Accurately Tracking Relative Positions of Moving Trackers based on UWB Ranging and Inertial Sensing without Anchors

TL;DR

This paper introduces a novel anchor-free relative positioning system using UWB and inertial sensors, employing a multi-stage EKF and MDS for robust tracking of moving nodes in dynamic environments.

Contribution

It presents a new method combining EKF and MDS for accurate, anchor-free relative tracking of moving nodes using UWB and inertial sensors.

Findings

Achieved 10.2cm accuracy in 2D and 21.7cm in 3D tracking.

System operates effectively without stationary anchors or external infrastructure.

Handles occlusions and dynamic group changes in real-time environments.

Abstract

We present a tracking system for relative positioning that can operate on entirely moving tracking nodes without the need for stationary anchors. Each node embeds a 9-DOF magnetic and inertial measurement unit and a single-antenna ultra-wideband radio. We introduce a multi-stage filtering pipeline through which our system estimates the relative layout of all tracking nodes within the group. The key novelty of our method is the integration of a custom Extended Kalman filter (EKF) with a refinement step via multidimensional scaling (MDS). Our method integrates the MDS output back into the EKF, thereby creating a dynamic feedback loop for more robust estimates. We complement our method with UWB ranging protocol that we designed to allow tracking nodes to opportunistically join and leave the group. In our evaluation with constantly moving nodes, our system estimated relative positions with an error of 10.2cm (in 2D) and 21.7cm (in 3D), including obstacles that occluded the line of sight between tracking nodes. Our approach requires no external infrastructure, making it particularly suitable for operation in environments where stationary setups are impractical.