Dachuan Liu

A MEMS Vibratory Gyroscope With Real-Time Mode-Matching and Robust Control for the Sense Mode

This paper presents a method to accomplish automatic and real-time mode-matching control for a microelectromechanical systems vibratory gyroscope based on improved fuzzy algorithm and neural network algorithm. Meanwhile, robust control for the sense mode is applied to enhance the reliability of the closed-loop system. Experimental results demonstrate that it only needs ~8 s to achieve mode-matching intelligently in the improved fuzzy control system. In addition, a mismatching error <;0.32 Hz is achieved over the temperature range from -40 °C to 80 °C in the neural network real-time control system, which is improved by more than one order of magnitude compared with that of once-time control system. In addition, the temperature coefficient of the zero bias is also improved to be 0.5°/h/°C in the real-time mode-matching control system. Experimental results of phase margin, gain margin, and sensitivity margin indicate that the closed-loop system is stable and robust enough over the full temperature range. Moreover, the bandwidth and bias instability of the mode-matching gyroscope with closed-loop controlled sense mode are >85 Hz and <;5°/h, respectively.

Research on temperature dependent characteristics and compensation methods for digital gyroscope

In recent years, MEMS gyroscope which is a kind of angular-rate-sensor has been improved greatly. In this paper, the effect of temperature changing on MEMS gyroscope is analysed. An evaluation and compensation platform based on the MCU and PC software has been fabricated. The temperature tests were done and some novel compensation algorithms were presented to fit the temperature curve. The thermal bias drift of the gyroscope compensated by the platform was reduced to 0.0667deg/s/degC compared with 0.618deg/s/degC before compensation.

Digital closed-loop controller design of a micromachined gyroscope based on auto frequency swept

This paper describes the design of a digital signal processing system for a MEMS vibratory gyroscope. It focuses on automatically obtaining the parameters of the gyroscope and ensure it vibrate at the resonance frequency through auto frequency swept. A closed-loop control method based on phase locked loop (PLL) and the automatic gain control (AGC) [1–3] with a proportion-integral (PI) controller. The angular rate demodulation is realized by adaptive filter algorithm. The whole closed-loop system is implemented on a field-programmed-gate-array (FPGA) platform with a Z-axis tuning fork gyroscope. The sensitivity is 3.7mv/deg/s with non-linearity 0.075% and the bias stability is 0.02°/s (1σ).

Digital control and performance test of a symmetrical doubly decoupled micro-machined gyroscope

This paper describes a system for digital signal processing to control vibrating gyroscopes which will allow more flexibility and increase performance through a reduction in electronics noise. A close-loop control method based on quadrature demodulation (QD) is presented. Improvements in signal demodulation, noise suppression, phase shift and direct digital frequency synthesizer (DDS) are also proposed. The whole open-loop system is implemented on a FPGA (Field Programmable Gate Array) platform and tested. The resulting scale factor and nonlinearity are 7.1mV/°/s and 0.55% respectively with the full scale of 400°/s.

Fast self-resonant startup procedure for digital MEMS gyroscope system

This paper describes a control procedure for the startup of a digital MEMS gyroscope system. Unlike the normal operating mode in which the gyroscope is actuated by synthesized sinusoidal drive signal, self-resonance of the gyroscope is stimulated by feeding back the drive-sense signal and converting it to a square-wave drive signal. During this procedure the resonant frequency that is near the natural frequency of the gyroscope can be calculated, and then provides a key parameter for the sinusoidal wave synthesizer, which will generate high-quality reference signals for driving and demodulation. Experiment shows a rapid rising of the magnitude of vibration, resulting a faster startup procedure for the system.

A novel scale factor calibration method for a MEMS gyroscope based on virtual coriolis force

This paper presents a novel scale factor calibration method for a MEMS vibratory gyroscope based on virtual Coriolis force. Frequency and amplitude programmable voltage signals generated by the system can be used to emulate the Coriolis force induced by external angular rate signals. The system contributes to the development procedure of control system for gyroscope and provides a scale factor calibration method for the digital control system of a gyroscope. The experiment results show the digital system can acquire the frequency response of gyroscope and detect the frequency response of reference virtual rate signal effectively.

Digital closed-loop driver design of micromechanical gyroscopes based on coordinated rotation digital computer algorithm

A novel digital closed-loop driver is presented for a micromechanical vibratory gyroscope in this paper. Coordinated rotation digital computer algorithm is applied to generate the sine and cosine signals for driving and demodulation processing. Meanwhile, automatic gain control and phase-locked loop are adopted to maintain a constant velocity of the drive mode and guarantee the gyroscope working in the resonant mode. All the control methods are implemented in FPGA device. Experimental results demonstrate that the stability of the amplitude of the drive velocity is about 18ppm, which verifies the effectiveness and accuracy of the digital closed loop for the drive mode. The scale factor, nonlinearity and bias instability of the gyroscope with closed loop controlled sense mode are measured to be 18.5mV/deg/s, 0.088% and 19.4deg/h, respectively.

A temperature control system used for improving resonant frequency drift of MEMS gyroscopes

This paper introduces a temperature control system which uses incremental PID algorithm to improve the resonant frequency stability of a MEMS gyroscope. The frequency drift for the drive mode of the gyroscope is 0.3Hz/°C, while after adopting the temperature control system, the frequency is nearly stable and the standard deviation of the output is about 0.027. The experimental results has proved this methods effectiveness and feasibility.

A resonnat accelerometer based on ring-down measurement

In this paper, a micromachined differential resonant accelerometer with electrostatic stiffness tuning is presented. The ring-down measurement is used for the first time to pick-up the real-time resonant frequencies of the accelerometer, which is more robust to device parameter variations and parasitic capacitances compared with the self-sustained oscillation based read-out. The total output drift over the temperature range of 120 °C for a single resonator and differential ones are 40.9 Hz and 1.0 Hz respectively, indicating a self-calibration capability of the differential configuration.

Digital fast startup procedure for micro-machined vibratory gyroscopes using optimized fuzzy control strategy

In this paper, we present an optimized digital fuzzy control strategy in order to realize fast startup of MEMS gyroscopes in various ambient temperatures. In the proposed procedure, the MEMS (Micro-ElectroMechanical Systems) vibratory gyroscope is driven with a sinusoidal wave synthesizer of adjustable frequency based on CORDIC algorithm. The drive frequency is fixed on the resonant frequency of the gyroscope with a frequency controller. By deliberate design of startup frequency controller using fuzzy control strategy, the startup time is decreased effectively in different ambient temperatures verified with test results. A series of startup test is performed under ambient temperatures ranging from -30 to 60°C, the tested startup time is improved from ~2.5s (tested with PID frequency controller) to ~100ms. Whats more, this procedure has a higher SNR of 88dB.