A Combined Path Planning and Path Following Method for Underwater Glider Navigation in a Strong, Dynamic Flow Field

In this paper, path planning is used to design the time-optimal path for an underwater glider subject to realistic flow conditions, while flow canceling strategy is used to calculate glider's steering angle such that it will follow the planned path. Navigation performance, defined in terms of path tracking error and travel time for glider to reach the destination, is discussed for cases of using flow canceling algorithm with respect to different flow conditions and relative strength of the time-varying and averaged flow. Mathematical analysis shows that performing path following with the averaged flow results in shorter travel time compared to performing path following with instantaneous flow, when non-tidal flow is the dominant component in the field. But it may result in longer travel time when tidal flow is the dominant component in the field. Path following with averaged flow results in increasing path following error if flow speed is less than the glider's forward speed. When flow speed is comparable to glider speed, the path tracking error can be unbounded when using flow canceling with instantaneous flow. Simulated experiments near Cape Hatteras, NC show that performing flow canceling algorithm with averaged flow will result in shorter travel time, but may induce larger path tracking error than performing flow canceling algorithm with instantaneous flow.