Extract state space from Simulink - Blocks without pre-programmed exact Jacobian

Hello people,

I am trying to extract the state space of the 'sldemo_autotrans' demo in Simulink. This file includes some look-up tables and a state flow. when I am trying to linearise that model using the 'linear analysis' tool, I am receiving a response that does not make sense. I use snapshots that the model has reached a steady state.

The diagnostic messages in the linear analysis tool return me the following message: “7 block(s) without pre-programmed exact Jacobian (linearized using numerical approximation)”

Does anyone have any ideas about that?

Thank you in advance!

Answer 1

[Panagiotis Panos Katranitsas]

Thank you for your answer Kaustubha and sorry for my late response.

I overcame this problem by changing the lookup method from "interpolation-extrapolation" to "use input nearest".

Answer 2

[Kaustubha Govind]

I don't know a lot about linearization, but here are some linearization methods. I believe the Linear Analysis Tool tried to perform numerical approximations for blocks that provide an exact Jacobian (a representation that is a numerical approximation of the block behavior). However, not all blocks may be able to provide such an approximation, in which case a perturbation based method is used for those blocks. However, the perturbation method yields results that are sensitive to the operating point, so you may need to look more closely to see how you should move your operating point or change the level of perturbation. See Troubleshooting Linearization for more information.