Disturbance Observer-Based Saturated Attitude Tracking Control of Flexible Spacecraft with Measurement Uncertainties

Abstract

Measurement uncertainties associated with actuator saturation, parametric uncertainties, and external unknown disturbances always exist in flexible spacecraft attitude tracking control systems, and complicate the advanced robust saturated controller design. In the framework of the backstepping design, this study combines the nonlinear disturbance observer and linear anti-windup compensator to respectively handle measurement uncertainties and actuator saturation for uncertain flexible spacecraft attitude tracking systems. The major advantage of the proposed control approach is that it can theoretically guarantee uniformly ultimately bounded tracking performance with saturated control inputs, in the presence of additive measurement uncertainties, parametric uncertainties, and unknown external disturbances. Computer simulations reveal that the proposed saturated robust nonlinear controller is effective in practice, and a great performance improvement can be achieved, in comparison to traditional controllers.