Research On Outside Calibration Methods For Ring Laser Gyroscope North-finder Based On Rotation-Modulation

With the development of Ring Laser Gyroscope (RLG) technology, our country has made a great step forward in RLG north-finder field. But research on outside calibration of high-precise RLG north-finder is on the initial phase, examples of outside calibration have not been used maturely. This thesis made research with the vehicular high-precise Rotation-modulation north-finder which is made up of three rate-biased RLG and three accelerations (north-finder is called for short in this thesis). Based on the 1-axis turntable which provides invariable rate for the north-finder, outside calibration method without taking the north-finder down from the car are investigated in this thesis. This will make sure the RLG north-finder working well outside the door, and will protract calibration period based on a precise 3-axis turntable in laboratory.The main contents and work include the following aspects:(1) This thesis sets up the outside calibration model that parameterized as fix matrix, scale factor of gyroscopes and accelerations. The equations, which describe the relationship between model error and north-seeking error have been derived, the north-seeking error can be calculated by these equations. The periodic measure error model of turntable has been set up. To analyse the grade of north-seeking error came form periodic measure error of turntable, the equations, which describes the relationship between the periodic measure error of turntable and north-seeking error has been derived.(2) To validate north-seeking precision influenced by the outside calibration model of gyroscopes and accelerations, lots of real tests have been conducted. The results show that gyroscopes'level-projection angles error dominates rotation-modulation north-seeking error, and this error is proportion to the fix matrix error of gyroscopes, which validates the equations between model error and north-seeking error.(3) To validate north-seeking precise influenced by periodic measure error of turntable, real tests have been made. The results show that periodic measure error aroses fluctuation of north-seeking yaw, and amplitude is proportion to periodic measure error, which validate the equations between periodic measure error and north-seeking error. So the periodic measure error is the key factor to north-seeking error. Based on the periodic measure error model of turntable, the calibration method of turntable periodic measure error is proposed, and real tests have been made. Real tests results show that the calibration method can avoid the fluctuation of north-seeking yaw and advance the north-seeking precise availably.(4) The north-seeking result with two gyroscopes can get high precision based on the rotation-modulation north-finder with three rate biased RLG and three accelerations, when the turntable is level on the stationary base. Based on the north-seeking error of three gyroscopes'north-seeking result and two gyroscopes'north-seeking result, a kind of outside calibration method is proposed for rate biased RLG north-finder. A kind of north-seeking arithmetic with two real gyroscopes and one virtual gyroscope is designed. The equations, which describe the relationship between gyroscope's level-projection angles error and north-seeking error of three gyroscopes have been derived. The equations, which describe the relationship between gyroscope's level-projection angles error and north-seeking error of two gyroscopes with one virtual gyroscope have been derived. Then, based on the north-seeking results of three gyroscopes and two gyroscopes with one virtual gyroscope, outside calibration equations are set up. When gyroscopes have been replaced, the new gyroscopes'fix parameter can be calibrated by this calibration method in outfield, this advances the maintainable performance.(5) Real tests have been conducted for calibration method of gyroscopes'fix matrix model. Base on the fix matrix model of gyroscopes (two level-projection angles and three sloping angles), the level-projection angles error and sloping angles error have been got by outside calibration method, when the turntable level-precision is less than 15″on the stationary base. The results based on outside calibration method are close to the results based on a precise 3-axis turntable. The error based on outside calibration method is about 4″(1σ). This kind of outside calibration method is worth to the engineering application.