Amirreza Kosari - Assistant Professor
Hossein Salehghaffari - M.Sc

This paper presents a new PID controller architecture to control a geostationary spacecraft attitude and avoid actuator saturation. External disturbances may have high effect on performance of a conventional PID, and PID controller may have some problems in terms of integral wind-up such as the large overshoot and long settling time. Intelligent integrator is an efficient approach to overcome integral wind up, but the paper shows proposed PID are more flexible than intelligent integrator. The proposed nonlinear PID solves actuator saturation problem by multiplying a nonlinear factor in integral term. The error-rate is used in the nonlinear factor, and possesses two advantages. First, integral will only reset in situations where integral wind-up is a possibility, and second, step response has almost no overshoot. The simulation results of proposed controller have been compared with conventional PID and intelligent integrator controller. The simulation results verify high performance of proposed satellite attitude controller versus conventional PID and intelligent integrator controller

Spacecraft Control, PID Controller, Integral Wind-up, Actuator Saturation