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The problem of finite-time attitude-tracking control (ATC) for a rigid spacecraft subject to inertial uncertainties, external disturbances, actuator saturations and faults is addressed. First, a fast nonsingular terminal sliding mode (FNTSM) manifold is constructed to improve robustness. Second, the fuzzy logic system (FLS) is integrated into the manifold derivative to deal with the lumped unknown function. The specific assumptions about uncertainties in most of the existing achievements are no longer needed. Combining the FNTSM and fuzzy approximation techniques, an enhanced fault-tolerant control scheme is developed. Compared to almost all finite-time ATC results based on FLS or neural network, a new Proof line is proposed to prove that the approximation errors are finite-time stable instead of asymptotically stable. Therefore, the attitude controller presented herein guarantees the real finite-time stability in a complete sense. Finally, numerical experiments are conducted to verify the effectiveness of the solution, and comparisons with related works are displayed. • Assumptions on uncertainties in the existing achievements are abolished. • Finite-time stability of fuzzy approximation errors is proved via a new Proof line. • Norm approximation is exploited to reduce the parameters to be estimated online. • The attitude controller guarantees the finite-time stability in a complete sense. [ABSTRACT FROM AUTHOR]

Summary: In this article, the problem of finite‐time attitude‐tracking control for rigid spacecraft is addressed. Uncertainties caused by external disturbances, unknown inertial matrix, actuator failures, and saturation constraints are tackled simultaneously. First, a smooth function that is more qualified to approximate the standard saturation characteristics is presented to deal with the actuator saturation constraints. Second, a fast nonsingular terminal sliding mode (FNTSM) manifold is constructed as a foundation of controllers design. By incorporating the fuzzy logic system into FNTSM technique, a less demanding solution of coping with model uncertainties is provided because the requirement of a prior knowledge of unknown inertial parameters and external disturbances in many existing achievements is removed. To reduce the number of parameters to be estimated, the norm approximation approach is exploited. Subsequently, an antichattering attitude controller is presented such that all the tracking errors converge into arbitrary small domains around the origin in finite time. The result is further extended to obtain a fault‐tolerant controller against completely failed actuators. Finally, numerical simulation is conducted to verify the effectiveness of the proposed control scheme and comparison with relevant literature demonstrates its high performance. Furthermore, an experiment for the large satellite Hubble Space Telescope is carried out to validate the practical feasibility. [ABSTRACT FROM AUTHOR]

This paper studies the issue of finite-time prescribed performance control for spacecraft attitude tracking with inertia perturbations, external disturbances, actuator saturations and faults. To the best of the authors' knowledge, limited results have been reported in the relevant literature, and how to achieve the prescribed performance attitude tracking within a preset time interval is still an open problem. A novel finite-time prescribed performance function (FTPPF) whose settling time can be arbitrarily preset is first proposed. With the FTPPF predefining the envelope of tracking-error trajectories, the original spacecraft model is transformed into a new error system. Based on the barrier Lyapunov function of converted errors, the attitude controller is derived via backstepping design. During the process, the fuzzy approximation is used to handle inertia perturbations and external disturbances, while the Nussbaum gain technique is adopted to compensate for the efficiency loss caused by actuator saturations and faults. Finally, a finite-time fault-tolerant control scheme that guarantees both transient and steady-state performances (e.g., the maximum overshoot, steady-state error, and settling time) is developed. To verify the effectiveness of the solution, numerical experiments involving comparisons with related achievements are performed. [ABSTRACT FROM AUTHOR]