Adaptive Impedance Control for Docking of Space Robotic Arm Based on Its End Force/Torque Sensor

Aiming at space transposition using Space Robotic Arm (SRA), flexible docking between SRA's end effecter (EE) and grapple fixture (GF) is the most important for space tasks. To avoid position errors leading to large contact force between EE and GF in the docking process, an adaptive impedance control method is proposed in this paper. PID feedforward with adaptive parameters is added into the impedance controller, and the force error function is used to deduce the adaptive parameters according to Lyapunov stability theory, which makes the force error decrease automatically during the connection process. Simulation proves that the adaptive impedance strategy gets better force control effect than the traditional impedance algorithm. Finally the SRA EE/GF connection experiments were conducted respectively based on traditional and adaptive impedance control strategy. The results showed that the adaptive impedance control strategy can achieve better control effect than the traditional strategy.