Why does my 'SimulationInput' object not have any effect on my simulation results?

I am using the Simulink.SimulationInput class to define simulation parameters for multiple simulations. I am using the following lines of code:

simIn = Simulink.SimulationInput(model);

simIn.setModelParameter('SaveTime','on','TimeSaveName','tout');
simIn.setModelParameter('SaveState','on','StateSaveName','xout');
simIn.setModelParameter('SaveOutput','on','OutputSaveName','yout');
simIn.setBlockParameter('model/Proportional Gain', 'Value', '-9.4');

simOut = sim(simIn);

I can tell that none of these parameters are changed when I simulate the model. I expect that the gain value of -9.4 will cause the system to become unstable. However, the plot of the system response is exactly the same as that of the default model. What step am I missing to be able to use the 'SimulationInput' object for running multiple simulations?

 

Answer 1

[MathWorks Support Team]

The SimulationInput object methods must be reassigned to the object itself after being called e.g. 'simIn =' should appear on the left-hand side of the call to 'simIn.setModelParameter' as in this documentation page:

https://www.mathworks.com/help/releases/R2019b/simulink/slref/simulink.simulationinput-class.html#d117e455657

 

Otherwise, the resulting SimulationInput object will be returned to 'ans' in the workspace and executing the 'sim' command on the originally created object will run the model without any changes.

The correct way to use the methods for the SimulationInput object for your example is shown below:

simIn = Simulink.SimulationInput(model);

simIn = simIn.setModelParameter('SaveTime','on','TimeSaveName','tout');
simIn = simIn.setModelParameter('SaveState','on','StateSaveName','xout');
simIn = simIn.setModelParameter('SaveOutput','on','OutputSaveName','yout');
simIn = simIn.setBlockParameter('model/Proportional Gain', 'Value', '-9.4');

simOut = sim(simIn);