Hello to all

i need an accurate description or resource for linearizing a nonlinear servo-pneumatic system model and so as a matter of result, the state space equation, in order to design a linear controller for it. i have a nonlinear model of the system. i want to design an intelligent robust control (fuzzy-pid or LMI-pid) for a servo pneumatic positioning system and i think i need the state space equation firstly.

any suggestion or resources to doing so is appreciated.