航天器姿态系统的分数阶滑模容错控制器设计

Objective Spacecraft attitude control under complex operational conditions remains limited by inadequate controller adaptability, insufficient precision, and rapid chattering near the sliding surface. Fractional-Order Sliding Mode Control (FOSMC), which integrates fractional calculus into control algorithms, offers improved modeling flexibility and robustness. Compared with conventional integer-order controllers, fractional-order controllers yield smoother responses and enhanced dynamic behavior. This study proposes a novel fault-tolerant control strategy that combines FOSMC with fault accommodation mechanisms to achieve accurate spacecraft attitude tracking in the presence of system faults and environmental disturbances. Methods A finite-time disturbance observer is proposed to unify actuator faults, inertia uncertainties, and external disturbances into a single lumped term. This formulation allows for accurate estimation of both the system state and disturbances, supporting effective compensation. The observer’s fast convergence and robustness are analytically demonstrated using finite-time stability theory. To further accelerate convergence and mitigate the chattering typically observed in conventional sliding mode control, a finite-time fault-tolerant controller based on fractional-order sliding mode is developed. This controller ensures finite-time stabilization of spacecraft attitude and angular velocity. Results and Discussions To evaluate the effectiveness and performance advantages of the proposed method, a comparative analysis is conducted against an Integer-Order Sliding Mode Controller (IOSMC) using MATLAB simulations. Figure 1 shows the estimation error of the proposed finite-time observer, demonstrating its ability to rapidly and accurately estimate the lumped disturbance term. Figure 2 presents the attitude response trajectories under both control strategies, with blue and red lines corresponding to the fractional-order and integer-order controllers, respectively. Although both methods successfully track the desired attitude, the FOSMC exhibits significantly faster convergence. Figure 3 displays the angular velocity error curves, indicating that the FOSMC achieves finite-time stabilization. In comparison with the IOSMC, the proposed controller yields quicker convergence and reduced steady-state error. Figure 4 illustrates the control torque profiles, revealing that the FOSMC produces smoother torque outputs. Conclusions This study proposes a spacecraft attitude controller based on fractional-order sliding mode theory to reduce the high-frequency chattering observed near the sliding surface in conventional terminal sliding mode control. By incorporating fractional-order calculus into the control framework, a fault-tolerant strategy is developed to enhance the performance of spacecraft attitude systems under uncertain and faulty conditions. Simulation results validate the following advantages: (1) Compared with the IOSMC algorithm, the proposed controller achieves faster convergence and improved chattering suppression. (2) Actuator faults, inertia uncertainties, and external disturbances are consolidated into a unified disturbance term, which is accurately estimated by a finite-time disturbance observer for effective compensation. (3) The use of a fractional-order non-singular terminal sliding surface, together with Lyapunov-based analysis, provides a rigorous guarantee of finite-time stability. Moreover, the fractional-order sliding surface increases the design flexibility, allowing broader optimization of controller parameters. This work addresses finite-time fault-tolerant control for spacecraft attitude systems. Future research may investigate fixed-time fault-tolerant control approaches to further improve robustness and ensure consistent response times.