A synchronous controller for multiple mobile robots in time-varied formations

This paper presents a synchronization control strategy for formation control of swarm of mobile robots. The formation control problem is successfully posed as a synchronization control problem, and the concept of synchronization error is created for measuring the formation control effect. A decentralized trajectory tracking controller is developed with feedback of both position and synchronization errors, formed with a combination of feedforward, feedback and a saturation control, without significant use of robot models. It is proven that this synchronization controller guarantees both position and synchronization errors to converge to zero. The rotary control, in the form of a computed torque control, ensures that the robot is always oriented towards its desired position to assist the formation control in translation. Experiments were performed on three mobile robots in a formation switch task. The experimental results demonstrate the effectiveness of the proposed synchronous formation control approach.