Improved Design and Control Experiments of an Underwater Electric Manipulator

Autonomous/semi-autonomous working underwater vehicle is a development trend of underwater vehicles. This paper briefly analyzes the requirements of underwater electric manipulator to be equipped on autonomous underwater vehicles, and designs a three-function underwater electric manipulator test-bed. The test-bed has the characteristics of compact configuration, complete function and with big moment output. But exterior cable layout increases the possibility to arise malfunction especially when the manipulator working in water. An improved design of the manipulator with inner cable layout is also presented in this paper. Based on the frequency characteristics of the rotary joint driven module, the PI correction is designed to control the shoulder and elbow joint´s angular rate. Then the angle error is regarded as the input of angular rate control loop after a PID controller, and a non-regressor adaptive controller, which has been widely adopted as an effective means in underwater vehicle control, is also used to control the manipulator as a selective method. Experiment results demonstrate the good effect of the PID and the adaptive controllers in controlling joint angle, and with the inner control loop, the non-regressor adaptive controller is more robust than that without inner-loop, and it is a more appropriate controller than PID controller especially in protecting the manipulator´s motors from saturated voltage