DEVELOPMENT OF CONTINUOUS SUBJECTIVE AND PHYSIOLOGICAL ASSESSMENT TECHNIQUES FOR THE DETERMINATION OF DISCOMFORT AND ACTIVITY- INTERFERENCE IN TRANSPORTATION SYSTEMS

Abstract

The ever expanding. technological growth in modern society has led to increase in movement of people. This has resulted in increased number of people getting affected by whole-body vibrations during transportation. These vibrations are known to have effects such as sensory responses like comfort and discomfort, interference in activities, injuries and health issues. Human response to vibration is very complex and nonlinear. In order to find out the vibration discomfort, the vibrations must be measured, evaluated ' and assessed. The standards provide guidelines for measurement and evaluation of whole-body vibration, although there are some ambiguities related to about the axes which should be used for measurements. Also these standards do not provide exact thresholds for discomfort. Current methods for discomfort assessment involve various psychophysical methods like subjective rating scales, magnitude estimation methods etc. These methods are useful in assessing the discomfort, but they produce discrete measurement data. A continuous assessment method for subjective discomfort and physiological response due to whole-body vibration was developed. Laboratory experiments were conducted to study the effect of vibration magnitude and different feet vibrations on subjective discomfort, heart rate and heart. rate variability using these assessment methods. The three vibration stimuli i.e. car stimulus, train stimulus, and excavator stimulus were replicated on the vibration simulator at magnitude of 0.3 m/s2, 0.55 m/s2, and 0.75 m/s2 respectively. The three vibration conditions at feet were: feet on vibrating platform, feet on foam and feet on stationary platform. The measurement and evaluation was done with 12-axis accelerometer with a real-time data acquisition. The vibration magnitude was found to have a positive effect on discomfort level and partially on heart rate. A regression was done to find out the growth rate of discomfort with increasing vibration magnitude. The value of n was found to be close to unity in all the postures. However there was no significance of vibration magnitude found on heart rate variability. There was also no significant effect either of different vibration input conditions at feet on any of the factors i.e. discomfort, heart rate and heart rate variability.