Time Synchronisation Error and Calibration in Integrated GPS/INS Systems

1/9 ABSTRACTThe necessity for precise time synchronisation of measurement data from multiple sensors is widely recognised in the field of GPS/INS integration. Having precise time synchronisation is critical for achieving high data fusion performance. The limitations and advantages of various time synchronisation scenarios and existing solutions are investigated in this paper. A criterion for evaluating synchronisation accuracy requirements is derived based on the comparison of the Kalman filter innovation series and the platform dynamics. An innovative time synchronisation solution using a counter and two latching registers is proposed. The proposed solution has been implemented with off-the-shelf components and tested. The resolution and accuracy analysis shows that the proposed solution has the capability to reach a time synchronisation accuracy at 0.1ms level if INS could provide hard-wired timing signal. A synchronisation accuracy of 2 ms has been achieved when the test system was used to synchronise a low-grade MEMS IMU which has only an RS-232 data output interface.