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Characterising the coupling between the occupant and vehicle seat is necessary to understand the transmission of vehicle seat vibration to the human body. In this study, the vibration characteristics of the human body coupled with a vehicle seat were identified in frequencies up to 100 Hz. Transmissibilities of three volunteers seated on two different vehicle seats were measured under multi-axial random vibration excitation. The results revealed that the human-seat system vibration was dominated by the human body and foam below 10 Hz. Major coupling between the human body and the vehicle seat-structure was observed in the frequency range of 10-60 Hz. There was local coupling of the system dominated by local resonances of seat frame and seat surface above 60 Hz. Moreover, the transmissibility measured on the seat surface between the human and seat foam is suggested to be a good method of capturing human-seat system resonances rather than that measured on the human body in high frequencies above 10 Hz.Practitioner Summary: The coupling characteristics of the combined human body and vehicle seat system has not yet been fully understood in frequencies of 0.5-100 Hz. This study shows the human-seat system has distinctive dynamic coupling characteristics in three different frequency regions: below 10 Hz, 10-60 Hz, and above 60 Hz.

Background: Passive posture variation in vehicles could enable variation in pressure distribution and muscle activity to counter physical fatigue from static seating resulting in more comfort. The difference in posture, however, should not lead to perceived discomfort and aspects of driving should be considered such as operating the steering wheel, pedals and vision in the mirrors., Objective: This study sets out to find out how much postural variation occurs during the driving task and how sensitive is the human body to these changes., Methods: The first experiment was user evaluation and assessed how and when the changes in seat configuration were noticeable to the human body. The second experiment evaluated the influence of varying inclination of the backrest and the seat pan by the rating of typical aspects of driving., Results: The differences in seat configuration during experiment 1, were so small that there was no consistency in the ratings for the same configuration. The most critical feature that restrains the posture is the location of the rear view mirror., Conclusions: The range-of-motion is defined as -1° to +1° for the seat pan and 0° to +1.5° for the backrest based on the results of experiment 2 because of the restraints of the driving task.

BACKGROUND: Passive posture variation in vehicles could enable variation in pressure distribution and muscle activity to counter physical fatigue from static seating resulting in more comfort. The difference in posture, however, should not lead to perceived discomfort and aspects of driving should be considered such as operating the steering wheel, pedals and vision in the mirrors. OBJECTIVE: This study sets out to find out how much postural variation occurs during the driving task and how sensitive is the human body to these changes. METHODS: The first experiment was user evaluation and assessed how and when the changes in seat configuration were noticeable to the human body. The second experiment evaluated the influence of varying inclination of the backrest and the seat pan by the rating of typical aspects of driving. RESULTS: The differences in seat configuration during experiment 1, were so small that there was no consistency in the ratings for the same configuration. The most critical feature that restrains the posture is the location of the rear view mirror. CONCLUSIONS: The range-of-motion is defined as -1° to +1° for the seat pan and 0° to +1.5° for the backrest based on the results of experiment 2 because of the restraints of the driving task. [ABSTRACT FROM AUTHOR]

When traveling by train, passengers are exposed to vibration. A well designed seat will attenuate the vibration path to the person in the frequency region where it is the most perceptible, between 3 and 10 Hz. This paper studies the relationship between posture and the human response to vibration. The pressure on the spinal discs has been measured for different postures and it has been found that sitting in a relaxed posture results in a lower intervertebral discs pressure than standing; however, sitting in a upright posture without a suitable back support causes the greatest loading on the spine. Experiments have been performed to examine the perceived discomfort of sitting in a seat with varying backrest angles. Generally, as the backrest is reclined, the discomfort decreases. It has been found that for a tense posture, both the magnitude and frequency of the resonant peak increase comparated to a relaxed posture. This paper concluded that the seat has a great influence on the posture adopted by the passenger, and that a seat with mechanical damping in the 3 to 10 Hz range and a design that encourages a relaxed posture with a slightly reclined backrest will minimize discomfort. [ABSTRACT FROM AUTHOR]