Modelling Integrator with Transfer Fcn Block

Hi, I'm trying to model a feedback control system in Simulink. I've noticed some odd behaviour when modeling an integrator using a Transfer Fcn block. When I add the integrator to my model the LTI Viewer low frequency loop gain becomes massively negative, even when the integrator isn't wired up to the rest of the model! Attached is a screen clipping of the integrator model. The problem seems to be with the coefficient of s^0. If I set the coefficient of s^0 to anything except zero the bode plot looks OK. Anyone know why the LTI Viewer doesn't like Transfer Fcn denominator s^0 coefficient to be equal to zero? Am I entering the integrator transfer function incorrectly or is there a better why to model the integrator?

Answer 1

[Sulaymon Eshkabilov]

Hi,

That would be helpful if you post system formulation (transfer function) of your feedback system. It looks like you are not performing linearization and linear analysis of your system simulation while performing lsim in your simulink model. That is a small extra step to be taken before performing the system analysis/performances such as bode, etc.

Good luck.