Designing a fixed-time observer-based adaptive non-singular sliding mode controller for flexible spacecraft

• Published in: ISA transactions Vol. 148; pp. 32 - 44
• Main Authors: Rezaei, Erfan, Bolandi, Hossein, Fathi, Mohammad
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.05.2024
• Subjects: Attitude Stabilization; Fixed-Time Control; Fixed-Time Observer; Flexible Spacecraft; Non-Singular Sliding Mode Control; Non-Singular Sliding Mode Control; Flexible Spacecraft; Fixed-Time Control; Fixed-Time Observer; Attitude Stabilization
• ISSN: 0019-0578; 1879-2022; 1879-2022
• DOI: 10.1016/j.isatra.2024.03.025

This paper investigates the stabilization problem with a fixed-time approach for a flexible spacecraft subject to vibrations of flexible modes, unknown bounded disturbance, and inherent uncertainty. To estimate the modal variables of a flexible spacecraft which are often unmeasurable in practice, an observer with guaranteed fixed-time convergence is designed. Using the estimated modal variables, a fixed-time non-singular sliding mode controller is designed so that the desired attitude can be reached before a pre-specified time threshold regardless of the spacecraft's initial attitude. By incorporating the estimated modal variables in the control design, significant reduction in the steady-state error of the system response is achieved. The proposed control system is further enhanced with an adaptive law to increase robustness against unknown external disturbances and uncertainties. Stability analysis based on Lyapunov theory guarantees the convergence of observer estimation error and spacecraft attitude error to a pre-determined set before a fixed threshold. Simulation results validate the promising performance of the proposed control system, highlighting its effectiveness in achieving accurate and robust attitude control for flexible spacecraft. •A fixed-time observer with guaranteed convergence is designed.•A fixed-time non-singular sliding mode controller is developed to guide the spacecraft's attitude towards a desired target.•To further enhance the robustness of the control system, an adaptive law is integrated into the proposed controller.•The stability of the closed-loop system is rigorously analyzed using Lyapunov theory.