Key Engineering Materials Vols. 609-610

Abstract: In this paper, the design of compensator to stabilize the micromachined accelerometer is considered based on stability analysis, and the determination of relevant parameter is also proposed. In the design of compensator, in order to minimize the noise effect into the system of micromachined accelerometer, the technology of correlated double sampling (CDS) is considered. The compensator is implemented under 0.5 μm CMOS process and simulated in Cadence. The final simulation result shows that the compensator can afford phase of 15°to micromachined accelerometer at least to stabilize the system.

Abstract: This paper focuses on obtaining high measurement precision for large step-height by double-interferometry using waveform transforming technology. The interferometer performing the measurement, which is stabilized by a feedback loop and is robust enough for on-line measurement, works simultaneously in both modes of single-wavelength interferometry (SWI) and two-wavelength interferoemetry (TWI). In order to make the peak point of the TWI signal prominent and unique, the cosine-amplitude-modulated TWI signal has been transformed to be a triangular signal with the same frequency as the cosine-amplitude modulating and being in phase with it. The positions of the one-to-one corresponding peaks of the TWI signal and the triangular signal are the same. As the peak point of the triangular signal can be addressed much more precisely than that of the TWI signal, by employing the shifting range of the peak of the triangular signal instead of that of the TWI signal to determine the amplitude of the step height while using the SWI signal to measure the value of it, the system could measure the height with high precision. The standard deviation of measuring a gauge block with the height of 0.5mm is 0.8nm.

Abstract: To reduce the measurement cost and time, a time domain measurement method of quality factor for MEMS resonator is presented in this paper. The relation curve between quality factor and vacuum level is obtained. The results indicate that measurement error is larger under high vacuum level when the sampling frequency is lower. The reason causing the error is analyzed and measurement precision is improved by increasing the sampling frequency. The measurement results indicate time domain measurement is advisable and improvable for MEMS resonator measurement.

Abstract: A novel noise reduction algorithm combined with compressive sensing (CS) and lifting wavelet transform (LWT) is proposed in this paper. This algorithm can overcome the limitations of traditional noise reduction methods based on Kalman filtering and wavelet threshold filtering. The characteristics of wavelet time-frequency distribution of the microelectromechanical system (MEMS) gyroscope are discussed to illustrate the demerit of the classical filtering methods. Noise reduction algorithm of MEMS gyroscope signal is studied in detail by combining CS theory with lifting wavelet transform. De-noising effect, time-consumption of computation as well as traditional CS reconstruction algorithms are analyzed. The results show that the signal reconstruction algorithm of conventional matching pursuit (MP) greedy algorithms contains more glitches and computation time-consumption, the basis pursuit de-noising (BPDN) algorithm is better and it has advantages of high computational efficiency and ease of implementation.

Abstract: Abstract:The micro-machined gyroscope that uses Coriolis force to measure angular velocity has non-linear error,which makes the amplitude of angular velocity have a relationship with its frequency,and fabrication technology error,which leads gyroscope’s drive shaft and detection shaft not to be vertical.All kinds of errors severely restrict this kind of gyroscope’s measuring accuracy and application range.This article obtained the reason for the formation of all kind of gyroscope’s errors and their mathematical expressions through analyzing the principle of micromachined gyroscope,which uses Coriolis force to measure angular velocity.At the same time,the gyroscope mathematical model was established and used to emulate to analyze each error’s influence on the angular velocity measured by gyroscope.The conclusion obtained by theoretical analysis and simulation provides the basis for gyroscope’s error analysis and elimination,and it has an important significance in improving the measuring accuracy of gyroscope.

Abstract: The wire bonding process in the package of MEMS accelerometer is analyzed by the finite element software ANSYS/LS-DYNA. Impact on the bonding strength of the ultrasonic amplitude, ultrasonic frequency and the friction between wire bond and bond pad are studied. The strength of wire bond is evaluated through the bond pull test experiment. The test result shows that the analysis on the wire bonding is helpful for improving the quality of wire bonding.

Abstract: To meet the performance test for the confocal laser scanning microscope (CLSM) accurately in some specific application occasions, the spatial resolution imaging principle of confocal laser scanning microscope was analyzed theoretically. And the micron line spacing as the measurement standard has tried to investigate the lateral resolution of CLSM in experiment. The value range of the lateral resolution was calculated by the fluctuation state of the output light intensity signal when there is the lateral movement between the objective with sample. At the same time, some reasons for spatial resolution are also been evaluated in theory. Experiments demonstrate that if the value of the line spacing standard is closer to the spatial resolution of CLSM, the standard can be utilized to test the spatial resolution. So we can use a a series of lines spacing standards with different lines spacing values to test the serial effective resolution. And in our experiment, we only measured line spacing standard with 8μm line width and 100μm line pitch with many times by CLSM, and the spatial resolution of the CLSM is obtained about more minimal than 0.3μm by the scanning curves.

Abstract: The scanning mirror has two gimbals structure, which are supported perpendicularly to each other by torsion beams. Dual-axis movement of the mirror is achieved by the tilt of inner and outer structures, respectively. The electromagnetic 2D MEMS scanning mirror is fabricated using a bulk silicon process, mainly including the wet etching, electroplating and ICP dry etching process. The permanent magnets are packaged together with the electromagnetic 2D MEMS scanning mirror in a compact size of 18×28×28mm³. The electromagnetic 2D MEMS scanning mirror has advantages of small volume, low voltage and high frequency, which has a broad application in sensor networks, target detection and optical imaging.

Abstract: Diaphragm gas meter is a specialized flow meter that measures the volume of fuel gas such as natural gas and coal gas. Valve bonnet and valve seat are the key parts of diaphragm gas meter, which compose the main factors of its metering error. The widely detecting ways are direct observational method and pneumatic pressure method. Direct observational method only realizes the qualitative detection with lacking science. Pneumatic pressure method can realize the quantitative detection, but with low accuracy and bad reliability. In order to evaluate the gas tightness of diaphragm gas meter valve accurately, surface texture method was adopted. Firstly, the surface roughness mathematical model of valve working face was established. A fast Gaussian filtering convolution algorithm was proposed based on the symmetry of Gaussian density function. Secondly, the working face of gas valve on the high-precision air floating stage was scanned by the chromatic confocal sensor. And the roughness profile of valve working face was got through the fast Gaussian filter when the cut-off wavelength was 0.8mm. Then the roughness parameters could be calculated with MATLAB by setting the sampling length and evaluation length. The results show that surface roughness has a difference of over 1μm between the qualified and unqualified valve. Besides, there is a little deviation of below 9% between the experimental value and the stylus profilometer measuring value, which has no influence on the judging result of qualified or unqualified about the measured workpiece. The gas tightness performance of gas valve can be judged by measuring surface roughness of its working face, which can provide a scientific basis for evaluating the quality of diaphragm gas meter valve in a quantitative way.

Abstract: Sigma Delta modulator is widely used in ADC for kinds of micro inertial sensors, Sigma Delta ADC can be easily integrated with digital circuits. It possesses some performances of good linearity and high accuracy, while it has no such strict requirements for the match of device dimensions. In this paper, the design of third-order Sigma Delta modulator with a structure of single-loop full feed-forward is accomplished, meanwhile it uses local feedback for zero optimization to improve the shaping capacity of the modulator noise within the signal bandwidth. The OSR (over-sampling rate) of the modulator is 128 and the signal bandwidth is 10 kHz. By the system model building and simulation in the Simulink of MATALAB, the SNR is 96.3 dB and the ENOB is 15.71 bits. Then the modulator is implemented into transistor-level circuits with 0.5um process, by the simulation in Spectre of Cadence, the SNR is 88.5 dB and the ENOB is 14.41 bits. 搜