The combination of ultrawideband (UWB) radios and inertial measurement units (IMU) can provide accurate positioning in environments where the Global Positioning System (GPS) service is either unavailable or has unsatisfactory performance. The two sensors, IMU and UWB radio, are often not co-located on a moving system. The UWB radio is typically located at the extremities of the system to ensure reliable communication, whereas the IMUs are located closer to its center of gravity. Furthermore, without hardware or software synchronization, data from heterogeneous sensors can arrive at different time instants resulting in temporal offsets. If uncalibrated, these spatial and temporal offsets can degrade the positioning performance. In this paper, using observability and identifiability criteria, we derive the conditions required for successfully calibrating the spatial and the temporal offset parameters of a tightly-coupled UWB-IMU system. We also present an online method for jointly calibrating these offsets. The results show that our calibration approach results in improved positioning accuracy while simultaneously estimating (i) the spatial offset parameters to millimeter precision and (ii) the temporal offset parameter to millisecond precision.

中文翻译：

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紧耦合超宽带辅助惯性定位的在线时空标定

超宽带 (UWB) 无线电和惯性测量单元 (IMU) 的组合可以在全球定位系统 (GPS) 服务不可用或性能不令人满意的环境中提供准确定位。IMU 和 UWB 无线电这两个传感器通常不在移动系统上共处一地。UWB 无线电通常位于系统的末端以确保可靠的通信，而 IMU 位于更靠近其重心的位置。此外，如果没有硬件或软件同步，来自异构传感器的数据可能会在不同的时刻到达，从而导致时间偏移。如果未校准，这些空间和时间偏移会降低定位性能。在本文中，使用可观察性和可识别性标准，我们推导出成功校准紧耦合 UWB-IMU 系统的空间和时间偏移参数所需的条件。我们还提出了一种用于联合校准这些偏移量的在线方法。结果表明，我们的校准方法提高了定位精度，同时估计 (i) 空间偏移参数到毫米精度和 (ii) 时间偏移参数到毫秒精度。