Dynamics & Control of Underwater Gliders II: Motion Planning and Control

This paper describes an underwater glider motion control system intended to enhance locomotive efficiency by reducing the energy expended by vehicle guidance and control. In previous work, the authors derived an approximate analytical expression for steady turning motion by applying regular perturbation theory to a sophisticated vehicle dynamic model. Using these steady turn solutions, including the special case of wings level glides, one may construct feasible paths for the gliders to follow. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure precise path following. This report describes the development and numerical implementation of a feedforward/feedback motion control system for a multi-body underwater glider model. Since the motion control system relies largely on steady motions, it is intrinsically efficient. Moreover, the nature of the steady turn approximations suggests a method for nearly energy-optimal path planning.