Prediction of discomfort due to transient whole body vibrations

Sammanfattning: This Licentiate is about Whole Body Vibrations and focuses on transient vibrations with human's discomfort and motion assessment. Whole Body Vibrations occurs when a body is in contact with a vibrating surface. Whole Body Vibrations is a major problem in terrain vehicle, which affects both the physiological and psychological health and discomfort. The first study, Paper A, focus on the prediction of vibration discomfort based on r.m.s.-values in z-direction of seat. In the case of individual results, the correlation coefficient was 0.54. Based on averages for each test condition, the correlation coefficient was 0.93. Study in Paper B focus on the prediction of vibration discomfort and perceived motions. By analysis of vibration values in one-third octave bands of x-direction in the top of the seat backrest, pitch motion and vertical motions in seat, pitch alone with variable length was found to give best correlation with the vector sum of perceived motions (r=0.677). Surprisingly, one-third-octave band higher than 50Hz give a high contribution to the prediction of perceived motions. One of the background variables, "Length of driver", was found to have a statistically significant effect on perceived motions. Tall driver perceived less motion than short drivers. In Paper C, focus on evaluating the effect of two seat design (sliding and fixed) in minimizing the discomfort from transient vibrations. Results showed that sliding seat is superior in attenuating vibration that contains transient vibration in horizontal direction. Sliding seat was perceived to give less overall and low back discomfort compared to fixed seat.