反作用轮低速特性观测补偿方法

反作用轮在现代高精度卫星姿态控制中占据着重要的地位。但由于反作用轮工作于低速状态,其转速过零时摩擦力矩的非线性特征将会对姿态控制精度产生较大的影响,并影响卫星运行寿命。基于Dahl摩擦模型建立了直流电机驱动的反作用轮系统数学模型,在此基础上设计了用于改善反作用轮低速性能的补偿观测器,并将其应用于三正交结构姿态控制系统。数字仿真说明此方法可以有效地抑制反作用轮低速摩擦产生的扰动,从而大幅度改善卫星姿态控制精度及其姿态稳定性。最后探讨了该观测器方法同变结构控制方法的综合应用前景。

The Compensation Method of the Observation of the Reaction Wheel at Low Speed

Reaction wheels are widely used for spacecraft attitude control in missions that require fine pointing accuracy and stabilization nowadays. But the friction produced by the reaction wheel assembly (RWA) itself when crossing zero is one of the most significant sources of disturbance. And it is necessary to eliminate these disturbances, especially for those cases that the wheels are running at low-speed throughout the space mission. The mathematical model of the reaction wheel assembly driven by a DC motor is presented on the base of Dahl friction equations. And a state observer is constructed to estimate the friction torque in order to compensate for it. A numerical simulation model, which assumes the satellite attitude is controlled by three reaction wheels arranged in an orthogonal geometry, is established. The simulation results prove that this method can improve the satellite attitude pointing accuracy and stability efficiently. Finally, the integration of the observer method and a sliding-mode control law is discussed.