Key Engineering Materials Vol. 503

Abstract: In this paper, an integrated 3-axis MEMS accelerometer was analyzed. Because of asymmetrical structure, z-axis sensing element, which was imbedded in the proof mass of lateral accelerometers, had large mechanical coupling. Simulation result showed that the cross talk in z-axis was as high as 64.3%. To solve the problem, a fully symmetrical structure with vertical springs was adopted in z-axis sensing element. The movement of z-axis was linear vertical displacement instead of torsional displacement. Simulation results showed there was no obvious cross talk in z-axis sensing element.

Abstract: A new hexagonal actuator arrangement continuous face-sheet MEMS deformable mirror is proposed, a mirror array with 19 elements is fabricated by a surface micromachining process. This design has a good fitting capability and a fast dynamic response. The fabricated sample is tested by an optical profiler. Simulation and test results indicate that it has a small aperture size, a high fill factor, a fast response time and a high working bandwidth. This new device provides a possibility of manufacturing a large-actuator-count DM for high speed wavefront control.

Abstract: Because of the imperfections of the manufacture, the quadrature and offset error become the major concerns in Micro-gyroscopes for high performance. So in order to eliminate and minimize quadrature and offset error, various methods employing improvement of manufacture and suppression circuitry have been put forward to improve the performance. And this paper summarize most of the suppression methods those who have better performance.

Abstract: Closed-loop driving circuit is widely used in the high performance micrimachined gyroscope. But in the capacitive micromachined gyroscope, this circuit can be self-oscillation incapability because of signal coupling by parasitical capacitance. A novel closed-loop driving circuit based on the frequency modulation method is present in this paper. Since the frequency of driving signal is modulated, it is different from the frequency of sensing current. Even if there is coupling, the phase requirement of closed-loop driving method is not destroyed, which overcomes the disadvantage of self-oscillation incapability. Both the simulations and test results are provided, which demonstrates the feasibility of this method.

Abstract: This paper describes novel multi-microchannel, which is the major component of wind velocity and direction sensor based on MEMS technology. The multi-microchannel built in a cylinder, and the channels have been optimized to produce a flow rate that depends on the wind direction according to a cosine function. When two such cylinders placed orthogonally in wind condition, wind speed and direction can be inferred from flow rate data measured from the channels. With the help of Fluent simulation software, this paper not only provides the design ideas of multi-microchannel but also proposes one design approach which meets the practical needs.

Abstract: The quality of designing structure and properties of sensor photoionization room，directly determines its weak signal detection sensitivity detection and effecting ionization chamber detection efficiency .The paper experiments on four factors of affect the sensitivity of sensor. The results show that: the signal intensity proportional to the area of the ionization chamber; signal intensity goes up with the increase of bias voltage, and with bias voltage into a square the relationship; signal strength was first increased and then decreased with the growth of the distance between electrodes; signal strength was first increased and then decreased. With the growth of light-driven power.

Abstract: This paper presents a capacitive biaxial microaccelerometer with a single proof mass. The theoretical analysis results are confirmed by finite element analysis. The experimental results indicate the biaxial accelerometer with uniform axial sensitivities, good linearity and high cross-axis sensitivity immunity to the z-axis input.

Abstract: An analytical method was presented to predict the three-dimensional (3-D) magnetic flux density distribution in the air gap produced by NdFeB permanent magnets of the planar motor. First, the analytical model of the planar motor was established, and Laplace equations of magnetic scalar potential and a series of boundary conditions were given. Then, the analytical expressions of magnet field strength and magnet flux density were obtained in the air gap of produced by NdFeB permanent magnets by the method of separation of variables. Finally, Comparisons the analytical results and finite element results, and the error never exceed five percent. Therefore, high precision has been derived. The analytical field results provide a basis for comparative studies, design optimization, and machine dynamic modelling of the planar motor.

Abstract: This paper reports on a system level design and analysis of a mash fourth-order sigma-delta (ΣΔ) modulator. Compared with a high-order single-loop ΣΔ modulator (ΣΔM), there’s no need to consider about the system stability of a mash ΣΔM, which has the advantages of better signal to quantization noise ratio (SQNR). System level simulation results indicate that the SQNR is 122.0 dB, and the effective number of bits (ENOB) is 19.97 bits when the over sampling ratio (OSR) is 128.

Abstract: A closed-loop control system designed for a SOI-MEMS resonant accelerometer is proposed in this paper. The sensor chip was developed by silicon-direct-bonding SOI wafer (10+2+290 um) with MEMS fabrication technology. Z-axis acceleration is differentially detected by using two H-style vibrating beams through a frequency shift caused by the inertial force acting as bending stress loading. The electromagnetically excitation and detection is adopted to make the closed-loop control of the sensor easier. The whole closed-loop control system designed for the accelerometer mainly consists of amplifier, automatic gain control (AGC) circuit, buffer and phase shifter. Testing results show that the accelerometer with the closed-loop system can work stable at the frequency of 58.958 kHz when 1g z-axis acceleration is applied which is consistent with the open-loop testing.