Gradient-Based Cluster Space Navigation for Autonomous Surface Vessels

This paper presents an experimentally demonstrated gradient-based multirobot technique for adaptively navigating within a parameter field. To implement this technique, simultaneous measurements of the parameter are made at different locations within the field by a spatially controlled cluster of mobile robots. These measurements are shared in order to compute a local gradient of the field. Depending on the task to be achieved, the multirobot cluster is directed with respect to this direction. Moving in or opposite to the gradient direction allows efficient navigation to local maxima/minima in the field, a capability of interest for applications such as detecting pollution sources or the location of resource-starved areas. Moving perpendicular to the gradient direction allows parameter contours to be navigated, a behavior useful for applications such as defining the extent of a field or establishing a safety perimeter at a defined field level. This paper describes the multirobot control technique which combines a full degree-of-freedom “cluster space” multirobot controller with a gradient-based adaptive navigation capability. Verification of the technique through field experiments using a fleet of three robotic kayaks is also presented. Finally, a discussion of results, a review of challenges, and a review of ongoing and future work are presented.