Research On Formation Control For Multiple Mobile Robots

In recent years, along with the development of the computer technology and wireless communication technology, the development of multi-robots cooperation has became possible, and got more and more applications. Multi-robots cooperation and coordination can complete the tasks that a robot cannot complete. Formation control is the foundation of other coordination problems, and a hot research field at home and abroad. The so-called formation control refers to multiple robots in the process of moving to the goal, maintaining the formation as desired, at the same time, adapting to the constraint of environment.For the problem mentioned above, formation control of multi-robots under the obstacles environment and the obstacle-free environment is studied separately, for formation control of multi-robots system, this thesis built system model, designed the controller, and analyzed stability of the system. Main achievements are as follows:Firstly, this thesis researches on formation control of multiple mobile robots under obstacle-free environment. Using the Leader-follower way control formation, establishing kinematics models in Cartesian coordinate, which can avoid the singularity points when using polar coordinate, by using the input/output feedback linearization approach, a control law is designed, which guarantees that the system output exponentially tracks the given desired output. Then the stability of formation is analyzed, and come to the conclusion that under the closed-loop control law the system is steady, it lays a theoretical foundation for formation control in leader-follower way under the closed-loop control law. Simulation results show the effectiveness of the method.Secondly, a sliding-mode control is put forward; it can avoid the shortcoming of the input/output feedback linearization approach, and deal with uncertainty problem in practical application. First, the sliding surface and the control law are designed, and then asymptotic stability of the system is proved by Lyapunov stability theory. Simulation results verify that the controller not only can stabilize the formation, but also has robustness for uncertainty.Finally, the thesis studies on formation control of multi-robots under the obstacles environment. The layered control method is put forward, to avoid faults in the centralized control and decentralized control. Using a virtual robots as the team leader robot, which can solved the problem that demanding too much of the security of the leader robot. Put forward the ideas that the whole team have a troop feedback to solve the problem that the stability is not guarantee by using behavior-based methods, then the smooth control will be realized. Both Theoretical results and simulation results show that the systemic robustness and the system stability have improved significantly.