Research On Attitude Control Of Small Satellite Via Variable-structure Adaptive Control

From the 1980s, the U.S. military introduced the modern concept of small satellites, modern small satellite technology has developed very rapidly due to the advantages of lightweight, good performance, short development cycle, and low cost. Thus modern small satellite becomes an important direction. The attitude control system is the precondition of fulfilling all kinds of tasks, is the key technology and emphasis of study. The focus of this paper is to study the attitude control system of small satellite.In order to study small satellite attitude control system, the author first gives the theories of Euler Angle and the Quaternion, the attitude representation of Euler Angle and Quaternion are analyzed and generalized. Then the small satellite dynamics, kinematic models are established.A sliding mode control system is designed according to the feature that small satellite model is highly nonlinear and includes perturbation parameters, which can guarantee global and asymptotical stability of the system, and can ensure the system reaches the sliding surface within a limited time. Saturation characteristics instead of switching term is used to reduce flapping which results from the switching term.Adaptive attitude control system of small satellite based on feedback linearization is designed according to strong nonlinearity and coupling exist in the small satellite attitude dynamic and kinematic equations based on four quaternion. So the attitude channel of small satellite is decoupled into three SISO linear systems by means of feedback linearization. Then model reference adaptive controller based on the Lyapunov stability theory is designed for each attitude channel, so as to achieve robustness versus perturbation and disturbance, and to track the expected attitude.Then small satellite attitude control system based on sliding mode control and parameter adaptive algorithm is developed. The sliding mode control system which was designed previously is improved. An adaptive algorithm is proposed for the system parameters which are difficult to determine. The improved algorithm shows good system performances under parameters variance. Simulation results are given to illustrate the efficiency of the proposed method.