Streamline-Based Control of Underwater Gliders in 3D Environments
This work addresses path planning for slow-moving underwater gliders in complex ocean currents, which is an incremental advancement in domain-specific robotics.
The paper tackles the problem of controlling autonomous underwater gliders in 3D oceanic flows by extending streamline-based control from 2D to 3D using a 2.5D model, resulting in an efficient algorithm integrated into sampling-based motion planning with simulation examples showing performance gains.
Autonomous underwater gliders use buoyancy control to achieve forward propulsion via a sawtooth-like, rise-and-fall trajectory. Because gliders are slow-moving relative to ocean currents, glider control must consider the effect of oceanic flows. In previous work, we proposed a method to control underwater vehicles in the (horizontal) plane by describing such oceanic flows in terms of streamlines, which are the level sets of stream functions. However, the general analytical form of streamlines in 3D is unknown. In this paper, we show how streamline control can be used in 3D environments by assuming a 2.5D model of ocean currents. We provide an efficient algorithm that acts as a steering function for a single rise or dive component of the glider's sawtooth trajectory, integrate this algorithm within a sampling-based motion planning framework to support long-distance path planning, and provide several examples in simulation in comparison with a baseline method. The key to our method's computational efficiency is an elegant dimensionality reduction to a 1D control region. Streamline-based control can be integrated within various sampling-based frameworks and allows for online planning for gliders in complicated oceanic flows.