A rotary valve controlled electro-hydraulic vibration exciter

2016 ◽  
Vol 230 (19) ◽  
pp. 3397-3407 ◽  
Author(s):  
He Wang ◽  
Guofang Gong ◽  
Hongbin Zhou ◽  
Wei Wang ◽  
Yi Liu
Keyword(s):  
Vibration Frequency ◽  
Harmonic Distortion ◽  
Response Speed ◽  
Slide Valve ◽  
Vibration Exciter ◽  
Rotary Valve ◽  
Sinusoidal Vibration ◽  
Servo Valve ◽  
Electric System ◽  
Supply Pressure

When sinusoidal vibration waveform is required, the frequency bandwidth of conventional electro-hydraulic vibration exciter controlled by servo valve is always limited to a rather narrow range due to the limits of slide valve structure and response speed, and no parameter is available for defining and evaluating the waveform quality. In this paper, a novel electro-hydraulic vibration exciter controlled by electromotor driven rotary valve is proposed to significantly extend the frequency range compared to the conventional servo valve controlled counterpart. Total harmonic distortion (THD) theory which is usually used to cope with voltage and current in electric system is borrowed to evaluate the quality of theoretical and experimental vibration waveforms at different supply pressures and vibration frequencies, quantitatively and qualitatively. The results show that the waveform quality is mainly influenced by the 3rd harmonic resonance. The proposed vibration exciter can output sinusoidal waveform with THD less than 5% at the vibration frequency higher than 70 Hz. In this frequency domain, the supply pressure has an extremely low impact on the THD of the waveform. The amplitude of the waveform can be adjusted by changing the supply pressure with almost no effect to the waveform quality at a certain vibration frequency.

Analytical solution to orifice design in a rotary valve controlled electro-hydraulic vibration exciter for high-frequency sinusoidal vibration waveform

2019 ◽  
Vol 233 (5) ◽  
pp. 1098-1108
Author(s):  
He Wang ◽  
Chengwen Wang ◽  
Long Quan ◽  
Guofang Gong ◽  
Wenjing Li
Keyword(s):  
Analytical Solution ◽  
Vibration Frequency ◽  
Axial Length ◽  
High Frequency ◽  
Harmonic Distortion ◽  
Total Harmonic Distortion ◽  
Design Solution ◽  
Vibration Exciter ◽  
Rotary Valve ◽  
Sinusoidal Vibration

The present study is focused on a novel method for the acquisition of high-frequency sinusoidal vibration waveform with electro-hydraulic vibration exciter. A rotary valve controlled electro-hydraulic vibration exciter is proposed to make it easier to obtain high vibration frequency than the conventional servo valve controlled counterpart. Three common used offices are taken into consideration: rectangular orifice, triangular orifice, and semicircular orifice. Analytical solution to orifice design of shape and axial length is suggested for the accurate control of vibration waveform. Harmonic theory borrowed from electronic technology is used as an evaluation index for the shape of vibration waveform. The orifice shape design decision is made according to the total harmonic distortion of vibration waveform. The nonlinear differential equation which models vibration waveform is established. The orifice axial length is designed according to the supply pressure, vibration frequency, and amplitude. Both theoretical and experimental results show that rectangular orifice is desirable for high-frequency sinusoidal vibration waveforms. With the orifice design solution, the proposed vibration exciter can output the vibration waveform with total harmonic distortion of less than 1% as compared with sinusoidal waveform and maximum error of 5% as compared with experimental value at vibration frequency of higher than 100 Hz, and greatly extend the frequency bandwidth when sinusoidal vibration waveform is required.

A novel method for high-frequency non-sinusoidal vibration waveforms with uniaxial electro-hydraulic shaking table based on Fourier series

2020 ◽  
pp. 107754632096171
Author(s):  
He Wang ◽  
Zhen Chen ◽  
Jiahai Huang
Keyword(s):  
Fourier Series ◽  
Vibration Frequency ◽  
High Frequency ◽  
Narrow Range ◽  
Harmonic Distortion ◽  
Shaking Table ◽  
Rotary Valve ◽  
Sinusoidal Vibration ◽  
Supply Pressure ◽  
Novel Method

In this article, a rotary valve is developed to obtain accurate high-frequency sinusoidal vibration waveforms. Then, a uniaxial electro-hydraulic shaking table controlled by a set of parallel rotary valves is constructed, which can superpose the sinusoidal vibration waveforms. The non-sinusoidal vibration waveforms including triangular vibration waveform, rectangular vibration waveform, sawtooth vibration waveform and trapezoidal vibration waveform are generated by adjusting the spool rotation speed based on the Fourier series. The results show that with one rotary valve, the uniaxial electro-hydraulic shaking table can output accurate high-frequency sinusoidal vibration waveforms and the total harmonic distortion is less than 1% at high vibration frequency. Compared with the standard vibration waveform, the error of the generated vibration waveform is very small. For the rectangular vibration waveform and sawtooth vibration waveform, the error is less than 6%, and for the triangular vibration waveform and trapezoidal vibration waveform, the error is less than 3%. The impacts of the working conditions on the error of the generated vibration waveform are very small. The proposed method for the accurate high-frequency non-sinusoidal vibration waveform is very effective and can be applied in high vibration frequency and different load masses. With the increase of the supply pressure, the amplitude of the generated vibration waveforms increases, while the error changes in a rather narrow range. The amplitude can be adjusted by changing the supply pressure with almost no effect on the accuracy of the vibration waveform.

scholarly journals Design of a P-wave seismic vibrator with advanced performance

GeoArabia ◽  
2008 ◽  
Vol 13 (2) ◽  
pp. 123-136
Author(s):  
Zhouhong Wei
Keyword(s):  
Broad Band ◽  
Harmonic Distortion ◽  
P Wave ◽  
Key Factors ◽  
Servo Valve ◽  
Supply Pressure ◽  
Seismic Resolution ◽  
Force Signal ◽  
Flow Pressure ◽  
Frequency Controller

ABSTRACT For optimal seismic imaging, the vibroseis method requires the vibrator to generate synchronous, repeatable sweeps over a broad frequency range and output the ground-force energy with minimum harmonic distortion. This requires re-evaluating each element of the vibrator system to ensure that it contributes to the success of the method. Key factors that cause the vibrator to suffer from severe harmonic distortion are fluctuations in the hydraulic power supply pressure, flexing of the baseplate, coupling or loading between the baseplate and the ground, nonlinear servo-valve flow-pressure characteristics, and servo-valve characteristics near null. This paper examines these factors and describes the design of a new P-wave vibrator by ION (previously I-O) to improve seismic resolution. Experimental results demonstrate that the newly designed vibrator dramatically reduces harmonic distortion in the ground-force signal under various coupling conditions, particularly on hard and uneven ground. With the high-frequency controller and Pelton DR valve, a broad-band sweep frequency is achieved. Cavitations in the supply pressure, a long-standing problem in vibrator mechanics, are almost completely eliminated.

scholarly journals Analysis on vibration for a high-frequency electro-hydraulic cleaning system controlled by improved two-dimensional rotary valve

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881141
Author(s):  
Xiancheng Ji ◽  
Yan Ren ◽  
Hesheng Tang
Keyword(s):  
Vibration Frequency ◽  
High Frequency ◽  
Functional Materials ◽  
Pressure Amplitude ◽  
Two Dimensional ◽  
Rotary Valve ◽  
Sinusoidal Vibration ◽  
High Frequency Vibration ◽  
Cleaning System ◽  
Sinusoidal Waveform

Conventional high-frequency cleaners utilize functional materials (e.g. piezoelectric ceramics, magnetostrictive materials) excited by electrical signals to realize high-frequency vibration, even ultrasonic vibration. However, it is difficult to produce a large force without sacrificing bandwidth because of the physical characteristics of materials themselves. Therefore, a high-frequency high-power cleaner driven by electro-hydraulic excitation is proposed. Only a few studies are performed on electro-hydraulic cleaners, owing to the limitation of frequency bandwidth of the electro-hydraulic system. Thus, a rotary valve named two-dimensional valve is improved and adopted to improve high-frequency performances of the electro-hydraulic cleaner. In this article, a two-dimensional rotary valve with a linear variable differential transformer is designed, and the vibration characteristics of the electro-hydraulic cleaner controlled by this valve are discussed in detail, especially vibration acceleration, vibration frequency, and pressure amplitude. A prototype of the electro-hydraulic cleaner is modeled and both a theoretical analysis and experimental investigation are carried out. Theoretical and experimental results indicate that the electro-hydraulic cleaning system outputs sinusoidal vibration waveforms, especially in a high-frequency domain, which could realize the vibration frequency of 2669 Hz. The measured waves at different frequencies (below the resonant frequency) demonstrate different distortions compared with the sinusoidal waveform. These distortions can be associated with the hydraulic resonance. At hydraulic resonance (1903 Hz), the amplitude is increased significantly and the vibration waveform becomes more pronounced. Nevertheless, the study does provide an access to the electro-hydraulic high-frequency vibration applied in cleaning or other engineering cases.

scholarly journals Vibration Frequency Characteristic Study of Two-stage Excitation Valve Used in Vibration Experiment System

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Yongping WU ◽  
Chengwei XIONG ◽  
Yi LIU ◽  
Jiafei ZHENG ◽  
Mingxuan ZOU
Keyword(s):  
High Frequency ◽  
Rotary Valve ◽  
Two Stage ◽  
Maximum Displacement ◽  
Experiment System ◽  
Oil Supply ◽  
Supply Pressure ◽  
Vibration Experiment ◽  
Working Principle ◽  
Large Flow

To satisfy the demands of higher frequency and amplitude in hydraulic vibration experiment system, the two-stage excitation valve is presented, and a mathematical model of two-stage excitation valve is established after analyzing the working principle of two-stage excitation valve, then the influence of relevant parameters on the displacement of main spool of two-stage excitation valve is studied by using Matlab/Simulink to calculate and analyze. The results show that the displacement of main spool will be smaller with bigger diameter and more secondary valve ports. When the reversing frequency is higher and the oil supply pressure is lower as well as the axial guide width of valve ports is smaller, the maximum displacement of main spool is smaller. The new two-stage excitation valve is easy to adjust reversing frequency and flow. The high frequency can be achieved by improving the rotation speed of servo motor and adding the number of secondary valve ports; the large flow can be realized by increasing the axial guide width of secondary valve ports and oil supply pressure. The result of this study is of guiding significance for designing the rotary valve for the achievement of higher reversing frequency and larger flow.

scholarly journals The Why of Adaptive Protections in Modern Electrical Networks

2019 ◽  
Vol 39 (2) ◽  
Author(s):  
Juan Martín Guardiola Montenegro ◽  
Eduardo Gómez Luna ◽  
Eduardo Marlés Sáenz ◽  
Jorge Armando De la Cruz Saavedra
Keyword(s):  
Renewable Energy ◽  
Distributed Generation ◽  
Renewable Resources ◽  
Harmonic Distortion ◽  
Distribution Networks ◽  
Electrical Networks ◽  
Dynamic Changes ◽  
Interconnected System ◽  
Electric System ◽  
Micro Grids

Electrical networks are evolving and taking on more challenges as the inclusion of renewable energy and distributed generation units increase, specially at distribution levels. Big trends of generating electricity with alternative and renewable resources has promoted the formation of distribution networks subsystems or micro grids, capable of supplying their own electric demand and to export energy to the interconnected system, if necessary. However, the effects of these generation units into the network and into the microgrid as well are many, as harmonic distortion, voltage flickers and especially in electrical protections.This paper provides an overview about implementation of renewable energy and distributed generation worldwide, as well as an introduction to microgrids concept and its main impacts and challenges into the electric systems. Finally, the main impacts of microgrid on protection equipments are presented at a distribution level, being adaptive protections one of the solutions to the dynamic changes of the electric system.

scholarly journals Vibration Compensation of the Frequency-Scanning-Interferometry-Based Absolute Ranging System

2019 ◽  
Vol 9 (1) ◽  
pp. 147 ◽  
Author(s):  
Fu-Min Zhang ◽  
Ya-Ting Li ◽  
Hao Pan ◽  
Chun-Zhao Shi ◽  
Xing-Hua Qu
Keyword(s):  
Standard Deviation ◽  
Vibration Frequency ◽  
Phase Modulation ◽  
Vibration Velocity ◽  
Sinusoidal Vibration ◽  
Vibration Effect ◽  
Frequency Scanning ◽  
Blind Area ◽  
Frequency Scanning Interferometry ◽  
Vibration Compensation

The frequency-scanning-interferometry-based (FSI-based) absolute ranging technology is a type of ranging technology possessing a high precision and no ranging blind area, so it can be used for non-cooperative targets. However, due to a tiny movement of a target, the Doppler shift and the phase modulation are introduced into the beat signal which results in ranging accuracy decrease. In order to solve this problem, first the model of vibration effect is established, and then the beat signals of two adjacent scanning periods are processed to produce a signal that is immune to vibration. The proposed method is verified by the experiments, and the experimental results show that the effect of vibration compensation is better for the target with a lower vibration velocity and at a lower vibration frequency (lower than 6 Hz). When the target is subjected to a sinusoidal vibration with an amplitude of 10 μm at a frequency of 1 Hz, by using the proposed method the standard deviation is reduced from 775 to 12 μm. Moreover, in the natural environment, by using vibration compensation the standard deviation is reduced from 289 to 11 μm.

scholarly journals Admittance Reshaping Control Methods to Mitigate the Interactions between Inverters and Grid

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2457 ◽  
Author(s):  
Ling Yang ◽  
Yandong Chen ◽  
An Luo ◽  
Kunshan Huai
Keyword(s):  
Design Method ◽  
Harmonic Distortion ◽  
Response Speed ◽  
Control Methods ◽  
Dynamics Model ◽  
Specific Design ◽  
Three Phase ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
System Phase

With the increasing impedance coupling between inverters and grid caused by the phase-locked loop (PLL), traditional three-phase inverters suffer from the harmonic distortion or instability problems under weak grid conditions. Therefore, the admittance reshaping control methods are proposed to mitigate the interactions between inverters and grid. Firstly, a dynamics model of traditional inverter output admittance including main circuit and PLL is developed in the direct-quadrature (dq) frame. And the qq channel impedance of the inverter presents as a negative incremental resistance with the PLL effect. Secondly, two admittance reshaping control methods are proposed to improve the system damping. The first reshaping technique uses the feedforward point of common coupling (PCC) voltage to modify the inverter output admittance. The second reshaping technique adopts the active damping controller to reconstruct the PLL equivalent admittance. The proposed control methods not only increase the system phase margin, but also ensure the system dynamic response speed. And the total harmonic distortion of steady-state grid-connected current is reduced to less than 2%. Furthermore, a specific design method of control parameters is depicted. Finally, experimental results are provided to prove the validity of the proposed control methods.

Spool Hydraulic Stiffness and Flow Force Effects in Electrohydraulic Servo-Valves

1987 ◽  
Vol 201 (3) ◽  
pp. 193-199 ◽  
Author(s):  
H A Arafa ◽  
M Rizk
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Linear Feedback ◽  
Magnetic Saturation ◽  
Stable Operation ◽  
Experimental Assessment ◽  
Servo Valve ◽  
Supply Pressure ◽  
Wide Range ◽  
Good Agreement

This paper deals with an analytical and experimental assessment of the flow force effects on electrohydraulic servo-valve steady state characteristics. The system mathematical model is derived, and special consideration is given to non-linearity of the feedback wire stiffness and magnetic saturation of the armature. The ‘spool hydraulic stiffness’ is defined and expressed in terms of the servo-valve parameters and supply pressure to allow clear interpretation of the nature of flow force effects. Experimental results of spool displacement decrement due to flow force versus net displacement are in good agreement with the predicted performance in a wide range of input current up to almost full magnetic saturation. The results provide evidence, on an alternative basis, of the non-linear feedback behaviour. Correlation is also made between flow force and limits of stable operation, and an expression is derived for the maximum allowable supply pressure.

Analytical Solution to Excited Waveform of Bias Control on Electro-Hydraulic Vibration Exciter

2010 ◽  
Vol 44-47 ◽  
pp. 1729-1733
Author(s):  
Yan Ren ◽  
Jian Ruan ◽  
Ji Yan Yi
Keyword(s):  
Analytical Solution ◽  
Low Frequency ◽  
Experimental System ◽  
Analytic Solutions ◽  
Slide Valve ◽  
Central Position ◽  
Vibration Exciter ◽  
Sinusoidal Waveform ◽  
The Mathematical Model ◽  
Single Slide

For precisely controlling the bias position of an electro-hydraulic vibration exciter, a scheme of a parallel mechanism of a two-dimensional valve (2D valve) and a servo valve is proposed. In the low frequency section, the mathematical model of the electro-hydraulic vibration exciter is simplified reasonably. A vibration central position is first analytically derived by assuming that 2D valve connected with parallel valve is equivalent to a single slide valve with neutral positive opening and the time-average flow rate through them is identical. And then the analytic solutions to excited waveforms superimposed on the bias position are further obtained. Finally, the experimental system is built to verify the theoretical analysis. The results reveal that this approximate analytical solution could describe excited waveform of bias control on electro-hydraulic vibration exciter. When the opening area of 2D valve is a constant, the bias position follows a linear relation with the throttling areas of the parallel valve which is no more than the maximum position. The excited waveform is close to the sinusoidal waveform. At the same opening area of the parallel valve, the bias position is reduced as the area coefficient of 2D valve increases. The proposed scheme not only ensures the frequency and the amplitude to be controlled independently but also the bias position to be adjusted precisely.

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