Avoiding Flip Ambiguities During Sequentially-Grown Formations

Flip ambiguities are a well-known problem in distance-based formation control, owing to the existence of multiple equilibrium points in the closed-loop dynamics. In this paper, we introduce a simple solution for avoiding such ambiguities in planar formations that are sequentially grown via triangulations. The control system consists of a low-level control law in the form of the standard distance-based controller and a high-level switching scheme that steers the formation to the region of attraction of the desired formation. The control system ensures convergence to the desired formation for all initial conditions except for the collocated and collinear cases. Experimental results are presented to demonstrate the formation control in action.