Multi-Formation Planning and Coordination for Object Transportation

Multi-robot formations have numerous applications, such as cooperative object transportation in smart ware-houses. Here, robots must deliver objects in formation while avoiding intra- and inter-formation collisions. This requires solutions to multi-robot task assignment, formation generation, rigid formation maintenance, and route planning. In this paper, we present a cooperative multi-formation object transportation system which explicitly handles inter-formation collisions. For formation generation, we propose a distributed motion planning approach which combines artificial potential field methods and leader-follower based control. For formation planning, we present a heuristic search-based algorithm which uses convex segmentation techniques, and extend the minimum snap method to synthesise smooth trajectories while maintaining the formation. We also propose a variant of the dynamic window approach to avoid collisions between formations. We demonstrate the efficacy of our approach in simulation.

I. Introduction

A common approach for large object transportation in robotics is to use multiple robots to collaboratively push, cage, or grasp the objects [1]. This paper addresses cooperative transportation problems where multiple formations carry objects on top of them (see Fig. 1), which we refer to as multi-formation planning and coordination (MFPC). Here, the formations are rigid, i.e. the formation remains unchanged during transportation, which is necessary to balance heavy loads. To solve MFPC, we must generate and maintain effective formations until a goal location is reached while avoiding collisions with other formations and obstacles.