Underwater glider motion control

Abstract

This paper describes an underwater glider motion control system intended to enhance locomotive efficiency by reducing the energy expended by vehicle guidance. In previous work, the authors derived an approximate analytical expression for steady turning motion by applying regular perturbation theory to a realistic vehicle model. The analysis results suggested the use of a well-known time-optimal path planning procedure developed for the Dubins car, an often-used model of a wheeled mobile robot. For underwater gliders operating at their most efficient flight condition, time-optimal glide paths correspond to energy-optimal glide paths. Thus, an analytically informed strategy for energy-efficient locomotion is to generate sequences of steady wings-level and turning motions according to the Dubins path planning procedure. Because the turning motion results are only approximate, however, and to compensate for model and environmental uncertainty, one must incorporate feedback to ensure convergent path following. This paper describes the dynamic modelling of the complete multi-body control system and the development and numerical implementation of a motion control system. The control system can be combined with a higher level guidance strategy involving Dubins-like paths to achieve energy-efficient locomotion.