scholarly journals Simulation of Motion Interactions of a 2-DOF Linear Piezoelectric Impact Drive Mechanism with a Single Friction Interface

2018 ◽  
Vol 8 (8) ◽  
pp. 1400 ◽  
Author(s):  
Haojie Xia ◽  
Liling Han ◽  
Chengliang Pan ◽  
Huakun Jia ◽  
Liandong Yu
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Piezoelectric Actuators ◽  
Friction Model ◽  
Duty Ratio ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Coupled Motion ◽  
Drive Mechanism

A two-degrees-of-freedom (2-DOF) linear piezoelectric impact drive mechanism (PIDM) is actuated by two independent piezoelectric actuators (PAs). The coupled motion interactions of a two orthogonal DOF linear PIDM with a single friction interface are introduced and analyzed. A complete dynamic model of the 2-DOF PIDM is established with the Karnopp friction model considering the distribution of friction in the x-axis and y-axis. The output displacements of the 2-DOF PIDM and two corresponding independent 1-DOF PIDMs are investigated numerically. When the two input exciting signals of a 2-DOF PIDM have the same driving voltage of 100 V with a duty ratio of 98% at 10 Hz and two 1-DOF PIDMs are driving under the same conditions, the step displacements in the two axes of 2-DOF PIDM are improved compared to the corresponding 1-DOF PIDM. When the two input exciting signals of a 2-DOF PIDM have the same driving voltages of 100 V with a duty ratio of 98% but the driving frequency is 10 Hz in the x-axis and 20 Hz in the y-axis, the results show that the displacement of high frequency achieves a slight decrease and displacement of low frequency shows a large increase compared to the two corresponding 1-DOF PIDMs.

scholarly journals Design of a Low-Frequency Harmonic Rotary Piezoelectric Actuator

Actuators ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Kang Liang ◽  
Chong Li ◽  
Yujian Tong ◽  
Jiwen Fang ◽  
Wei Zhong
Keyword(s):  
Piezoelectric Actuator ◽  
Harmonic Wave ◽  
Low Frequency ◽  
Experimental System ◽  
Piezoelectric Actuators ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Output Characteristics ◽  
Driving Signal ◽  
Harmonic Displacement

Piezoelectric actuators usually operate under a high frequency driving signal. Here we report a harmonic rotating piezoelectric actuator by coupling a harmonic wave generator and a friction rotor, in which the actuator can be actuated by a low-frequency sinusoidal signal with positive bias. The harmonic wave is generated by a two-stage magnifying mechanism consisting of a displacement amplifier and a harmonic rod. Applying piezoelectricity theory, the actuator’s output characteristic equations are deduced. What is more, the output characteristics of piezoelectric actuators are tested with the established experimental system. Results show that the generated harmonic displacements can drive the actuator to work normally at a driving voltage of larger than 90 V and the maximum total harmonic displacement of the piezoelectric actuator comes up to 427.6 μm under the driving voltage of 150 V. Meanwhile, the error between the measured and calculated values of the harmonic displacement is less than 7%. Furthermore, the rotational speed of the piezoelectric actuator reaches 5.45 rpm/min at 150 V voltage and 5 Hz driving frequency.

Research on the dynamic characteristic of semi-active hydraulic damping strut

2019 ◽  
Vol 234 (6) ◽  
pp. 1779-1791 ◽  
Author(s):  
Daoyong Wang ◽  
Wencan Zhang ◽  
Mu Chai ◽  
Xiaguang Zeng
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Maxwell Model ◽  
Friction Model ◽  
Damping Capacity ◽  
Frequency Range ◽  
Stiffness Model ◽  
Rubber Bushing

To reduce the vibration and shock of powertrain in the process of engine key on/off and vehicle in situ shift, a novel semi-active hydraulic damping strut is developed. The purpose of this paper is to study and discuss the dynamic stiffness model of the semi-active hydraulic damping strut. In this study, the dynamic characteristics of semi-active hydraulic damping strut were analyzed based on MTS 831 test rig first. Then, the dynamic stiffness model of semi-active hydraulic damping strut was established based on 2 degrees of freedom vibration system. In this research, a linear, fractional derivative and friction model was used to represent the nonlinear rubber bushing characteristic; the Maxwell model was used to describe the semi-active hydraulic damping strut body model; and the parameters of rubber bushing and semi-active hydraulic damping strut body were identified. The dynamic stiffness values were calculated with solenoid valve energized and not energized at amplitudes of 1 mm and 4 mm, which were consistent with experimental results in low-frequency range. Furthermore, the simplified dynamic stiffness model of the semi-active hydraulic damping strut was discussed, which showed that bushing can be ignored in low-frequency range. Then, the influence of equivalent spring stiffness, damping constant, and rubber bushing stiffness on the stiffness and damping capacity of the semi-active hydraulic damping strut were analyzed. Finally, the prototype of the semi-active hydraulic damping strut was developed and designed based on the vehicle in situ shift and engine key on/off situations, and experiments of the vehicle with and without semi-active hydraulic damping strut were carried out to verify its function.

A comparison of the spectral features of the collision-induced light scattering by the molecular gases CH4 and CF4 and by argon

1977 ◽  
Vol 55 (22) ◽  
pp. 1962-1969 ◽  
Author(s):  
F. Barocchi ◽  
M. Zoppi ◽  
D. P. Shelton ◽  
G. C. Tabisz
Keyword(s):  
Light Scattering ◽  
High Frequency ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Detailed Comparison ◽  
Absolute Intensity ◽  
Molecular Spectra ◽  
Similar Data ◽  
Unknown Parameters ◽  
Three Body

The collision-induced light scattering from compressed gaseous CH4 and CF4 has been observed at room temperature at densities up to 100 and 166 amagats, respectively. Absolute intensity measurements have been made and the two- and three-body components to the spectra have been identified. A detailed comparison is made with similar data on argon and significant differences emerge between the atomic and molecular cases. The two-body molecular spectra contain an excess of intensity over predictions of the dipole–induced-dipole (DID) model; the argon intensity is less than predicted. At low frequency, the two- and three-body spectra of all species are dominated by the DID interaction. At high frequency the two-body molecular spectra decay much more slowly than the profile due to argon. A moment analysis has been performed wherein the pair polarizability is assumed to be of the form, β(r) = 6α2/r3 + B/rp. The unknown parameters B and p are determined from the experimental zeroth and second moments of the spectra. For the molecules B is found to be greater than unity and p is 7.2 for CH4 and 8.5 for CF4. The difference in the values of B and p, together with the fact the shape of the high frequency tail is not consistent with pure translational broadening, lead to the suggestion that the internal degrees of freedom of the molecules are playing a role in the scattering process.

scholarly journals A Novel Rotation-Structure Based Stick-Slip Piezoelectric Actuator with High Consistency in Forward and Reverse Motions

Actuators ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 189
Author(s):  
Jizhou Tang ◽  
Jingsong Wei ◽  
Yuming Wang ◽  
Zhi Xu ◽  
Hu Huang
Keyword(s):  
Piezoelectric Actuator ◽  
Piezoelectric Actuators ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Maximum Displacement ◽  
Stick Slip ◽  
Reverse Motion ◽  
Symmetric Structure ◽  
Deviation Rate ◽  
High Consistency

Under the same driving voltage and frequency, the forward and reverse motion inconsistency of stick-slip piezoelectric actuators would bring difficulty for subsequent control. To solve this problem, a rotation-structure based piezoelectric actuator with completely symmetric structure and two driving feet was initially proposed. By testing its output performances under various driving voltages and frequencies, it was confirmed that, although similar speeds could be achieved for forward and reverse motions, the maximum displacement and backward displacement in each step were still quite different. By analyzing the reasons leading to this difference, this actuator was further improved by using only one driving foot. The experimental results showed that the forward and reverse motion consistency of the improved actuator had been significantly improved. The deviation rate was only 1.6%, corresponding to a travel distance of 118.7 μm, obtained under the driving voltage of 100 V and driving frequency of 10 Hz. The comparison with some previously reported actuators further confirmed the advancement of this improved actuator.

scholarly journals Modeling and Compensation of Dynamic Hysteresis with Force-Voltage Coupling for Piezoelectric Actuators

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1366
Author(s):  
Wen Wang ◽  
Jiahui Wang ◽  
Ruijin Wang ◽  
Zhanfeng Chen ◽  
Fuming Han ◽  
...  
Keyword(s):  
Piezoelectric Actuators ◽  
Hysteresis Phenomenon ◽  
Dynamic Force ◽  
Driving Voltage ◽  
Driving Frequency ◽  
Positioning Accuracy ◽  
Output Displacement ◽  
Dynamic Hysteresis ◽  
Hysteresis Nonlinearity ◽  
The Impact

Piezoelectric actuators are widely used in the field of micro- and nanopositioning due to their high frequency response, high stiffness, and high resolution. However, piezoelectric actuators have hysteresis nonlinearity, which severely affects their positioning accuracy. As the driving frequency increases, the performance of piezoelectric actuators further degrades. In addition, the impact of force on piezoelectric actuators cannot be ignored in practical applications. Dynamic hysteresis with force-voltage coupling makes the hysteresis phenomenon more complicated when force and driving voltage are both applied to the piezoelectric actuator. Existing hysteresis models are complicated, or inaccurate in describing dynamic hysteresis with force-voltage coupling. To solve this problem, a force-voltage-coupled Prandtl–Ishlinskii (FVPI) model is proposed in this paper. First, the influence of driving frequency and dynamic force on the output displacement of the piezoelectric actuators are analyzed. Then, the accuracy of the FVPI model is verified through experiments. Finally, a force integrated direct inverse (F-DI) compensator based on the FVPI model is designed. The experimental results from this study show that the F-DI compensator can effectively suppress dynamic hysteresis with force-voltage coupling of piezoelectric actuators. This model can improve the positioning accuracy of piezoelectric actuators, thereby improving the working accuracy of the micro- or nano-operating system.

Design and Implementation of a Dimmable LED Driver with Low-Frequency PWM Control

2013 ◽  
Vol 284-287 ◽  
pp. 2538-2542
Author(s):  
Hung Liang Cheng ◽  
Chun An Cheng ◽  
Chao Shun Chen ◽  
Kuan Lung Huang
Keyword(s):  
High Frequency ◽  
High Efficiency ◽  
Low Frequency ◽  
Buck Converter ◽  
Duty Ratio ◽  
Buck Converters ◽  
Resonant Converter ◽  
Switching Loss ◽  
Led Driver ◽  
Frequency Pulse

This paper proposes a high-efficiency dimmable LED driver for light emitting diodes (LED). The developed LED driver consists of a full-bridge resonant converter and six buck converters. The function of the full-bridge resonant converter is to obtain a smooth dc-link voltage for the buck converters by phase-shift modulation (PSM) while that of the six buck converters is to drive six LED modules, respectively. The gate voltage of the active switch of each buck converter is a combination of high-frequency and low-frequency pulses. The duty ratio of the high-frequency pulse controls the LED voltage and thereby, controls the amplitude of LED current. LEDs are dimmed by low-frequency pulse-width modulation (PWM) to vary the average current flowing through LED. Circuit equations are derived and circuit parameters are designed. High circuit efficiency is ensured by operating the active switches at zero-voltage switching-on to reduce the switching loss. Finally, a prototype circuit was built to verify the accuracy and feasibility of the proposed LED driver.

Features of Nonlinear Sound Propagation in Vibrationally Excited Gases

2013 ◽  
Vol 38 (3) ◽  
pp. 357-362
Author(s):  
Anna Perelomova ◽  
Magdalena Kusmirek
Keyword(s):  
High Frequency ◽  
Degrees Of Freedom ◽  
Sound Propagation ◽  
Vibrational Excitation ◽  
Low Frequency ◽  
Vibrationally Excited ◽  
Weakly Nonlinear ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Nonlinear Distortions

Abstract Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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