| Silicon Micro-machined Gyroscope (SMG) has an extensive application prospect in both military and civilian fileds for its advantages such as small size, light weight and low power consumption. At present, the SMG develops in the direction of intelligence, integration and higher-performance. The technology of wafer-level vacuum packaging is utilized to improve the structure integration while using digital and ASIC (Application Specific Integrated Circuit) technology to improve the integration, which can give full play to the characteristics of SMG.In this dissertation, the research is based on the dual-mass vibration SMG which is designed by our group. Inorder to improve the stability of zero bias and scale factor, the research is focus on the ASIC implement and digitalization of the sense and control circuit for SMG which contains the following parts:the interface circuit design, the drive closed-loop technology, the sense closed-loop technology and the temperature compensation technology.Firstly, the overall scheme for sense and control circuit of SMG was discussed. Compared with the analog control technology, the digital control technology was selected as the SMG control technology and the overall sheme was designed. According to the performance index of SMG, the interface circuit of SMG was designed by analyzing the noise of C/V conversion circuit (Capacitance/Voltage conversion circuit). Then, other parts of digital control system was analyzed and designed, including the selection of ADC and DAC which were based on the sampling frequency and quantization bits analysis; and the selection of FPGA which is utilized as the digital signal processor by comparing with DSP. A digital hardware system of SMG was established which provided a test platform for signal processing and control algorithms.Secondly, the drive closed-loop technology of SMG was studied. The drive closed-loop was divided into the following two parts:the low-frequency part and the high frequency part. The low frequency part was AGC (Automatic Gain Control) used to control the amplitude while the high-frequency part was PLL (Phase Locked Loop) used to control phase and frequency. The stability analysis and noise performance analysis were carried out. The relationship between the parameters and performance of drive closed-loop and the stability conditions were obtained from stability analysis; the noise PSD (power spectral density) of C/V conversion circuit in drive closed-loop and the relationship between PLL output signal PSD and input signal PSD were obtained from noise performance analysis. In addition, the acquisition performance and tracking performance of PLL were analyzed in the paper, and obtained the relationship between the capture bandwidth and tracking bandwidth and the parameters of the PLL which provided a theoretical for PLL design. Based on the theoretical analysis, the third-order system of AGC and PLL was reduced to second-order in the way of setting the dominant pole, and then the optimization for the system parameters was done according to the loop design index. The correctness of the parameters for the system was verified by the Simulink simulation and experiment. The experiment has achieved good closed-loop performance.Then, the sense closed-loop technology of SMG was studied. The negative stiffness effect was analyzed including sine wave voltage feedback form and pulse density feedback form. The conclusion indicates that the negative stiffness effect caused by the sine wave voltage feedback form will be changed with the input angular velocity changes, but the negative stiffness effect caused by the pulse density voltage feedback form was independent from the input angular velocity. Therefore, the sense closed-loop based on mechanical and electrical integration Sigma Delta Modulator (SDM) was selected. The two major difficulties when design sense closed-loop which are the loop structure and the loop parameters were studied with an example, based on circuit SDM as the bridge, the Signal Noise Radio (SNR) of sense closed-loop as the design index, while using DSToolbox as the design tool. The simulation and experiment demonstrated the validity of the designed closed-loop.For the reason that the performance of SMG would be influenced by temperature, this paper focuses on the temperature compensation and with "control-oriented, compensation supplement" as a kernel. Through the analysis of the research, it has been found that the gain stability of C/V conversion is the key factor which affects the stability of the vibration velocity amplitude of gyroscope’s drive mode. Thus, in order to improve the stability of vibration velocity amplitude, the method using gain compensation for drive closed-loop was proposed. Further theoretical analysis shows that the gain compensation is independent of the structure parameters and circuit parameters, thus it is suitable for the temperature compensation of gyroscopes in batches. After the temperature compensation, the result shows that the temperature coefficient of scale factor and zero bias were reduced by89.5%and67.6%respectively. Because of the linear relationship between the natural frequency of drive mode and temperature, a temperature compensation method was researched using the natural frequency as the temperature sensitivity. The experiment shows that the temperature of scale factor and zero offest further reduced by59.3%and73.1%using this method based on the gain compensation for drive closed-loop.Finally, according to IEEE testing standards for Silicon Micro-machined Gyroscope, the performance of digital dual-loop Silicon Micro-machined Gyroscope was tested. The result shows that the zero bias stability and repeatability after temperature compensation is improved by38.0%and38.3%respectively compared with the result without temperature compensation; the temperature coefficient of scale factor and zero bias with temperature compensation are decreased by45.8%and61.7%separately. The experiment proved that the temperature compensation method is effective. |
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