Pairwise observable relative localization in ground aerial multi-robot networks

This paper addresses the problem of relative localization in a team of robots which consists both ground and aerial platforms. The robots are equipped with sensors for measuring both range and bearing of neighboring team members. Pairwise observability in such a team refers to the ability of two robots to estimate their relative poses, without strictly relying on information or measurements of other team members. This capability is important to realize many robotic behaviors such as sense and avoidance, formation control, and leader follower supervisory control, in a robust and minimally dependent manner. This paper presents an implementation and an analysis of a multi-robot relative localization network. In order to identify the necessary conditions for achieving pairwise observability, the study performs a nonlinear observability analysis. The analysis considers the cases where input velocities of the measured platforms are unknown, which is relevant to most drifting aerial platforms facing communication constraints and sensing limitations. The results of the analysis are experimentally demonstrated, along with the implications of the observability study in designing multi-robot teams and estimation frameworks.