Robust PID control for position tracking of an underwater manipulator

This article investigates a new robust nonlinear proportional integral derivative (PID) position tracking control applied on a serial underwater spatial manipulator with three degrees of freedom. The proposed controller integrates the known approximated inverse dynamic model output as a model-base portion of the controller. It uses a feed forward term to enhance the control activity with indulgence from known desired acceleration vector. The proposed control scheme carries an estimated perturbed term to compensate for the unknown effects namely external disturbances and unmodelled dynamics. Finally, it has a decoupled nonlinear PID controller as a feedback portion to enhance closed-loop stability and account for the estimation error of uncertainties. The usefulness and competency of the proposed approach are demonstrated with the help of numerical simulations.