Evader surveillance under incomplete information

This paper is concerned with determining whether a mobile robot, called the pursuer, is up to maintaining visibility of an antagonist agent, called the evader. This problem, a variant of pursuit-evasion, has been largely studied, following a systematic treatment by increasingly relaxing a number of restrictions. In, we considered a scenario where the pursuer and the evader move at bound speed, traveling around a known, 2D environment, which contains obstacles. Then, considering that, in an attempt to escape, the evader travels the shortest path to reach a potential escape region, we provided a decision procedure that determines whether or not the pursuer is up to maintain visibility of the evader and obtained complexity measures of this surveillance task. In this paper, we prove that there are cases for which an evader may escape only if it does not travel the shortest path to an escapable region. We introduce planning strategies for the movement of the pursuer that keeps track of the evader, even if the evader chooses not to travel the shortest path to an escape region. We also present a sufficient condition for the evader to escape that does not depend on the initial positions of the players. It can be verified only using the environment. All our algorithms have been implemented and we show simulation results.