Fuzzy logic and state variable control applied to a seeker servomotor system

This study presents a comparison of LQ optimal and fuzzy control on a complex mechanical servomotor system modeled after a missile seeker. Simulation results indicate that the fuzzy controller displays superior robustness to uncertainties in the physical system that tend to cause steady-state error. The fuzzy controller uses a variation of Sugeno inference, a variable input gain adaptation mechanism to accommodate variation in step response sizes, and an integral emulator that uses a gradient-descent philosophy to eliminate steady-state error. The state variable controller is augmented with the fuzzy integral emulator to significantly reduce its sensitivity to steady-state error without introducing the degradation in transient characteristics caused by use of linear integral control on a system with drastic limiting of the control output.