Playing hide and seek

One important task for a mobile robot is playing the game of hide and seek. Imagine entering a cave in complete darkness. You are given a lantern and asked to search for any people who might be moving about, as shown in Figure 1.6b. Several questions might come to mind. Does a strategy even exist that guarantees I will find everyone? If not, then how many other searchers are needed before this task can be completed? Where should I move next? Can I keep from exploring the same places multiple times? This scenario arises in many robotics applications. The robots can be embedded in surveillance systems that use mobile robots with various types of sensors (motion, thermal, cameras, etc.). In scenarios that involve multiple robots with little or no communication, the strategy could help one robot locate others. One robot could even try to locate another that is malfunctioning. Outside of robotics, software tools can be developed that assist people in systematically searching or covering complicated environments, for applications such as law enforcement, search and rescue, toxic cleanup, and in the architectural design of secure buildings. The problem is extremely difficult because the status of the pursuit must be carefully computed to avoid unnecessarily allowing the evader to sneak back to places already searched. The information-space concepts of Chapter 11 become critical in solving the problem. For an algorithmic solution to the hide-and-seek game, see Section 12.4.