Strapdown Inertial Meamurement Unit Of Test And Calibration

With the development of high-tech, laser gyro strapdown inertial navigation system has become an important concern of inertial technology. In order to improve navigation accuracy and reduce navigation error, the laser gyro IMU must be calibrated, and the error model is established to compensate for the errors during the navigation process.Based on the calibration of the laser gyro IMU, the laser gyro IMU calibration method is researched systematically. Since the errors from the inertial sensors are the main error source of the navigation error, the precision dividing head calibration to the inertial sensors should be done firstly. The calibration of accelerometers experiments on the multi-position with the precision indexing head. The gyro calibration uses the multi-rate method, obtains the coefficient of the single-table error model. The zero-bias and the scale factors of the dividing head reference can be used as the precision for the navigation system calibration.Because the traditional calibration tests must be based on the accurate direction to the north and the experiment progress is complicated, the static and dynamic mixing calibration experiment for the SIMU is designed, this method requires only 12 rotation experiments on 6 positions, can calibrate the scale factors of the accelerometer and laser gyroscope can be1calibrated, so as to the zero-bias and the installation error to the ideal inertial coordinate system. And under the premise of ensuring the experiment accuracy, the data processing method is simple, and improves the calibration efficiency. At last the static navigation experiment shows the rationality and effectiveness of the compensation method. A multi-position calibration model is established in connection with the arbitrary installation and the non-orthogonal installation. After the redefinitions of the error angels, compared with the traditional model, the new model reduces the number of the error angles from the orthogonal coordinate system to the coordinate system formed with the devices sensitive axis. The calibration experiment needs no precise orientation and leveling for the IMU. Using the least squares method the error model parameters can be identified, and test results are carried out by static navigation verification.Compared to the separate calibration, the system-level calibration need no accurate measurement of the Earth's rotation rate and the local gravity acceleration , and the calibration data can be handled off-line iterations for more accurate error model, which not only reduces the requirements to the test equipment, but also greatly reduces the calibration time and improve the calibration accuracy. Theory of system-level calibration is analyzed. According to the inertial navigation equation, a system-level calibration model is deduced. The causes that the traditional system-level calibration method can't fully identify the 24 parameters are researched. And the layout of the experiment is designed using the navigation velocity error. After discussion to the data processing method, the 24 steps solving the experimental error is given. As to the field calibration, the system error state equation is established, of which the convergence speed is analyzed, and the observed combined states are given.