Research On The Calibration Method Of Laser Gyro Strapdown Inertial Measurement Unit

Since laser gyro has the features of high precision, good reliability and low cost etc, laser gyro strapdown inertial navigation system has become an important development trend in recent years. Inertial measurement unit (IMU) which is the core of inertial navigation system (INS) is made up of laser gyros and accelerometers, sensitive to attitude and acceleration of carrier respectively. So the precision of IMU will affect the system navigation precision to a great extent. In this paper, research on error models, calibration methods and errors of the testing equipment on laser gyro strapdown inertial measurement unit are engaged.Firstly, based on the error sources and working environment of inertial instruments, the installing errors, the error model of the accelerometer, the laser gyro and the IMU are analyzed. The error equation of strapdown inertial navigation system is established according to the error propagation characteristics of inertial instrument when in navigation state. Accelerometers and laser gyros are calibrated for later error compensation.Then, methods of separate calibration of IMU are studied. Tests of turntable alignment, IMU calibration and dodecahedron 20 points plan are conducted on two-axis turntable, and all test results are compared and analyzed. Through methods of coordinate system transformation and harmonic analysis, the influence of turntable errors on accelerometers calibration precision is analyzed and verified by simulation. This can help to determine turntable precision specification more or less.Finally, according to calibration field, systematic calibration of IMU could be divided into the laboratory calibration and the outer field calibration. We can carry out systematic calibration through velocity errors under stationary based laboratory condition. In this paper the calibration mathematical model is established, identifiability of instruments errors is analyzed, one arrangement of calibration position is also designed. The observability and convergence rate of system states are analyzed in terms of theory.