A newly introduced comfort indicator was defined as the discomfort criterion (DiC). Based on several real-life driving scenarios and realistic assumptions. This criterion identified the comfort of a vehicle quantitatively, and therefore, it is possible to compare different types of vehicles in terms of ride comfort. The criterion was proposed in accordance with part one of the ISO 2631standard for mechanical vibration and shock evaluation of human exposure to whole-body vibration. Also, road surface conditions were extracted from ISO 8608 for mechanical vibration road surface profiles by applying the power spectral density (PSD) of a specific road class. Knowing that during the ride of a vehicle, occupants are exposed to vibrations from the road surface which causes the feeling of discomfort, reduces working ability, which in the long run can affect health in an adverse manner; a parametric optimization technique was then used to investigate the effects of vibrations on comfort of occupants to maintain oscillations in an acceptable zone in accordance with ISO 2631 standard. In the following, the effectiveness of the proposed measure was investigated throughout the suspension optimization of different vehicle types including electric vehicles which almost doubled the unsprung mass by adding an electric motor to the wheel assembly. In line with this analysis, a spatial oscillatory model of a typical vehicle with eight degrees of freedom was developed and utilized. Then, the root-mean-square value of the weighted vertical acceleration exposure to the driver's seat position was calculated in the range of 1-80 Hz. The exceedance from the reduced comfort limit (in accordance with ISO 2631 standard) and wheel travel of the vehicle were considered as design objectives. Finally, the optimum condition and impact factor of the design variables, i.e. suspension and driver's seat damping coefficients and stiffnesses were investigated. The results of this study showed the effectiveness and convenience of the proposed methodology. Moreover, this study is significant form a boarder perspective as a preliminary framework to develop a vehicle comfort rating system in the near future.
Mr. Milad Abbasi, School of Automotive Engineering, Iran University of Science and Technology, IRAN (ISLAMIC REPUBLIC OF) Mr. Hossein Salmani, School of Automotive Engineering, Iran University of Science and Technology, IRAN (ISLAMIC REPUBLIC OF) Prof. Mohammad Fard, School of Mechanical and Automotive Engineering, RMIT University, AUSTRALIA Prof. Reza Jazar, School of Mechanical and Automotive Engineering, RMIT University, AUSTRALIA