考虑约束的卫星抗扰反步姿态控制

Disturbance Rejection Backstepping Attitude Control for Satellite with Saturation Constraints

针对具有不确定性、外干扰及饱和约束的卫星非线性姿态跟踪问题,将约束反步法与状态观测器相结合,提出分块自适应抗扰反步控制器。卫星模型由修正罗德里格参数进行描述。利用带参数投影的非线性扩张状态观测器对时变的"总干扰"项进行在线估计补偿,以提高反步控制器的鲁棒性。在设计反步控制器时,引入指令滤波器和修正跟踪误差信号以施加系统状态和执行器的饱和限制,同时较容易获得虚拟控制导数,并且放宽了干扰估计律投影算子的投影集范围。Lyapunov理论证明了闭环系统在非线性阻尼的作用下输入-状态稳定。对比仿真表明,与传统自适应反步法相比,所提出的控制器具有更高的姿态跟踪性能和干扰估计精度。

A modular adaptive disturbance rejection backstepping controller is proposed for the nonlinear attitude tracking of satellite in the presence of uncertainties ,external disturbances and saturation constraints, which combines the theory of Nonlinear Extended State Observer （NESO） with constrained backstepping. Firstly,the satellite attitude is represented by Modified Rodrigues Parameters （MRP）.And the NESO with parameter projection is employed to estimate and compensate the time -varying total disturbances on line for improving the robustness of backstepping controller .Then the backstepping controller is derived by introducing command filters and modified tracking errors to implement any operating constraints and obtain the derivatives of virtual control easily,which can also enlarge the projection sets of the disturbance estimation laws .Lyapunov theory proves that the closed -loop input-to-state stability is guaranteed under the effect of nonlinear damping . Comparative simulations state that the proposed controller has better performance in achieving precise attitude tracking and estimation of disturbance than classical adaptive backstepping .