改进型自适应变结构的挠性卫星姿态机动控制

Modified adaptive variable structure control for flexible spacecraft with input nonlinearities

针对带有输入非线性的挠性卫星的姿态机动问题,提出一种仅利用输出信息的变结构输出反馈控制方法.首先,采用拉格朗日方法建立挠性卫星的动力学模型.然后,在基于非线性和低阶模态的动力学模型基础上,给出滑模存在条件以及变结构输出反馈控制器设计的方法;另外,为了避免确定不确定性和外干扰界函数上界的困难,又给出一种改进型自适应变结构输出反馈控制器的设计方法,通过增加一负反馈项,防止了不确定界函数的参数过大而导致控制过大及系统失稳,从而使对不确定界函数的参数的估计达到更好的效果.最后,将本文提出的控制方法应用于三轴稳定挠性卫星的姿态机动控制,并进行数值仿真研究.仿真结果表明:在反作用飞轮的控制受限条件下,完成姿态机动的同时,有效地抑制挠性附件的振动.

This paper proposes a robust control algorithm for stabilization of a three-stabilized flexible spacecraft in the presence of model uncertainty, external disturbances and control input nonlinearities. The proposed variable structure output feedback controller ensures the global reaching condition of the sliding mode of the spacecraft dynamics system and the control input nonlinearities are explicitly accounted for in the stability analysis. The structure of the controller is independent of the elastic mode dynamics of the spacecraft. Furthermore, a modified adaptation control law is given for the upper bound on the uncertainty to improve the adaptive performances by adding a negative feedback term. Thus a new controller is designed to guarantee the boundness of the closed-loop system and can be described as a combination of sliding mode control law and the modi- fication adaptive law. Numerical simulations show that the precise attitude control and vibration suppression can be accomplished using the derived controller for both cases with and without adaptive control.