Dual-axis Rotating FOG Strapdown Inertial Navigation System Technique

The constant and slow-varying bias of the inertial sensors is the main influence on thestrapdown inertial navigation system (SINS) precision. So the bias of the sensors must becalibrated before it can be used. But the results of the calibration change in time after theSINS used in a long time. And usually the bias of the inertial sensors is different in each start.So the bias of the inertial sensors should be re-calibrated before the SINS running. Theinertial sensors bias and the misalignment will be calibrated with the rotating mechanism andKalman filter in a short time.The rotary SINS changes the constant or slow-varying errors into periodical andzero-mean form with the rotating periodically to counteract the effects to the SINS. So theprecision of the SINS is enhanced without high precision inertial sensors by the SINS self-compensation method.The self-calibration and self-compensation methods of rotary SINS are researched in thiswork. The main works include:(1) The concept of the inertial navigation system observability is introduced. And thenormal observability analysis methods are sketched. The theory shortage and the reason ofPWCS observability analysis method are clarified. Then the global observability analysismethod witch a fine observability analysis method is introduced. With this method, therelationship between different rotating modes and rotary SINS observability is analyzed indetail. The rotating modes which includes static, rotating with constant speed, rotating withvaried speed and so on. The principle of rotary inertial navigation system self-calibration isdesigned.(2) A new self-calibration method called eight-position self-calibration method is showedin this paper based on the principle of rotary inertial navigation system self-calibration. Theinertial navigation error model and Kalman filter is introduced. And Kalman equation of stateand measurement are built up which is used for simulating the self-calibration rotatingmethod.(3) The inertial sensors bias self-compensation method of rotary inertial navigationsystem is introduced. The principle of rotary inertial navigation system self-compensation isdesigned. The position error influenced by the angular acceleration is focused on and theoptimal angular acceleration is designed. With the analysis results and the predecessors’self-compensation achievements, a new self-compensation method called16-time dual-axis rotating method is designed and simulated.(4) With the SINS developed in Harbin Engineering University and tri-axis turntable, theprototype of dual-axis rotary inertial navigation system is built up. The eight-positionself-calibration experiments and the16-time self-compensation experiments are carried outwith the prototype. The experiment results are analyzed off-line.