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Driver perception of steering feel

Abstract: Steering feel is optimized at a late stage of vehicle development, using prototype vehicles and expert opinion. An understanding of human perception may assist the development of a good 'feel' earlier in the design process. Three psychophysical experiments have been conducted to advance understanding of factors contributing to the feel of steering systems. The first experiment, which investigated the frames of reference for describing the feel (tic properties) of a steering wheel, indicated that subjects focused on the steady state force that they applied to the wheel rather than the steady state torque, and on the angle that they turned the wheel rather than the displacement of their hands. In a second experiment thresholds for detecting changes in both steady state steering-wheel force and steady state steering-wheel angle were determined as about 15 per cent. The rate of growth in the perception of steady state steeringwheel force and steady state steering-wheel angle were determined using magnitude estimation and magnitude production. It was found that, according to Stevens' power law, the sensation of steady state steeringwheel force increases with a power of 1.39 with increased force, whereas the perception of steady state steeringwheel angle increases with a power of 0.93 with increased steeringwheel angle. The implications for steering systems are discussed steering feel, proprioceptive, haptic feedback INTRODUCTION

Driving a car is a complex task and involves many interactions between the driver and the vehicle through the various controls. Good performance of the system depends on how well a car 1 s able to create the driver's tensions, and how well differ- ences between those in-u-ns and the vehicle's response can be detected the driver. The steering system is one of the primary controls in a car, allowing the driver to control the direction of the vehicle. The steering system not only allows the driver to control the car but also provides the driver with feedback through haptic (i.e. touch) senses, giving cues to the state of the road-tyre interface

Forces originating at the road tyre interface (and related to the road wheel angle, vehicle red, and road adhesion), present themselves at the steering wheel (subject to kinematic losses through the steer-ing system, and subject to various assist methods in steering systems, e.g. hydraulic and electric power assist) where the driver can interact with them and develop an internal model of the steering propertiesand the environment

The relationship between the steering-wheel torque and the steering-wheel angle has been considered a useful means of describing steering feel Various metrics' of the relationship are used to define steering feel, and experiments have found that changing the relation between the steering-wheel force and steering-wheel angle can alter the driving experience. Knowledge of the way in which haptic stimuli at the steering wheel are