A Planetary System-based Approach To Multi-robot Formation

With the development of distributed computing, scientists' range of study is gradually extended to multi-robots from single robot. Multi-robot system has many advantages, such as having good fault tolerance, being more robust, being more stable, etc., so multi-robot system has broad application prospects in the military, aerospace, industrial manufacturing and other areas. Formation, coordination and cooperation, path planning, and target tracking are included in the study of multi-robot system. As to multi-robot formation, there are two common control structures, namely the centralized control structure and the distributed control structure, and there are common formation approaches, such as the leader-follower-based approach, the behavior-based approach, and the potential field-based approach. To improve the traditional formation approach, this paper puts forward a new approach, namely a planetary system-based approach to multi-robot formation, which is theoretically analyzed in depth and verified by the simulation experiment. In this paper, the results are as follows:According to the planetary system operation rules, a planetary system-based approach to formation is proposed, which takes an advantage of the centralized structure and the distributed structure, and makes a use of potential field-based approach, behavior-based approach and leader-follower approach. As compared with the traditional approach to multi-robot formation, the planetary system-based approach takes an advantage of easy formation transformation, which is achieved by changing the distance and angle between the leader and the followers and therefore enables robots to successfully avoid obstacles and go through narrow roads.It is proved that the planetary system-based approach is stable by building up the mobile robot's transfer function and a Lyapunov function. Moreover, a necessary condition is given,where the constant of proportionality and differential constant should meet some relational expression in the PID controller.A scheme based on potential field is proposed to realize the planetary system-based approach, and the corresponding mathematical model is built, where the leader is equivalent to a fixed star, and the followers are equivalent to planets around the fixed star. There is attraction and repulsion between the leader and the followers, repulsion between robots and obstacles, and attraction between robots and goals.A simulation platform based on planetary system-based approach to multi-robot formation is independently established, where the multi-robots can form desired formations. It is verified that the planetary system-based approach is reasonable and the multi-robot system is stable. The mass proportion factor which reflects the leader's ability to migrate to the desired orbit and the capacity to maintain the scheduled orbit, is analyzed selectively and qualitatively as well as the spring proportion factor which reflects the multi-robots' ability to maintain the desired formation. Keywords: Multi-robot formation; planetary system-based approach; Leader-follower model; Potential field-based approach...