Power frequency spectrum analysis of surface EMG signals of upper limb muscles during elbow flexion – A comparison between healthy subjects and stroke survivors

ABSTRACT:Cutaneous reflexes in the upper limb were elicited by stimulating digital nerves and recorded by averaging rectified EMG from proximal and distal upper limb muscles during voluntary contraction. Distal muscles often showed a triphasic response: an inhibition with onset about 50 ms (Il) followed by a facilitation with onset about 60 ms (E2) followed by another inhibition with onset about 80 ms (12). Proximal muscles generally showed biphasic responses beginning with facilitation or inhibition with onset at about 40 ms. Normal ranges for the amplitude of these components were established from recordings on 22 arms of 11 healthy subjects. An attempt was made to determine the alterent fibers responsible for the various components by varying the stimulus intensity, by causing ischemic block of larger fibers and by estimating the afferent conduction velocities. The central pathways mediating these reflexes were examined by estimating central delays and by studying patients with focal lesions

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Research on Shearer Rocker Gearbox Fault Location Based on Wavelet Envelope Demodulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.528.210 ◽

2014 ◽

Vol 528 ◽

pp. 210-216

Author(s):

Zeng Qiang Wang ◽

Hong Wei Ma ◽

Mei Hua Tao ◽

Xu Hui Zhang ◽

Qing Hua Mao

Keyword(s):

Fourier Transform ◽

Frequency Spectrum ◽

Spectrum Analysis ◽

Fault Location ◽

Vibration Signal ◽

Morlet Wavelet ◽

Frequency Spectrum Analysis ◽

Mechanical Faults ◽

Faults Diagnosis ◽

Feature Frequency

To solve the problem of faults location for shearer rocker gearbox, the multiple sites vibration signal of faulty rocker gearbox are collected, as well as the Morlet wavelet envelope demodulation is applied to demodulate vibration signal and Fourier transform is used to carry out frequency spectrum analysis of vibration signal. Experimental results show that this method can effectively extract the faults feature frequency from complex vibration signal. The faults location result is consistent with actual faults part. This mean realizes to locate faults accurately. It provides an effective method for mechanical faults diagnosis of shearer.

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Vibrational Monitoring of Nested Planetary Geartrain with Unground Pinion

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-1852 ◽

2021 ◽

Vol 263 (5) ◽

pp. 1471-1487

Author(s):

Jianxiong Feng ◽

Yangfan Liu ◽

Kai Ming Li

Keyword(s):

Frequency Spectrum ◽

Spectrum Analysis ◽

Time History ◽

Critical Factor ◽

Planetary Gear ◽

Gear Train ◽

Frequency Spectrum Analysis ◽

Vibration Strength ◽

Automobile Transmissions ◽

Modulation Sideband

The nested planetary gear train, which has two integrated single-stage planetary gearsets, is one of the newly developed compound gear train that has been successfully applied to the automobile transmissions. In the current study, a certain type of gear fault in the nested gear train, ungrounded pinion, is investigated using a non-destructive approach monitoring its vibration levels. A novel experimental test stand with open and vertical setup has been designed to collect the vibrational data by mounting the accelerometer directly to the gear clutches. Each of the two layers of the compound gear was tested separately. The measured vibrational data were processed with several signal processing techniques, which includes (a) frequency spectrum analysis, (b) time synchronous averaging (TSA) and (c) modulation sideband analysis. The experimental results show that the existence of the ungrounded pinion can be identified with the frequency spectrum analysis of the vibrational data. In addition, the modulation sidebands are also modeled using a modified version of the traditional technique of physical signal modeling. It is shown that the relative phase of the planet and the meshing vibration strength changed by the unground gear is the critical factor for determining the modulation sideband behavior. In addition, the location of the ungrounded pinion can also be determined by the time history processed by TSA.

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