DynCont#10 Linearising closed loop in simulink, Equilibrium point, trim point.

1.  When linearising a non linear plant, about a trim point, always open the feed back loop
2. Do not place input perturbation and output pickup in simulink in the closed loop
3. Linearising is applicable for unstable systems, so open the feedback loop and linearise the plant alone.
4. Important : Trim point is not Equilibrium point
5. At equilibrium point, all state vector derivatives are zero
6. At trim point, only the constrained state vector derivatives are zero. Example, linearising the aircraft model at a constant forward speed.. 

 

From Analyzing Models (Getting Started) (urv.es)