Formation Control Of Multi-mobile Robots

With the fast development of robot technology and automation products, coordination of multi-robot technology has become an important research direction in robotics and automation fields. As a basic problem of coordination of multi-robots, multi-robot formation control has been one of hot topic. The essential question of formation control lies on the ways to coordinate the system of multi-robot to accomplish the expected formation tasks.The cross-coupling approach enhances the coupling property of all system, not only makes formation control more precise, but also increases the robust of the whole system. The main idea is to control each robot to track its desired trajectory while synchronizing its motion with those of others to maintain relative kinematics relationships, as required by the formation.This thesis first describes the development and current research on multi-robot formation control technology. Then a brief introduction on the non-linear control theory is presented, which will be used in the following parts. This thesis combines the cross-coupling technology with traditional nonlinear control methods to accomplish the multi-robot formation control. The main contributions of this thesis are as follows:1. A simple nonlinear proportional-derivative(PD) control strategy is proposed for multi-robot formation control, based on cross-coupling approach. The proposed nonlinear PD control is formulated with a class of nonlinear saturated function with the characteristics of ‘enlargement of small error and saturated in large error’. The proposed control gives a better response and smaller position-tracking error and synchronization error.2. As for multi-robot formation control with uncertain disturbance, a class of approximate fast terminal sliding mode control is developed to give higher robustness against the impact of disturbances and better control performance. The proposed control is formulated with the robust of sliding mode and cross-coupling approach.3. Cross-coupling-based adaptive control approach is also proposed for uncertain system. The advantages of the proposed control include the absence of model parameter in the control law formulation and improved robustness.Lyapunov stability theory is employed to prove global asymptotic stability of the closed-loop system and zero convergence of the synchronization error. Simulation results on the multi-robot formation system demonstrate the effectiveness and performances of the proposed schemes.