GPS-Aided Inertial Navigation System (GAINS) Evaluation Methodology for Airborne Missile Applications

Victor J. Estrada, Kenneth K. Yoo, Todd A. Moore, James L. Anders

Abstract:	The GPS-Aided Inertial Navigation System (GAINS) developed by Raytheon Systems Company has proven to be an effective GPS/INS system for several applications. In this paper, we discuss the GAINS test and evaluation process which has been developed to help ensure it meets all navigation requirements for its mission and prepare it for missile free-flight test. Raytheon has developed a battery of tests designed to exercise each level of GAINS functionality. These tests range from a pure software simulation to hardware-in-the-loop (HIL) testing, and finally to full dynamic testing. A software simulation is initially used to test the functionality of the navigation and Kalman filter algorithm implementation. This simulation embeds GAINS operational software into a high-fidelity software simulation of the hardware and dynamic environment. This provides a way to test software and algorithmic changes quickly. After the software simulation phase has been completed, the HIL simulation is used to evaluate the combination of the embedded hardware and software in a simulated dynamic environment. The HIL environment uses a time-synchronized Inertial Measurement Unit (IMU) and GPS signal simulator to “fly” GAINS through the predicted trajectory. In both the simulation and HIL tests, the results are compared to a high-fidelity truth model which has been developed using high-order navigation equations, as well as to the predicted accuracies from an error covariance analysis. Using these techniques, resultant errors of each test can be quantified and analyzed. The final phase of testing includes full system-level dynamic tests. These dynamic tests are divided into low-dynamic van tests and higher-dynamic aircraft flight tests. For the dynamic test GAINS, which includes an IMU, and the necessary support equipment, is mounted into the test vehicle and exercised by operating through pre-determined dynamic routes. Support equipment includes the GPS antenna and independent “scoring systems.” The low-dynamic van tests are a relatively quick and low-cost way to test the functionality of the fully-integrated system. The flight tests (using an A-3 aircraft as the test vehicle) are conducted to test GAINS performance at higher dynamics including roll, pitch, altitude, and velocities which can not be achieved in van testing. The components which make up the scoring system are a Differential GPS system which provides a high-accuracy position and velocity reference, and an Embedded GPS/INS (EGI) for attitude reference. The GAINS navigation errors are quantified by comparing its solution with those of the scoring system components. With this information, GAINS performance can be characterized for current applications as well as evaluated in varying dynamic situations to help determine the applicability of GAINS to future applications. The test philosophy employed by Raytheon for GAINS has been critical to reducing risk in its primary role as a tactical missile navigation system. The test approach described herein--which has proven successful in previous applications--may be helpful to other GPS/INS developers.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	611 - 616
Cite this article:	Estrada, Victor J., Yoo, Kenneth K., Moore, Todd A., Anders, James L., "GPS-Aided Inertial Navigation System (GAINS) Evaluation Methodology for Airborne Missile Applications," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 611-616.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In