Development and Assessment of a Low Dynamic Vehicle Navigation System

摘要

There is a need in military operations for reliable, highaccuracy,rnand low-cost vehicle navigation systems for usernin both manned and unmanned ground and air vehicles.rnGeodetics' Geo-LDV product is an integrated GPS/INSrnnavigation system providing real-time, high-accuracyrnTime Space Positioning Information (TSPI) in a low-cost,rnlight-weight ruggedized package.rnPositioning accuracy in the Geo-LDV is achieved throughrnthe use of dual-frequency carrier phase differential GPSrnsolutions provided by Geodetics' Epoch-by-Epoch?rn(EBE) technology. EBE performs Precise InstantaneousrnNetwork (PIN) positioning utilizing data from one orrnmore GPS reference receivers and the vehicles on-boardrnGPS receiver to produce a rigorous network solution atrneach measurement epoch. Unlike traditional differentialrnGPS approaches, there is no need for re-initializationrnimmediately following loss-of-lock problems, such asrnoccurs when GPS satellites are occluded from thernantennas view. This feature of instantaneous integerrnambiguity resolution is of utmost importance when tryingrnto position dynamic platforms operating in environmentsrnwhere GPS reception is lost and regained often, such as in urban terrain or a maneuvering military aircraft wherernGPS becomes blocked by airframe masking.rnEBE generated GPS solutions are integrated on-board thernGeo-LDV with data from a 6-DOF IMU using a looselycoupledrnExtended Kalman Filter (EKF). The function ofrnthis integration is to propagate the strapdown attitude,rninertial velocity and position using the IMU angular raternand acceleration outputs, incorporating EKF corrections.rnHowever, since this integration is sensitive to thernsystematic errors of the IMU, correct modeling of IMUrnerrors is essential for achieving high-accuracy TSPI. Inrnthis paper, we focus the approach used in the Geo-LDVrnfor modeling IMU errors. The approach was implementedrnin an IMU calibration tool box. We present resultsrnobtained when the toolbox was used to calibrate severalrnIMU's supported by the Geo-LDV platform.