A Low-Cost Foot-Placed UWB and IMU Fusion-Based Indoor Pedestrian Tracking System for IoT Applications

Abstract

Among existing wireless and wearable indoor pedestrian tracking solutions, the ultra-wideband (UWB) and inertial measurement unit (IMU) sensors are the popular options due to their accurate and globally referenced positioning, and low-cost and compact size, respectively. However, the UWB position accuracy is compromised by the indoor non-line of sight (NLOS) and the IMU estimation suffers from orientation drift as well as requiring position initialization. To overcome these limitations, this paper proposes a low-cost foot-placed UWB and IMU fusion-based indoor pedestrian tracking system. Our data fusion model is an improved loosely coupled Kalman filter with the inclusion of valid UWB observation detection. In this manner, the proposed system not only adjusts the consumer-grade IMU’s accumulated drift but also filters out any NLOS instances in the UWB observation. We validated the performance of the proposed system with two experimental scenarios in a complex indoor environment. The root mean square (RMS) positioning accuracy of our data fusion model is enhanced by 60%, 53%, and 27% compared to that of the IMU-based pedestrian dead reckoning, raw UWB position, and conventional fusion model, respectively, in the single-lap NLOS scenario, and by 70%, 34%, and 12%, respectively, in the multi-lap LOS+NLOS scenario.

Integrated UWB/MIMU Sensor System for Position Estimation towards an Accurate Analysis of Human Movement: A Technical Review

“…The most commonly used UWB sensor hardware system is the DW/M1000 OR DMW1001 (DecaWave, Dublin, Ireland) [ 31 , 32 , 33 , 35 , 44 , 46 , 47 , 50 , 51 , 57 , 58 , 59 , 60 , 61 , 62 , 65 , 66 , 67 ], which was used in 18 articles, while the Unisense series 7000 was used in 4 articles [ 7 , 38 , 39 , 41 ]. The PlusOn 410 UWB [ 34 ], UWB Mini4sPlus [ 54 ], and BeSpoon [ 43 ] were each used in one article.…”

“…UWB sensors are henceforth referred to as ‘nodes’, and those used in these articles were classified into two classes based on their functionality and named accordingly as ‘anchors’ and ‘tags’. UWB nodes are referred to as anchors when they are placed in fixed known positions around the measurement region and typically form a frame of reference for the position of the tags, while tags are the UWB nodes with an unknown, dynamically changing, position that is worn by the subject [ 65 ].…”

“…The resulting distance estimates between the tags and anchors were then used to estimate the 2D or 3D position of the tag by the method of trilateration or multilateration, or by an optimization method minimizing least square position errors [ 69 ]. For both methods, at least the (required) minimum of three anchors was used to locate each tag in 2D space and at least the (required) minimum of four anchors was used to locate a tag in 3D space [ 65 ]. However, in some of the reviewed articles the UWB distance estimates were used as a direct input for their data fusion approach.…”

Pedestrian Localization with Stride-Wise Error Estimation and Compensation by Fusion of UWB and IMU Data

“…In [ 19 , 20 , 21 ], the authors used IMU data to propagate the user position estimate. In this approach, a UWB measurement is discarded if its difference to the propagated estimate exceeds a predetermined threshold.…”

“…Here, Var( U ) is known from (21) and Var(ϕ U ) is known from (34). The expected value in Cartesian coordinates k = V U e is known from (7b), and the expected value in polar coordinates p = ϕ U is known from (5).…”