A Comparative Analysis on Rigid and Flexible Formations of Multiple Differential-Drive Mobile Robots: A Motion Capability Perspective

Abstract

This paper analyzes the motion capability of multiple differential-drive mobile robot formations, when strict velocity and angular velocity constraints of individual robots are explicitly taken into consideration. Different from most of the existing related studies on multi-robot formation, which mainly concentrate on motion planning or control algorithm design, this work pay attention to a long-neglected issue that whether the desired formation can be maintained with velocity and angular velocity constraints imposed on individual robots. To solve this problem, a quantitative metric, the feasible set of formation angular velocity, is introduced to characterize the turning ability of a formation. Three common formations, namely perfect rigid formation, semi-perfect rigid formation and flexible formation, are discussed in this paper. It has been proven that perfect rigid formation has a rather limited mobility, while flexible formation is more agile than rigid formation in that it can execute more flexible maneuvers than the corresponding rigid formation with the same formation width. Simulations have been performed to illustrate the theoretical analysis.