How to correct the error "Error in default port dimensions function of S-function 'X'. This function does not fully set the dimensions of output port x" under Simulink?

Question

Amin Moradi 2019-1-3

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回答： yohan diaz 2022-3-7

Hi

I'm a master's student and i'm studying electrical engineering - control systems.

I've been assigned (by my Supervisor professor) to simulate a feedback linearization control method so I chose a paper (attached below) and I made a simulink model for it. The problem is when I try to run the simulation, it gives the error:

Error in default port dimensions function of S-function 'FeedbackLinearization/Controller'. This function does not fully set the dimensions of output port 2

So i turned on the signal dimensions display to check for signal dimensions and check whether i've made an error or not. I see a problem for the 'e' signal. It should be a 3*1 vector that indicates error for tracking x-y-z. As you can see, output of the mux the dimension is 3 so everything is ok. the problem is when the signal reaches a block (MATLAB function or derivative) its dimension reduces down to one. I have attached my slx model so you please be kind and take a look.

I've checked both Controller Matlab func and Plant Matlab func and they are working fine.

Please help me. This is so vital for me! Thank you for your time, and consideration!

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JAMES OKELLO 2020-5-5

编辑：JAMES OKELLO 2020-5-5

Please debug the controller "fcn" separetly. Simulink could not compile the "fcn" and consequently could not determine with certainity the port widths. This should be able to solve your problem.

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Answer 1

Mark McBroom 2019-1-5

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此回答的直接链接

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FeedbackLinearizationFixed.slx

Hi Amin,

It looks like Simulink was having trouble inferring the size of the for e_dot, e_doubledot and e_tripledot signals that are input to the controller MATLAB Function Block. I was able to fix by explicitly setting the size of e_dot to 3 ( rather than -1) in the Ports and Data Manager dialog for the MATLAB Function block. After making this cahnge, your model updates. See attached. NOte that the model does not simulation. There is a singularity somewhere in your algorithm.

Thanks.

Mark.