URBAN NAVIGATION SYSTEM FOR AUTOMOTIVE APPLICATIONS USING HSGPS, INERTIAL AND WHEEL SPEED SENSORS

摘要

Land vehicle navigation in urban areas, where masking effects are very frequent, is a major challenge for both the accuracy and the integrity of GPS-only solution. Several strong effects linked to urban canyon environments can seriously degrade the final position solution. Thus, the sole use of a GPS to navigate in urban areas has been proven to be challenging when high performances are expected in terms of accuracy and integrity of the computed solution. This paper proposes a "Smooth correction function" applied to the GPS received signals. This function works on the reliability of the pseudo-range measurements when affected by diverse sources of errors. Thus, to deal with different phenomena such as multipath or low C/No signals, a merging technique between the pseudo-range and Doppler measurements is proposed. The coupling of GPS with other positioning systems has been shown to be part of a solution to overcome satellites visibility problem in urban areas. The idea is to combine external measurements together with GPS measurements in order to improve the overall navigation system performance even during complete GPS signal outages. Dead-reckoning sensors are a classical solution to this problem. Nevertheless, due to the lack of stability of these sensors, GPS is still required to correct their correlated errors and give an absolute position when available. Classical land vehicle navigation solutions perform GPS augmentation by using Wheel Speed Sensors (WSS) and gyros. This paper looks at the potential benefits of a coupling approach between these two types of sensors for a complete land vehicle navigation solution. WSS provide wheel angular rate measurements and are fundamental components in the antilock braking system (ABS). Finally, this paper introduces a multi-aided navigation system specifically designed for land vehicle navigation in urban environments. Not only sensors particularly developed for land vehicle navigation are tested, but also an interesting use of the received GPS signals (pseudo-range and Doppler) is done, leading to an optimized tight integration scheme. Test campaigns are conducted to validate the performance of the proposed integrated land vehicle navigation system. The contribution of the system is evaluated for different scenarios (urban and open areas).