Human exposure to vehicular vibration can cause sensations (e.g. physical discomfort or annoyance), health issues and safety problems. In industry, several measurement methods have been proposed to improve ride quality and increase the drivers’ or passengers’ expectations in terms of comfort. The measurement and evaluation methods of quantifying whole-body vibration exposure in relation to human comfort and vibration perception are defined by the International Standard ISO 2631-1. This is the most used standard which provides Health guidance caution zones for risk assessment. The human discomfort threshold limits are not given in this standard. Human discomfort, in general, is defined by measurements based on a shaker table and seat combination. These results when used for “in vehicle situations” may not accurately indicate the level of human discomfort in a vehicle. In this thesis, a seated human’s discomfort is quantified in heave, pitch and roll motions using a four-post rig simulator in order to determine a comfort metric. The quantifying and assessment of discomfort are studied in two categories, which are vehicle dynamics with road inputs, and the human response with human perception to vibration. Comfort/discomfort is a subjective variable; therefore the in-situ experiments were performed based on an objective measurement method with a subjective judgement method. The main novel contribution of this thesis is that subjective and dynamic responses of twenty four seated subjects, in a car on the four post rig excitation, exposed to vertical sinusoidal vibration at five magnitudes in heave, pitch and roll motions were taken at Oxford Brookes University. The physical properties of participants such as age, height, and weight were recorded because human sensitivity, perception and threshold levels may be person dependent. The subjective assessment data was developed based on the response of twenty-four seated subjects to vibration in a car on the four post rig which makes this thesis unique in terms of quantifying of human feeling. From the experimental data (RMS acceleration and subjective assessment), a discomfort metric was developed in terms of the cause-effect relations between the road and the human body. Based on the analysis and results, it was observed that the sensitivity to acceleration decreased with decreasing amplitude and increasing frequency. This discomfort metric was applied to a developed analytical model to predict the vibration response. A predictive integrated vehicle-seat-human model was developed to characterize the biodynamic response behaviour of a seated human subject and analyse the influence of vibration transmitted on the human body segments. The transmissibility results from an integrated model and in-situ discomfort curve measurements were combined to develop a human body discomfort model in a car. The discomfort index curves were predicted by combining the modelling study and the experimental results for heave, pitch and roll modes.
Ibicek, T
Faculty of Technology, Design and EnvironmentDepartment of Mechanical Engineering and Mathematical Sciences
Year: 2012
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