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Problem using lsqnonlin with a simulink model

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Raffaele
Raffaele 2023-5-13
评论： Raffaele 2023-5-13
Hello, I'm trying to use an lsqnonlin optimization with a simulink model: the simulink model requires as input the variables "sigma_1" and "Km_1", which are the parameters that I want to optimize. since the error function is obtained from the output of the model I inserted all in the function err_fun. The code I used is the following:
p = lsqnonlin(@(p) err_fun(p, acq_data),p0, lb, ub, options);
function err = err_fun(p, acq_data)
sigma_1 = p(1);
Km_1 = p(2);
duration = 0.14;
sim('Simulink_model',[0,duration]);
S_model = spostamento.signals.values;
err = S_model - acq_data;
end
This code gives me an error, which I am almost sure is related to the fact that sigma_1 and Km_1 result undefined for the simulink model. The errore is the following:
Error using Launcher>err_fun (line 83)
Error due to multiple causes.
Error in Launcher>@(p)err_fun(p,acq_data)
Error in lsqnonlin (line 206)
initVals.F = feval(funfcn{3},xCurrent,varargin{:});
Error in Launcher (line 76)
p = lsqnonlin(@(p) err_fun(p, acq_data),p0, lb, ub, options);
Caused by:
Error using Launcher>err_fun (line 83)
Error evaluating parameter 'stiff_up' in 'VESevo_sim_V1/Translational Hard Stop1'
Error using Launcher>err_fun (line 83)
Undefined function or variable 'Km_1'.
Error using Launcher>err_fun (line 83)
Variable 'Km_1' has been deleted from base workspace.
Suggested Actions:
• Undo the deletion. - Fix
• Load a file into base workspace. - Fix
• Create a new variable. - Fix
Error using Launcher>err_fun (line 83)
Error evaluating parameter 'D_up' in 'VESevo_sim_V1/Translational Hard Stop1'
Error using Launcher>err_fun (line 83)
Undefined function or variable 'sigma_1'.
Error using Launcher>err_fun (line 83)
Variable 'sigma_1' has been deleted from base workspace.
Suggested Actions:
• Undo the deletion. - Fix
• Load a file into base workspace. - Fix
• Create a new variable. - Fix
Failure in initial objective function evaluation. LSQNONLIN cannot continue.
I don't understand why the two parameters results undefined since this method of using a function to calculate the error and give the function as input to the lsqnonlin, works in other context without a simulink model.
Do you know how to solve this problem? Is it right that the errorrs are caused by sigma_1 and Km_1? Maybe with a simulink model this is not the right way to use lsqnonlin?
Thank you!

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采纳的回答

Torsten
Torsten 2023-5-13
移动：Torsten 2023-5-13
  3 个评论
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Torsten
Torsten 2023-5-13
I have no experience with Simulink, but input of parameters seems to work via
in = in.setVariable('Kp',pid(1),'Workspace',mdl);
in = in.setVariable('Ki',pid(2),'Workspace',mdl);
in = in.setVariable('Kd',pid(3),'Workspace',mdl);
doesn't it ?
So it seems natural to set
in = in.setVariable('sigma_1',p(1),'Workspace',mdl);
in = in.setVariable('Km_1',p(2),'Workspace',mdl);
in your case.
Raffaele
Raffaele 2023-5-13
Yes, sorry this is my first time using simulink. It actually worked. Thank you!

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