Abstract
By aiding GPS receiver tracking loops with INS estimates of signal dynamics, GPS/INS ultra-tight coupling can improve the navigation performance in challenging environments. Traditionally the INS data are injected into the loops once every loop update interval, which limits the levels of dynamics accommodated. This paper presents a sample-wise aiding method, which interpolates the aiding Doppler into each digital sample of the local signal to further eliminate the dynamic errors. The relationship between the tracking error and the aiding rate is derived analytically. Moreover, the effects of sample-wise aiding using linear and spline interpolations are simulated and compared with traditional aiding under different INS data update rates. Finally, extensive tests based on a digital IF (intermediate frequency) signal simulator and a software receiver validate the theoretical equations and demonstrate that the dynamic stress error can be significantly reduced by sample-wise aiding.
Highlights
GPS and INS have complementary characteristics and their integration has been widely explored [1]
The scalar tracking based GPS/INS ultra-tight integration has been implemented in our software receiver. Both the traditional Doppler aiding and the sample-wise aiding with spline interpolation are incorporated into the receiver PLL and DLL, and their tracking performance in high dynamic scenarios can be tested by using our digital IF GPS signal simulator
Three factors have been considered in the design of dynamic scenarios for the tests: (1) to ensure that the receiver achieves steady state tracking before the aiding begins, no VAJ jumps are included in the trajectory, because carrier tracking loops are sensitive to dynamic jumps
Summary
GPS (global positioning system) and INS (inertial navigation system) have complementary characteristics and their integration has been widely explored [1]. Presented a federated GPS/INS deep coupling system employing three Kalman filters and providing adaptation ability to improve the navigation performance under various jamming conditions. All of these reported aiding methods, inject the externally-estimated carrier Doppler directly into the tracking loop as a constant during the coherent integration period, which is at least. The test results coincide with theoretical expectations and demonstrate that the sample-wise aiding can eliminate the dynamic errors much more effectively than the traditional aiding
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