Ultra-wideband (UWB) systems are becoming increasingly popular as a means of inter-robot ranging and communication. A major constraint associated with UWB is that only one pair of UWB transceivers can range at a time to avoid interference, hence hindering the scalability of UWB-based localization. In this paper, a ranging protocol is proposed that allows all robots to passively listen on neighbouring communicating robots without any hierarchical restrictions on the role of the robots. This is utilized to allow each robot to obtain more range measurements and to broadcast preintegrated inertial measurement unit (IMU) measurements for relative extended pose state estimation directly on SE_2(3). Consequently, a simultaneous clock-synchronization and relative-pose estimator (CSRPE) is formulated using an on-manifold extended Kalman filter (EKF) and is evaluated in simulation using Monte-Carlo runs for up to 7 robots. The ranging protocol is implemented in C on custom-made UWB boards fitted to 3 quadcopters, and the proposed filter is evaluated over multiple experimental trials, yielding up to 56% improvement in localization accuracy.

翻译：超宽带（UWB）系统作为机器人间测距与通信的手段正日益普及。UWB的主要限制在于，为避免干扰，同一时间仅允许一对UWB收发机进行测距，从而阻碍了基于UWB定位的可扩展性。本文提出一种测距协议，允许所有机器人被动监听邻近通信机器人，且对机器人角色无层次限制。据此，每个机器人可获取更多测距测量值，并广播预积分惯性测量单元（IMU）测量值，用于直接在SE_2(3)上进行相对扩展位姿状态估计。进而，利用流形上的扩展卡尔曼滤波器（EKF）构建了同步时钟与相对位姿估计器（CSRPE），并通过蒙特卡洛仿真对多达7个机器人进行了评估。该测距协议已在配备于3架四旋翼飞行器的定制UWB板卡上用C语言实现，所提滤波器经多次实验验证，定位精度提升幅度高达56%。