Electromagnetic Vibration Exciter Research Articles

Analysis of Coupled Vibration Characteristics of Linear-Angular and Parameter Identification

Abstract A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere’s law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper.

Velocity feedback control method of low-frequency electromagnetic vibration exciter based on Kalman filter estimation.

The absence of an appropriate low-frequency vibration velocity detection method to establish feedback control limits the further improvement of the low-frequency vibration performance of electromagnetic vibration exciters. In this article, a low-frequency vibration velocity feedback control method based on the Kalman filter estimation is proposed for the first time to reduce the total harmonic distortion of the vibration waveform. The rationality of establishing velocity feedback control in the velocity characteristic band of the electromagnetic vibration exciter is analyzed. Based on an identification model of the system and measured vibration displacements, the vibration velocity is estimated with high accuracy through the Kalman filter. The velocity feedback control system is established to suppress the impacts of disturbances effectively. Experimental results show that the method proposed in this paper can reduce the harmonic distortion of vibration waveform by 40%, which is 20% higher than the traditional control method, thoroughly verifying its superiority.

Universalization of the elastic system of vibration feeders with vertical electromagnetic vibration drive

Vibrating feed bins with electromagnetic drive are widely used in the automation of production processes in mechanical engineering and instrument engineering. They are used for feeding miniature, small, or medium-sized parts to automated production equipment. This equipment is used in automatic lines, automated complexes, or any other flexible automated production facilities. These devices are most widely used for loading parts to assembly positions in automated assembly complexes. In this case, the parts fed to these positions must be located in a certain stable position. Various orientation tools are used for this purpose. They are located directly on the transport trays in the bins of these devices. Therefore, for reliable operation of orientation devices, the movement of parts on the trays should be smooth without sensitive tossing. The designs of vibrating hopper feeders with a hopper connected to a reactive plate by a directional elastic system in the form of a lattice torsion bar are considered. An electromagnetic vibration exciter is placed between the torsion flanges. The disadvantage of such vibration feeders is low productivity in operating modes, especially when there are increased requirements for the smooth movement of transported parts. An increase in the productivity of such feeders is carried out by increasing the amplitude of hopper vibrations in the direction of movement of parts, that is, the horizontal component of vibrations. However, this also leads to an increase in the vertical component, since vibrations are carried out at an angle to the feeder transport tray. When the vertical component of vibrations increases, the transportation of parts switches to the intensive tossing mode. A further increase in the oscillation amplitude leads to a violation of the normal mode of vibrational transport. Modern production involves the modernization of existing structures, as well as the creation of new models of machines with high technical and economic indicators Therefore, the universalization of existing equipment and the development of new machine schemes is an important task for developers and manufacturers of technological equipment, since even a minimal improvement in its technological or operational indicators can lead to a significant economic effect. The paper considers a complex of additional elements used that make it possible to universalize the design of vibrating hopper feeders with electromagnetic drives having a directional elastic system. These changes make it possible to adjust the horizontal component of the device hopper vibrations at a constant vertical one. Additional structural elements are proposed that increase the range of application of such feeders.

Design and development of miniature vibration shaker

Vibration shaker is a machine produces mechanical vibratory motion to test DUT (device under test). Vibration shakers are used to determine the dynamic characteristics of device under test and structures and fatigue testing of materials. This article presents design, development, performance and testing of electromagnetic vibration exciter (shaker) by using flexural bearings. Flexural bearings are used for frictionless vibration generation. Design of flexural bearing is done by using CATIA software and by using ANSYS software finite element analysis is done. Experiments are conducted on vibration shaker and identified the frequency response, damping property and force deflection characteristics. It is observed that theoretical results and experimental results are nearly similar.

Автоколебательные процессы в системе двух электромагнитов, соединенных по дифференциальной схеме

A number of modern technological processes can be significantly intensified by applying vibratory excitation in a wide range of oscillation frequencies and amplitudes. In many cases, an electromagnetic vibration exciter (EMVE) may serve as the most effective source of vibration, especially at power levels up to several kilowatts and more; push-pull EMVEs developing a non-pulsating and sign-variable exciting force are considered to be the most appropriate ones. The excitation of self-oscillations in a system of two electromagnets connected according to a differential scheme, which allows the range of operating frequencies to be widened and the system power capacity to be increased, is analyzed. An equation describing the interaction between the EMVE mechanical vibration subsystem and the power supply system is given. A method for analyzing a dual-circuit self-contained electromechanical system (EMS) taking into account electromechanical links is developed. It is pointed out that during operation in the autonomous mode one stable state ensuring frequency stability is realized.

Experimental and Numerical Analyses for Auto-Parametric Internal Resonance of a Framed Structure

The auto-parametric internal resonance experiment of a [Formula: see text]-shaped frame is first conducted in this research. A non-contact electromagnetic vibration exciter is used to exert a periodic force on the vertical beam of the frame. The phenomena of internal resonance and non-internal resonance are observed and measured in this test. A common resonance of the vertical beam is excited by the external electromagnetic force, and the auto-parametric internal resonance of the horizontal beam is subsequently induced by the common resonance. The numerical method is also used to simulate the internal resonance and non-internal resonance. The stability boundaries of internal resonance and non-internal resonance are numerically and experimentally determined and compared. The numerical stability boundaries are in agreement with the experimental results. The results indicate that a small external excitation can excite a strong internal resonance response of a framed structure. The unstable domain of the internal resonance is much bigger than that of the non-internal resonance. The auto-parametric internal resonance is much more dangerous than the non-internal resonance. The risk of auto-parametric internal resonance should be emphasized and avoided in the designs of engineering structures.

INVESTIGATION OF AN ELECTROMAGNETIC TWO-STROKE VIBRATING ACTIVATOR IN OSCILLATORY MODE

The article considers the results of the study of electromagnetic vibration exciter with sequentially included capacitor in the electrical circuit, consisting of mechanical and electrical subsystems. It is shown that by means of the Lagrangian-Maxwell equation the interconnection between mechanical and electric subsystems can be realized. The relations describing processes of establishment of amplitudes and phases of oscillations both in mechanical and in electric subsystems are deduced. The equations connecting the output (amplitude) of vibration of the vibrating exciter with its input (voltage) of the network are presented. As a result, the formulas allowing making corrections at the solution of the system describing operation of the electromagnetic vibrating exciter in two-stroke mode are presented.

Vibration damping of the anti-vibration platform intended for use in combination with audio/music devices

The article presents research on the damping properties of an anti-vibration platform (designed and manufactured by Stacore), which is intended for use in combination with high class audio devices. The platform comprises two parts that are capable of passive vibration damping. The design of this platform is unique and has been developed by applying several technical solutions in a combination not found on any other anti-vibration platform on the audio market. These solutions are described in the article. The first part of the platform is pneumatically operated and the second part uses ball bearings. The casing also fulfils the most important function – vibration damping. It is made of amorphous slate (known for its good vibration-damping properties) and includes a metal plate covered with a special visco-elastic layer that fulfils the role of binding material. The first part of the platform realises the pneumatic damping. It comprises four elastomer pneumatic springs, each with its own air tank. The air tanks are designed to operate at a maximum pressure of 5 bar. The second vibration-damping part of the platform is located above the first part (pneumatic) and consists of ball bearings, used for the isolation of transverse vibration, being relatively difficult to deal with pneumatic springs. The upper part consists of three bearings, each of which comprises of a polished, deep hardened steel racings and a ball made of tungsten carbide. The scientific literature describes many solutions enabling vibration damping, including many anti-vibration platforms. However, the literature lacks the descriptions of analyses conducted on anti-vibration platforms for audio devices. This article is a novelty in the literature as it concerns the experimental research aimed at verifying the vibration-damping capacity of the anti-vibration platform that can be used with audio devices owned by people who appreciate high-quality music. The article describes in detail the whole measurement procedure applied to the vibration damping platform. For research purposes, the anti-vibration platform was suspended on flexible ropes. At first, an electromagnetic vibration exciter was attached to the base on which the platform rested, and then the displacements of the upper and lower part of the platform were measured using laser sensors. Based on these signals, the vibration damping capability (transmissibility) of the platform was determined in two mutually perpendicular directions. In addition to the graph that shows the vibration damping capability of the anti-vibration platform, the signals of the applied force and displacements measured during the research are also presented in this article.

A Method of Modal Parameter Estimation of the Motor Based on Electromagnetic Vibration Exciter

The experimental modal test of the structure of the driving motor has always provided a major contribution to understand and control the vibration phenomena encountered in practice. The hammer test is a common experimental method to obtain a mathematical model of the structure and to validate the theoretical model and finite element method model. However, the hammer or the real vibration exciter will increase the test cost. In this article, an electromagnetic vibration exciter is proposed to achieve the frequency response functions and then the modal parameters can be extracted. Its principle of modal parameters estimation is presented and described in detail. The finite-element analysis and experiments of a 6p/36s permanent magnet motor have been conducted to verify the proposed method.

On the energy efficiency of electromechanical systems with an electromagnetic vibration exciter

Study shake the phenomena in the electromechanical systems (EMS) are presented by permanent interest for the wide circle of researchers. The most effective source of vibrations in many cases is an electromagnetic causative vibration exciters (EMCV) in that there is transformation of electric power to energy of mechanical vibrations, that is related to the change of inductance. Electromagnetic vibration exciters have a number of significant advantages over other types of exciters. Due to the absence of rubbing parts they have high reliability and durability. They allow you to smoothly adjust the amplitude of vibrations over a wide range. EMCV are easy to integrate into production lines, they have easy maintenance, low operating costs and extensive automation capabilities. This phenomenon presents interest at development of electromechanics devices for intensive vibrotechnologies. Especially development guided on frequency of resonant EMCV promotes the economy of consumption of electric power and productivity of vibrotechnique. To the article the results of theoretical and experimental researches are driven on the increase of energy efficiency of EMCV and determination of output-input ratio. It is shown that losses of electric power in EMS with EMCV related to the origin of permanent constituents and ultra-harmonics of current, choice of magnetic chain and dynamic.

Резонансный электромагнитный вибровозбудитель колебаний с обратной связью

A number of modern technological processes can be significantly intensified due to the use of vibrations with a wide range of oscillation frequencies and amplitudes. In many cases, electromagnetic vibration exciters (EMVE) can serve as the most effective vibration source. Direct conversion of electric energy into mechanical vibration energy opens the possibility for developing devices controlled by electrical methods. However, the oscillatory processes in the circuits containing electromagnetic exciters have been studied to an insufficient extent as applied to vibration engineering. This is connected with the complexity of the effects caused by the nonlinearity of vibration exciter electromagnets and power source on the vibration processes, i.e., a nonlinear dependence of the vibration amplitude and phase on the system parameters and a nonlinear dependence of inductance from the armature displacement. The results from theoretical and experimental studies of oscillating electromechanical systems (EMC) built on the basis of an EMVE with feedback, and the development of methods for analyzing resonant EMVE circuits with a view to obtain the optimal characteristics in low-frequency oscillation modes (LFO) demonstrate the possibilities of economically efficient consumption of electric energy and the performance of the EMVEs used in different industry branches. With the introduction of feedback proportional to the control frequency and the output voltage amplitudes of the EMVE power supply source, it becomes possible to automatically adjust the vibration frequency to the resonance frequency of the elastically suspended EMVE load-carrying member for maintaining constancy of vibration velocity amplitudes and, hence, the system performance. To achieve a stable resonance operation mode of the electromagnetic vibration exciter, the voltage proportional in phase between the inverter output voltage and the load-carrying member motion speed are analyzed. The study results have shown that, owing to the feedback effect that adjusts the driving frequency in phase toward tuning to resonance, a rational EMVE operation mode can be secured.

ABOUT OF THE DYNAMICS OF FORCED OSCILLATIONS IN NONLINEAR SYSTEMS

The article discusses the issues of determining the effectiveness indicators of an electromagnetic vibration exciter in a dynamic mode of operation. It is established that this system is whole system of electrical and mechanical circuits. In this case, the mechanical part operates in the mode of forced vibrations. The oscillation parameters of the system, such as amplitude, frequency, and phase, largely depend on the parameters of the system load. For the analysis of this system, differential equations describing an electromagnetic vibration exciter have been compiled. For this purpose, the dependence L(x) of the inductance on the displacement is used. The dynamic modes of one of the ways of asynchronous excitation of an electromagnetic vibration exciter are investigated. The accuracy analysis and the evaluation of the results were performed by the Fisher criterion for the regression model. To analysis of transients in the electromagnetic vibration exciter, were used the software packages WinFact and MatLab to simulate and optimize dynamic systems. It is established that the system, depending on the initial conditions in the simulation, goes into one of two very different modes. In this case, the initial zero conditions switch the system into a “cyclic” mode, and in other, non-zero conditions, the system goes into an approximate cyclic mode, characterized by a higher speed of movement of the anchor. The parameters of the steady state cyclic movement are determined by the method of harmonic balance.
 The obtained results allow us to describe autoparametric oscillations of the electric equivalent circuit. It has been established that the compilation of harmonic balance equations corresponding to a linear system helps simplify the solution of the task of determining the dynamics of forced oscillations. The expressions for determining the tractive force and the current flowing through the circuit are obtained, the wavelet spectra of vibration are constructed using the MatLab software package. As a result, for the mechanical part of a nonlinear system, in fact, it is necessary to solve only harmonic balance equation. The results show that this theoretical model allows a more qualitative and accurate assessment of the observed phenomenon. Based on this, the asymptotic conditions for solving the harmonic balance equations of a nonlinear system are determined. The expressions for the electromagnetic force acting on the anchor are obtained, the conditions for the harmonic balance of the mechanical part of the system are determined. The expressions obtained allow us to construct the amplitude-frequency characteristics of the electromagnetic vibration exciter. In conclusion, not only qualitative, but also quantitative estimates of the observed phenomena were obtained. It has been established that mechanical oscillations of a nonlinear system are insensitive to changes in the supply network and practically have a large amplitude with a constant frequency.

Semi-active vibration control of two flexible plates using an innovative joint mechanism

Abstract With the advancement of space technology, space flexible jointed appendages have been applied widely. The low-frequency vibration problem is inevitable because of the external disturbances or attitude maneuvering in micro-gravity environment. In this study, an innovative joint mechanism was proposed and a new methodology for semi-active technique of joint variable stiffness control was utilized to suppress the low-frequency vibration of flexible jointed appendages. The joint mechanism, based on the direct drive principle, exhibits a compact structure and integrates with an electro-permanent-magnet driving mechanism. First, the concept design of joint mechanism is introduced. Second, dynamic equations of active joint and two flexible plates are obtained using Lagrange equation and assumed mode method. Finally, two types of non-contact periodic vibration excitation methods along rotation direction are proposed. A self-made electro–magnetic vibration exciter was employed to achieve single-frequency excitation, and two fans were placed on both sides of flexible appendages to induce multi-frequency excitation. According to numerical simulations and experimental results, when the joint torsional stiffness changes, frequency-shift phenomenon occurs, and the natural frequency of the system varies subsequently. Furthermore, the experimental results demonstrated that the major frequency bandwidth of interference signal was 0.06–0.63 Hz with a significant vibration attenuation of 5.41–26.94 dB for joint-1 and 5.63–16.48 dB for joint-2 in effective bandwidth. The low frequency vibration of flexible appendages system can be attenuated robustly, which verifies the effectiveness of this semi-active methodology.

RESEARCH Of THE INFLUENCE OF LONG-LASTING CYCLIC LOADING ON THE GEOMETRY OF THE BUMP FOIL OF A GAS FOIL BEARING

The article describes the research aimed at checking the effect of a long-lasting pulsating load on the geometry of the bump foil of a foil bearing. The tested foil was made of Inconel 625, which is one of the most popular alloys used to manufacture components of foil bearings. The foil was tested both before and after its heat treating in an electric furnace. The foil was subjected to loading using an electromagnetic vibration exciter, whose exciting force and frequency were appropriately selected. The height of the individual bumps of the foil was the basic parameter controlled after each measurement series. In addition, wear of the foil at the contact points with the plates of the test rig was checked. The materials of which the elements of the tested system were made are the same as the ones used in a real bearing. The article presents graphs that show how the geometry of the bump foil changed during the research. The wear of the elements mating with the bump foil was also evaluated.

A double-magnetic-source magnetic circuit with pole shoes for an electromagnetic angular vibration exciter

A double-magnetic-source magnetic circuit with pole shoes for an electromagnetic angular vibration exciter

Analyzing the validity of a DFT-based improved acoustic OFDM transmission along rotating simulated drillstring

In the oil industry, drillstring can be used as a transmission medium to send downhole information via a modulated compressional acoustic wave. However, the accompanied reverberation is a major constraint in the transmission rate and distance because of the multipath fading caused by the heterogeneous drillstring. In combination with discrete Fourier transform-spread (DFT-S) mapping/demapping, high-power amplitude squeezing and DFT-based least squares channel estimation methods, an improved orthogonal frequency division multiplexing (OFDM) scheme is proposed in this paper to overcome the symbol interference inherent in the drillstring multipath channel and reduce the peak-to-average power ratio of the signal. Then an experimental rig is established by using a rotatable electromagnetic vibration exciter and a piezoelectric accelerometer arranged at the position closer to acoustic impedance terminal along a 6.3-m periodic simulated drillstring. The OFDM data sequences at a data rate of 200bit/s over a limited bandwidth of 140Hz are applied to the rotating simulated drillstring. The experimental results show that the proposed scheme using QPSK modulation can offer an error-free acoustic communication at rotation speeds up to 90r/min.

Multiple-Echo Suppression Modeling and Experimental Verification for Acoustic Transmission along Periodic Drillstring Using Dual Receivers

In the oil industry, the accompanied reverberation is a major constraint in the transmission rate and distance because the drillstring is a heterogeneous assembly. Based on the transient impulse responses in uplink and downlink channels, an improved simplified echo suppression model with two acoustic receivers is presented in consideration of position optimization of single acoustic receiver. Then the acoustic receiving characteristics of transmitted signals in a length-limited periodic drillstring channel are obtained in single- and dual-receiver modes. An additive downward white Gaussian noise is also introduced in the channel. Moreover, an experimental rig is established by using a rotatable electromagnetic vibration exciter and two piezoelectric accelerometers, which are spaced one-quarter wavelength apart along a 6.3-meter simulated periodic drillstring. The ASK-, FSK-, and PSK-modulated square-wave pulse sequences at a transmission rate of 200 bit/s are applied to the simulated drillstring at a rotation speed of 0, 80, and 140 r/min, respectively. The experimental results show that the dual-receiver mode can exhibit a significantly improved average error bit ratio, which is approximately 2.5 to 3 times lower than that of the single-receiver mode, especially under the conditions of higher rotation speeds.

전기집진기의 직렬 및 병렬식 배열에 따른 효율적인 진동 탈진에 대한 연구

전자기 진동 가진기를 적용한 전기 집진기의 효과적인 탈진 여부를 판단할 수 있는 기준은 집진기내 집진판들의 진동 가속도이다. 이러한 진동 가속도는 외부로부터의 가진 주파수와 시스템의 고유주파수의 일치로 인하여 공진이 일어날 때 간헐적으로 최대치를 보이며 효율적인 탈진성능을 기대할 수 있다. 본 연구에서는 한대의 전자기 진동 가진기를 이용하는 단일 객체를 대상으로 한 관점에서 더 나아가, 실제 현장에서 복수의 전기집진탈진기가 설치됨을 고려하여 진동 탈진기의 설치방식에 따라 시스템을 모델링 하였다. 이러한 직렬 및 병렬회로로 연결된 가진기를 적용한 시스템을 대상으로 진동 가속도 계측 실험을 수행하여 직렬 및 병렬식 연결에 따른 진동 가속도의 차이를 비교함으로써 가진기의 배열 방식과 그에 따른 기대 탈진 성능 및 소비전력의 유효성을 검증하였다. 최종적으로 직렬 배열형 모듈이 증가할수록 선형적으로 필요전류량이 증가할 것으로 예상하였으나 급격한 감소나 (6.9% ~ 37.6%) 증가를 (5% ~ 45%) 보여주었다. 단독의 가진기가 사용된 병렬 배열보다, 2대의 가진기가 사용되고 그 전기회로의 연결이 병렬일 때 동일한 전류가 인가되었음에도 약 11.64% 의 가속도 감소 현상을 보였다. 2대의 가진기를 사용하고 입력전류의 값을 소비 전력의 관점에서 동일하게 보정하였을 경우 약 16.80 % 의 가속도 증가 현상을 확인하였다. One of the most significant requisite that should be considered for effective rapping of the electrostatic precipitator using electromagnetic vibration exciter is vibration acceleration and resonance frequency of collecting plates. This vibration acceleration shows its peak points when natural frequencies of the system are corresponded with excitation frequency from the power source, and effective rapping performance can be expected. In this research, extend view of single electrostatic precipitator using one electromagnetic vibration exciter, the system was remodeled by arrangement of the exciters in view of multiple modules of the electrostatic precipitator in fields. And vibration acceleration measurement experiment is performed and measured values are compared with these remodeled systems. By this experimental comparison in series and parallel arrangement, effectiveness of arrangement methods for the electromagnetic vibration exciter, expected rapping performance, and power consumption are verified.

Closed-Double-Magnetic Circuit for a Long-Stroke Horizontal Electromagnetic Vibration Exciter

A novel closed-double-magnetic circuit (CDMC) was presented to achieve high and uniform magnetic flux density (MFD) in the long air gap (LAG) of a long-stroke horizontal electromagnetic vibration exciter. First, the normal single-magnetic circuit (SMC) and the proposed CDMC were modeled by lumped element circuit using equivalent circuit principle, analyzed theoretically by the Kirchhoff's law and the superposition theorem. The comparison between the two circuits shows that the CDMC can have more intensive and more uniform MFD in the LAG. To strengthen the uniformity of the MFD in the LAG, the improved CDMC with uneven air gap and its design method were proposed theoretically. Thereafter, the uneven air gap structure expressed as a three-line-segment form was presented and its optimization was also conducted based on a finite element model referring to a prototype of a one-meter-stroke horizontal electromagnetic vibration excite. Then, the magnetic flux leakage of the magnetic circuits and the influence of slits in the outer magnetic yoke for practical application was also analyzed with the finite element method (FEM). The simulation demonstrates that the CDMC with optimal air gap can further improve the uniformity of the MFD in the LAG. In addition, it is also indicated that the CDMC has less flux leakage than the SMC and the influence of slits can be negligible. Finally, the experiment on the prototype also verifies the effectiveness of proposed CDMC with optimal air gap.

Force distortion in a coil/magnet vibration exciter for shallow structures subjected to large displacements

An electromagnetic noncontact vibration exciter has been designed for investigating nonlinear vibrations of shallow structures such as gongs, cymbals, and spherical shells. It is composed of two devices: a coil driven by a current and a small magnet glued on the structure. One interest of this system is that the mass of the magnet is small compared to the mass of the structure, so that its dynamic properties are only slightly modified. The magnitude of the force applied to the structure via the magnet depends on the relative position of magnet and coil. As a consequence, an harmonic distortion appears in the force wave form as the magnitude of the magnet displacement increases. A theoretical study is first carried out in order to find an optimal geometry for the coil that minimizes the force distortion. In a second step, a simple degree-of-freedom model is used to evaluate the distortion rate. It is found that this rate not only depends on the exciter properties, but also on the dynamics of the system under testing. A multiple-scale technique is used for the resolution of the nonlinear model that governs the distortion. Experimental results will be presented which confirm the theoretical predictions.