In Situ Measurement of Discomfort Curves for Seated Subjects in a Car on the Four-Post Rig

The aim of this study is to measure and quantify perceived intensity of discomfort due to vibration in a vehicle in situ considering complete vehicle dynamic behaviour. The shaker table based discomfort curves or the road test results may not accurately and universally indicate the true level of human discomfort in a vehicle. A new experimental method, using a seated human in a car on the four-post rig simulator, is proposed to quantify discomfort. The intensity of perception to vibration decreased with decreasing input and increasing frequency; the rate of change is different from the published literature; the difference is large for angular modes of inputs. Vehicle dynamic response is used to inform and analyse the results. The repeatability of the method and the fact that they are in situ measurements may eventually help reduce reliance on the road tests. Furthermore, discomfort curves obtained, subsequently, can be used in predictive models. 1. Introduction One of the measures of vehicle competitiveness is the vehicle ride comfort. The manufacturers allocate significant resources in order to improve the performance by making appropriate vehicle design refinements. The requirements which are contradictory often result in a compromised solution. The variables involved in the multidisciplinary design are many. One such variable is the human perception of vehicle vibration, which significantly depends on the vibratory excitation spectrum and the duration of exposure. The vibratory inputs, often correlated and model specific, are dependent on the vehicle dynamics and the road inputs. Furthermore, the feeling of discomfort may depend on the system surrounding the occupant-seat combination. All these complexities make the design for good ride comfort performance, in general, very difficult to achieve. Often prototype based experimental optimization approaches are used by the industry, which are inefficient and costly and may not be repeatable. Ideally, it is desirable to have predictive models which, however, require the knowledge of the relation between the vehicular vibration stimulus and the intensity of perceived discomfort. Considerable literature is available on quantification of vibration perception based on idealized excitation. It is not known how well these results relate to in situ perception. The current study aims to measure and quantify perceived intensity of discomfort due to vibration in a vehicle, considering complete dynamic behaviour of the vehicle and, eventually, generating in situ measured discomfort curves which can be compared with