The linearization input/output port specification of the 'statespac​e_compensa​tion/Bode Plot' block resulted in linear system with a value of zero.

Hello, Im trying to get the bode plot of the compensated system and the following warning occurs:

Warning: The linearization input/output port specification of the 'statespace_compensation/Bode Plot' block resulted in linear system with a value of zero. Change the input/output specification, the blocks connecting the input and output points, or the snapshot time/event to yield a non-zero linear model. See the Simulink Control Design documentation for details on how to diagnose these conditions. > In linearize/CheckBlkExecutionEngine/processJacobian (line 326) In linearize.CheckBlkExecutionEngine>localProcessJacobian (line 436)

Ive tried to change the snapshot timpe but im not sure if i did it well and it yields to no response

do you have any idea what should i do?

Answer 1

[Yoshi Minagawa]

Hi Vasilica,

The main reason of this warning is that this model has discontinuous non-linearity. In making not only bode-plot but also linear model(LTI object), MATLAB try to linearize the model using "Taylor expansion". But that method can't be used for discontinous model because derivative operation can't be perfomed. (In the case of this model, the Relay block is a discontinous non-linear block.)

In such case, generally, "Estimation of frequency response" is used to linearize the model with discontinuity. For more information of that, please see the website below.

https://jp.mathworks.com/help/slcontrol/ug/estimate-frequency-response-using-linear-analysis-tool.html

I hope this will help.