Gathering of Mobile Robots Tolerating Multiple Crash Faults

We study distributed coordination among autonomous mobile robots, focussing on the problem of gathering the robots at a single location. The gathering problem has been solved previously using deterministic algorithms even for robots that are anonymous, oblivious, disoriented, and operate in the semi-synchronous ATOM model. However these solutions require all robots to be fault-free. The recent results of Agmon and Peleg [1] show how to gather all correct robots when one of the robots may crash permanently. We study gathering in n-robot systems with f crashes for any f <; n. In such a scenario, no robot can wait for another robot, i.e., the algorithm must be wait-free. We provide such a wait-free algorithm to gather all correct robots assuming the capabilities of strong multiplicity detection and chirality. Unlike previous solutions, our algorithm does not impose the requirement of initially distinct locations, and works for any arbitrary initial configuration of robots (except the bivalent configuration where deterministic gathering is not possible).