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How to customize a Built-in PID Block?

Asked by Mike on 3 Oct 2012

I am using a PID controller in a feedback system. I need to change the gain's multiplication type from element-wise to the matrix. I right clicked on the PID block then from link options, I disabled the link. Now after I looked under the mask, I could change the Gain's multiplication type. but after I save the model and run the simulation again everything goes back to its initial settings like I never applied any change! So my question is How can I customize the PID block in SIMULINK?

2 Comments

Ryan G on 8 Oct 2012

Since you are doing matrix multiplication are you implying that this will have more than 1 input to the PID?

Mike on 8 Oct 2012

Yes, i have 6 inputs. 3 of them are positions and others are velocities.

i uploaded my model so you can take a look inside it easier. http://fs1.filegir.com/pamadour/model.zip run Main.m it will execute the model automatically. first the model should run without any errors because i am using my own PID block (blue block). then you can substitute this with the MATLAB's built-in block (it exists unattached above the model), although i have set all initial fcn's but still it doesn't work. please note that the PID gains are P, I and D which come from the workspace.

Mike

3 Answers

Answer by Arkadiy Turevskiy on 8 Oct 2012
Edited by Arkadiy Turevskiy on 8 Oct 2012
Accepted answer

Hello Mike,

At the moment, you won't be able to customize the standard PID block and still retain the automatic tuning functionality. The best workaround I can suggest is creating your own block for implementation, and using the standard block for tuning. Once the gain are tuned using the standard block, you can use them in your customized block. You could probably somewhat automate the process by using block callbacks and variants.

Arkadiy

2 Comments

Mike on 8 Oct 2012

Dear Arkadiy

Thanks for your answer but how can i use Standard block for tuning while using it causes errors in my system?

Standard blocks use element-wise multiplication which cause to dimension error. if the multiplication type is matrix no error will occur. you can look at my system here: http://fs1.filegir.com/pamadour/model.zip

Arkadiy Turevskiy on 19 Oct 2012

Hello Mike, PID Controller block in Simulink, as well as the PID Tuner, only work on SISO systems. For a MIMO system, you need to specify your controller as a set of SISO PID loops. PID Tuner would not be able to tune a multi-loop design, you will need to use tools from Robust Control Toolbox, like shown in this example.

Arkadiy

Arkadiy Turevskiy
Answer by Azzi Abdelmalek on 4 Oct 2012
Edited by Azzi Abdelmalek on 4 Oct 2012

I see your problem, but you can change these setting by code, just after loading your model named 'model.mdl'

set_param('model/PID Controller/Proportional Gain','Multiplication','Matrix(K*u)')

or you can associate this code with your model:

right click on your model- properties-callbacks-init Fcn (copy and paste the code)

10 Comments

Mike on 6 Oct 2012

Ok, thank you.

Azzi Abdelmalek on 6 Oct 2012

I think the setting vanishes just when the simultion start, not after like I said. I suggest to Edit mask of your PID block then unmask it. when you start simulations other errors will occur, asking about:

  • output/param (min/max). set them to []
  • datatype(etc...) set them to double

save the target of this link

http://azzimalikcom.ipage.com/model_main2.mdl

Mike on 7 Oct 2012

Thanks, but it is like the controller which I made by my own. I can't use PID Tuner in this case.

Azzi Abdelmalek
Answer by Babak on 3 Oct 2012

You don't want to edit Simulink's Built in blocks.

Instead you want to create your own custom blocks. You could do it with creating an S-function block and creating a mask for it or making a MATLAB based block which runs an m-file.

1 Comment

Mike on 3 Oct 2012

Dear Babak

I can create a simple PID controller in Simulink. but the Matlab's built-in PID block has advanced features Like "Tune" which helps me to select the proper Gain coefficients by visualizing the overshoot, settling time.. etc.

that's why i need to find a way to customize the Simulink's built-in PID block.

Babak

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