MATLAB: How does the linearization option “Ignore Discrete States” work for a system with an integrator in series connection with a discrete time-transfer function

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I have a simple system of an integrator in series connection with a discrete time-transfer function as in the attached model 'ignore_discrete_states.mdl'. I am trying to linearize the system with "Ignore Discrete States " option. The linearization returns a static gain of '0' instead of discarding the discrete transfer function and returning '1/s'.

Best Answer

The reason for the issue is how the "Ignore Discrete States" option works.
The "Ignore Discrete States" option operates on discrete-time blocks by converting them to the corresponding state-space representations and use the matrix 'D' for each block as the result of the linearization for the block. Therefore, if there exists a discrete-time block which has a state-space representation where 'D' matrix is zero and in series with the rest of linearization path, then the whole linearization operation returning a static gain of zero is the expected behavior when the "Ignore Discrete States" option is checked.
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