Fan Shangchun

On flexural vibration of hemispherical shell

This paper makes detailed analyses for the flexural vibration (frequency) of the hemispherical shell and presents the varying laws of frequency with the varying boundary angles and the wall thickness of the above shell. It is an important value to develop the instrument, such as hemispherical resonator gyro (HRG), whose sensing component is a hemispherical shell.

Dynamic stability of parametrically-excited linear resonant beams under periodic axial force

The parametric dynamic stability of resonant beams with various parameters under periodic axial force is studied. It is assumed that the theoretical formulations are based on Euler—Bernoulli beam theory. The governing equations of motion are derived by using the Rayleigh—Ritz method and transformed into Mathieu equations, which are formed to determine the stability criterion and stability regions for parametrically-excited linear resonant beams. An improved stability criterion is obtained using periodic Lyapunov functions. The boundary points on the stable regions are determined by using a small parameter perturbation method. Numerical results and discussion are presented to highlight the effects of beam length, axial force and damped coefficient on the stability criterion and stability regions. While some stability rules are easy to anticipate, we draw some conclusions: with the increase of damped coefficient, stable regions arise; with the decrease of beam length, the conditions of the damped coefficient arise instead. These conclusions can provide a reference for the robust design of parametrically-excited linear resonant sensors.

Dynamic characteristics of resonant gyroscopes study based on the Mathieu equation approximate solution

Dynamic characteristics of the resonant gyroscope are studied based on the Mathieu equation approximate solution in this paper. The Mathieu equation is used to analyze the parametric resonant characteristics and the approximate output of the resonant gyroscope. The method of small parameter perturbation is used to analyze the approximate solution of the Mathieu equation. The theoretical analysis and the numerical simulations show that the approximate solution of the Mathieu equation is close to the dynamic output characteristics of the resonant gyroscope. The experimental analysis shows that the theoretical curve and the experimental data processing results coincide perfectly, which means that the approximate solution of the Mathieu equation can present the dynamic output characteristic of the resonant gyroscope. The theoretical approach and the experimental results of the Mathieu equation approximate solution are obtained, which provides a reference for the robust design of the resonant gyroscope.

Characteristics Analysis of Joint Acoustic Echo and Noise Suppression in Periodic Drillstring Waveguide

A new method of wireless data telemetry used by oil industry uses compressional acoustic waves to transmit downhole information from the bottom hole to the surface. Unfortunately, acoustic echoes and drilling vibration noises in periodic drillstring are a major issue in transmission performance. A combined acoustic echo and noise suppression method based on wave motion characteristic in drillstring is adopted to enhance an upward-going transmitted acoustic signal. The presented scheme consists of a primary acoustic echo canceller using an array of two accelerometers for dealing with the downward-going noises and a secondary acoustic insulation structure for restraining the upward-going vibration noises. Furthermore, the secondary acoustic insulation structure exhibits a banded and dispersive spectral structure because of periodic groove configuration. By using a finite-differential algorithm for the one-dimensional propagation of longitudinal waves, acoustic receiving characteristics of transmitted signals are simulated with additive Gaussian noise in a periodic pipe structure of limited length to investigate the effects on transmission performance optimization. The results reveal that the proposed scheme can achieve a much lower error bit ratio over a specified acoustic isolation frequency range with a 30–40 dB reduction in the average noise level compared to traditional single-receiver scheme.

An ultra-high sensitivity Fabry-Perot acoustic pressure sensor using a multilayer suspended graphene diaphragm

A 10~15-layer suspended graphene diaphragm was adhered onto the endface of a ferrule with a 125-μm inner diameter by van der Waals interactions to construct a miniature ultra-high sensitivity Fabry-Perot acoustic sensor. Considering the dynamic acoustic pressure measurement, the properties of film natural frequency and optical reflectivity were investigated by ANSYS modal simulation and Fresnels equation, respectively. The average reflectivity of the multilayer graphene diaphragm was measured to be about 1.49%. Acoustic testing demonstrated a pressure-induced deflection of 2.38 nm/Pa at 15 kHz with a nice omnidirectionality. The sensitive diaphragm structure breaks the sensitivity limitations imposed by the increased thickness and the decreased dimension of a diaphragm used in traditional Fabry-Perot pressure sensors.

Multiple-Echo Suppression Modeling and Experimental Verification for Acoustic Transmission along Periodic Drillstring Using Dual Receivers

In the oil industry, the accompanied reverberation is a major constraint in the transmission rate and distance because the drillstring is a heterogeneous assembly. Based on the transient impulse responses in uplink and downlink channels, an improved simplified echo suppression model with two acoustic receivers is presented in consideration of position optimization of single acoustic receiver. Then the acoustic receiving characteristics of transmitted signals in a length-limited periodic drillstring channel are obtained in single- and dual-receiver modes. An additive downward white Gaussian noise is also introduced in the channel. Moreover, an experimental rig is established by using a rotatable electromagnetic vibration exciter and two piezoelectric accelerometers, which are spaced one-quarter wavelength apart along a 6.3-meter simulated periodic drillstring. The ASK-, FSK-, and PSK-modulated square-wave pulse sequences at a transmission rate of 200 bit/s are applied to the simulated drillstring at a rotation speed of 0, 80, and 140 r/min, respectively. The experimental results show that the dual-receiver mode can exhibit a significantly improved average error bit ratio, which is approximately 2.5 to 3 times lower than that of the single-receiver mode, especially under the conditions of higher rotation speeds.

Experimental study on the closed-loop control system of Coriolis mass flowmeter for oil-water two-phase flow measurement

Coriolis mass flowmeter (CMF) is significant in many industrial and commercial areas. The two-phase flow, external vibration or flow pulsation in a Coriolis mass flowmeter can cause errors in the meters measurements of density and mass flow rate. Some errors may be due to the closed-loop control system. In this paper, they are investigated from analog and digital closed-loop control system by experiment study. And also the advantage and disadvantage ware tested between analog and digital closed-loop control system by using the oil-water two-phase flow. It was found that the relative precise error of mass flowrate was relatively small for oil-water two-phase flow, not changed with the quantity of oil. Experimentally-derived data was used to illustrate that the digital closed-loop control system has more precise than the analog, and provide stable oscillation and selection of a sustainable setpoint for amplitude of oscillation, even during situations such as a highly-damped operation of the flowtube, vibration or beginning/ending operation of the flowtube.

A dynamic performance improvement method of Coriolis Mass Flowmeters

Coriolis Mass Flowmeter(CMF) provides direct measurement of mass flow and is widely used in steady flow measurement. With the development of dynamic flow measurement technology and the increasing of application requirement, the question about dynamic response of CMF has become a hotspot. Recently a lot of research work has been done on this issue and a few papers have been yielded. This paper provides a summary and analyses of the dynamic research method of CMF in latest research work. Furthermore, we proposes a new concise way of specifying and improving the dynamic performance of CMF, discusses the feasibility of this method on the basis of existing investigation and describes the emphases of the future development work.

A time-varying signal processing method for Coriolis mass flowmeter based on adaptive filter:

In this paper, the normalized least mean square (NLMS) algorithm, a time-varying signal processing method, is employed in a Coriolis mass flowmeter (CFM) to improve its weak anti-jamming capability. Initially, the fundamental principles of the NLMS algorithm adopted in the adaptive filter are analysed. Then, the NLMS algorithm is applied to analyse the signal processing of the CFM at different flow rates in experiments. By comparing several performance indicators and spectrum diagrams from being filtered by the NLMS algorithm and the least mean square (LMS) algorithm, the results indicate that the NLMS algorithm can lead to a better anti-jamming capability and reduce the influence of noise efficiently for the CFM. In addition, the NLMS method has a faster convergence speed and fewer stable errors than the LMS method. Therefore, the NLMS can improve the quality of the output signal of the CFM.

Design of a new differential silicon resonant accelerometer with dual proofmasses using two-stage microlever

A novel micromechanical silicon resonant accelerometer using a two-stage microlever and dual-proofmass architecture is presented. Based on the structural model of the accelerometer, the ANSYS simulations are performed to investigate the effects of sensitive structural parameters on the acceleration sensitivity and operating frequency of accelerometer, and the sensitivity change in response to temperature acclimation. The results show that the proposed accelerometer achieves a sensitivity of 150 Hz/g and a linear accuracy of 1.91%o with a nominal frequency of 22482 Hz in the dynamic range of ±50 g. Moreover, in addition to doubling the sensitivity, the introduced two-proofmass structure enables to cancel the lock-in phenomenon existing in a double-ended tuning fork resonator, in contrast with a monolithic proofmass structure.