Nonlinear Robust Tracking Control of an Underwater Vehicle-Manipulator System

This paper develops an improved robust multi-surface sliding mode controller for a complicated five degrees of freedom Underwater Vehicle-Manipulator System with floating base. The proposed method combines the robust controller with some corrective terms to decrease the tracking error in transient and steady state. This approach improves the performance of the nonlinear dynamic control scheme and makes the states stable even in presence of unknown effects of hydrodynamic disturbances and unmodelled dynamics. In this regard, the dynamic model of an UVMS is extracted using the Newton–Euler formulation which has been validated by using an ADAMS 3-D model. The control algorithm is based on Lyapunov technique and is able to provide the stability of the whole system during tracking of the desired trajectory with an acceptable precision. The controller parameters are also optimized utilizing the concept of Genetic Algorithm with the aim of increasing the speed of system while decreasing the tracking error which leads to bounded control inputs. Finally, the efficacy of the control scheme, is compared with other conventional methods and the simulation results show the short settling time, low and smooth control effort and asymptotic stability of the states as well as the sliding surfaces of the proposed controller.