MATLAB: Do LINMOD2 and LINMODV5 not work with Derivative blocks in Simulink 7.8 (R2011b)

bodederivativelinmod2linmodv5simulink

I was trying out the LINMOD, LINMOD2 and LINMODV5 functions to linearize a model which contained a Derivative block.
With the LINMOD function, this worked fine. With LINMOD2 and LINMODV5, the state associated with the Derivative block was not present in the State-Space system generated. In addition, when creating a Bode plot, the output associated with the Derivative block was empty.
Why is this?

Best Answer

The LINMOD2 and LINMODV5 algorithms use full perturbation as opposed to the preprogrammed Jacobian approach of LINMOD. As a consequence, it is recommended to not use Derivative blocks when using LINMOD2 and LINMODV5 as shown at the end of the following document:
    <http://www.mathworks.com/help/toolbox/simulink/ug/f1-2052.html>
As discussed in the link above, replacing the Derivative block with a transfer function or a "Switched Derivative for linearization" block from Simulink Extras/Linearization helps to resolve this issue.
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