A Novel Design of an Adaptive Hybrid Low-cost GPS/INS Integration System

Junchuan Zhou, Stefan Knedlik, Pakorn Ubolkosold, Ezzaldeen Edwan, Zhen Dai, Otmar Loffeld

Abstract:	The global positioning system (GPS) has been widely used for navigation in various applications. Although it meets in many cases the positioning requirements, the receiver might show deficiencies in attenuated signal environments due to multipath, weak signal power, high dynamics, and some other limitations. GPS receiver aiding with information obtained from external sensors or sensor systems like an inertial navigation system (INS) has been proposed for solving this problem. In many commercial applications, especially in automotive industry, the micro-electro-mechanical system (MEMS) based inertial measurement unit (IMU) is preferred in an integrated GPS/INS system due to the lower cost, lower power-consumption and smaller size. However, its own positioning performance is usually relatively poor, that is, the INS position and attitude errors grow quickly over time. For the GPS/INS integration, in open sky environments, the loosely-coupled integration can provide a good positioning accuracy with fast response to INS errors, but in urban canyons or other highly attenuated signal environments, the ultra tightly-coupled integration (or deeply-coupled integration) is much better and hence, is receiving more attention recently. In this paper, a novel adaptive hybrid low-cost GPS/INS integration system architecture (while exploiting GPS L1 coarse/acquisition code (C/A-code) pseudorange measurements) is proposed. We call it hybrid architecture, because different types of integration are presented in one system as different working modes, which are running alternatively according to the GPS signal conditions. In open sky environments, the loosely-coupled integration is preferred due to its higher INS error correction rate. In challenging environments, the tightly-coupled integration is used to achieve INS error corrections even when less than four satellites are tracked. With the precisely estimate and control of the IMU error sources, the GPS signal tracking capability can be enhanced by utilizing the inertial velocity aiding. But for consumer grade IMUs (often MEMS-IMUs) it is still a challenge.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	521 - 531
Cite this article:	Zhou, Junchuan, Knedlik, Stefan, Ubolkosold, Pakorn, Edwan, Ezzaldeen, Dai, Zhen, Loffeld, Otmar, "A Novel Design of an Adaptive Hybrid Low-cost GPS/INS Integration System," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 521-531.
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