Robust Nonlinear Task Space Position Tracking Control of an Autonomous Underwater Vehicle-Manipulator System

This paper presents a robust nonlinear control scheme for task-space trajectory control for an autonomous underwater vehicle-manipulator system (AUVMS) based on an improved proportional integral derivative (PID) control scheme used for deep-sea intervention tasks. A planar underwater vehicle manipulator system (consists of an underwater vehicle and two link rotary (2R) serial planar manipulator) with dynamic coupling between them is considered for the study and numerical simulation. The actuator and sensor dynamics of the system are also considered. The proposed controller integrates the known approximated inverse dynamic model output as a model-base portion of the controller; uses a feed forward term to enhance the control activity with indulgence from known desired acceleration vector; carries an estimated perturbed term to compensate for the unknown effects namely external disturbances and un-modelled dynamics and a decoupled nonlinear PID controller as a feedback portion to enhance closed-loop stability and account for the estimation error of uncertainties. The primary objective of the proposed control scheme is to track the given end-effector task-space trajectory despite of external disturbances, system uncertainties and internal noises associated with the AUVMS system, which show the robustness of the proposed control scheme. Simulation results confirmed that the AUVMS can successfully track the given desired spatial trajectory.