MEMS AC voltage reference for miniaturized instrumentation and metrology

This work explores MEMS (Micro-Electro-Mechanical Systems) potentialities to fabricate AC voltage references through mechanical-electrical transduction that could be used for high precision electrical metrology and for applications in miniaturized instrumentation. AC voltage reference ranging from 5 V to 90 V have been designed and fabricated using the same Epitaxial Silicon On Insulator (SOI) surface micromachining process allowing an accurate control of both dimensions and material properties. The measured MEMS AC voltage reference values have been found in a good agreement with CoventorWare calculations. These tests structures have also been used to develop the read-out electronics to drive the MEMS.     

Pull-in-based μg-resolution accelerometer: Characterization and noise analysis

The pull-in time (t_pi) of electrostatically actuated parallel-plate microstructures enables the realization of a high-sensitivity accelerometer that uses time measurement as the transduction mechanism. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making pull-in time very sensitive to external accelerations. Parallel-plate MEMS structures have been designed and fabricated using a SOI micromachining process (SOIMUMPS) for the implementation of the accelerometer. This paper presents the experimental characterization of the microdevices, validating the concept and the analytical models used. The accelerometer has a measured sensitivity of 0.25 μs/μg and a bandwidth that is directly related to the pull-in time, BW = 1/2t_pi ≈ 50 Hz. These specifications place this sensor between the state of the art accelerometers found both in the literature and commercially. More importantly, the resolution of the measurement method used is very high, making the mechanical-thermal noise the only factor limiting the resolution. The in-depth noise analysis to the system supports these conclusions. The total measured noise floor of 400 μg (100 μs) is mainly due to the contribution of the environmental noise, due to lack of isolation of the experimental setup from the building vibrations (estimated mechanical thermal noise of 2.8 μg/√Hz). The low requirements of the electronic readout circuit makes this an interesting approach for high-resolution accelerometers.     

发动机装配用曲轴拉入机的开发设计

介绍的曲轴拉入机是机电一体化产品,是发动机装配线上的重要设备,并已得到广泛应用。     

范德华力对硅基微悬臂梁抗粘附稳定性的影响

通过在硅微悬臂梁与基底表面上涂覆低表面能的憎水性OTS(CH3(CH2)17SiCl3)膜,以除去接触面间的表面张力;把梁与基底均接地,以除去接触面间的静电力,研究仅有范德华力作用时,硅微悬臂梁结构的抗粘附稳定性.根据两接触面均为粗糙表面的微观实际接触模型,在接触表面产生塑性变形的情况下,计算范德华粘附能大小,并分析表面形貌对其影响,得到粗糙表面接触的微梁抗粘附临界长度.     

The role of fabrication techniques on the performance of widely tunable micromachined capacitors

Coventorware 2001.1^® is used to identify key vertical dimensions for the low voltage operation of a two-gap widely tunable capacitor. Using identical masking stages, two varieties of tunable capacitor are presented. Nickel structures are demonstrated which have a tuning ratio of 5.1:1 from an initial capacitance of 0.7 pF. Gold devices exhibit a tuning ratio of 7.3:1 from an initial capacitance of 1.5 pF. These are the most widely tunable devices reported to date.     

中,低频超宽捕捉带跟踪滤波PLL环路的设计与实现

介绍由新型复合集成ＰＬＬ组成的超宽捕捉带跟踪滤波环路。当输入信号电平≥５０ｍＶ；Ｓ／Ｎ≥１时，捕捉及跟踪带均达９０％ｆ０以上。     

Nonlinear electrostatic behavior for two elastic parallel fixed–fixed and cantilever microbeams

In this paper, the electrostatic pull-in behavior of two elastic parallel fixed–fixed and cantilever microbeams in microelectromechanical systems (MEMS) are investigated. The nonlinear electrostatic equations are considered due to some important effects including: residual stresses, fringing field and axial stresses. Various residual stresses in two elastic parallel fixed–fixed models are considered. Step by step linearization method is used to solve the equations. The numerical results reveal that the step by step linearization method is highly efficient, and it is the easiest one to calculate the pull-in voltage. In the proposed models, the pull-in voltages are considerably decreased when compared to the pull-in voltages of simple fixed–fixed and cantilever models.     

Effects of system dynamics and applied force on adhesion measurement in colloidal probe technique

Dynamic pull-in/pull-off forces were quantitatively measured using an AFM colloidal probe technique. Two spherical colloids made of silicon dioxide (SiO₂) and gold (Au) that were attached to an AFM cantilever were approached to and retracted from a silicon wafer specimen, where the speed of tip approaching/retracting (i.e., vertical dynamics) and specimen sliding (i.e., horizontal dynamics) was controlled. First, when the vertical dynamics of colloidal tip was applied on the stationary silicon wafer specimen, it was observed that the slower tip approaching showed higher pull-in force, while the pull-off force was dependent on both the applied force and the retracting speed. For the two colloidal tips, it was found that the higher applied force and the faster tip retraction led to the higher pull-off force. Next, under the constant speed of tip approach and retraction, horizontal dynamics was applied to the silicon wafer specimen. It was observed that the horizontal motion of the specimen made the pull-off force lower, which could be attributed to the breakage of adhesive asperity junctions at the interface. The pull-off force was further decreased at faster horizontal motion of the specimen due to the longer sliding distance. Therefore, from the systematic experiments of dynamic adhesion measurement, it could be known that if a micro/nano-system is under dynamic surface interaction, its adhesive force cannot be fully described by a conventional quasi-static adhesion model but it should include the effects of applied system dynamics in both normal and tangential directions.     

22kW、6极高效高起动转矩永磁同步电动机的设计

为满足抽油机的配套电机高效高起动转矩及经济运行范围宽的要求。对22kW、6极永磁同步电动机进行了设计、试制和试验。结果表明:该产品可替代37kW、6极异步电动机,节能效果明显。     

Electromagnets calibration utilizing the pull-in instability

Precise determination of electromagnetic characteristics is crucial for many applications employing magnetic actuators such as magnetic bearings and precision machine controls. Traditionally, this task is achieved by the constant air gap type of calibration. Although this method can achieve high accuracy, the requirements for dedicated instrumentation and precise machining impose limitations to most users. In this article, an alternative approach utilizing pull-in instability to calibrate electromagnets is presented. The electromagnet to be calibrated exerts a force on the tip of a cantilever beam and causes deflection. The deflection-current curve is recorded to obtain the exact pull-in current. Finally, the electromagnetic force constant can be derived from the pull-in current, the initial air gap, and the equivalent stiffness of the cantilever beam. Experimental results showed that the calibrated force coefficients agreed with those obtained from the standard constant air gap method within 3–10% accuracy. In comparison with the constant air gap method, this approach is potentially cheaper and can achieve an accuracy level sufficient for subsequent robust control purpose.