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Liu H.,Nanjing University of Technology | Liu H.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Liu X.-X.,China Academy of Engineering Physics | Zhang F.-T.,China Academy of Engineering Physics | Su W.,China Academy of Engineering Physics
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2011

By analyzing the requirement of the closed-loop control for the vibratory gyroscope, the behaviour of the self-oscillation system with automatic gain control was analyzed with averaging method to achieve system stability and stable equilibrium. The theoretic analysis and experiment show that the reference voltage must be larger than a critical value; the larger the reference voltage is, the larger the signal-noise-ratio is; the system phase error will cause the resonance frequency drift and decrease the vibrating amplitude; different constants of the low pass filters result in different time to achieve the stable states. The experiment shows the frequency accuracy of the close-loop self oscillation system is about ±8ppm in 10 minutes and vibration amplitude is about 0.1% error in an hour.


Liu H.,Nanjing University of Technology | Liu H.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Meng R.,Nanjing University of Technology | Meng R.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing
Chinese Journal of Sensors and Actuators | Year: 2012

The nonlinear principle of the typical MEMS resonator was introduced, according to the phase relation between input electrostatic force and output displacement, phase-locked loop technology was adopted for resonator. The control equations based on phase-locked technology were also built for the system. With the help of the averaging method, the system stability was analyzed and the equilibrium for the amplitude vibration was achieved. The theoretical analysis and simulation show the integral gain is critical to the system stability. When it larger than the critical value, the system stable time is less, but the frequency tracking process would fluctuate;if it smaller than the critical point, the system stable time is longer, but the frequency tracking process would un-fluctuating.


Liu H.,Nanjing University of Technology | Liu H.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | LlU Q.,Nanjing University of Technology | LlU Q.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | And 2 more authors.
Chinese Journal of Sensors and Actuators | Year: 2011

The ynamic model for the novel type resonant accelerometer is built based on electrostatic negative stiffness theory. The no-linear relationship between the output frequency and acceleration is given. Built the equivalent interface model for the same frequency disturbance in the detecting end, some advices were given in structure design to restrain the disturbance. Chose the square wave as the sensing voltage,made use of the switch to demodulate the input weaken signal for experiment. The static capacitance is 0. 4pF, coupling part is 0. 04pF and the effective sensing capacitance is 3. 1fF in the sensing end. The method is useful to acquire the open loop characteristic for resonant accelerometer. The resonant frequency is 35.476kHz, Q factor is about 1400.


Liu Q.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Liu Q.,Nanjing University of Information Science and Technology | Yang J.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Yang J.,Nanjing University of Information Science and Technology | And 5 more authors.
Chinese Journal of Sensors and Actuators | Year: 2012

In the field of upper air meteorological observation, cloud droplets, ice and frost contamination on the surface of radiosonde humidity sensor may compromise the measurement accuracy. Heated twin humidity sensor opens up a new opportunity to tackle this problem. In order to optimize the heating strategy of heated twin humidity sensor, studying the steady and transient characteristics of the sensor is of great interest. The parameters of the four stages in a measurement cycle have been optimized by using a computational fluid dynamics(CFD)method in this work. Steady-state analysis has been implemented to simulate the interaction of the twin sensors with different spacing. Transient analysis has been carried out to obtain dynamic parameters, including the lengths of heating and cooling stages. The results show that the ranges of the measurement period of heated twin humidity sensor is 45 s~145 s. For cases where the radiosonde rising velocity is 6 m/s, the temperatures of two sensors do not affect each other, if their distance is no less than 3 mm. Two different heating strategies, high-altitude and low-altitude modes, are proposed to optimize the measurement cycle, where 40°C and 46°C are selected as the amplitudes of temperature drop, respectively.


Zhang L.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Zhang L.,Nanjing University of Information Science and Technology | Liu Q.,Jiangsu Key Laboratory of Meteorological Observation and Signal Processing | Liu Q.,Nanjing University of Information Science and Technology | And 5 more authors.
Chinese Journal of Sensors and Actuators | Year: 2013

Air temperature of high altitude is considered as an important factor in both weather forecast and climate change research. Due to the increasing amount of attention that has been focused on disaster prevention as well as the need of dealing with climate change, it is expected that the accuracy of the measurement air temperature with high altitude can reach to 0.1°C. However, the errors caused by solar radiation may reach 3°C or worse in upper air, which has become the bottleneck when improving the accuracy. A computational fluid dynamics (CFD) method is employed to study the errors induced by solar radiation, under the condition of various air pressures, lead angle, solar incident angle, from sea level to 32 km altitude. The results show that lead angle and solar incident angle are important factors that affect the errors. With the increasing of sea level elevation, the solar heating error appears a parabola correlation, which owns a growing slop.

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