Velocity and orientation control of underwater snake robots using absolute velocity feedback

This article presents a control system for velocity and orientation control of underwater snake robots using absolute velocity feedback. The control system is structured in a hierarchical way, where the highest priority is to enforce virtual constraints encoding a planar gait on the body shape of the robot. To this end, we propose an adaptive joint controller and show that it asymptotically stabilizes the constraint manifold. The virtual constraints are parametrized by the states of two dynamic compensators, which can be used to control the velocity and the orientation of the robot, the second and third control priority. We design an adaptive controller that asymptotically stabilizes the forward velocity to a reference and an orientation controller that utilizes the current estimate of the velocity controller. It is shown that the zero dynamics of the closed-loop system remains bounded, and we present simulation results that demonstrate the performance of the controller.