Weak Rigidity Theory and its Application to Multi-agent Formation Stabilization
For multi-agent formation control, this work reduces the sensing and communication requirements by relaxing the rigidity condition, enabling formation stabilization with fewer constraints.
This paper introduces weak rigidity, requiring fewer graph edges than distance-based rigidity for shape determination, and designs gradient and non-gradient control laws for multi-agent formation stabilization. The gradient law achieves local exponential stability for infinitesimally weakly rigid formations, while the non-gradient law does not require a rigid sensing graph for stability.
This paper introduces the notion of weak rigidity to characterize a framework by pairwise inner products of inter-agent displacements. Compared to distance-based rigidity, weak rigidity requires fewer constrained edges in the graph to determine a geometric shape in an arbitrarily dimensional space. A necessary and sufficient graphical condition for infinitesimal weak rigidity of planar frameworks is derived. As an application of the proposed weak rigidity theory, a gradient based control law and a non-gradient based control law are designed for a group of single-integrator modeled agents to stabilize a desired formation shape, respectively. Using the gradient control law, we prove that an infinitesimally weakly rigid formation is locally exponentially stable. In particular, if the number of agents is one greater than the dimension of the space, a minimally infinitesimally weakly rigid formation is almost globally asymptotically stable. In the literature of rigid formation, the sensing graph is always required to be rigid. Using the non-gradient control law based on weak rigidity theory, the sensing graph is unnecessary to be rigid for local exponential stability of the formation. A numerical simulation is performed for illustrating effectiveness of our main results.