Robust control for a two-axis gimbaled sensor system with multivariable feedback systems

Abstract

A dynamic model for the stabilisation loop of a two-axis gimbaled sensor system is formulated and system parameters have been identified by practical experiments. The validity of the dynamic model is illustrated by the experimental and simulation result. The Lead-proportional-integral (PI) controller design using a loop-shaping method based on the frequency response for the stabilisation loop of the sensor system is realised. This practical design approach has been proven to be simple and robust in actual application. The robust H(infinity) controller design approach combining model matching and mixed sensitivity problem to improve the command following and disturbance rejection performance in the presence of external disturbances and model uncertainties is implemented, which is designed within the framework of the standard H(infinity) optimisation problem by combining a conventional mixed sensitivity and model matching problem with robust stability. The experimental and simulation results show that the both two proposed controllers satisfy all desired requirements for the stabilisation loop associated with the gain crossover frequency, the gain and phase margin and the body-motion decoupling performance. It is shown through performance comparison and analysis that the proposed H(infinity) controller is preferable to the proposed Lead-PI controller in terms of system stability, the disturbance rejection rate and because of its fast time response characteristics. However, it is clear that the two proposed controller design procedures for the robust control of the stabilisation loop of a two-axis gimbaled sensor system can be very effective in practical applications in terms of both stability and disturbance rejection.