Multi-Target Search Strategies

This paper addresses the problem of searching multiple non-adversarial targets using a mobile searcher in an obstacle-free environment. In practice, we are particularly interested in marine applications where the targets drift on the ocean surface. These targets can be surface sensors used for marine environmental monitoring, drifting debris, or lost divers in open water. Searching for a floating target requires prior knowledge about the search region and an estimate of the target's motion. This task becomes challenging when searching for multiple targets where persistent searching for one of the targets can result in the loss of other targets. Hence, the searcher needs to trade-off between guaranteed and fast searches. We propose three classes of search strategies for addressing the multi-target search problem. These include, data-independent, probabilistic and hybrid search. The data independent search strategy follow a pre-defined search pattern and schedule. The probabilistic search strategy is guided by the estimated probability distribution of the search target. The hybrid strategy combines data-independent search patterns with a probabilistic search schedule. We evaluate these search strategies in simulation and compare their performance characteristics in the context of searching multiple drifting targets using an Autonomous Surface Vehicle (ASV).