Practical Formation Tracking Control of Multiple Unicycle Robots

This note presents a distributed formation tracking scheme for multiple nonholonomic unicycle robots with any smooth reference trajectory, either feasible or non-feasible. The formation tracking problem is solved via a local tracking control law and a distributed virtual reference trajectory, converting the cooperative formation problem into a local tracking case. Several state transformations, dynamic oscillator approach, graph theory, and Lyapunov's method are combined to design formation tracking control law. We prove that the closed-loop formation tracking errors are globally uniformly ultimately convergent to an arbitrarily small neighborhood of the origin. This convergence does not depend on any persistent excitation (PE) condition of the reference trajectory. The simulation results validate the proposed formation tracking design.