Design and full-link trajectory tracking control of underwater snake robot with vector thrusters under strong time-varying disturbances

In this paper, an underwater snake robot with vector thrusters and axis-intersect joints is designed. The dynamic model of the newly designed robot is established. A new decoupling control strategy is proposed for full-link trajectory tracking. The control strategy decouples the movements between the body and the links. The tra-jectory of the body (represented by the head link) is controlled by thrusters, and the rest links follow its trajectory by controlling the relative angles to the head link with servo motors on the joints. To eliminate the influence of strong time-varying external and internal disturbances, the control method based on sliding mode and a nonlinear disturbance observer with linear matrix inequality is proposed to realize the full-body trajectory tracking. The results show that the proposed method performs better than the reference under strong time -varying external and internal disturbances.