Novel Euler-LaCoste linkage as a very low frequency vertical vibration isolator

2012 ◽  
Vol 83 (8) ◽  
pp. 085108 ◽  
Author(s):  
M. A. Hosain ◽  
A. Sirr ◽  
L. Ju ◽  
D. G. Blair
Keyword(s):  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Isolator ◽  
Very Low Frequency

Ultra-low frequency vertical vibration isolator based on LaCoste spring linkage

2014 ◽  
Vol 85 (10) ◽  
pp. 104502 ◽  
Author(s):  
G. Li ◽  
H. Hu ◽  
K. Wu ◽  
G. Wang ◽  
L. J. Wang
Keyword(s):  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Isolator

An active ultra-low frequency vertical vibration isolator

2016 ◽  
Author(s):  
G. Wang ◽  
H. Hu ◽  
K. Wu ◽  
G. Li ◽  
L. J. Wang
Keyword(s):  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Isolator

scholarly journals Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure

2016 ◽  
Vol 65 (20) ◽  
pp. 200702
Author(s):  
Wang Guan ◽  
Hu Hua ◽  
Wu Kang ◽  
Li Gang ◽  
Wang Li-Jun
Keyword(s):  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Isolator ◽  
Beam Structure ◽  
Two Stage

An Ultra-Low Frequency Active Vertical Vibration Isolator With Geometric Anti-Spring Structure

2017 ◽  
Author(s):  
Jiamin Yao ◽  
Kang Wu ◽  
Jin Qian ◽  
Guan Wang ◽  
Meiying Guo ◽  
...  
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Ground Vibration ◽  
Stage Structure ◽  
Target Object ◽  
Vertical Vibration ◽  
Vibration Isolator ◽  
Restoring Force ◽  
Second Stage ◽  
Allowable Load

Vibration isolators have been widely used to keep the target object from the ground vibration in order to improve the measurement accuracy. Nowadays, the ultra-low frequency vibration isolator based on a two-stage structure shows the best performance. Traditionally, vertically suspended springs are usually applied as the second-stage. As the requirement of the low stiffness, the springs need to be long, which brings the disadvantages of relatively large size and small allowable load. A novel ultra-low frequency active vertical vibration isolator is proposed in this paper, which applies geometric anti-spring (GAS) instead of the second-stage suspended springs. The isolated object (the second stage) is supported by GAS fixed on an inner frame (the first stage), and the inner frame is hung with supporting springs from the base of the vibration isolator. The inner frame is driven by a voice coil to track the motion of the isolated object according to the relative motion signal detected by a photoelectric detector. Ideally, GAS provides zero restoring force for the object, thus realizing a long natural resonance period. Experimental results show that the isolator can achieve a resonance period of 14.7 s, compared with a simulated result of 20.7 s. Therefore, it is accessible to reduce the isolator’s volume and increase the allowable load by replacing the traditional second-stage suspended springs with GAS, without harming the vibration isolation effect. Promisingly it will be applied in free-falling and atomic-interference absolute gravimeters, and other precise measurements.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

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