Finding a State-Space Representation for Helicopter Pitch Angle Control

[Nico Frontmann]

I need help finding a state-space representation for the given system and locally linearizing it...

Objective is to control the pitch angle theta, as an output, of the helicopter by regulating the rotor angle u, as an input.

This is what I've done, but apparently it isn't correct, and I don't understand why:

 

[donpacino]

in your A matrix you are saying X3'=9.8*theta-14.3*theta'-0.198*theta.