High Stability Signal Processing Architecture And Power Consumption Reducing Of Slot-structrue MEMS Gyroscopes

Micro-electro-mechanical system(MEMS)gyroscope is a kind of sensor to measure the angular velocity or angular displacement.After decades of development,the performance of the MEMS gyroscope continues to improve and the system is gradually integrated through the advancement of device structure,processing circuit and control algorithm.The main research contents of this project are divided into two aspects.One is the research on the high stability signal processing architecture and control algorithm of MEMS gyroscope system,and the other is the research on reducing power consumption of MEMS gyroscope system aiming at engineering application.Based on the existing work of research group,the major work and contributions in this paper are given as follows:1)Double side band demodulation algorithm(DSB algorithm)and single side band demodulation algorithm(SSB algorithm)are widely used in capacitance voltage conversion circuit(C/V circuit)of MEMS gyroscopes.First,the two signal processing architectures respectively based on DSB and SSB demodulation algorithms are applied in drive loop of MEMS gyroscopes.Theoretical derivations reveal the influence on bias resulting from the phase delay fluctuations of C/V circuit in drive mode.The advantages and limitations of the two demodulation algorithms are summarized.A simulation model which is set up to evaluate the two signal processing architectures verified the correctness of theoretical analysis.A high stability control method(D&S)combining two demodulation algorithms is proposed.In D&S method,the DSB and SSB processing architecture are used to extract motional phase and motional amplitude in drive mode of MEMS gyroscope,respectively.Theoretically,D&S method can increase the robustness to phase delay fluctuations of C/V circuit in drive loop.A series of comparative experiments are conducted among DSB,SSB and D&S method,using an FPGA-based digital platform on a MEMS gyroscope.Experiment results demonstrate that only in D&S method,motional amplitude and motional phase are both immune to phase delay fluctuations of C/V circuit,and bias output has the best robustness among the three methods.The performance test results of a slot-structure MEMS gyroscope under atmosphere show that bias instability is 0.64 °/h(Allan variance)and ARW is 0.16 °/?h using D&S method.Compared with DSB and SSB methods,the performance of ARW has been improved by 1.06 and 1.09 times,respectively.And bias instability has been improved by 2 and 4.3 times,respectively.In addition,it's the best stability performance of MEMS gyroscopes of our research group under atmosphere.Then,D&S method is applied to a comb-structure gyroscope,and the bias instability has also been improved.It is verified that the superiority of D&S method is not limited to a specific structure of MEMS gyroscope.Further,Allan variance analysis reveals that D&S method can suppress rate ramp and improve long-term bias drift of gyroscopes.The improvement of turn-on bias drift in the slot-structure gyroscope system is a strong proof.2)This project takes the aim at reducing power consumption of MEMS gyroscope by optimizing the interface circuit and the balanced force generating circuit.C/V circuit based on diode ring detection is applied to the new system.Compared with charge amplification detection used in original system,it can demodulate the motional signal modulated by high frequency carrier signal.In other words,motional amplitude and motional phase can be obtained by only once demodulation.This circuit reduces the power consumption through reducing complexity of system algorithm.The balanced force generating circuit of new system is implemented by a low-power DAC chip instead of the circuit consisting of a DAC chip,interface circuit of DAC and push-pull circuit in original system.This design not only simplifies the structure,but also reduces the power consumption of this part.The power consumption of digital PCB in new system is tested to 454 mW,which is reduced by 55%compared to original system.The power consumption of analog PCB in new system is not improved due to the large supply voltage,because the atmospheric packaged gyroscope with low Q factor needs large drive voltage to guarantee better performance.For vacuum packaged gyroscopes going to be processed of our research group,the supply voltage of analog PCB can be reduced from ±15 V to ±5 V,and the driving force generating circuit can be implemented by a low-power DAC chip as the balanced force generating circuit.Then,the power consumption can be sharply reduced.Experiment results show that bias instability of new system is better than original system.ARW and non-linearity deteriorate a little.