基于两相幂次趋近律的航天器姿态控制

Two-phase power reaching law-based spacecraft attitude control

针对带有系统不确定性的航天器姿态控制系统,提出一种基于两相幂次趋近律的姿态控制方法.在趋近律设计中,根据滑模变量值的变化调整趋近律的幂次值,确保滑模变量在远离滑模面和接近滑模面时均具有更快的收敛速度.同时,通过分别计算两个趋近阶段的收敛时间,可直接获得较为准确的滑模变量收敛时间表达式.此外,在控制器设计中采用鲁棒项补偿未知不确定性与外界扰动的影响,从而增强系统的鲁棒性.最后,基于Lyapunov函数方法证明系统的稳定性,并给出仿真对比验证所提控制方法的有效性.

A two-phase power reaching law-based attitude control scheme is proposed for spacecrafts with system uncertainties.In the presented reaching law design,the power value is adjusted according to the change of sliding mode variable value,such that the fast convergence rate of the sliding mode variable can be achieved when it is far away from and approaching to the equilibrium.Meanwhile,a relatively accurate convergence time expression of the sliding mode variable is obtained directly by calculating two convergence time in different reaching stages,respectively.A robust term is adopted in the control design to compensate for the effect of uncertainties and disturbances,and thus the system robustness is enhanced.Finally,the stability of the system is analyzed based on the Lyapunov stability synthesis,and the effectiveness of the proposed control scheme is verified by comparative simulations.