Decentralized collision avoidance, deadlock detection, and deadlock resolution for multiple mobile robots

This paper describes a method for coordinating the independently planned trajectories of multiple mobile robots to avoid collisions and deadlocks among them. Whenever the distance between two robots drops below a certain value, they exchange information about their planned trajectories and determine whether they are in danger of a collision. If a possible collision is detected, they monitor their movements and, if necessary, insert idle times between certain segments of their trajectories in order to avoid the collision. Deadlocks among two or more robots occur if a number of robots block each other in a way such that none of them is able to continue along its trajectory without causing a collision. These deadlocks are reliably detected. After a deadlock is detected, the trajectory planners of each of the involved robots are successively asked to plan an alternative trajectory until the deadlock is resolved. We use a combination of three fully distributed algorithms to reliably solve the task. They do not use any global synchronization and do not interfere with each other.