Measurement and Frequency Weighting Functions for Human Vibration

Dohyung Kee,Hee Sok Park 대한인간공학회 2013 大韓人間工學會誌 Vol.32 No.4

Objective: The aim of this study is to review and summarize human vibration measurement process, and necessity and methods of frequency weightings for human vibration. Background: Prolonged human exposure to hand-arm vibration and whole-body vibration can result in a range of adverse conditions and the development of occupational diseases such as vibration white finger. For preventing these adverse effects, it is important to correctly apply human vibration measurement process. Method: This manuscript was based on the review and summary of mechanical and human vibration relevant texts, academic papers, materials obtained through web surfing. Results: This manuscript summarizes human vibration measurement process described in ISO standards and relevant texts. The sensitivity of the human body to mechanical vibration is known to be dependent on both the frequency and direction of vibration. To take this into account, varying frequency weighting functions have been developed, and RMS frequency-weighted accelerations are used as the most important quantity to evaluate the effects of vibration on health. ISO provided nine frequency weighting functions in the form of curves and tables. Researches on frequency weightings are focused on development and validation of new frequency weightings to truly reflect the relationship between vibration exposure and its adverse effects. Application: This would be useful information for systematically applying human vibration measurement and analysis process, and for selecting appropriate frequency weighting functions.

인체진동이 뇌파변동리듬에 미치는 영향평가

민병찬(Byung-Chan Min),김형욱(Hyoung-Wook Kim),김지관(Ji-Kwan Kim) 한국산업경영시스템학회 2007 한국산업경영시스템학회지 Vol.30 No.4

  In this study, reactions of central nervous systems working against different conditions of forced frequency and acceleration were measured and analyzed. The experiment are conducted with health men. The steady vibration conditions of forced frequency (0.315㎧2-1.0㎐, 0.315㎧2-10㎐ and 10㎐-1.0㎧2) are used and the waves of EEG (Electroencephalogram) are measured. As a result, this paper shows that the α-wave of frontal lobe transfers from low to high frequency band under the vibration environment. Additionally, the average frequency of α-wave is higher under the vibration than under non-vibration environment. In the case of forced frequency of 1.0㎐-0.315㎧2, the feeling with the vibration are nearly same compared with the non-vibration condition. But in the case of 10㎐-1.0㎧2, uncomfortable feeling increased compared with the non-vibration condition. This study also shows the relationship between fluctuation slop and feeling. From this study, it is found that the effect of vibration on human depends on acceleration characteristics. Highly accelerating vibration is more harmful to human.

다중동조 질량감쇠기를 이용한 교량의 진동제어

이용교,박연준,박인준,권형오,박진완,Lee,Yongkyo,Park,Yoen-Jun,Park,Inn-Joon,Kwon,Hyungo,Park,Jinwan 한국방재학회 2014 한국방재학회논문집 Vol.14 No.3

최근 급속한 경제발전과 생활수준의 향상에 따라 도로주행차량이 급속히 증가하고 차량의 중량화 및 고속화 현상이 가속되고 있다. 이에 따라, 공용중인 교량에서 발생하는 과도한 진동, 처짐 등의 문제가 교량의 사용성 및 안전성을 위협하고 있다. 선진 외국에서는 교통량에 의한 교량의 과도한 진동을 저감시키기 위한 대책에 대한 연구를 활발히 수행하고 있으나 국내에서는 아직 이에 대한 실용화된 기술을 확보하고 있지 못한 실정이다. 본 연구에서는, 교량의 차량주행시 진동응답 및 교량의 동특성을 분석하여 과도진동 응답의 원인을 고찰하였다. 다양한 주파수 대역의 진동에 대해 효과적으로 진동을 저감시키기 위해 다중동조질량감쇠기 고안하여 적용하였다. 적용결과 교량의 다양한 주파수 대역에 대한 효과적으로 진동을 저감할 수 있었다. 본 연구를 통해 다양한 주파수 대역의 진동을 가지는 교량을 효과적으로 진동을 저감시킬 수 있는 진동제어기술을 확보하였다. It have been increasing traffic, vehicle weight and speed because of recently rapid economic development and the improvement of living standards. As a result, problems such as excessive vibration, deflection of the bridge threatens the safety and usability. In developed countries, Studies have carried out actively on the methods to reduce the excessive vibration of the bridges. But, there were no such a practical technology in korea. In this study, the vibration response of bridge at the time of vehicle operation and to analyze the dynamic characteristics of bridge may cause excessive vibration response was investigated. For different frequency bands of vibration, In order to reduce effectively the vibration, Multiple tuned mass damper was applied. As a result, Bridges for various frequency bands could be reduces effectively by the vibration. In this study, The effective vibration control technology on the different frequency band of vibration bridge was secured.

Vibration effects on remote sensing satellite images

Haghshenas, Javad Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.5

Vibration is a source of performance degradation in all optical imaging systems. Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency sinusoidal vibrations on the system MTF are known exactly in closed form but the low frequency vibration effects is a random process and must be considered statistically. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. For analyzing low frequency effects, designer must know all the systems specifications and parameters. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let the designer to eliminate just harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF equal or greater than a pre-defined budget for different missions. The worst and average cases have been discussed and finally we have proposed "look-up figures". Using these look-up figures, designer can choose the electro-optical parameters in such a way that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.

VIBRATION REDUCTION OF H/SHAFT USING AN ELECTROMAGNETIC DAMPER WITH MODE CHANGE

K. H. LEE,J. H. BAK,J.-L. PARK,C. H. Lee 한국자동차공학회 2017 International journal of automotive technology Vol.18 No.2

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.

진동시험에 의한 참외의 진동특성

김만수,정현모,김기석,박정길 충남대학교 농업과학연구소 2005 농업과학연구 Vol.32 No.1

During a long journey of agricultural products from the production area to markets, the quality of agricultural products was always affected by some degree of vibration. The vibration input during the transportation may cause serious agricultural product injury, and this damage is particularly severe whenever the vegetable inside package is free to bounce, and is vibrated at its resonant frequency. The objectives of this study were to determine the resonant frequency of the oriental melon and to investigate the relationships between resonant frequency and physical properties of the oriental melon such as mass, volume and major and minor axes. In this study vibration testing device was constructed to determine the vibration response of the oriental melon in frequency ranges of 5 to 150 Hz. The computer program for controlling the vibration shaker and the function generator and measuring the vibration characteristics of the oriental melon was developed. The ranges of resonant frequency and peak acceleration at resonance of the oriental melon were 51 to 73 Hz and 1.24 to 1.92 G-rms, respectively. The resonant frequency and the peak acceleration decreased with the increase of the sample mass, volume, major and minor axes of the oriental melon. Multiple regression models for resonant frequency and peak acceleration of the oriental melon as a function of mass, major axis and minor axis of the sample were developed and analyzed.

콘크리트 댐체의 고유진동수 측정과 변화거동

홍웅기(Woong-Gi Hong),이광재(Kwang-Jae Lee),진영문(Young-Moon Jin),송정언(Jeong-Un Song) 한국엔터테인먼트산업학회 2015 한국엔터테인먼트산업학회논문지 Vol.9 No.2

본 연구는 환경공해진동을 평가하기 위한 기초자료를 얻기 위하여 수행되었다. 콘크리트 댐체에서 고유진동수를 측정하여 다음과 같은 결론을 얻었다. 댐체의 양 끝단에서 저주파수 대역으로 측정되었고, 특히 E 측점과 J 측점 사이에서 주파수 대역의 편차가 크고 랜덤하게 나타났다. 이는 바람의 영향과 수압, 댐체 중앙 부근으로 갈수록 고유진동수가 다른 측점보다 더욱 크게 나타나는 특성 때문이라 판단된다. 변위가속도 또한 고유진동수와 유사한 경향을 보였다. 외부에서 전달되는 외력의 강제진동수는 댐체의 고유진동수 영역보다 항상 작은 값으로 산출되었으며, 주파수 대역은 대부분 충격성 저주파영역을 나타냈다. 이러한 전달 과정에서 매질자체가 갖는 고유특성이나 수진점의 고유진동수, 또는 실시간 주파수분석 등을 고려한 환경공해진동의 정량적인 진동영향평가 기법이 필요하며, 아울러 고유진동수를 고려한 예측모델을 구성하기 위하여 구조체의 기초물성 및 기여도를 분석하고, 계측 데이터의 오차분석, 표준편차 및 보정에 의한 모델의 타당성 평가와 검증 과정이 수행될 때 환경공해진동의 정량적인 평가가 확립될 수 있을 것으로 사료된다. The purpose of this study is to obtain basic data for assessment the vibration as one of the environmental pollution. Natural frequencies in free field were measured as follows: At both ends of the dam crest, the natural frequency was measured with a relatively low frequency. Particularly, the deviation of frequency domain at E and J M.Ps were large and determined randomly. Because toward the central part of the dam crest, the effects of wind, water pressure, and natural frequencies are more large compared to the other M.Ps. Additionally, acceleration values were also measured similar to the trend of natural frequency. Vibration impact assessment that considered the natural characteristics of the medium in the delivery process, natural frequency of vibration receptor and the real-time frequency analysis reached the point of need. This is intended to identify vibration amplification by the resonance of frequency and additional vibration energy. And in order to configure the prediction model which considering the characteristics of frequency, the basic physical properties and contributiveness to the general structure must be analyzed. Feasibility assessment and verification of the model using standard deviation, correction and error analysis of measurement data must be carried out. As a result, the quantitative assessment of the vibration as one of the environmental pollution can be expected to be established.

스마트 기기용 강화유리&사파이어 유리 전용 가공기의 진동해석을 통한 설계 개선에 관한 연구

조준현(Jun-Hyun Cho),박상현(Sang-Hyun Park),안범상(Beom-Sang An),이종찬(Jong-Chan Lee) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.2

High brittleness is a characteristic of glass, and in many cases it is broken during the process of machining due to processing problems, such as scratches, chipping, and notches. Machining defects occur due to the vibration of the equipment. Therefore, design techniques are needed that can control the vibration generated in the equipment to increase the strength of tempered glass. The natural frequency of the machine tool via vibration analysis (computer simulation) must be accurately understood to improve the design to ensure the stability of the machine. To accurately understand the natural frequency, 3D modeling, which is the same as actual apparatus, was used and a constraint condition was also applied that was the same as that of the actual apparatus. The maximum speeds of ultrasonic and high frequency, which are 15,000 rpm and 60,000 rpm, respectively, are considerably faster than those of typical machine tools. Therefore, an improved design is needed so that the natural frequency is formed at a lower region and the natural frequency does not increase through general design reinforcement. By restructuring the top frame of the glass processing, the natural frequency was not formed in the operating speed area with the improved design. The lower-order natural frequency is dominant for the effects that the natural frequency has on the vibration. Therefore, the design improvement in which the lower-order natural frequency is not formed in the operating speed area is an optimum design improvement. It is possible to effectively control the vibrations by avoiding resonance with simple design improvements.

A Method Based on Spectrum Superposition for Minimizing the Hazards of Blasting Vibration

Tiejun Tao,Sipeng Wan,Liansheng Liu,Tongyan Pan 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.5

The selection of delay time will directly affect the effect of vibration reduction in millisecond delay blasting. The commonly used frequency spectrum control methods have some problems such as the difficulty of seed wave selection and the complexity of nonlinear superposition model. Based on the principle of waveform linear superposition, this study proposes a new spectrum superposition method for minimizing the vibration hazards in an open deep-hole bench blasting. This method, with no need to select the seed waves, mainly uses the ratio of the Fourier spectrum of the combined vibration waveform and the single hole vibration waveform to quantify the suppressed vibration. By defining the suppression ratio K, the suppression ratio with frequency range of 10 − 60 Hz under different delay times was calculated, and the theoretical optimal vibration reduction delay time value of 10 − 15 ms was given. A high precision digital electronic detonator was used to verify the proposed spectrum superposition method. The test results show that the best delay time of field vibration reduction is 5 − 10 ms, which is lower than the theoretical best delay time of 10 − 15 ms. It is the authors’ belief that this phenomenon is mainly caused by the joints and cracks in the rock mass, which will prolong the actual superposition time of blasting seismic waves between adjacent holes. In addition, it is found that there is a negative correlation between the delay time and the main vibration frequency, which is mainly caused by the low-pass filtering characteristic of rock medium. In order to minimize the probability of resonance failure, an optimal delay of 5 ms based on the main vibration frequency was given.

광섬유 간섭계 센서를 이용한 선삭가공 공구진동 측정 연구

이종길 대한공업교육학회 2007 대한공업교육학회지 Vol.32 No.2

The purpose of this study is to measure the lathe tool vibration and verify its usefulness using the fiber optic interferometeric sensor instead of using common accelerometer. To compare two vibration signals a Fabry-Perot fiber optic sensor(FOS) is directly attached to the left-side surface of the lathe tool and an accelerometer is attached near to the fiber optic sensor. Measurement signals from the FOS and theoretical results of receptance simulation are compared. When the amplitude of tool vibration increased the frequency shift phenomena was occurred. This means that mass effect occurred and vibration spectrum moved to the low frequency region. Generally this results is agreement to the regenerative chatter. The chatter frequency is not same as the natural frequency of the tool itself. The FOS can also applied to laboratory experiments for students. This experimental technique is perhaps the first attempts because of directly attachment technique. Therefore, suggested Fabry-Perot fiber optic sensor can be used to monitoring the tool wear and vibration. 이 연구의 목적은 선삭 가공시 발생하는 채터 진동을 계측하기 위하여 일반적인 가속도계가 가진 단점을 보완한 페브리-페롯형(Fabry-Prtot) 광섬유 간섭계 센서를 공구에 직접 부착하여 채터 진동을 측정하고 이것의 유용성을 확인하는 것이다. 측정된 주파수 스펙트럼과 이론해석 상의 리셉턴스 곡선과 비교하였는데 공구진동이 클수록 가진 주파수 이동이 생성되며 이는 공구의 날 끝에 질량효과가 더해짐을 의미함을 알 수 있었다. 질량효과가 더해지면 진동 주파수는 저주파 쪽으로 이동한다. 진동 주파수의 저주파 영역의 이동은 일반적인 재생형 채터에서 흔히 일어나는 현상이다. 또한 측정한 채터 주파수는 고유진동수가 아닌 외부 가진 주파수인 것으로 확인 됐으며 측정 결과와 같이 본 실험에 사용된 광섬유 센서는 외부 진동 주파수를 잘 계측 하였으며 페브리-페롯 센서는 특히 공구진동의 측정에 유용함을 보았다. 본 연구를 통하여 적용분야로 간섭계형 광섬유 센서를 공구 표면에 직접 설치하고 공구 진동을 관찰하는 교육목적의 실험에도 응용할 수 있다. 본 실험과 같은 페브리-페롯 간섭계 센서의 공구 직접 접촉식 방법에 대한 연구는 국내외 적으로 그 사례를 찾아보기 힘든 독창적인 방법인 것으로 추정된다. 본 연구결과는 또한 향후 공구진동과 마멸을 연구하는데 기초 자료로 활용할 수 있을 것으로 판단된다.