A Tightly-Coupled Reduced Multi-Sensor System for Urban Navigation

T. Karamat, J. Georgy, U. Iqbal, A. Noureldin

Abstract:	In land vehicle navigation, global positioning system (GPS) suffers from various signal blockages. GPS can be augmented with an inertial navigation system (INS) which typically uses three accelerometers and three gyroscopes housed in an inertial measurement unit (IMU) to aid during GPS outages. The GPS and IMU data fusion is most commonly achieved through Kalman filter (KF) by either loosely coupled or tightly coupled integration. To reduce the cost and size of the integrated system, microelectromechanical system (MEMS) based sensors are preferred for land vehicles. However, such low cost sensors have complex error characteristics. One way that can mitigate the effect of such errors is the use of fewer inertial sensors in an IMU with some constraints. In the past, various such partial IMU configurations have been proposed for integration with GPS which are mostly based on loosely coupled integration that does not benefit from GPS aiding when the satellite signals drop below four.. This paper explores the benefits of using tightly coupled integration of GPS and a reduced inertial sensor system (RISS) to compute a three dimensional (3D) navigation solution. This integration mitigates the errors associated with the use of a full MEMS-based IMU and, at the same time, extracts maximum possible aiding from GPS during limited availability of satellites. In this research a total of four sensors are used to aid GPS. The gyroscope is mounted so that its sensitive axis is aligned with the vertical axis of the vehicle to obtain heading information and the odometer provides forward speed. To calculate pitch and roll angles, two accelerometers (instead of gyroscopes) are used which are aligned with forward and transversal axes of the vehicle body. The pitch and azimuth angles are used to calculate the East, North and vertical (Up) velocities from the forward speed. Consequently, the latitude, longitude and the altitude are determined providing a 3D position of the vehicle. This research has a direct influence on land vehicle navigation which promises to overcome the frequent GPS outages in degraded GPS environments and alleviate the errors ascribed to MEMS sensors. An additional consequence of this research is significant reduction in the cost of an integrated system due to the use of fewer MEMS inertial sensors.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	582 - 592
Cite this article:	Karamat, T., Georgy, J., Iqbal, U., Noureldin, A., "A Tightly-Coupled Reduced Multi-Sensor System for Urban Navigation," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 582-592.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In