79 research outputs found
A data correction method for surface measurement of vibration on the human body
No full textA data correction method to eliminate the effect of local tissue-accelerometer vibration from surface measurements of vibration over the spine has been developed and compared with previous direct measurements. A single degree-of-freedom linear model for the local tissue-accelerometer system in the vertical and the fore-and-aft axes is assumed. The natural frequency and the damping ratio of the local system are estimated so as to form a correction frequency function, using spectral analysis of the free vibration response of the local system caused by transient displacements of the accelerometer attached to the body surface. Accelerometers were attached to the skin over the spinous process of the vertebra L3 and on the abdominal wall. For four different masses and each site, correction frequency functions were computed. Seated subjects were then exposed to vertical random vibration (0.5-35 Hz) and acceleration transfer functions from the seat to each accelerometer were calculated. Different transfer functions were obtained with different additional masses but the differences were eliminated by the correction method so as to indicate the transfer functions to the spine and the viscera. For vertical responses, the correction method was effective at frequencies below the estimated natural frequencies of the local system. Fore-and-aft response over the spine did not require correction at frequencies below 35 Hz.</p
Modelling mechanical responses to human whole-body vibration
No full textSIGLEAvailable from British Library Document Supply Centre- DSC:DX186108 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Resonance behaviour of the seated human body and effects of posture
No full textUnderstanding of the resonance behaviour of the human body is important in the identification of vibration frequencies and body postures associated with back problems. In this study, experimental modal analysis was applied to whole-body vibration. Eight subjects were exposed to vertical random vibration while adopting three different postures on a rigid seat without a backrest. Motions of the spine, pelvis and viscera in the mid-sagittal plane were derived from skin-mounted accelerometers; head responses were measured using a bite-bar. Eight modes of vibration response were extracted below 10 Hz. A principal resonance of the human body at about 5 Hz consisted of an entire body mode, in which the skeleton moved vertically due to axial and shear deformations of buttocks tissue, in phase with a vertical visceral mode, and a bending mode of the upper thoracic and cervical spine. A bending mode of the lumbar and lower thoracic spine was found with a pitching mode of the head in the next higher mode located close to the principal mode. The second principal resonance at about 8 Hz corresponded to pitching modes of the pelvis and a second visceral mode. When subjects changed posture from erect to slouched, the natural frequency of the entire body mode decreased, resulting in a decrease in the principal resonance frequency. Shear deformation of buttocks tissue increased in the entire body mode due to the same change of posture. The complex body motions suggest that any forces causing injury from whole-body vibration will not be well-predicted by biodynamic models incapable of representing the appropriate body motions and the effects of body posture. It seems likely that the greatest risk of back problems will arise from the bending deformations of the spine.</p
Effects of Non-Verbal Communication Cues on Decisions and Confidence of Drivers at an Uncontrolled Intersection
No full textDrivers read other drivers’ intentions using various non-verbal communication cues in situations where traffic regulations play only a limited role. Although such communication is important to reach safe joint actions with other driver(s), effects of communication have not been fully understood. The objective of this study was to understand effects of communication cues on driver’s decisions and confidence. Straight-cross-path and left-turn scenarios around an uncontrolled intersection were studied in an interview-based experiment using 65 subjects. The subject’s car approached the intersection while another car was approaching the same intersection and sent communication cues consisting of various combinations of vehicle behaviors (constant speed, speeding up, and slowing down) and hand gestures (meaning “Go ahead” and “Stop”). Computer animations of the scenarios were presented to the subjects and terminated before the two cars reached the intersection. The subjects rated yielding frequency and confidence level for each cue combination in each scenario. The results showed that the vehicle behaviors and the hand gestures affected subjects’ yielding frequencies and confidence levels. The cues also interacted with the priority rule in the left turn scenarios. The hand gestures were especially effective to consolidate subjects’ decisions to yield or go with confidence when the priority rule was ineffective (i.e. in the straight-cross-path scenarios). The hand gestures were also effective to change the yielding frequencies to accept the cues conflicting with the effective priority rule (i.e. in the left-turn scenarios). Some requirements and recommendations for autonomous vehicle were discussed
Improvement of Ease of Viewing Images on an In-vehicle Display and Reduction of Carsickness
No full textConsiderations in Mechanism of Carsickness of Rear Passengers When Watching a Car-Mounted Display
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