Collision-free tracking control of unicycle mobile robots

We propose a tracking control with collision avoidance for a group of unicycle mobile robots. A supervisory system assigns to each robot its reference path, together with the desired velocity profile as a function of the position along the path. The robot paths and velocity profiles do not necessarily prevent collisions of the robots. Based on the actual robot coordinates, reference velocities of individual robots are coordinated in real-time such as to ensure collision-free robot movements along the assigned paths. The robot motion controllers realize globally asymptotic stable tracking of the reference trajectories under constraints on the actuator inputs. The controllers proposed here offer several advantages with respect to those in the literature, such as better suppression of tracking errors due to more freedom in controller tuning and relaxed constraints on the reference velocities. The suggested tracking control with collision avoidance has successfully been validated in experiments. It can be used for the realization of autonomous transportation tasks in warehouses, harbors, factories, etc.