The influence of steering wheel size when tuning power assistance

This paper describes how steering assistance should scale with steering wheel size. A method has been developed to scale complete torque felt by the driver, both for continuous and discontinuous feedback. This was used in an experiment with 17 subjects all driving a truck with three differently sized steering wheels. The test took place on a handling track at 45–90 km/h. Continuous feedback was evaluated subjectively; discontinuous feedback by measuring angular response. Results show that torque feedback should decrease as steering wheel size decreases. A rule of thumb is to keep driver force level constant to maintain perceived handling and comfort. This also maintained the average steering wheel angle change response to discontinuous assistance. Furthermore large variance in angular response was observed. The direction, measured 0.25 s after start of a pulse, was the same as that of the pulse applied in 88% of the recordings