Abstract
Pedestrian navigation especially indoors suffers from the unavailability of useful GNSS signals for positioning. Alternatively, a low-cost Inertial Measurement Unit (IMU) positioning system that does not depend on the GNSS signal can be used for indoor navigation. However its performance is still compromised because of the fast-accumulating heading drift error affecting such a low-cost IMU sensor. This results in a huge positioning error when navigating more than a few seconds using only the low-cost sensor. In this study, real field trials results are presented when a foot-mounted IMU is rotated on a single axis. Two promising results have been obtained. First, it mitigates the heading drift error significantly and second, it increases the observability of IMU z-axis gyro bias error. This has resulted in a greatly reduced error in position for the low-cost pedestrian navigation system.
Highlights
In indoor pedestrian navigation where a good and reliable Global Navigation Satellite System (GNSS) signal is often unavailable, the use of inertial sensors for a navigation system is not uncommon, for example in (Alvarez et al, 2012)
For the modelled Inertial Measurement Unit (IMU) errors in this trial, which are the accelerometer bias error and gyro bias error, only zaxis gyro bias is presented because it is considered the unobservable state when IMU is used with Zero Velocity Updates (ZUPT) only
After about 50s, the rotating IMU has resolved and stabilized to within 0.05 0/s from the reference, whilst the non-rotating IMU has not yet resolved to the reference, even until the end of the trial. This indicates that z-axis gyro bias is made observable through the use of the rotating IMU as opposed to the non-rotating IMU where the z-axis gyro bias converged to a wrong value
Summary
Because it is not possible to estimate the heading error using only ZUPT measurements. Unlike GNSS, it does not require external signals for positioning and navigation. It uses the concept of dead reckoning where the consecutive position and attitude relative to its initial position and initial attitude are computed from the IMU acceleration and gyro data. For a foot-mounted low-cost Pedestrian Navigation System (PNS), the frequent use of Zero Velocity Updates (ZUPT) measurements consistently bounds many of the IMU errors (Foxlin, 2005). The focus of this study is on how to address the heading drift problem-caused by the accumulated IMU heading error-which will degrade the accuracy of the IMU position solution (Jiménez et al, 2012). In this study, real field trial results are presented to demonstrate an approach to mitigate heading drift for the low-cost footmounted IMU after mechanically rotating the IMU.
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