Ground Moving Target Handover between UAVs accompany with the Most Regional Coverage

In ground moving target tracking missions by UAVs, there are many reasons, such as running out of battery or fuel, to handover the mission to another UAV. In this paper we present an online handover algorithm with low probability of losing target while trying to maximize regional coverage along the takeover trajectory. The UAV that takes over the target predicts the target path using the estimated motion model and the last position of the target that is provided by the other UAV. Afterwards, the uncertainty surrounding each position of the target over the predicted path is computed. The position of the target in which the position uncertainty and the UAV's field of view have minimum difference, is the best place for retrieving the target. Among the possible paths to the retrieval point, the path that provides the most coverage is the best retrieval path. To determine this path, we have proposed an algorithm based on a “forward selection” strategy. In this algorithm, the uncovered and important positions of the region are clustered based on the distance from each other. Then, the centers of these clusters are added to the previous retrieved path recursively based on their effectiveness on the coverage value if the time of traveling on the new path is smaller than the time required for the target to reach the retrieval point. In each execution of the algorithm, using a “backward elimination” strategy, the coverage value of the retrieval path after recursive combination of each two adjacent clusters is checked to avoid from falling in local optima. We have simulated the proposed method and compared it with the optimal offline calculated path which shows the success of the proposed approach in retrieving the target and maximizing the regional coverage.