Predefined-time disturbance observer-based fuzzy tracking control for uncertain space robot with global prescribed performance.

Abstract

In this paper, an adaptive fuzzy prescribed performance control strategy based on predefined-time theory is proposed for a space robot under external disturbances and dynamic uncertainties. Firstly, an adaptive fuzzy backstepping framework that integrates predefined-time control theory is presented. To mitigate the impact of external disturbances on tracking performance, a predefined-time nonlinear disturbance observer (PTNDO) is introduced to compensate for them, thereby enhancing the convergence accuracy of trajectory tracking control. Next, global predefined-time prescribed performance control (PTPPC) is introduced to improve the transient and steady-state performance of the control system. Additionally, a single-parameter fuzzy logic system (FLS) is introduced to compensate for dynamic uncertainties in the system. An adaptive fuzzy predefined-time controller is then developed based on PTNDO, PTPPC, and single-parameter FLS. Compared to multi-parameter FLS, single-parameter FLS reduces the consumption of computational resources while retaining the desired level of approximation accuracy. By utilizing PTNDO and PTPPC, the transient and steady-state performance of the space robot control system are enhanced and the limitations of traditional prescribed performance control caused by initial states are avoided. The predefined-time stability of the proposed controller is rigorously proven by using Lyapunov theory, and numerical simulations demonstrate its superiority and effectiveness compared with existing methods.