Research On The Related Technologies Of Four Frequency Differential Laser Gyro

The four frequency differential laser gyro (FFDLG) is a kind of whole solid dual-gyro. The characteristics of its principle make it have good advantages in wide dynamic and high precision application, but the study and manufacture of FFDLG is of great difficulty. The performance of domestic FFDLG needs to be enhanced, for many problems should be solved. This thesis does research on the frequency stabilization,magnetic effect,gain stabilization and temperature characteristics of FFDLG. Results of the research are valuable to discuss how to enhance the performance of domestic FFDLG, and afford the experimental supports to the solution of related problems in engineering application.The main contents and conclusions are as follows:(1) Brief analysis of the basic theory and primary errors of FFDLG. Basic physics model is built, then derivation by semi-classical theory is done, and the self-consistent equations are obtained. The independent dual-gyro approximation model is introduced, which can grasp primary contradiction and work as an important tool to study the errors of FFDLG. The error factors of FFDLG are analyzed by the independent dual-gyro approximation model, the solutions of the primary errors such as frequency stabilization error,magnetic effect error,gain stabilization error,thermo effects are analyzed briefly.(2) Research on the dithering frequency stabilization technology, different from the routine light intensity difference frequency stabilization. Physics model of the dithering frequency stabilization is built, the characteristics of frequency discrimination and mode distinguishing are analyzed. The noise disturbance of the same frequency in application is pointed out as the primary error to limit the frequency stabilization precision. The perpendicular reference signal can be used to monitor the noise and scale the precision. Experiment results indicate that: the frequency stabilization precision can reach more than 0.5MHz. The drift performance of FFDLG is nearly the same using either the dithering frequency stabilization or the light intensity difference frequency stabilization both under the room temperature and the high-low temperature environment. Hence the feasibility of the dithering frequency stabilization technology for FFDLG is verified.(3) Research on the first kind of dispersion equalization technology, different from the routine methods to enhance the frequency stabilization precision. Physics model of the first kind of dispersion equalization is built and the error influence is analyzed. Calibration scheme is designed, calibration algorithm based on the comparision of clockwise light and anticlockwise and calibration algorithm based on the equation solution are put forward. Experiment results indicate that: the first kind of dispersion equalization can improve the frequency stabilization sensitivity of FFDLG at least 150 times under large scale temperature environment in long term, decrease the startup drift by 0.00396 0 /h, decrease the long term drift by 0.00152 0 /h, decrease the drift difference by at least 0.6 0 /h under high-low temperature environment.(4) Research on the second kind of dispersion equalization technology, different from the routine magnetic-shielding. Physics model of the second kind of dispersion equalization is built and the error influence is analyzed. Calibration scheme is designed, the updating algorithm is discussed deeply. Experiment results indicate that: the light intensity technology is helpful to guarantee the effect of calibration for FFDLG. Associating the magnetic-shielding at 200 times, the second kind of dispersion equalization can decrease the magnetic sensitivity to 0.0000975 0 /h/Gauss under room temperature environment in long term and 0.00645 0 /h/Gauss under high-low temperature environment. The feasibility of updating algorithm and its time restriction are verified.(5) Research on the new gain stabilization technology, different from the routine current stabilization scheme. Physics model of the gyro gain is built, the error influence is analyzed. Scheme of gain stabilization through light intensity stabilization is designed and the rationality is explained. The circuits of light intensity stabilization are designed and the key points of every part and the control algorithm are given. Experiment results indicate that: light intensity stabilization can hold the light intensity of FFDLG at the stability of 1. 7×10?5 under large scale temperature environment, decrease the drift vibration resulting for gain unstability to 2. 01×10?50 /h, decrease the startup drift by 0.0016 0 /h, decrease the long term drift by 0.0029 0 /h.(6) Experimental research on the thermo effect of FFDLG. The spatial invert experiment results indicate that: the thermo effect is maximal when the gain tube is upright to the ground while minimal when the gain tube is horizontal to the ground. So the gain tube should be assured to fix at the horizontal direction.The startup experiment results indicate that: (i) the startup drift trend is irregular when the quartz crystal exists inside the cavity; (ii) the startup drift at the early stage decreases slightly after the circuits has been warmed up; (iii) the startup drift can be improved after adopting the first kind of dispersion equalization; (iv) the startup drift can be improved after adopting the light intensity stabilization; (v) the startup drift becomes apparently different if materials with different thermo characteristics are placed next to the gyro surface; (vi) the thermo balance time of startup drift is affected by the thermo distribution environment inside the shielding box of FFDLG.The high-low temperature experiment results indicate that: (i) the linearity between the drift and temperature is different for the two operating mode; (ii) the effect of the first kind of dispersion equalization to improve the high-low temperature performance is limited; (iii) complex magnetic environment can aggravate the high-low temperature performance; (iv) adding holes to minimize the stress can improve the drift vibration; (v) the correlation between the sum frequency and the temperature is different for different gyros; (vi) temperature compensation using multiple variables linearly regression mode can improve the high-low temperature performance.These experimental phenomena is valuable to discuss how to improve the temperature characteristics of FFDLG through optimizing the gyro design.In addition, this thesis also corrects some formulas of FFDLG considering the mode coupling effects between LCP and RCP, puts forward a kind of correcting method for the radiation trapping effect and discusses two fine mode coupling effects: population pulsation effect and ellipticity effect, which are valuable to enrich the theory of FFDLG. The concrete analysis is in the appendix of the thesis.