Investigation of bus users’ motion comfort due to wind and bridge motion excitations

Abstract

This paper is based on a project in the 2023 ”Automotive Engineering Project” course atChalmers University of Technology. As a part of a large-scale project to reduce travel times,a floating bridge is planned to be built over Bjørnafjorden on the west coast of Norway. The planned floating bridge is prone to be sensitive to environmental factors (e.g. wind andwaves). Previous papers have studied the lateral stability of a bus riding over the bridge, and the Norwegian Public Roads Administration now sought an analysis of how riding over the bridge would affect bus passengers in terms of comfort and motion sickness. An existing 8 DOF bus model was extended to 13 DOF by adding a bus driver, and three passengers and also accounting for pitch motion. The model was simulated in Simulink. Accelerations from 8 axes for each bus occupant were retrieved and then weighted according to weighting filters from the ISO 2631-1. By using the mentioned ISO standard, bus users’ comfort could be assessed by comparison of bus occupants’ acceleration limits. Motion sickness was assessed numerically by the Motion Sickness Dose Value equation given in ISO 2631-1, however, it is a highly subjective illness.

With the 1- and 2-year storm conditions and the bus model, ride comfort and motion sickness levels were assessed. According to the received results from the simulations, it could be seen that the key contributing factors to the ride comfort were vertical and lateral accelerations. It could also be concluded that the wind forces acting on the vehicle affected the ride comfort to a great extent. The seat position and the travelling speed were also big contributors to the ride comfort. Increasing speed and a seat position away from the bus’ centre of gravity had a negative impact on comfort. From a motion sickness perspective, the motions in the lower frequency range and accumulative travelling time were the main contributors. Travelling at a slower speed would negatively affect the Motion Sickness Dose Value, due to increased travelling time with motions at the low-frequency responses from the bus and bridge (e.g. wave load, current, wind excitations).