An improved tightly coupled approach for GPS/INS integration

The GPS/INS integration system has been widely applied for navigation due to its complementary characteristics. The tightly coupled integration approach has the advantage over the loosely coupled approach by using raw GPS measurements, but hence introduces nonlinearity into the measurement equation of the Kalman filter. So, linearization is usually used. Consequently, the errors of linearization may make the Kalman filter unstable or even divergent, especially under the situation that low quality inertial devices are included. To solve this problem, an improved tightly coupled approach by adding second-order derivative information to retain some nonlinear characteristics is proposed in this paper. Simulation results indicate that the nonlinear terms included in the filtering process greatly influence the performance of integration, especially in the case where the low quality INS is used in the integrated system.