Define max and min of tunable parameters using SYSTUNE in Simulink

I'm trying to optimize the gain K of my Simulink model using Systune, which looks like the model below. I precise that I'm using the r2013b version of Matlab/Simulink. My problem is to define the max and min values of K reachable in the optimization process.

For the moment, after initializing the value of K, I've tried this :

    st0 = slTunable('model','K');
    K = getBlockParam(st0,'K');
    K.Gain.Maximum = K_max;
    K.Gain.Minimum = K_min;

Then I've defined some soft and hard requirements and then I call the systune function.

    [st1,fsoft,gHard,Info] = systune(st0,req_soft,req_hard);

It is compiling but after verifying the optimized value of K, it does not respect my bounds K_man and K_min. Indeed, when we type :

    st0.getBlockParam('K').Gain.Maximum
    st0.getBlockParam('K').Gain.Minimum

we obtain +Inf and -Inf, respectively, which are the default values...

I tried also simply to type

   st0.getBlockParam('Ks').Gain.Maximum = K_max;

But this returns the error "No public field getBlockParam exists for class slTunable."

I saw that it is done pretty easy when using Systune in Matlab only thks to the ltiblock.gain class but when we want to interface with Simulink, things are getting harder due to the slTunable class.

Thank you for your help !

Answer 1

[Stakis93]

Found my answer ! To access the properties of the ltiblock (in my example it is a ltiblock.gain), as maximum and minimum reachable values, you have to create an ltiblock parameterized as you need and then use the setBlockParam function. This could be done like this for my example :

    st0 = slTunable('model','K'); % Definition of the interface between Simulink and Matlab for Systune
    K_wanted = ltiblock.gain('K',Ny,Nu); % Def of a tunable gain with Ny outputs and Nu inputs
    K_wanted.Gain.Maximum = K_max;
    K_wanted.Gain.Minimum = K_min;
    st0.setBlockParam('K',K_wanted);

This last lign changes the default parameterization of K into the parameterization defined by the ltiblock.gain K_wanted which contains the bounds. We can verify that with :

    st0.getBlockParam('K').Gain.Maximum 
    % or
    st1.getBlockParam('K').Gain.Minimum

It is not really a straightforward solution but at least it works !