DIGITAL-FILTERS TO INTEGRATE GLOBAL POSITIONING SYSTEM AND DEAD RECKONING

The design, test and results of a positioning system consisting of a d ifferential global positioning system (DGPS) receiver, a radar velocit y sensor, a wheel velocity sensor and an electronic compass are discus sed. The characteristics of the individual sensors were investigated a nd with these results a Kalman filter was designed to integrate the di fferent signals into a single estimate of position, velocity and headi ng. Field tests were conducted to investigate both the real-time perfo rmance of the system and the robustness against distortions caused by malfunctioning of the sensors. An extended Kalman filter was found to improve accuracy of positioning and was able to bridge gaps in positio n information due to blockage of the GPS receiver. The position measur ements from the GPS receiver had a standard deviation of 1.18 m. The u se of a nine-state filter reduced the standard deviation of positionin g to 0.71 m. On a track which ran along a line of trees and between bu ildings, the filter was able to maintain position for 12 s, while the GPS receiver lost satellite fix. (C) 1998 Silsoe Research Institute.