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 SE2(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 48% improvement in localization accuracy.

翻译：超宽带系统正日益成为机器人间测距与通信的主流手段。超宽带技术面临的主要限制在于，为避免信号干扰，同一时间仅能有一对收发器进行测距，这制约了基于超宽带的定位系统的可扩展性。本文提出一种测距协议，允许所有机器人被动监听相邻通信机器人，且对机器人角色无任何层级限制。该协议使各机器人能够获取更多距离测量值，并广播预积分的惯性测量单元数据，从而直接在SE2(3)流形上进行相对扩展位姿状态估计。基于此，我们采用流形上的扩展卡尔曼滤波器构建了时钟同步与相对位姿联合估计器，并通过蒙特卡洛仿真对最多7个机器人的场景进行了评估。该测距协议在定制超宽带板卡上以C语言实现并搭载于3架四旋翼飞行器，所提滤波器经过多组实验验证，定位精度最高提升达48%。