Abstract
KEYWORDS- Steering feel, vehicle handling, subjective, objective, correlation
The steering feel and handling characteristics of a vehicle are determining factors regarding vehicle safety and the overall enjoyment of the driving experience. Time-consuming and expensive development is required by the vehicle manufacturer before these qualities can be achieved.
Due to a lack of reliable links between subjective evaluation and objective measurements, the tuning process still relies primarily on subjective evaluation by test drivers. In order to improve the understanding and consequently prediction of steering feel and vehicle handling in the development process, the BMW Group set up a research project in cooperation with the University of Bath involving the measurement and subjective evaluation of over twenty cars from four different vehicle segments.
This paper focuses on the development of a methodology to establish a successful correlation between subjective evaluations and objective measurements. In order to obtain consistent subjective evaluations, a new questionnaire has been formulated and with the use of experienced test drivers, reliable subjective evaluations have been achieved. To improve the basis for objective subjective correlation, a new mapping method for the subjective evaluation has been developed.
The quality of the attained measurements has been very high due to the exclusive use of a steering robot in combination with open loop driving manoeuvres. Automated analysis algorithms have also been presented, which ensure efficient and consistent data processing to identify high quality objective parameters from the measurements.
Linear and multi linear correlation methods have been used to establish reliable links between the measurements and the subjective evaluations. Example results are shown to describe steering feel and vehicle handling characteristics such as steering, centring, response etc...
The steering torque gradient and the vehicle response described by lateral acceleration or yaw rate gradient at low steering wheel angles have been found to be key parameters in defining the on-centre steering feel.