Single UWB Anchor Aided PDR Heading and Step Length Correcting Indoor Localization System

In this paper, we present a simple-structure Pedestrian Dead Reckon (PDR) system based on commercial IMU sensor and UWB ranging system. In PDR system, the accuracy of step and heading angle estimation completely decide the precision of location result. In order to select proper zero-velocity intervals for step and heading estimations in the foot stance/still stage, a modified zero-velocity detection way called Heuristic Step Detection (HSD) has been designed based on zero-velocity update algorithm (ZUPT). Based on the modified zero-velocity detection algorithm, i.e., HSD, an Kalman-type filter is used to get rough heading angle by fusing zero-velocity information and single UWB anchor ranging results. After that, a constrained sigma point based filter is used to further constrain heading angle range. Moreover, the range measures, provided by a UWB localization system with only one reference anchor, are used to correct the pedestrian step length. Trough UWB ranging measures analysis between two consecutive steps, the step length and pedestrian heading direction correcting processes are related to each other, and as a result, a more stable positioning result can be gotten. The corresponding practical experiments are conducted in real indoor environment over 2000 meters, and the results show that, compared with only INS-aided PDR, our scheme can reduce the average position error by more than 80%, and it can achieve long-term high accuracy and robust localization results.