Hybrid Kalman and unscented Kalman filters for INS/GPS integrated system considering constant lever arm effect

CHANG Guo-bin(常国宾)^{1, 2}, LIU Ming(柳明)³

(1. Tianjin Institute of Hydrographic Surveying and Charting, Tianjin 300061, China;
2. Department of Navigation Engineering, Naval University of Engineering, Wuhan 430033, China;
3. Key Laboratory of Aviation Information Technology in Universities of Shandong,
Binzhou University, Binzhou 256603, China)

Abstract:In inertial navigation system (INS) and global positioning system (GPS) integrated system, GPS antennas are usually not located at the same location as the inertial measurement unit (IMU) of the INS, so the lever arm effect exists, which makes the observation equation highly nonlinear. The INS/GPS integration with constant lever arm effect is studied. The position relation of IMU and GPS’s antenna is represented in the earth centered earth fixed frame, while the velocity relation of these two systems is represented in local horizontal frame. Due to the small integration time interval of INS, i.e. 0.1 s in this work, the nonlinearity in the INS error equation is trivial, so the linear INS error model is constructed and addressed by Kalman filter’s prediction step. On the other hand, the high nonlinearity in the observation equation due to lever arm effect is addressed by unscented Kalman filter’s update step to attain higher accuracy and better applicability. Simulation is designed and the performance of the hybrid filter is validated.

Key words:inertial navigation system; global positioning system (GPS); integrated system; lever arm effect; Kalman filter; unscented Kalman filter