Equivariant Morse theory and formation control

In this paper we study the critical points of potential functions for distance-based formation shape of a finite number of point agents in Euclidean space ℝ^d with d ≤ 3. The analysis of critical formations proceeds using equivariant Morse theory for equivariant Morse functions on manifolds of configuration spaces. We establish lower bounds for the number of critical formations. For d = 2 these bounds agree with the bounds announced in [3], while for d = 3 we obtain new bounds. We also propose a control law of the form of a decentralized gradient flow that evolves on a configuration manifold for agents in ℝ^d such that collisions among the agents do not occur. By computing the equivariant cohomology of the configurations spaces we establish new lower bounds for the number of critical collision-free formations in the configuration space. Our work parallels earlier research in geometric mechanics by Pacella [19] and McCord [18] on enumerating central configurations for the N-body problem.