Oscillation control in teleoperated underwater vehicles subject to cable perturbations

In this paper a control scheme in fixed and adaptive modus for path tracking of ROVs under perturbations of waves and uniform flow is presented. Particularly, the case of systematic sampling missions at constant depth or altitude with variable cable length are focused in the investigation. A model of the cable perturbation is developed in order to embed it in the controller design. The controller is based on speed-gradient laws in adaptive or fixed modes alternatively. The proposed scheme allows the estimation of the cable perturbation based on a model of force, shape and position of the extremes. Simulations show the presence of nonlinear oscillations particularly in the regulation about fixed positions, where chaotic behaviors can be observed. The paper compares the control performance obtained with and without the estimation of the cable perturbation in both the fixed and adaptive controls. The results are illustrated by means of a case study in six degrees of freedom for both path tracking and regulation.