Performance constrained trajectory tracking control for free-flying flexible-joint space robots based on adaptive sliding mode disturbance observer

Aiming at the trajectory tracking control with performance constraints and actuator saturation for free-flying flexible-joint space robots (FFSR) under uncertain external disturbance. In the framework of the command filter backstepping method, a composite controller combining tan- type barrier Lyapunov function (TBLF) and anticipatory activation anti-saturation (AAA) is proposed. A finite-time prescribed performance function (FPPF) is developed to improve the transient performances of trajectory tracking. In addition, an adaptive sliding mode disturbance observer (ASMDO) is designed to estimate the uncertain external disturbance, with a novel log- type barrier function based adaptive control law (LBFACL) to prevent successive monotonic increases in gain and mitigate the risk of gain tending to infinity at the regional boundary. The simulation results show that the trajectory tracking performance of FFSR system under the designed control scheme has fast convergence speed and high accuracy.