Adaptive fuzzy PID composite control with hysteresis-band switching for line of sight stabilization servo system

The line of sight (LOS) stabilization control based on gyro stabilized platform is required to isolate the LOS from the disturbance and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system. A composite adaptive fuzzy proportional-integral-derivative (PID) control with hysteresis-band switching is developed to achieve real-time and high stabilization precision for this nonlinear uncertainty servo system. First of all, in the adaptive fuzzy controller, the pre-designed self-tuning factors are able to modify the parameters of fuzzy controller online, and a new learning algorithm of fuzzy rules modifier is proposed to adjust control efforts. Then, an improved PID controller is chosen to restrain motor saturation and eliminate the static error originated from the fuzzy controller, and fulfill non-error control. The hysteresis-band switching strategy is given to deal with jitter caused by single-point switching condition. The experimental results in four-axis servo turntable show that the proposed method can achieve nice control performance and is proved to be effective in bating carrier disturbances within the scope of definite noise and sensitivity to acceleration. Crown Copyright (C) 2010 Published by Elsevier Masson SAS. All rights reserved.