Update S-function Parameters in Fast Restart

I have read the Mathworks documentation carefully and tried to find a solution on forums as well. However, I have not been able to find a solution to my problem yet.

I am using Matlab/Simulink to simulate the dynamics of a vehicle, which picks up an object during operation. The way I am planning to do this is to:

• Simulate the motions of the vehicle by itself at the start of the simulation;
• Stop the simulation, save the final state, update the model parameters (so that they now represent the vehicle and the object)
• Initialize the simulation again starting from the end time of the previous run and using the previous final state as input state to the new simulation.To do this, I have been using the options FastRestart, SaveFinalState, SaveCompleteFinalSimState and update. Unluckily, the simulation runs seamlessly, but the model parameters are not updated.

The dynamics of the vehicle and vehicle+body are modelled by the same C-coded S-function. This function receives the parameters of the dynamic equations (e.g. inertia, damping, etc.) as parameters to the S-function block. I think this is the main problem with my approach: even though I run the update command, the S-function does not recognize the update of the parameters in the workspace. Do I need to recompile it? I guess that is not feasible under Fast Restart mode, is it?

Any advice is really appreciated! Thank you!

Answer 1

[Meeshawn Marathe]

Try this exercise with a simple model ('vdp') first:

The following piece of code helps you automate the process of saving the last state (let's say xFinal) and using it as the initial state for the second run of your simulation:

vdp          % Opens the Van-der-Pol Oscillat0r Demo

set_param('vdp','SaveFinalState','on') % Saves the final states of the model

set_param('vdp','FinalStateName','xFinal')% Gives a name to the final states

sim('vdp')% Simulates the model

xFinal% Displays the value in Command Window for reference

set_param('vdp','SaveFinalState','off')% To prevent overwriting of xFinal for sake of comparison

set_param('vdp','LoadInitialState','on')% Set this on to load the initial state

set_param('vdp','InitialState','xFinal')% Load the initial state from the final state of the previuos simulation

set_param('vdp','SaveState','on','StateSaveName','xout')% Save states for all the time values

sim('vdp')% simulate 2nd time

xout(1,:)% Check for the initial state which equals the final state from previous simulation

If this works, try the same for your model. Comment back if this does not work.