Dynamics and approximate semi-analytical solution of an underwater glider in spiral motion

Abstract

Underwater gliders take advantages of the net buoyancy to operate in the water column at low speed, but the dynamic models are highly nonlinear, highly coupled, and difficult to describe. Comparing with the saw-tooth motion in the vertical plane, the steady state solutions in spiral motion have become much more challengeable in navigation control and path planning. This paper presents an approximate semi-analytical solution to the steady state spiraling motion of a glider. The nonlinear multi-body dynamic model of an underwater glider actuated by a single internal movable and rotatable mass is established. The semi-analytical solution to any spiral trajectory is obtained after rational simplifications of the thorough equations of motion. The approximate solutions are proved sufficiently close to actual values by comparing with the simulating results of the full dynamic model.