspace, but not in the Simulation. Is there any solution without using C/C++ S-Functions?

Answer 1

[Jan Houska]

Hi Leon,

please do set_param(gcs, 'SimulationCommand', 'update') after you change the value of the variable in the base workspace. This should update the model with new values of any workspace variables.

Good Luck, Jan

Answer 2

[Suchitra]

Hello Leon,

I understand that you want to update the workspace variables during a simulink simulation and have the new values used while the simulation is running.

There are several ways to achieve it, depending on your use case:

1. Saving and restoring the simulation state as the 'SimState':

The Simulink 'SimState' feature allows you to save all run-time data necessary for restoring the simulation state of a model. A SimState includes both the logged and internal state of every block (e.g., continuous states, discrete states, work vectors, zero-crossing states) and the internal state of the Simulink engine (e.g., the data of the ODE solver).

https://www.mathworks.com/support/search.html/answers/1736-saving-loading-the-simstate-programmatically.html?fq[]=asset_type_name:answer&fq[]=category:simulink/simulink-environment-customization&page=1

2. Tunable Block Parameters:

Simulink lets you change the values of many block parameters during simulation. Such parameters are called tunable parameters. You can tell whether a particular parameter is tunable by examining its edit control in the block's dialog box or Model Explorer during simulation. You can also tune a parameter at the MATLAB command line, using either the set_param command or by assigning a new value to the MATLAB workspace variable that specifies the parameter's value.

Refer to the following documentation link to learn more about usage of 'Tunable Parameters':

https://www.mathworks.com/help/sldrt/ug/tune-block-parameters-and-matlab-variables.html

3. Simulink.Parameter:

This class enables you to create workspace objects that you can then use as the values of block parameters, (for example, the value of the Gain parameter of a Gain block). You can create a Simulink.Parameter object in the base MATLAB workspace or a model workspace.

Refer to the following documentation link to learn more about 'Simulink.Parameter':

https://www.mathworks.com/help/simulink/slref/simulink.parameter.html

If a block parameter needs to be evaluated (and changed if needed) at every simulation time step, a programmatic way of stepping through the simulation is to use the following command in a loop:

set_param(modelName, 'SimulationCommand', 'step');

4. You can also employ event listeners to make parameter modifications only when certain events happened. Below is an example:

http://blogs.mathworks.com/simulink/2013/01/25/accessing-block-data-during-a-simulation/

I think this should resolve the issue you are facing. If doing the above does not help prevent the issue, please contact Technical Support

MathWorks Support information is available here:

https://www.mathworks.com/support/contact_us.html