Present Status and Prospect of High-Frequency Electro-hydraulic Vibration Control Technology

Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large output power,displacement and thrust,as well as good workload adaptation and multi-controllable parameters.Based on the domestic and overseas development of high-frequency EHVE,dividing them into servo-valve controlled vibration equipment and rotary-valve controlled vibration equipment.The research status and progress of high-frequency electro-hydraulic vibration control technology(EHVCT)are discussed,from the perspective of vibration waveform control and vibration controller.The problems of current electro-hydraulic vibration system bandwidth and waveform distortion control,stability control,offset control and complex vibration waveform generation in high-frequency vibration conditions are pointed out.Combining the existing rotary-valve controlled high-frequency electro-hydraulic vibration method,a new twin-valve independently controlled high-frequency electro-hydraulic vibration method is proposed to break through the limitations of current electro-hydraulic vibration technology in terms of system frequency bandwidth and waveform distortion.The new method can realize independent adjustment and control of vibration waveform frequency,amplitude and offset under high-frequency vibration conditions,and provide a new idea for accurate simulation of high-frequency vibration waveform.

Research on Blind Source Separation for Machine Vibrations

Blind source separation is a signal processing method based on independent component analysis, its aim is to separate the source signals from a set of observations (output of sensors) by assuming the source signals independently. This paper reviews the general concept of BSS firstly;especially the theory for convolutive mixtures, the model of convolutive mixture and two deconvolution structures, then adopts a BSS algorithm for convolutive mixtures based on residual cross-talking error threshold control criteria, the simulation testing points out good performance for simulated mixtures.

Low-frequency and broadband vibration energy harvester driven by mechanical impact based on layer-separated piezoelectric beam

Vibration energy harvesting is to transform the ambient mechanical energy to electricity. How to reduce the resonance frequency and improve the conversion efficiency is very important. In this paper, a layer-separated piezoelectric cantilever beam is proposed for the vibration energy harvester(VEH) for low-frequency and wide-bandwidth operation, which can transform the mechanical impact energy to electric energy. First,the electromechanical coupling equation is obtained by the Euler-Bernoulli beam theory.Based on the average method, the approximate analytical solution is derived and the voltage response is obtained. Furthermore, the physical prototype is fabricated, and the vibration experiment is conducted to validate the theoretical principle. The experimental results show that the maximum power of 0.445 μW of the layer-separated VEH is about3.11 times higher than that of the non-impact harvester when the excitation acceleration is 0.2 g. The operating frequency bandwidth can be widened by increasing the stiffness of the fundamental layer and decreasing the gap distance of the system. But the increasing of operating frequency bandwidth comes at the cost of reducing peak voltage. The theoretical simulation and the experimental results demonstrate good agreement which indicates that the proposed impact-driving VEH device has advantages for low-frequency and wide-bandwidth. The high performance provides great prospect to scavenge the vibration energy in environment.

Feather Vibration as a Stimulus for Sensing Incipient Separation in Falcon Diving Flight

Based on our preceding studies on the aerodynamics of a falcoperegrinus in diving flight along a vertical dam it is known that even when the body shape of the bird is rather streamlined in V-shape some feathers tips may elevate in certain regions of the body. These regions were identified in wind tunnel tests for typical diving flight conditions as regions of locally separated flow. A life-size model in V-shape of a falcoperegrinus with artificial feathers fixed along the body was studied in a wind tunnel to focus on the fluid-structure interaction of feathers located in this sector. The distal ends of the feathers show flow-induced vibrations at typical flight conditions which grow linear in amplitude with increasing angle of incidence until incipient separation. In light of the proven existence of vibration-sensitive mechanoreceptors in the follicles of secondary feathers in birds it is hypothesized that this linear amplitude response offers the bird to sense the angle of incidence during the diving flight using the vibration magnitude as sensory stimulus. Thus the bird in streamlined shape has still a good measure to control its attitude to be in the narrow window of safe angle of incidence. This might have implications also for other birds or technical applications of airfoil sensors regarding incipient separation detection.

Separate critical condition for ultrasonic vibration assisted grinding

Separate characteristic of the tangential ultrasonic vibration assisted grinding (TUAG) machining is analyzed based on TUAG process, and a critical speed formula is given to correctly set the machining parameters to insure the separate characteristics of TUAG process. The critical speed is not only related to the ultrasonic vibration amplitude and frequency, but also to the grinding wheel velocity and the cutting point space, and the grinding force can be decreased during the TUAG process with separability. Grinding force experiments are conducted, and the experimental results are in good agreement with the theoretical results.

Vibrational Spectroscopic Analysis of Borates in Mother Liquid of Brine after Potassium Separated

It is well known that boron exists as polyborate anions in aqueous solution.Boron atom can coordinates to three or four oxygen atoms and borate can exist as not only the monomer but also the polymer.The polymerization

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

Closed form solutions for free vibrations of rectangular Mindlin plates

A new two-eigenfunctions theory, using the amplitude deflection and the generalized curvature as two fundamental eigenfunctions, is proposed for the free vibration solutions of a rectangular Mindlin plate. The three classical eigenvalue differential equations of a Mindlin plate are reformulated to arrive at two new eigenvalue differential equations for the proposed theory. The closed form eigensolutions, which are solved from the two differential equations by means of the method of separation of variables are identical with those via Kirchhoff plate theory for thin plate, and can be employed to predict frequencies for any combinations of simply supported and clamped edge conditions. The free edges can also be dealt with if the other pair of opposite edges are simply supported. Some of the solutions were not available before. The frequency parameters agree closely with the available ones through pb-2 Rayleigh-Ritz method for different aspect ratios and relative thickness of plate.

CHARACTERISTIC EQUATIONS AND CLOSED-FORM SOLUTIONS FOR FREE VIBRATIONS OF RECTANGULAR MINDLIN PLATES

The direct separation of variables is used to obtain the closed-form solutions for the free vibrations of rectangular Mindlin plates. Three different characteristic equations are derived by using three different methods. It is found that the deflection can be expressed by means of the four characteristic roots and the two rotations should be expressed by all the six characteristic roots,which is the particularity of Mindlin plate theory. And the closed-form solutions,which satisfy two of the three governing equations and all boundary conditions and are accurate for rectangular plates with moderate thickness,are derived for any combinations of simply supported and clamped edges. The free edges can also be dealt with if the other pair of opposite edges is simply supported. The present results agree well with results published previously by other methods for different aspect ratios and relative thickness.

FINE COAL AND THREE PRODUCT DRY BENEFICIATION WITH VIBRATION AND DOUBLE-DENSITY FLUIDIZED BEDS

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Evaluation of pneumatic inclined deck separator for high-ash Indian coals

Application of pneumatic separators in coal beneficiation is increasing rapidly over the last decade primarily due to their low capital and operating costs, and waste handling problems associated with traditional wet processing methods. Large amount of shale/rock that is extracted in coal production can be removed prior to transportation at the mine face by using this methodology. Due to the limited washing facilities in India, most of the thermal power plants burn raw coal from run-of-mine （ROM） to generate electricity. This practice causes poor utilization efficiency, high operating and maintenance costs, and high emission rates for the power plants. One potential method that can be utilized is the air-fluidized inclined vibrating deck technology. The technology was demonstrated on a pilot-scale at different coal washeries in India at a feed rate of 5-ton per hour. The pilot-scale evaluation showed that 20 %-25 % high-ash incombustible material can be eliminated from ROM feed with only minor losses in energy content （〈10 %） from respective ROM coal. Furthermore, a feasibility analysis showed significant economic gains in terms of transportation cost, improving power-plant efficiency, and reducing emissions rates by using the technology.

Vertical vibration of a floating pile in a saturated viscoelastic soil layer overlaying bedrock

An axisymmetrical analytical solution is developed to investigate the vertical time-harmonic vibration of a floating pile in a saturated viscoelastic soil layer overlaying bedrock. The soil is described by porous medium model established by Boer, while the pile is described by a beam vibration theory. By using separation theory of differential operator and variables to solve the dynamic governing equations for the soil, the fundamental solutions for the soil reactions on side and bottom of the pile are obtained. The dynamic impedance of the pile head is then derived by solving the vibration equation for the pile according to the compatibility condition between the pile and the soil. The proposed model is validated by comparing special cases of our model with the existing results. Numerical examples are presented to analyze the vibration characteristics of the pile.

Theoretical analysis of nonlinear vibration characteristics of gear pair with shafts

The circumferential vibration of a gear pair is a parametric excitation caused by nonlinear tooth stiffness,which fluctuates with meshing.In addition,the vibration characteristics of the gear pair become complicated owing to the tooth profile error and backlash.It is considered that the circumferential vibration of the gear pair is affected by the torsional vibration of the shafts.It is important to understand quantitatively the vibration characteristics of the gear system considering the shafts.Therefore,the purpose of this research was to clarify the nonlinear vibration characteristics of a gear pair considering the influence of the shafts using theoretical methods.To achieve this objective,calculations were performed using equations of motion in which the circumferential vibration of the gear pair and the torsional vibration of the shafts were coupled.The nonlinear tooth stiffness was represented by a sine wave.The influence of tooth separation was considered by defining a nonlinear function using backlash and the tooth profile error.For the numerical calculations,both stable and unstable periodic solutions were obtained by using the shooting method.The effect of the shafts on the gear system vibration were clarified by comparing the results in the cases in which the shaft was not considered,one shaft was considered,and both shafts were considered.

Investigation of Eccentric PM on High-frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

This study investigates the negative influence of an eccentric permanent-magnet(PM)design on high-frequency electromagnetic vibration in fractional-slot concentrated-winding(FSCW)PM machines.First,an analytical expression for the sideband current harmonics was derived using the double Fourier series expansion method.Then,the characteristics of the flux-density harmonics are studied from the perspective of the space-time distribution and initial phase relationship.The influence of the eccentric PM design on high-frequency electromagnetic and concentrated forces was studied based on the electromagnetic force modulation effect.Consequently,an eccentric PM design is not conducive to reducing the 2pth-order high-frequency electromagnetic forces.Finally,two FSCW PM machines with conventional and eccentric PM designs are manufactured and tested to verify the theoretical analysis.The results show that the eccentric PM design worsens high-frequency vibrations.

Vertical vibration control using nonlinear energy sink with inertial amplifier

To reduce additional mass, this work proposes a nonlinear energy sink(NES)with an inertial amplifier(NES-IA) to control the vertical vibration of the objects under harmonic and shock excitations. Moreover, this paper constructs pure nonlinear stiffness without neglecting the gravity effect of the oscillator. Both analytical and numerical methods are used to evaluate the performance of the NES-IA. The research findings indicate that even if the actual mass is 1% of the main oscillator, the NES-IA with proper inertia angles and mass distribution ratios can still effectively attenuate the steady-state and transient responses of the main oscillator. Nonlinear stiffness and damping also have important effects. Due to strongly nonlinear factors, the coupled system may exhibit higher branch responses under harmonic excitation. In shock excitation environment, the NES-IA with a large dynamic mass can trigger energy capture of both main resonance and high-frequency resonance. Furthermore, the comparison with the traditional NES also confirms the advantages of the NES-IA in overcoming mass dependence.

Development of a 2D Vibration Stage for Vibration-assisted Micro-milling

Vibration-assisted machining(VAM) has the advantages of extending tool life,reducing cutting force and improving the surface finish.Implementation of vibration assistance with high frequency and amplitude is still a challenge,especially for a micro-milling process.In this paper,a new 2D vibration stage for vibration-assisted micro-milling is developed.The kinematics of the milling process with vibration assistance is modeled,and the effects of vibration parameters on the periodic tool-workpiece separation(TWS) is analyzed.The structure of the vibration stage is designed with flexure hinges,and two piezoelectric actuators are used to drive the stage in two directions.An amplifier is integrated into the vibration stage,and the dynamics of the whole vibration system are identified and analyzed.Micro-milling experiments are conducted to determine the effects of vibration assistance on cutting force and surface quality.

Low-magnitude high-frequency vibration reduces prostate cancer growth and extravasation in vitro

Prostate cancer(PCa)continues to rank among the most common malignancies in Europe and North America with significant mortality rates despite advancements in detection and treatment.Physical activity is often recommended to PCa patients due to its benefits in preventing disease recurrence and managing treatment-related side effects.However,physical activity may be challenging for elderly or bedridden patients.As such,vibration therapy has been proposed as a safe,effective,and easy to perform alternative treatment that may confer similar effects as physical exercise.Specifically,low-magnitude high frequency(LMHF)vibration has been shown to decrease breast cancer extravasation into the bone and reduce other types of cancer proliferation by impacting cell viability.Here,we investigated the effects of daily application of LMHF vibration(0.3 g,60 Hz,1 hour/day for 3 days)on prostate cancer growth and bone metastasis in vitro.Our findings suggest that LMHF vibration significantly reduces colony formation through a decrease in cell growth and proliferation.Moreover,using a 3D cell culture model,LMHF vibration significantly reduces PC3 spheroid size.Additionally,LMHF vibration reduces PCa cell extravasation into the bone microenvironment through the stimulation of osteocytes and subsequent osteocyte-endothelial cell cross talk.These findings highlight the potential of LMHF vibration for managing PCa growth and metastasis.

基于机器视觉的旋转机械微小振动放大方法实验研究

基于机器视觉的旋转机械微小振动放大过程中,未能将大运动和微小运动分离,导致其放大结果会产生伪影。针对这一问题,提出了一种基于加速度滤波和振幅阈值滤波的微小振动放大方法。首先,采用了复值可操纵金字塔分解图像,将图像信号转变为局部相位信号和局部幅值信号;然后,采用了加速度滤波算法从局部相位信号中分离出线性大运动信号,采用了振幅阈值滤波算法分离了非线性大运动信号,得到了微小振动信号,并对其进行了放大;最后,对放大信号和局部幅值信号采用复值可操纵金字塔逆变换重构了图像,构建了转子实验台,对上述微小振动放大方法的有效性进行了验证。研究结果表明:测点在水平和垂直方向上的振动位移幅值均低于0.15 mm,在局部放大图中可以明显分辨出低于5 Hz的转子基频信号,且其余频率成分未被放大。该方法在微小振动放大处理前增加大运动和微小振动分离过程,仅对微小振动进行处理,能够减少大运动对微小振动信号放大产生的干扰,有效改善了微小振动放大结果中的伪影问题。

劣化润滑脂对新能源汽车电机轴承性能的影响

为研究不同劣化时期润滑脂对新能源汽车电机轴承性能的影响,并选取合适的润滑脂,采用试验的方法,研究了两种候选润滑脂及其对轴承性能的影响。首先,采用静态热劣化法获得了21组不同劣化时期的润滑脂样品,并分析了润滑脂样品的锥入度、分油率等特性变化;然后,在考虑轴承工况的基础上,利用高速轴承漏脂温升性能试验机等设备试验研究了不同劣化时间润滑脂对轴承漏脂、温升、振动和噪音等性能的影响;最后,综合分析了润滑脂的劣化及其对轴承性能的影响,为新能源汽车电机轴承选择了合适的润滑脂。研究结果表明:A型润滑脂的性能更稳定,其非工作锥入度变化率为32.53%,分油率在0~0.053%范围内波动,其特性变化均小于B型润滑脂;两种劣化润滑脂均导致轴承外圈温度升高、轴承振动速度和噪音增大,但B型润滑脂对轴承振动速度和噪音的影响较大,其部分高频增加900%、噪音升高27%。因此,综合考虑润滑脂的分油率、锥入度,以及润滑脂对轴承温升、振动和噪音等使用性能的影响,推荐A型润滑脂为新能源汽车电机轴承润滑介质。该研究结果对新能源汽车电机轴承润滑介质的选择具有较为重要指导意义。

Effect of High-Frequency Vertical Vibration of Track on Formation and Evolution of Corrugations

The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation.