Fringe-Effect Capacitive Proximity Sensors for Tamper Proof Enclosures

In this paper, electrohydrodynamic atomization combined with a polymeric micromoulding technique was used to form PZT single element devices using a PZT sol-gel slurry without an etching process. The PZT single element device was initially designed to work as a piezoelectric ultrasonic transducer consisting of a circular or a square of various sizes, which was produced and used to evaluate the process. The resulting PZT device had a homogenous microstructure. It was observed that the relative permittivity of the circular and square single element devices was especially high at small size due to the fringe effect. The results show that the radius and width of the PZT single circular and square element devices with a thickness of 15µm should be bigger than 400µm in order to reduce the fringe effect.

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A Novel Method for the Micro-Clearance Measurement of a Precision Spherical Joint Based on a Spherical Differential Capacitive Sensor

Sensors ◽

10.3390/s18103366 ◽

2018 ◽

Vol 18 (10) ◽

pp. 3366 ◽

Cited By ~ 2

Author(s):

Wen Wang ◽

He Yang ◽

Min Zhang ◽

Zhanfeng Chen ◽

Guang Shi ◽

...

Keyword(s):

Capacitive Sensor ◽

Differential Capacitance ◽

Industrial Robots ◽

Parallel Mechanisms ◽

Spherical Joint ◽

Compact Structure ◽

Spacing Variation ◽

Novel Method ◽

The Mathematical Model ◽

Fringe Effect

A spherical joint is a commonly used mechanical hinge with the advantages of compact structure and good flexibility, and it becomes a key component in many types of equipment, such as parallel mechanisms, industrial robots, and automobiles. Real-time detection of a precision spherical joint clearance is of great significance in analyzing the motion errors of mechanical systems and improving the transmission accuracy. This paper presents a novel method for the micro-clearance measurement with a spherical differential capacitive sensor (SDCS). First, the structure and layout of the spherical capacitive plates were designed according to the measuring principle of capacitive sensors with spacing variation. Then, the mathematical model for the spatial eccentric displacements of the ball and the differential capacitance was established. In addition, equipotential guard rings were used to attenuate the fringe effect on the measurement accuracy. Finally, a simulation with Ansoft Maxwell software was carried out to calculate the capacitance values of the spherical capacitors at different eccentric displacements. Simulation results indicated that the proposed method based on SDCS was feasible and effective for the micro-clearance measurement of the precision spherical joints with small eccentricity.

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An Improved Capacitive Sensor for Detecting the Micro-Clearance of Spherical Joints

Sensors ◽

10.3390/s19122694 ◽

2019 ◽

Vol 19 (12) ◽

pp. 2694 ◽

Cited By ~ 1

Author(s):

Wen Wang ◽

Wenjun Qiu ◽

He Yang ◽

Haimei Wu ◽

Guang Shi ◽

...

Keyword(s):

Mathematical Model ◽

Real Time ◽

Measurement Accuracy ◽

Detection Method ◽

Capacitive Sensor ◽

Parallel Manipulators ◽

Differential Capacitance ◽

Industrial Robots ◽

The Mathematical Model ◽

Fringe Effect

Due to the flexible and compact structures, spherical joints are widely used in parallel manipulators and industrial robots. Real-time detection of the clearance between the ball and the socket in spherical joints is beneficial to compensate motion errors of mechanical systems and improve their transmission accuracy. This work proposes an improved capacitive sensor for detecting the micro-clearance of spherical joints. First, the structure of the capacitive sensor is proposed. Then, the mathematical model for the differential capacitance of the sensor and the eccentric micro-displacement of the ball is deduced. Finally, the capacitance values of the capacitive sensor are simulated with Ansoft Maxwell. The simulated values of the differential capacitances at different eccentric displacements agree well with the theoretical ones, indicating the feasibility of the proposed detection method. In addition, the simulated results show that the proposed capacitive sensor could effectively reduce the capacitive fringe effect, improving the measurement accuracy.

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Fringe effect on critical current of a gold film percolation system

Acta Physica Sinica (Overseas Edition) ◽

10.1088/1004-423x/6/7/008 ◽

1997 ◽

Vol 6 (7) ◽

pp. 526-530

Author(s):

Ge Hong-liang ◽

Zeng Yue-wu ◽

Feng Chun-mu ◽

Ye Gao-xiang ◽

Zhang Qi-rui

Keyword(s):

Critical Current ◽

Gold Film ◽

Fringe Effect

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Quantitative measurements of dielectric spectra using microdielectric fringe-effect sensors

Proceedings of the 2002 American Control Conference (IEEE Cat. No.CH37301) ◽

10.1109/acc.2002.1024606 ◽

2002 ◽

Author(s):

Yunn-Hong Choi ◽

M. Skliar

Keyword(s):

Dielectric Spectra ◽

Quantitative Measurements ◽

Fringe Effect

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Reduced Order Model Analysis of Frequency Response of Alternating Current Near Half Natural Frequency Electrostatically Actuated MEMS Cantilevers

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4023164 ◽

2012 ◽

Vol 8 (3) ◽

Cited By ~ 23

Author(s):

Dumitru I. Caruntu ◽

Israel Martinez ◽

Martin W. Knecht

Keyword(s):

Natural Frequency ◽

Microelectromechanical Systems ◽

Multiple Scales ◽

Alternating Current ◽

Reduced Order Model ◽

Order Model ◽

Reduced Order ◽

Electrostatically Actuated ◽

Mems Resonator ◽

Fringe Effect

This paper uses the reduced order model (ROM) method to investigate the nonlinear-parametric dynamics of electrostatically actuated microelectromechanical systems (MEMS) cantilever resonators under soft alternating current (AC) voltage of frequency near half natural frequency. This voltage is between the resonator and a ground plate and provides the actuation for the resonator. Fringe effect and damping forces are included. The resonator is modeled as a Euler-Bernoulli cantilever. ROM convergence shows that the five terms model accurately predicts the steady states of the resonator for both small and large amplitudes and the pull-in phenomenon either when frequency is swept up or down. It is found that the MEMS resonator loses stability and undergoes a pull-in phenomenon (1) for amplitudes about 0.5 of the gap and a frequency less than half natural frequency, as the frequency is swept up, and (2) for amplitudes of about 0.87 of the gap and a frequency about half natural frequency, as the frequency is swept down. It also found that there are initial amplitudes and frequencies lower than half natural frequency for which pull-in can occur if the initial amplitude is large enough. Increasing the damping narrows the escape band until no pull-in phenomenon can occur, only large amplitudes of about 0.85 of the gap being reached. If the damping continues to increase the peak amplitude decreases and the resonator experiences a linear dynamics like behavior. Increasing the voltage enlarges the escape band by shifting the sweep up bifurcation frequency to lower values; the amplitudes of losing stability are not affected. Fringe effect affects significantly the behavior of the MEMS resonator. As the cantilever becomes narrower the fringe effect increases. This slightly enlarges the escape band and increases the sweep up bifurcation amplitude. The method of multiple scales (MMS) fails to accurately predict the behavior of the MEMS resonator for any amplitude greater than 0.45 of the gap. Yet, for amplitudes less than 0.45 of the gap MMS predictions match perfectly ROM predictions.

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