Real-time Cycle-slip Detection and Correction for Land Vehicle Navigation using Inertial Aiding

摘要

Carrier phase measurements require resolution of integerambiguities before precise positioning can be achieved.The GPS receiver can keep track of the integer number ofcycles as long as the receiver maintains lock to thesatellite signal. However, in reality, the GPS signal couldbe interrupted momentary by some disturbing factorsleading to a discontinuity of an integer number of cyclesin the measured carrier phase. This interruption in thecounting of cycles in the carrier phase measurements isknown as a cycle slip. After a cycle slip, ambiguities needto be resolved again or cycle slips need to be corrected toresume the precise positioningavigation process. Thesecycle slips can, to some extent, be detected and fixed toavoid delay and computation complexity attributed to theprocess of integer ambiguity resolution. Capitalizing onthe complementary characteristics of INS and GPS, INS isused to provide external information to detect and correctcycle slips. Lately, MEMS grade inertial sensors are beingused for low cost navigation applications. Moreover,recent research is geared towards the use of fewernumbers of sensors avoiding their complex errors andreducing the cost. This paper introduces integration ofGPS and reduced inertial sensor system (RISS) to addressthe problem of cycle slips. The performance of proposedmethod is examined on several real-life land vehicletrajectories which included various challenging drivingscenarios including high and slow speeds, suddenaccelerations and decelerations, sharp turns and steepslopes etc. Results demonstrate the effectiveness of theproposed algorithm in these severe conditions whichcause intensive and variable-sized cycle slips. Thisresearch has a direct influence on navigation inchallenging environments where frequent cycle slipsoccur and resolving integer ambiguities is not affordablebecause of time and computational constraints. Anadditional consequence of this research is the significantreduction in the cost of an integrated system due to theuse of fewer MEMS inertial sensors.