Appointed-time velocity-free prescribed performance control for space manipulators

This paper investigates the appointed-time velocity-free prescribed performance control for the space manipulators. A novel exponential-modified tracking differentiator is developed for estimating differential signals to address missing velocity information measurements. The original tracking problem is converted into the boundedness control, achieved through the bidirectional constraint-free mapping, which incorporates a novel performance function characterized by appointed-time convergence property. The coordinated control law is contributed with the designed velocity-free reference stable schemes. Ultimately, we achieve effective tracking of time-varying trajectories, ensuring simultaneous tracking of the desired values for the base and the manipulator. The tracking errors are constrained by the performance functions and convergence to the steady values at an appointed time. Simulation results validate the effectiveness of the proposed control scheme.