Abstract: In order to realize the diversity of the unknown environment target capture of underwater manipulator, the adaptive impedance control method is proposed to ensure grasping, holding and minimizing the damage of the target. A force tracking control system based on position impedance model is established, and the target impedance parameter is identified by recursive least square method, and the expected value of grasping force is adjusted online according to the impedance parameter and the manipulator motion characteristic with fuzzy inference. According to the expectation force and grasping force error, the adaptive PID controller adjusts the desired position, realizes the tracking of different expected force signals while tracking the target position, and realizes the simulation verification on the MATLAB/Simulink platform. The results show that the adaptive impedance control has good force and displacement tracking performance in free space and constrained space. The realtime expectation force adjustment satisfies the diversity of grasping target, and the adaptive adjustment of the desired position realizes the tracking of the desired force.

Key words: underwater manipulator, impedance model, adaptive, fuzzy inference, recursive least square method