Saturated output feedback control of free-floating space manipulator with fragility-avoidance prescribed performance

This article proposes an output feedback control methodology for the free-floating space manipulator with fragility-avoidance prescribed performance subject to parameter uncertainties, unexpected disturbances, actuator faults, and input saturation. Firstly, asymmetrical prescribed boundaries are utilized to eliminate overshoots, and an artificial potential function-based adjustment strategy for prescribed performance bounds is developed to tackle the fragile problem of traditional prescribed performance control. Subsequently, an extended state observer is constructed to estimate unmeasurable states and disturbances. Finally, the Nussbaum gains are introduced to overcome the time-varying control coefficient arising from actuator faults and input saturation. The stability of the closed-loop system is analyzed via the direct Lyapunov method . Two comparative numerical simulations verify the effectiveness and advancement of the proposed method. • The fragility problem of prescribed performance control methodology is addressed. • The problem of algebraic rings for prescribed performance bounds adaptation is circumvented by the artificial potential function. • The Nussbaum gain technology is introduced to cope with actuator faults and input saturation. • The extended state observer is adopted to estimate the velocity information of the end-effector directly in task space.