Key Technology Research On The Digital Interface ASIC For MEMS Disk Resonator Gyroscopes

Gyroscope is the core device in inertial navigation system.The performance of MEMS vibratory gyroscope with traditional structure has reached the tactical level.MEMS vibratory gyroscope with new structure has attracted much attention because its performance,limited by principle,is difficult to be further improved.MEMS disk resonant gyroscope is one of the micro gyroscopes with the highest accuracy at present.It is composed of mechanical structure and interface circuit.In order to improve the performance of MEMS disk resonant gyroscope,higher requirements are put forward for the interface circuit of gyroscope.Therefore,the research on the key technologies of MEMS disk gyroscope interface ASIC is of great significance to the development of MEMS disk gyroscope.At present,the research on the interface circuit of MEMS disk resonant gyroscopes mainly has the following aspects to improve: the starting time of the gyro with existing control methods is too long to achieve high-precision resonance;As for the design of low noise interface circuit,it is necessary to creat a noise model of the sensing circuit to study the noise characteristics.There is a mismatch between the driving mode and sensing mode due to the process error.The existing electrostatic correction method can not realize the automatic mode matching.The chip integration of interface circuit needs to be further developed,because the interface circuit is integrated by FPGA and analog discrete device PCB.To solve the problem of long start-up time of driving mode,the frequency locking time and step response time are analyzed respectively.A step-by-step fast start method is proposed.On this basis,a st ep-by-step fast start circuit is designed,including a fast frequency locking circuit and a fast vibration starting circuit.The correctness of the design is verified by the circuit test.The test results show that the start-up time is reduced by 88 % compared with the existing one-step start-up method.By analyzing the noise in the MEMS disk resonant gyroscope sensing circuit,the noise model of the MEMS disk resonant gyroscope sensing circuit is established.The design guidance of low-noise detection circuit of MEMS disk resonant gyroscope is obtained.The correctness of the model is verified by experiments.In order to realize automatic mode matching,the electrostatic tuning characteristics of MEMS disk resonant gyroscope are studied.The relationship between electrostatic stiffness and electrode azimuth and voltage is obtained.On this basis,a step-by-step automatic frequency modulation control method is designed by automatic linear voltage control method and PI control method.Firstly,the approximate mode matching is realized by automatic linear adjustment of electrostatic force.Then,the mode matching and dynamic holding are realized more accurately by PI control method.The frequency splitting after mode matching is less than 0.006 Hz.Based on the above research,a high-precision MEMS disk resonant gyroscope interface ASIC chip with the functions of fast start-up and automatic mode matching is designed by 0.35μm BCD process.The test results show that the starting time of the driving circuit is less than 9s(reaching and maintaining the steady-state value±1%).Allan variance zero bias stability is 0.4°/hr.The test results verify the correctness of ASIC integrated circuit design.