With the development of the vehicle industry and the innovation of technology, driving experience is improving in all aspects. Volvo is more and more focusing on improving the comfort of driving. Part of this is to minimize squeaks and rattle (S&R) from vehicle seats. A physical measurement method was studied from component level in this thesis. The communication with the supplier has helped to better understand the definition and measurement method of play. Based on the previous work from Volvo and the supplier, a new improved algorithm has been developed to suit current production demands in this thesis work. A Graphical User Interface (GUI) has been finished for general engineers. The Study and exploration of a FEM simulation method make it possible to measure play in an economical way in the future.

In recent years increased emphasis has been placed on improving seat comfort in automobiles. This is partly due to research showing that prolonged driving is associated with increased risk of musculoskeletal disorders, but largely because driver comfort is now viewed as an increasingly important aspect of the competitive marketing of vehicles. Driving is firmly cemented as a major part of most people s daily life across the world and people are now spending more time in their vehicles than ever before. As urban congestion continues to rise, commuting distances and durations will progressively increase, subjecting drivers to the risks of long duration driving more often. Consequently the automotive industry has invested in designing seats that perform better under increased usage durations and ergonomics has played a vital role in the design of new seats. However, the ability to design a successful seat relies heavily on the capacity to accurately evaluate the comfort of a vehicle seat and one major issue that has been highlighted with the current state of automotive ergonomics research is the standardisation of comfort evaluation techniques. This research aimed to tackle these issues by investigating the effects of long duration driving on discomfort and the range factors associated with driver discomfort. Furthermore, the ultimate goal of this research was develop and evaluate a novel objective measure of driver discomfort that focused on driver seat fidgets and movements (SFMs) with the aim of standardising discomfort evaluation within the automotive industry. Three laboratory studies and one field observation were conducted to address these aims whereby subjective and objective evaluations of discomfort were conducted during long term driving (ranging from 60 - 140 minutes). The results determined that a measure of driver SFMs can be effectively implemented into long duration driving trials to evaluate the effects of long term driving and vibration exposure on driver discomfort and subsequently used to make accurate predictions of overall discomfort. Large positive correlations have been determined between measures of SFMs and subjective ratings of overall discomfort (r2 > 0.9, P < 0.05) and the SFM method has been successfully repeated under a range of driving conditions. Driver seat fidget and movement (SFM) frequency is shown to significantly increase congruently with subjective ratings over the duration of a long term drive as drivers seek to cope with increased discomfort. It is proposed that drivers will record movements in the vehicle seat when discomfort reaches a threshold that is consciously or unconsciously perceived and as the duration of driving accrues, drivers will reach this threshold with increased frequency. A measure of both SFM frequency and total accumulative SFMs have been shown to accurately predict discomfort ratings and provides the basis for discomfort evaluations to be made via remote monitoring, removing the need for subjective assessment. During a long term drive, there becomes a point upon which improvements in seat design become ineffective as extended duration driving will result in discomfort regardless of how well the seat has been designed. It was shown that drivers will move in the vehicle seat to cope with increased discomfort and in addition, another method of combatting the negative effects of long term driving was investigated. Subjective and objective evaluation determined that breaks from driving will reduce discomfort both immediately and upon completion of a long term drive. Furthermore, these benefits were increased when drivers left the vehicle seat as discomfort was reset when drivers took a 10 minute walk. Walking during a break from driving can be considered the ultimate SFM. Drivers are recommended to plan breaks from driving when conducting a long duration journey in order to minimise discomfort and when taking a break, drivers should take a walk rather than remain seated in the vehicle.