| Hemispherical Resonator Gyro (HRG) is a solid state gyroscope with features ofhigh accuracy, long life span, inherent high reliability, anti-impact and natural radiationhardness. With its excellent performance, the HRG can be used for spacecraft andsatellite stabilization, precision pointing, as well as oil borehole exploration. However,there is still much room to improve the quality of dometic HRG, especially in the aspectof gyroscope bias stability, scale factor nonlinearity and so on. In addition, Americangovernment bans Northrop Grumman which is the world’s only high-performance HRGproducer from exporting HRG to China. Therefore, in the areas of aircraft navigation,strategic accuracy systems and oil borehole, it is of great necessity to make researcheson improving the performance of HRG.In this dissertation, the math model of HRG, error analysis, control technology andtemperature drift compensation are studied, which provide valuable suggestions for thefurther improvement of HRG. The main content of this dissertation is as follows:1. On the basis of thin shell theory, a theoretical modeling is established in order tostudy the vibration feature of HRG. By applying methods of virtual work principle andcalsulus of variations, the complicated solid wave virabtion phenomenon is simplifiedinto a two dimensional mass vibration model through equivalent method. As a result,the differential equation of the point virabtion is established from which the peocessionphenomenon of the solid wave can be revealed.2. The error analysis of HRG is carried out basing on two dimensional massvibration model. With a detailed analysis of the main error sources, the errorpropergation equations are established. Then, different influences on the vibrationmodel parametres of HRG by each error term are simulated, from which some usefulconclusions are drawn.3. It is the first time that the control method of HRG under the force to rebalancemode is thoroughly described. HRG can work not only under whole angle mode butalso under force to rebalance mode, and the latter one has a higher accuration. Besides,four control loops, namely, reference-phase loop, amplitude-control loop,quadrature-control loop and rebalance control loop, which are employed for HRGworking under force to rebalance mode are introduced in details. Furthermore, the errorsuppress principle of control loop is theoretically analysed and validated throughexperiments. Finally, the main performance parameters such as bias stability and scalefactor of HRG are obtained through calibration on the turntable.4. The digital detection and drive systems of HRG based on FPGA are designedaccording to the math mode and the control method metioned before. Capacitivereadout and exciation circuit principle are studied and the interfaces of DAC and ADC seperatedly with FPGA are designed in this chapter. The design framework and overallarrangement are introduced according to the control method. The modulation anddemodulation unit, the embedded control unit and signal synthesize unit are thoroughlydescribed. The communication interface module which is used to transfer data betweenFPGA board and upper computer is implemented, through which the working status ofthe HRG can be easily obtained and can also facilitate the realization of debuggingmode.5. A temperature compensation model for HRG based on the natural frequency ofthe resonator is established. A math model of the relationship between the temperatureand the natural frequency of HRG is deduced. On the basis of these deductions, a newmethod decting the temperature changes through analysing frequcncy change of theresonater is proposed in this chapter. As a result, this new method can be used tocompensate the temperature drift of HRG. The compensation results show thattemperature-frequency method is valid and suitable for the gyroscope driftcompensation, which would ensure HRG’s application in a larger temperature range inthe future without any more hardware cost. |
PDF Full Text Request