关键词: 固定时间稳定系统, 干扰观测器, 自适应增益, 空间机械臂, 滑模控制

Abstract: To address the problem of high-precision joint trajectory tracking control for space manipulators under unknown environmental disturbances, this paper proposes an adaptive fixed-time sliding mode control strategy based on a fixed-time disturbance observer. First, a fixed-time observer is designed to estimate unknown environmental disturbances. The observer ensures that the estimation error converges within a fixed time without requiring strict assumptions such as known upper bounds of disturbances, and the observer gain can be adjusted according to changes in the actual environment, thereby improving the adaptability of the observer to unknown environments. Second, a novel fixed-time stable system is constructed, which features a smaller upper bound of convergence time compared with conventional methods. On this basis, a nonsingular fixed-time sliding mode surface is designed, which not only avoids the singularity problem but also rigorously guarantees the continuity of the sliding mode surface and its derivative. Finally, this paper designs a fixed-time controller combined with an adaptive estimation law, which can perform equivalent processing of complex nonlinear terms in the dynamic equations and suppress the residuals of disturbance estimation, enabling the entire system to converge within a fixed time while ensuring convergence accuracy. Numerical simulation experiments have demonstrated the effectiveness of the proposed control strategy.

Key words: Fixed-time stable system, Disturbance observer, Adaptive gain, Space manipulator, Sliding mode control