Key Engineering Materials Vols. 562-565

Abstract: This paper presents a new microelectromechanical hybrid gyroscope (MHG) with three equilibrium rings. This structure can eliminate the error caused by the double rotation frequency of the driving shaft successfully. The MHG kinematic equations with three equilibrium rings are derived in this paper. Meanwhile, a new digital design and simulation of the MHG closed-loop detection circuit are proposed based on FPGA. The noise interference is weakened by using differential mode signal detection and the resources of FPGA are decreased by the loop diode demodulation in this paper. The cross axis coupling of the decoupled system is about 2.4%. The phase margin is 70deg and the magnitude margin is 22db after correction. The transcient response simulation is tested when the inputs are sinusoidal functions. The bandwidth and scale factors of x-axis and y-axis closed loops are analyzed in the paper. The bandwidth can reach about 70Hz and the scale factors of x-axis and y-axis closed loops are 0.1467V/o/s and -0.1467V/o/s respectively.

Abstract: The influence of dimension and temperature on a MEMS-based capacitive humidity sensor is researched in this paper. Looyenga’s equation and Dubinin’s semi-empirical data are used to describe the change of dielectric constant of sensing film when absorbing or desorbing water. For these equations and data, a picture of the relationship between dielectric constant and temperature, relative humidity is presented. In the basis of this theory, a simulation is finished, a curve showing good linearity and presenting the relationship between capacitance and relative humidity is obtained. A graph showing the influence of temperature on capacitance at different %RH is given, which considers the change of dielectric constant of Looyenga’s equation and Dubinin’s semi-empirical data only. the result shows that the capacitance decreases with the increasing of temperature. Influence of sensing layer thickness on sensitivity is presented. It shows that when the thickness of sensing layer is about 0.6 micron, the model of humidity sensor has the highest sensitivity.

Abstract: Zero bias is an important performance index of FBW gyroscope. Based on the given gyroscope experiments,we studied zero bias of random error properties,temperature characteristic, large overload environment variation, and then calculate FBW gyro bias, bias stability, zero bias repeatability.We use Kalman filter into FBW gyroscope for random error compensation.Through least-square method,we fit temperature scale factor and temperature bias of FBW gyro.The experimental results show that the compensation method has the advantages of simple operation,effectively compensation for measuring error of FBW gyroscope which is induced by temperature, and has strong engineering using value.

Abstract: A novel temperature and pressure sensor based on a single film bulk acoustic resonator (FBAR) is designed. This FBAR support two resonant modes, which response opposite to the change of temperature. By sealed the back cavity of a back-trench membrane type FBAR with silicon wafer, an on-chip single FBAR sensor suitable for measuring temperature and pressure simultaneously is proposed. For unsealed device, the experimental results show that the first resonant mode has a temperature coefficient of frequency (TCF) of 69.5ppm/K, and the TCF of the second mode is -8.1ppm/K. After sealed the back trench, it can be used as a pressure sensor, the pressure coefficient of frequency (PCF) for the two resonant mode is -17.4ppm/kPa and -6.1 ppm/kPa respectively, both of them being more sensitive than other existing pressure sensors.

Abstract: In order to develop the SOI micro-accelerometer front release process, this paper discusses in details the key technologies of the process. There are three problems need to be resolved: the corrosion of the electrode, the corrosion rate of the buried silicon dioxide layer as well as the anti-adhesion of the micro-structure. The corrosion characteristic of the electrode is studied, and a metal electrode of high ability of anti-HF acid corrosion is designed, after release of the micro-structure, the electrode does not fall off. The corrosion property of the buried silicon dioxide is studied, and the corrosion rate is exactly known for 2um and 5um thick buried silicon dioxide layer. Based on this, the buried silicon dioxide layer etching time can be controlled, preventing over-etching of the oxide layer. The adhesion of comb fingers and the mass with the substrate is settled at last. By electron microscopy tests, found that the process can get a good micro-structure surface, with smaller footing effects. By test, the sensitivity of the accelerometer is about 144.5mv/g.

Abstract: Platinum resistance temperature sensor is applied to the temperature range higher than 200K currently. Through studying the principle of platinum temperature sensor, the platinum resistance temperature microsensor can be used in the temperature region between 10K and 200K was studied. It employs symmetrical turn back structure, which effectively avoids the inductance caused by alternating current (AC). Fabrication process based on MEMS technology was illustrated. The platinum film was obtained by direct current (DC) magnetron sputtering deposition and the platinum resistance temperature microsensor was fabricated with 200nm thickness layer film. The relationship between resistance and temperature of platinum microsensor was tested by Quantum QD PPMS instrument. When T>30K and T<30K, TCR of platinum microsensor could achieve 16490ppm/K and 6430ppm/K respectively. Thus, the microsensor can be used as temperature sensing element between 10K and 200K in the cryogenics.

Abstract: Large mode coupling error would seriously restrict the improvement of gyroscope performance. In order to decrease the adverse influence from mode coupling error, this paper studied the formation mechanism of mode coupling error for a micro-machined vibratory gyroscope and certified the result studied by ANSYS analysis. Based on our analysis, it is found that removing material from both sides of the center lines of oscillation could arouse errors of anti-phase each other, which demonstrates that trimming could reduce mode coupling error on the other hand. Finally, experimental study was implemented on the micro-machined vibratory gyroscope by UV laser micromachining technology. Results indicated that laser trimming method on the basis of the phase relationship between mode coupling error signal and driving signal could effectively degrade the error. For certain prototype, the peak-peak voltage of the mode coupling error could be reduced from 6.6V to 0.2V after trimming when there is no angular velocity input.

Abstract: The projectile-borne meteorological information detection dropsonde is designed to be launched by a missile and dropped at altitude as the missile reached its peak to detect real-time meteorological information as the device falls to the surface. The high acceleration shock deriving from missile launch, violent changes of atmospheric parameter and stochastic disruptions from external environment are the main difficult to design this device. To deal with those problems, we apply sensors based on MEMS technology as their high performance in accuracy, anti-overload and easy integration, we explore best locations on the dropsonde body for sensors based on simulation, we develop effective arithmetic for data processing. At last, the performance of dropsonde is verified by some ground static experiments.

Abstract: In order to achieve thedynamic flight environment simulation assessment for the micro-accelerometer usedin the inertial navigation or guidance systems, it is necessary to reform the precisionstatic centrifuge’s mechanical and electronic architecture, accompanied withthe development of the novel data acquisition system. System design, hardwareand software implementation of the DAQ system for the micro-accelerometer’s dynamiccentrifuge test is reported, which is a subsystem of the dynamic precisioncentrifuge, Involving its system architecture, hardware and softwareimplementation. The DAQ system is developed based on the virtual instrument architecture,which has the ability to handle 4 analog or digital output micro-accelerometerssimultaneously. Error analysis shows that when the micro-accelerometer’s outputvoltage signal range is +2.5 V ~-2.5V, the comprehensive measurement accuracyis less than 2.5mV; when the output voltage signal range is +12.5 V ~-12.5V, thecomprehensive measurement accuracy is less than 12.5mV. When the sampling timeinterval is 20ms, synchronization error between each sampling point and thecentrifuge controller is less than 0.1ms.

Abstract: Resonant Micro-Optic Gyro (RMOG) is a kind of optical sensors measuring angular velocity via Sagnac Effect, which yields different central resonant frequency between the clockwise (CW) and counterclockwise (CCW) light path of a ring-resonator when rotating. In this paper, Y-type branch waveguide is put forward to replace K-type coupler in RMOG to reduce the influence of splitting ratio asymmetry due to fabrication errors and temperature drift. Y-type branch waveguide based on silicon-on-silica is designed and analyzed. Simulation results show that Y-type branch waveguide performs better fabrication tolerance than K-type coupler, which reduces the nonlinear Kerr-Effect induced noise excited by power nonuniformity of the counter-propagating beams, therefore the detection sensitivity of RMOG can be improved.