Relative Pose Estimation for Nonholonomic Robot Formation With UWB-IO Measurements

This article studies the problem of distributed formation control for multiple robots by using onboard ultra wideband (UWB) distance and inertial odometer (IO) measurements. Although this problem has been widely studied, a fundamental limitation of most works is that they require each robot’s pose and sensor measurements are expressed in a common reference frame. However, it is inapplicable for nonholonomic robot formations due to the practical difficulty of aligning IO measurements of individual robot in a common frame. To address this problem, first, a concurrent-learning-based estimator is first proposed to achieve relative localization between neighboring robots in a local frame. Different from most relative localization methods in a global frame, both relative position and orientation in a local frame are estimated with only UWB ranging and IO measurements. Second, to deal with information loss caused by directed communication topology, a cooperative localization algorithm is introduced to estimate the relative pose to the leader robot. Third, based on the theoretical results on relative pose estimation, a distributed formation tracking controller is proposed for nonholonomic robots. Both 2-D and 3-D real-world experiments conducted on aerial robots and grounded robots are provided to demonstrate the effectiveness of the proposed method.