Method to objectively evaluate subjective ratings of ride comfort

Abstract

Research on human vibration is concerned with the response of the human body to the amounts, frequencies, directions, and exposure times of exerted forces. Processes have been developed to standardize these factors, and the typical examples are ISO 2631-1 and BS 6841, which are related to whole-body vibration and ISO 5349-1, which is related to hand-transmitted vibration. Because ride comfort and human vibration are, in some sense, a mental and environmental problem that is influenced by psychological effects, human sensation in relation to vibration has both intra- and inter-subject variability. When the ride comfort index is defined as a physical quantity and is written as an equation, it is related to acceleration using both the r.m.s. (root mean square) and r.m.q. (root mean quadrature) as descriptors. In this study, two passenger cars were driven at several speeds over several road profiles to evaluate the subjective rating of ride comfort. To measure the acceleration signals that are transmitted to the feet, hip, back and hand, four tri-axial translational accelerometers and one tri-axial gyro sensor were mounted on the steering wheel and on the passenger seat and floor, respectively. Correlations were performed to determine the relationship between the measured accelerations and the subjective ratings of 4 expert drivers using a psychophysical power law. Regression models correlating the 5 subjective assessments were developed. Subjective ratings of the comfort at the hip had the highest correlation with the objective measurements.