A novel vibration velocity measurement method for electromagnetic vibrators

Abstract

A novel vibration velocity measurement method for electromagnetic vibrators based on a vibration velocity measurement coil that can extract the vibration velocity without any extra commercial vibration sensors is proposed. An extra and independent vibration velocity measurement coil is wound on the armature together with the drive coil of the vibrator, and a velocity extractor is designed to extract the vibration velocity from the output voltage of the velocity measurement coil. The frequency response and the linearity of the vibration velocity measurement system are calibrated through a series of experiments. The uncertainty analysis shows that the uncertainties (k = 2) in the amplitude of the sensitivity and the phase shift are 1% and 2 • respectively in the frequency band from 5 to 100 Hz, and the uncertainties (k = 2) in the amplitude of the sensitivity and the phase shift are 3% and 4 • respectively in the frequency band from 100 to 1000 Hz. The proposed method is not only simple in structure, but also low in cost, and it could well be applied in the various types of electromagnetic vibrators, whose vibration level should easily be got.

A harmonic suppression method for low-frequency electromagnetic vibrators

“…It is common to use polynomials of vibration displacement to fit the nonlinear relationship between the stiffness and displacement, and it can facilitate the subsequent analysis. Besides, the influence of the uneven magnetic field on the second coil was discussed in Gao et al 23 Considering that the driving coil and the second coil are close to each other and both are in the working magnetic field, the influence of uneven magnetic field on both is similar. For a symmetric magnetic field, B l d can be approximated as a function of x 2 .…”

“…As a result, the self-inductance voltage on the driving coil will decrease, which means the equivalent inductance coefficient of the driving coil is reduced. 21–23 Referring to the derivation in Gao et al 21 and Gao et al 23 , L d i . d + M d 1 i . 1 + M d 2 i . 2 can be approximate to L e i . d . So (1) can be simplified as…”

“…Especially, a shading coil is properly designed and installed around the driving coil to reduce the highfrequency impedance of the driving coil, decrease the influence of inductance nonlinearity on the system, simplify the design of the electric driving system and reduce energy consumption. [21][22][23] According to Figure 1(b), the electrical and dynamical equations of the electromagnetic vibrator is expressed as…”

“…As a result, the selfinductance voltage on the driving coil will decrease, which means the equivalent inductance coefficient of the driving coil is reduced. [21][22][23] Referring to the derivation in Gao et al 21 and Gao et al 23 ,…”

Waveform harmonic suppression technology for electromagnetic standard vibration actuators based on current feedback control

“…As a result, some methods are difficult to be put into practice, which limits the application of this kind of technology. To solve this problem, a velocity extraction method of EVA coil based on self-induction method was proposed (Chi and Shang, 2018; Gao et al, 2020; Zhang et al, 2017), which can achieve velocity feedback control without sensing, but requires a more complex velocity extraction method and is only applicable to waveform improvements in the velocity characteristic frequency band. At present, there is a lack of suitable control techniques without sensing in the acceleration characteristic frequency band to suppress waveform distortion of low-frequency vibration of an EVA, which makes it difficult to improve the quality of vibration waveforms in this frequency band.…”