Apparatus for the automatic determination of a vehicle position

Abstract

The position of a vehicle is derived from vehicle speed and heading. A two-axis electrically restrained gyro, the spin axis of which is parallel to the vehicle vertical axis, serves at first to determine the north direction with stationary vehicle. The attitude of the vehicle about the longitudinal and transverse axes is measured by means of a pair of vehicle-fixed accelerometers. True north direction is derived from the signals of the accelerometers and of the gyro. Subsequently the gyro is rotated through 90.degree. about one input axis and serves as heading-attitude reference during the mission. The rotary speed about a third axis perpendicular to the input axes of the gyro is measured by means of a rotary acceleration meter the output of which is applied to an integrator. During the mission, the attitude parameters of the vehicle are computed continuously from the initial attitude parameters and the rotary speeds. An estimated value of the gyro drift is obtained in a filter by comparison with a magnetic heading and is taken into account. The speed signal from a vehicle speed sensor and inertial speed signals which are derived from the acceleration signals are applied to a filter which provides an estimated value of the error of the speed signal. The speed signal is corrected for this estimated value. The corrected speed signal is resolved into components in accordance with the attitude parameters. The position of the vehicle is derived from these speed components by integration.