Research On Integrated GPS/INS System And Realization

Global Positioning System (GPS) provides the high accuracy of positioning output under normal environment, but the GPS receiver can't work well when the signal is attenuated under the complex environment. The Strapdown Inertial Navigation System (SINS) has the advantage of being independent of external electromagnetic signals, and it can operate in any environment. But the SINS system suffers from time-dependent error growth which causes a drift in the solution for the work principle. The integration of GPS and SINS can overcome the defects of SINS or GPS standalone systems, and benefits from the complementary characteristics of the two systems. When the GPS signal is outage, the SINS can work alone till the GPS signal is gotten back to provide the continuous positioning output.Based on a detailed analysis of the SINS and the GPS, the crucial technology of GPS/INS is discussed in detail, which includes the time synchronization between the data from GPS receiver and IMU and the integration algorithm. For reducing the influence of time synchronization error on the data fusion performance of hybrid filter, some equations are derived to determine the influence of time synchronization error on the Kalman filter and a new solution for time synchronization based on a Field Programmable Gate Array (FPGA) is proposed. The loose integration and the tight integration algorithm is simulated to approve the validity, specially the validity of tight integration algorithm of GPS/INS is discussed under the environment of fewer than four satellites. In the context of engineering, a loose GPS/INS integration scheme is implemented based on MEMS IMU, and the non-holonomic constraints for land vehicle applications is introduced to keep the position accuracy within bounds when the GPS is not available. The result of the field test demonstrated the validity of the system.