Abstract
Pedestrian Navigation System (PNS) is one of the research focuses of indoor positioning in GNSS-denied environments based on the MEMS Inertial Measurement Unit (MIMU). However, in the foot-mounted pedestrian navigation system with MIMU or mobile phone as the main carrier, it is difficult to make the sampling time of gyros and accelerometers completely synchronous. The gyro-accelerometer asynchronous time affects the positioning of PNS. To solve this problem, a new error model of gyro-accelerometer asynchronous time is built. The effect of gyro-accelerometer asynchronous time on pedestrian navigation is analyzed. A filtering model is designed to calibrate the gyro-accelerometer asynchronous time, and a zero-velocity detection method based on the rate of attitude change is proposed. The indoor experiment shows that the gyro-accelerometer asynchronous time is estimated effectively, and the positioning accuracy of PNS is improved by the proposed method after compensating for the errors caused by gyro-accelerometer asynchronous time.
Highlights
Outdoor pedestrian positioning mainly relies on the Global Navigation Satellite System (GNSS)
The reference coordinate frames used in this paper are defined as follows: oixiyizi(i-frame): Earth-Centered Inertially Fixed (ECIF) orthogonal reference frame. oexeyeze(e-frame): Earth-Centered Earth-Fixed (ECEF) orthogonal reference frame. obxbybzb(b-frame): Body orthogonal reference frame aligned with Right-Forward-Up axes of MEMS Inertial Measurement Unit (MIMU). ob xb yb zb (b -frame): Accelerometer orthogonal reference frame aligned with accelerometer-sensitive axes. omxmymzm(m-frame): Carrier orthogonal reference frame aligned with Right-ForwardUp axes of foot . ohxhyhzh(h-frame): Horizontal orthogonal reference frame with X-axis and Y-axis in the local horizon. onxnynzn(n-frame): Navigation orthogonal reference frame aligned with local EastNorth-Up geodetic axes
Since the position errors caused by gyro-accelerometer asynchronous time will be accumulated over time, the proposed calibration method contributes to improving the stability of pedestrian navigation system (PNS) in a long time
Summary
Outdoor pedestrian positioning mainly relies on the Global Navigation Satellite System (GNSS). Ding and Skog et al utilized MIMU arrays to improve the positioning accuracy [24,25] These above methods do not consider the effect of the asynchronization of sampling time between gyros and accelerometers. Wen et al built a model of gyro-accelerometer asynchronous time in Dual-axis RINS, and proposed a calibration method that can improve the navigation velocity accuracy and system stability under long time navigation [27] These experimental results showed that the methods proposed by Yan and Wen succeed in calibrating the parameter of gyro-accelerometer asynchronous time and compensating for the errors in a low-dynamic environment by making IMU rotate around a single axis or double axes regularly.
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