The Robustness Of The Space Aircraft Attitude Control

The current research in developing next generation reusable flying vehicles is focused on aerospace vehicles (ASV). It is of significance to control the aerocraft vehicle's attitude system. The control system of the ASVs attitude several challenges due to the nonlinear, strongly coupled and uncertain model with uncertain disturbance and complicated condition.As a synthesis method in control system, the most outstanding advantage of the sliding mode of variable structure control is distinct and ideal robustness and holds the invariance for the change of system parameters, outside and uncertainty of the system and its algorithm is very simple. But the chattering phenomenon is a big barrier for the sliding mode control to apply to engineering practice .This paper combines fuzzy control with traditional variable structure control, to construct fuzzy variable structure control, which applies to the ASVs attitude system. The study addresses the following topics:Firstly, the dissertation refers to comparatively full literatures in the field of VSC and FLC, and the development history and characteristics of VSC and FLC are summarized, and the elementary concepts, elementary definitions, elementary properties, elementary principles and design methods are particularly introduced and the causes of the chattering phenomenon are systematically analyzed. The chattering reduction strategies are classified and studied. At the end of this survey, the future direction of chattering reduction is provided.Secondly, a six degree-of -freedom simulation model of a conceptual ASV is presented, which includes the whole of kinetic equations and motion equations. Based on the nonlinear, strongly coupled and uncertain model of the aerocraft vehicle's attitude system, a fuzzy variable structure control method is proposed. Based on the feedback-linearization technique, the system was firstly decoupled into three independent SISO subsystems, and then controllers for each subsystem were designed. Modeling error and unknown disturbance is effectively restrained with the proposed adaptive fuzzy control with variable structure control. Theoretical analysis and simulation results show that the proposed method has high control accuracy, high robust and easy realization.