Research On Disassembly-free Calibration Method For Missile-borne SINS

The Calibration technique is one of the most important technologies for the strap-down inertial navigation system (SINS). For a missile-borne strap-down inertial measurement unit (IMU), the error parameters mainly include the transducers'bias, the scale factor error and the installation error, etc. The traditional calibration method is to disassemble the IMU from the projectile and calibrate the IMU on a three-axis turntable of high accuracy. However, the error of inertial sensors changes over time, and the installation error also changes in the process of IMU disassembly and installation, which might result in the parameters of laboratory calibration do not conform to the actual situation of the missile launch. This thesis puts forward a disassembly-free calibration method for the missile-borne SINS, which is able to calibrate the IMU without taking it off the projectile. The method can reduce the cost of calibration and improve the rapidity of the missile launch. In this thesis, the main contents are as follows:1. This thesis presents the basic principle of inertial navigation, and introduces the commonly used coordinate system in inertial navigation systems. Then, the inertial navigation algorithm in the north-up-east coordinate system has been deduced. Meanwhile, the error model of the inertial system has been established, the error parameters of the optical fiber SINS have been introduced, and the influence of errors on the navigation accuracy has been analyzed by simulation.2. The principle of disassembly-free calibration method based on the Kalman filter has been elaborated, and the measurement equations of different kinds of match type have been derived. The observability analysis of different maneuvers has been performed to evaluate the estimable level of each system state. Accordingly, a proper path has been designed according to the result of observability analysis so as to actuate all kinds of the SINS error.3. The simulation program of the SINS has been compiled, and the simulations have been performed to test the proposed calibration method. The effects of different calibration paths on the calibration results are studied and compared.4. The semi-physical experiment is carried out on the three-axis turntable, different maneuvers of the missile launching vehicle are simulated by corresponding movements of the three-axis turntable, and the obtained turntable data is used as the main SINS data. The IMU is calibrated according to the disassembly-free calibration procedures, and the calibration results with both the traditional method and the proposed method are compared. Through 10mins inertial navigation with the calibrated parameters, the effectiveness of the disassembly-free calibration method is demonstrated.