Driver Preferences of Steering Characteristics

Abstract: The future of vehicle steering systems lies within by-wire technology. With by-wire technology mechanical or hydraulic systems are replaced by electronic systems. Removal of the steering column and possibly other linkage and gears yields vast potential of further improvement of performance, comfort and safety. Steer-by-wire technology also enables the manufacturer to tailor the steering feel to better suit the individual drivers’ need and preference. Since a driver gains critical information about the vehicle from feedback through the steering wheel, steering feel will play a very important part in consumer acceptance of steer-by-wire systems. It will also be possible to customize steering characteristics to the individual driver.This thesis presents a methodology for investigating steering characteristics through analysis of simulator experiments and to find the impact of specific steering characteristics on drivers of varying skill. There are many key aspects to consider when designing simulator experiments. A validated vehicle model is required. Evaluation criteria need to be well defined as well as concise and simple. The utilized scenario has to be able to capture the selected evaluation criteria. Recruitment of test subjects should represent the target population. How to utilize the available time in the simulator most effectively and how to analyze the results are also important. In this work three studies are performed. Paper A investigates how steering gear ratio and steering wheel effort of a passenger car affect preferences of high and low mileage drivers. Paper B is an extended study of Paper A, where the resolution is higher, speed dependence is investigated and performance of the drivers is also evaluated. In Paper C the impact of four important steering system characteristics on driver performance and preference is evaluated.The major conclusions drawn from this work are that variation of steering gear ratio has considerable impact on perceived steering feel and manoeuvrability as well as on driver performance. Variation in steering wheel effort affect perceived steering feel and stability, but no significant influence is detected in perceived manoeuvrability or driver performance. There are distinguishable differences in preferences of the investigated evaluation criteria between driver categories of varying skill. However, general trends of the preferences for the categories are fairly similar. Low skilled drivers prefer lower effort and higher ratio than high skilled drivers, especially at the highest investigated speed, 100 km/h.The developed methodology for performing simulator experiments to evaluate steering characteristics has proven satisfactory through findings of three different studies. This work also shows that there are several important steering characteristics that need to be considered when designing steering systems, particularly steering systems with by-wire applications and especially considering drivers of varying skill.