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New strategies for anonymous mobile robots to form a desired circle

Peking University, May 9, 2014: Cooperative mobile robots have been utilized more and more often to carry out a growing variety of team tasks. In many scenarios, these agents are required to cooperatively generate and maintain certain desired geometric shapes to improve the quality of the data collected collectively or the robustness of group motion. Forming circle formations becomes a benchmark problem. Professor Xie Guangmin’s group from College of Engineering, PKU has made new progress in formation control of such multi-agent system and published two papers in leading international journals.

Professor Xie’s group is among the early researchers in multi-agent system, which involves multiple subjects such as control, mathematics, physics, biology, computer, robotics, communication and artificial intelligence. It has become a significant research area in the frontiers of multi-subject crossing field, and also attracts scholar’s attention worldwide.

Based on their previous researches, the group focuses on formation control in multi-agent system, especially circles formation, and has achieved systematic and profound results.

In the first paper, they propose distributed control laws for a group of anonymous mobile agents to form desired circles when the agents move in the one-dimensional space of a circle. To make the control strategies more practical, they further discuss sampled-data control laws, which by utilizing the technique of adopting time-varying gains are able to guide the agents to form the desired circle formation within any given finite time. One feature of the proposed control laws is that they guarantee that the spatial ordering of the agents is preserved throughout the system’s evolution, and thus no collision may take place during the process of forming circle formations. The results are published in IEEE Transactions on Automatic and Control (C. Wang, G. Xie, M. Cao, Forming circle formations of anonymous mobile agents with order preservation, IEEE Transactions on Automatic Control, 58(12), 3248—3254, 2013).

Considering that some robots cannot go backwards, Professor Xie’s group studies the circle forming problem in which the agents are constrained to move in the one-dimensional space of the circle only in the counterclockwise direction. They propose a sampled-data distributed control law and prove that the multi-agent system under such constrained control input can be guided to reach the prescribed circle formation asymptotically and in addition can guarantee that no collision between agents ever takes place. The theoretical analysis is further validated through simulations. Their research is published as regular paper in Automatica (C. Wang, G. Xie, M. Cao, Controlling anonymous mobile agents with unidirectional locomotion to form formations on a circle, Automatica, 50(4), 1100—1108, 2014).

Ph.D. candidate Wang Chen, member of the group, is the first author of the two papers. Professor Xie is the correspondent author. Professor Ming Cao from University of Groningen, Netherlands, collaborates with the group and keeps close communication with them. The research was funded by National Natural Science Foundation of China.

Written by: Li Ruiqi
Edited by: Chen Long
Source: PKU News (Chinese)