Research on Auto Compensation Technique of Strap-down Inertial Navigation Systems

Inertial measurement unit(IMU), consisted of three mutually-perpendicular Ring Laser Gyros (RLG) and three accelerometers, is an important part of RLG -based strap-down inertial navigation systems(SINS). RLG provides measurement of change in vehicle attitude or its turn rate with respect to inertial space. Accelerometer provides measurement of specific force. These measurements provided by gyros and accelerometers are calculated to obtain the desired attitude, velocity and position information with respect to a pre-defined reference frame. So the accuracy of SINS clearly depends on the accuracy of the gyros and accelerometers. In order to improve the accuracy of SINS, auto compensation techniques of rotation is used. With IMU rotating about one or two axis of the vehicle, the bias errors of gyros and accelerometers may be modulated into periodical variable signal. So the modulated sensor errors reduce SINS errors. The theory of rotation auto compensation technique is analyzed. Single channel error propagation equations based on rotation compensation are derived. The simulation experiments of the SINS are carried out. Analytic results and the simulation results indicate that, with the help of rotation auto compensation, the effect of gyro's random drift and accelerometer’s bias on SINS errors is greatly reduced.