A Robust Motion Control Scheme of an Underwater Robot with Tiltable Thrusters

Abstract

A modern control approach for a submerged robot with tiltable thrusters is explored in this paper. The rotatable action capability of the four thrusters makes the system framework as over-actuated with only six degrees of freedom (DOF) to be carried out. The dynamic model of the submerged robot on account of rotatable angles results in highly nonlinear thrust vector mapping, where linearization of the model leads to the rejection of possibly advantageous nonlinearities. This issue can be abstained by utilizing model-based nonlinear control schemes such as backstepping in the presence of continuous rotatable action resulting in a better control action. The stability of the system is ensured by the Lyapunov stability criterion by tuning the control gain constants with the RMS values of tracking error. Finally, the numerical simulations demonstrate the cascaded nature of the derived tracking control, where the tracking errors asymptotically reduce to close vicinity of zero. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.