This work was supported by the Natural Science Foundation of Chongqing, China (cstc2019jcyj-msxmX0046), the project of Chongqing Education Commission of China (KJQN202001127), and the project of Banan District Science and Technology Commission, Chongqing, China (2020TJZ010). The authors would like to thank Prof. Yan Yang for providing the test site. We are also grateful to Dr. Jingshu Wang and Dr. Jinghua Ma for their guidance of using the vibration measurement instrumentation. Thanks are also due to the subjects for their wholehearted cooperation during the experiments.

All procedures were approved by the Ethics Committee of Chongqing University of Technology and each subject provided written informed consent prior to participation in this study.
1. Hand tractor preparation
<ol>
	<li>Ensure the hand tractor is subjected to proper test conditions with a full fuel tank, without looseness of bolts, and without other mechanical defects that would result in abnormal vibration. 
	NOTE: The specifications of the hand tractor used in this experiment are given ...

<ol>
	<li>Ahmadian, H., Hassan-Beygi, S. R., Ghobadian, B., Najafi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ANFIS+modeling+of+vibration+transmissibility+of+a+power+tiller+to+operator.">ANFIS modeling of vibration transmissibility of a power tiller to operator.</a> Applied Acoustics. 138, 39-51 (2018).</li><li>Heaver, C., Goonetilleke, K. S., Ferguson, H., Shiralkar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-arm+vibration+syndrome:+a+common+occupational+hazard+in+industrialized+countries.">Hand-arm vibration syndrome: a common occupational hazard in industrialized countries.</a> Journal of Hand Surgery. 36 (5), 354-363 (2011).</li><li>Geethanjali, G., Sujatha, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+Biomechanical+Response+of+Human+Hand-Arm+to+Random+Vibrations+of+Steering+Wheel+of+Tractor.">Study of Biomechanical Response of Human Hand-Arm to Random Vibrations of Steering Wheel of Tractor.</a> Molecular &amp; Cellular Biomechanics. 10 (4), 303-317 (2013).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO+5349-1:+Mechanical+Vibration:+Measurement+and+Evaluation+of+Human+Exposure+to+Hand+Transmitted+Vibration+Part+1:+General+requirements.">ISO 5349-1: Mechanical Vibration: Measurement and Evaluation of Human Exposure to Hand Transmitted Vibration Part 1: General requirements.</a> International Organization for Standardization. , (2001).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO5349-2:+Mechanical+vibration-+Measurement+and+evaluation+of+human+exposure+to+hand-transmitted+vibration.+Part+2:+Practical+guidance+for+measurement+at+the+workplace.">ISO5349-2: Mechanical vibration- Measurement and evaluation of human exposure to hand-transmitted vibration. Part 2: Practical guidance for measurement at the workplace.</a> International Organization for Standardization. , (2001).</li><li>Besa, A. J., Valero, F. J., Su&#241;er, J. L., Carballeira, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+the+mechanical+impedance+of+the+human+hand-arm+system:+The+influence+of+vibration+direction,+hand-arm+posture+and+muscle+tension.">Characterisation of the mechanical impedance of the human hand-arm system: The influence of vibration direction, hand-arm posture and muscle tension.</a> International Journal of Industrial Ergonomics. 37 (3), 225-231 (2007).</li><li>Marcotte, P., Aldien, Y., Boileau, P. &. #. 2. 0. 1. ;., Rakheja, S., Boutin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+handle+size+and+hand-handle+contact+force+on+the+biodynamic+response+of+the+hand-arm+system+under+zh-axis+vibration.">Effect of handle size and hand-handle contact force on the biodynamic response of the hand-arm system under zh-axis vibration.</a> Journal of Sound and Vibration. 283 (3-5), 1071-1091 (2005).</li><li>Pan, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationships+between+hand+coupling+force+and+vibration+biodynamic+responses+of+the+hand-arm+system.">The relationships between hand coupling force and vibration biodynamic responses of the hand-arm system.</a> Ergonomics. 61 (6), 818-830 (2018).</li><li>Dong, R. G., Rakheja, S., Schopper, A. W., Han, B., Smutz, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-transmitted+vibration+and+biodynamic+response+of+the+human+hand-arm:+a+critical+review.">Hand-transmitted vibration and biodynamic response of the human hand-arm: a critical review.</a> Critical Reviews In Biomedical Engineering. 29 (4), 393-439 (2001).</li><li>Marchetti, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+investigation+on+the+vibration+transmissibility+of+the+human+elbow+subjected+to+hand-transmitted+vibration.">An investigation on the vibration transmissibility of the human elbow subjected to hand-transmitted vibration.</a> International Journal of Industrial Ergonomics. 62, 82-89 (2017).</li><li>McDowell, T. W., Welcome, D. E., Warren, C., Xu, X. S., Dong, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+hand-transmitted+vibration+exposure+from+motorized+forks+used+for+beach-cleaning+operations.">Assessment of hand-transmitted vibration exposure from motorized forks used for beach-cleaning operations.</a> Annals of Work Exposures and Health. 57 (1), 43-53 (2013).</li><li>Tony, B. J. A. R., Alphin, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Finite+element+analysis+to+assess+the+biomechanical+behavior+of+a+finger+model+gripping+handles+with+different+diameters.">Finite element analysis to assess the biomechanical behavior of a finger model gripping handles with different diameters.</a> Biomedical Human Kinetics. 11 (1), 69-79 (2019).</li><li>Tony, B. J. A. R., Alphin, M. S., Velmurugan, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+handle+shape+and+size+to+reduce+the+hand-arm+vibration+discomfort.">Influence of handle shape and size to reduce the hand-arm vibration discomfort.</a> Work. 63 (3), 415-426 (2019).</li><li>Dewangan, V. K. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+hand-transmitted+vibration+of+a+hand+tractor+used+in+three+operational+modes.">Characteristics of hand-transmitted vibration of a hand tractor used in three operational modes.</a> International Journal of Industrial Ergonomics. 39 (1), 239-245 (2009).</li><li>Kalra, M., Rakheja, S., Marcotte, P., Dewangan, K. N., Adewusi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+coupling+forces+at+the+power+tool+handle-hand+interface.">Measurement of coupling forces at the power tool handle-hand interface.</a> International Journal of Industrial Ergonomics. 50, 105-120 (2015).</li><li>Gurram, R., Rakheja, S., Gouw, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+of+hand+grip+pressure+distribution+and+EMG+of+finger+flexor+muscles+under+dynamic+loads.">A study of hand grip pressure distribution and EMG of finger flexor muscles under dynamic loads.</a> Ergonomics. 38 (4), 684-699 (1995).</li><li>Tarabini, M., Saggin, B., Scaccabarozzi, D., Moschioni, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-arm+mechanical+impedance+in+presence+of+unknown+vibration+direction.">Hand-arm mechanical impedance in presence of unknown vibration direction.</a> International Journal of Industrial Ergonomics. 43 (1), 52-61 (2013).</li><li>Aatola, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transmission+of+vibration+to+the+wrist+and+comparison+of+frequency+response+function+estimators.">Transmission of vibration to the wrist and comparison of frequency response function estimators.</a> Journal of Sound and Vibration. 131 (3), 497-507 (1989).</li><li>Kihlberg, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biodynamic+response+of+the+hand-arm+system+to+vibration+from+an+impact+hammer+and+a+grinder.">Biodynamic response of the hand-arm system to vibration from an impact hammer and a grinder.</a> International Journal of Industrial Ergonomics. 16 (1), 1-8 (1995).</li><li>Gurram, R., Rakheja, S., Gouw, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibration+transmission+characteristics+of+the+human+hand-arm+and+gloves.">Vibration transmission characteristics of the human hand-arm and gloves.</a> International Journal of Industrial Ergonomics. 13 (3), 217-234 (1994).</li><li>Burstr&#246;m, A. S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transmission+of+vibration+energy+to+different+parts+of+the+human+hand-arm+system.">Transmission of vibration energy to different parts of the human hand-arm system.</a> Int Arch Occup Environ Health. 70 (3), 199-204 (1997).</li><li>Hartung, E., Dupuis, H., Scheffer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+grip+and+push+forces+on+the+acute+response+of+the+hand-arm+system+under+vibrating+conditions.">Effects of grip and push forces on the acute response of the hand-arm system under vibrating conditions.</a> International Archives of Occupational and Environmental Health. 64 (6), 463-467 (1993).</li><li>Pope, M. H., Magnusson, M., Hansson, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+upper+extremity+attenuates+intermediate+frequency+vibrations.">The upper extremity attenuates intermediate frequency vibrations.</a> Journal of Biomechanics. 30 (2), 103-108 (1997).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO+8041-1:+Human+response+to+vibration-Measuring+instrumentation.">ISO 8041-1: Human response to vibration-Measuring instrumentation.</a> International Organization for Standardization. , (2017).</li><li>Ying, Y. B., Zhang, L. B., Xu, F., Dong, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibratory+characteristics+and+hand-transmitted+vibration+reduction+of+walking+tractor.">Vibratory characteristics and hand-transmitted vibration reduction of walking tractor.</a> Transactions Of The ASAE. 41 (4), 917-922 (1998).</li><li>Dewangan, K. N., Tewari, V. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+vibration+transmission+in+the+hand-arm+system+and+subjective+response+during+field+operation+of+a+hand+tractor.">Characteristics of vibration transmission in the hand-arm system and subjective response during field operation of a hand tractor.</a> Biosystems Engineering. 100 (4), 535-546 (2008).</li><li>Xu, X. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrations+transmitted+from+human+hands+to+upper+arm,+shoulder,+back,+neck,+and+head.">Vibrations transmitted from human hands to upper arm, shoulder, back, neck, and head.</a> International Journal of Industrial Ergonomics. 62, 1-12 (2017).</li></ol>

The protocol presented in this study was established based on HTV standards4,5,24, and was developed as the standard steps for the measurement of the HTV of the human hand-arm system during the operation of a hand tractor in a stationary condition. This condition is the most stable state of the hand tractor to help ensure the reliable measurement of the vibration actually transmitted to the hand and arm. The range of variables c...

Hand tractors, also known as power tillers, are widely used in developing countries for the land preparation of small fields. The field operation of a hand tractor involves walking behind the machine and holding its handles to control its movement. The operators of hand tractors are exposed to high levels of vibration, which could be attributed to the small single cylinder engine and lack of suspension system of hand tractors1. The hand-arm vibration syndrome (HAVS)2 can be caused by long-period endurance from the vibration, named hand transmitted vibration (HTV), which generated by the hand tractor and received by the operator&#39;s hands. To assess the health risks derived by operators&#39; exposure to the HTV of hand tractors, it is necessary to establish a method for the measurement of the vibration response of the hand-arm system.
The hand-arm system is composed of bones, muscles, tissues, veins and arteries, tendons and skin3, and the direct measurement of HTV poses many problems. The relevant international standards4,5 provide guidelines pertaining to the measurement of the severity of vibration generated in the immediate vicinity of the hand, including the coordinate system for the hand, the location and mounting of accelerometers, the measurement duration, cable connector problems, etc. However, the standards do not take into consideration intrinsic variables, such as the grip force, the posture of the hand and arm, individual factors, etc. These factors have been examined extensively under a wide range of vibration excitations and test conditions6,7,8,9,10,11,12,13, but the results of different investigators are not in good agreement. Many of these factors have not been sufficiently understood to be incorporated into standard methods. This restriction is partially attributable to the complexities of the human hand-arm system, the test conditions, and the differences in the experimental and measurement techniques employed.
Moreover, most of the earlier measurements of HTV were performed under carefully controlled conditions with idealized vibration excitations, grip force, and postural conditions. The findings and experimental procedures of these measurements, therefore, may not truly replicate real-world conditions, such as the operating conditions of hand tractors. Moreover, only limited efforts have been undertaken to study the HTV of hand tractors with field measurements. These measurements were performed using accelerometers attached to the operator&#39;s wrist, arm, chest, and head to measure the whole body vibration under the tractor&#39;s transportation conditions1, or under the conditions of tilling in an untilled field and puddling in a submerged field with different levels of engine speeds14. The effect of the grip force, which could be a crucial factor of HTV7,8, was not isolated. These methods are therefore unsuitable as standardized measurement procedures due to the operator&#39;s various forced postures during farming ascribed to the harsh environmental conditions.
The present research was undertaken to contribute to the establishment of reliable and repeatable procedures for the HTV measurement of hand tractors in a stationary mode. Figure 1 presents the schematic diagram of the experimental design. A hand tractor manufactured in China and commonly used by Chinese farmers was employed, and ten research workers were chosen as subjects for the study. Seven lightweight piezoelectric accelerometers attached to the tractor-hand-arm system were used to measure the vibration. One tachometer and two thin-film pressure sensors monitored the engine speed and grip force during testing. The subjects were required to sequentially operate the hand tractor at specified engine speeds and with specified grip forces to obtain the vibration characteristics in various operational modes. This manuscript provides a detailed protocol for the HTV measurement of the tractor-hand-arm system with unique consideration of changes in the grip force and vibration frequency.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Accelerometers</td>
			<td>PCB Piezotronics Inc.</td>
			<td>352C33, 356A04</td>
			<td>Used to measure vibration signals. Including 2 tri-axial accelerometers and 5 single-axis accelerometers.</td>
		</tr>
		<tr>
			<td>CompactDAQ System</td>
			<td>National Instruments</td>
			<td>cRIO-9045,NI-9234 C</td>
			<td>Used for acceleration acquisition. The system consists of a chassis and 3 data acquisition cards.</td>
		</tr>
		<tr>
			<td>Digital caliper</td>
			<td>Sanliang</td>
			<td>160800635</td>
			<td>Used to measure dimensions of the hand.</td>
		</tr>
		<tr>
			<td>Digital goniometer</td>
			<td>Sanliang</td>
			<td>802973</td>
			<td>Used to measure hand and arm posture.</td>
		</tr>
		<tr>
			<td>Laptop computer</td>
			<td>Lenovo</td>
			<td>Ideapad 500s</td>
			<td>To run the softwares.</td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>MathWorks Inc.</td>
			<td>Version 2020a</td>
			<td>Used for data processing.</td>
		</tr>
		<tr>
			<td>NI SignalExpress</td>
			<td>National Instruments</td>
			<td>Trial version 2015</td>
			<td>Use to acquire, analyze and present acceleration data.</td>
		</tr>
		<tr>
			<td>Tachometer</td>
			<td>Sanliang</td>
			<td>TM 680</td>
			<td>Used to measure engine speed.</td>
		</tr>
		<tr>
			<td>Thin-film pressure sensing system</td>
			<td>YourCee</td>
			<td>n/a</td>
			<td>Used to measure grip force. The system consists of 2 thin-film sensors, a STM32 singlechip and a LED display.</td>
		</tr>
	</tbody>
</table>

measurement of the hand transmitted vibration of the human hand arm system during operation of a hand tractor

Operators of hand tractors are exposed to high levels of hand transmitted vibration (HTV). This vibration, which can be both irksome and hazardous to human health, is imparted to the operator via his or her hands and arms. However, a standardized method for measuring HTV of hand tractors has yet to be defined. The aim of the study was to present an experimental method for the investigation of the biodynamic response and vibration transmissibility of the hand-arm system during the operation of a hand tractor in a stationary mode. Measurements were performed with ten subjects using three grip forces and three handle vibration levels to examine the influences of the hand pressure and frequency on hand transmitted vibration (HTV). The results indicate that the tightness of grip on the handle influences the vibration response of the hand-arm system, especially at frequencies between 20 and 100 Hz. The transmission of lower frequencies in the hand-arm system was relatively unattenuated. In comparison, attenuation was found to be quite marked for higher frequencies during the operation of the hand tractor. The vibration transmissibility to different parts of the hand-arm system decreased with the increase of the distance from the vibration source. The proposed methodology contributes to the collection of consistent data for the evaluation of operator vibration exposure and the ergonomics development of hand tractors.

The experiment was carried out in the laboratory (air temperature 22.0 &#176;C &#177; 1.5 &#176;C) on ten healthy subjects (Table 2) during the operation of a hand tractor in a stationary condition.
Following the protocol, vibration acceleration data were collected from the handle of the hand tractor, as well as the back of the hand, the wrist, the arm, and the shoulder of each subject. The spectrum of the vibration acceleration occurring at the handle (input to the hand) was ...

Watch this Scientific Journal Video about Measurement of the Hand Transmitted Vibration of the Human Hand Arm System During Operation of a Hand Tractor at JoVE.com

Measurement of the Hand Transmitted Vibration of the Human Hand Arm System During Operation of a Hand Tractor

Here, we present a standardized method for measurement of the hand transmitted vibration from handles of a single-axle tractor with special reference to changes in grip force and vibration frequency.

Operators of hand tractors are exposed to high levels of hand transmitted vibration (HTV). This vibration, which can be both irksome and hazardous to ...

The overall goal of this experiment is to investigate the biodynamic response and vibration transmissibility of the hand-arm system during the operation for hand tractor. This study provides a protocol for hand transmitted vibration measurement of the tractor-hand-arm system with consideration of changes in the grip force and vibration frequency. This method will be helpful for the understanding of the vibration transmission characteristics of the hand-arm system.Begin, place the hand tractor in a test site with dry, firm and a level ground surface. Remove the elastomeric materials of the handles. After obtaining informed consent from all the subjects, measure each subject's body dimensions including standing height, mass, forearm lengths, upper arm length and hand length.Wrap the accelerometer adapters tightly on the hand and arm of each subject. Each adapter was a fabricated using a nylon strap and a piece of galvanized iron sheet to provide a rigid and light attachment. The accelerometer adapters were wrapped at the locations of the back of the hand, distal end of the forearm, proximal end of the forearm, distal end of the upper arm, proximal end of the upper arm and the acromion.Before initiating a measurement, gather all of the components of the measurement system, including accelerometers, data acquisition system, thin-film pressure sensing system, tachometer, digital goniometer, accelerometer adapters and other relevant components. To set up the acceleration measurement system, first, using the accelerometer cables, connect the accelerometers with the data acquisition card. using an Ethernet cable, connect the chassis with the computer.Then, attach one tri-axial accelerometer on the left handle or the hand tractor, and attach the other one on the accelerometer adapter of the subject's left hand. Attach single-axis accelerometers one by one, on the accelerometer adapters of the subject's arm and shoulder. Adjust orientations of the tri-axial accelerometers to be consistent with the specified coordinate system.Finally, using adhesive tape, secure the accelerometer cables on the skin surface of the subject's arm and the tractor's handlebar. To set up the grip force measurement system, first, using double-sided adhesive tape, attach two thin-film sensors on the left handle of the hand tractor. Then, place the screen system at a convenient height.So that the subject could monitor and adjust the grip force to the specified level during the operation of the hand tractor. After that, instruct the subject to hold and raise the handle to a horizontal position. Measure the subject's hand and arm posture using a digital goniometer, including the shoulder horizontal abduction, the shoulder vertical abduction, the elbow extension, the wrist extension and the wrist deviation.Ask the subject to maintain the posture until the end of the trial. Start the hand tractor in neutral, and keep running at a low engine speed until it is stabilized. Turn on the tachometer, thin-film pressure sensing device, laptop computer, and the acceleration data acquisition system.Set the parameters of acceleration, acquisition mode and sampling rate for data collection. Click Run and wait about ten seconds until the system stabilized, then click Record to start recording the acceleration data. During the testing, ask the subject to monitor the tachometer and adjust the engine speed to 1, 500 revolutions per minute until it is stabilized.Then, instruct the subject adjust the grip force carefully to 20 Newtons, and keep this grip force level for about 30 seconds. Next, adjust the grip force to 30 Newtons and keep about 30 seconds. And then, adjust the grip force to 40 Newtons and keep about 30 seconds.After that, adjust the engine speed to 2, 500 revolutions per minute and repeat the above procedure of grip force adjustment. Last, adjust the engine speed to 3, 500 revolutions per minute and repeat the above procedures of grip force adjustment. At the end of the trial, instruct the subject to put down the handle and shut down the engine of the hand tractor.Save the vibration acceleration data, remove and place the accelerometers on the next subject. Repeat the above steps until the end of the data collections of all the subjects. And export the acceleration time-series data for further analysis.These plots display samples of the time domain and frequency domain accelerations on the handle for half a second time duration. The maximum acceleration of the X and Z directions occurred at the frequency of 58 Hertz. Most of the vibration energy was found to be centralized in the frequency range from 50 to 200 hertz.The mean relationship between the grip force and root-mean square acceleration of the hand-arm system was obtained. It was observed that the increase in the grip force increased the vibration acceleration notably at frequencies between 20 and 100 Hertz. And the three resonance frequencies were found to increase almost linearly with the increase of the grip force.Meanwhile, the relationship between the engine speed and root-mean-square acceleration was obtained. As shown in the plots, lower frequencies were transmitted relatively unattenuated. While, attenuation was quite marked for higher frequencies.Thus, it is reasonable to conclude that, most of the vibrational energy was dissipated in the hand and the forearm. This figure presents the averaged transmissibility at different locations of the hand-arm system. It was found that the transmissibility of the hand-arm system decreased with the increase of the distance from the vibration source.The highest transmissibility was observed at the back of the hand. The resonant frequency of the wrist and elbow transmissibility was around 20 hertz. It was also found that only vibrations of less than 25 Hertz were effectively transmitted to the forearm, upper arm and the shoulder.This method was established based on hand transmitted vibration standards, and was developed as a standard protocol for the measurement of the hand transmitted vibration of the human hand-arm system during the operation of a hand tractor in a stationary condition. The total weight of the accelerometer and adapter should be as light as possible to reduce measurement errors. The test trial of each subject should be completed without interruption to reduce the effect of the operating posture.The main potential applications of the proposed methodology are the estimation of human-tractor interaction phenomena, the ergonomics development of hand tractors, and the development of protective devices such as isolators and gloves.

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4.2K visualizações.  Chongqing University of Technology. O objetivo geral deste experimento é investigar a resposta biodinâmica e a transmissibilidade de vibração do sistema de braço-mão durante a operação para trator de mão. Este estudo fornece um protocolo para medição de vibração transmitida à mão do sistema trator-braço com a consideração de mudanças na força de aderência e frequência de vibração. Este método será útil para a compreensão das características de transmissão de vibração do sistema de braço-mão.