Measurement and Subjective Evaluation of Vehicle Handling

Human Control of Road Vehicles

“…Changes in understeer steer coefficient from 92 to 195 degreeslg reliably affected the mean-maximum speed achieved in the test. Bergman [53] presented data which show that subjective rating was lower with excessive increase or decrease of understeer far beyond the range employed in passenger car designs.…”

“…It was found that they used a constant maximum yaw rate which was independent of speed for any given deviation angle of turn, provided the lateral acceleration was below 12 ftlsec. 2 Bergman [53] investigated braking while cornering to determine the effect on directional stability. He found that drivers' ratings were correlated with a "normalized understeer angle increment" and that this criterion is a meaningful measure of the ease of vehicle control.…”

Sensitivity of Driver-Vehicle Performance to Vehicle Characteristics Revealed in Open-loop Tests

“…Another steady-state system parameter of great importance is the stability factor K, or the related parameters, characteristic speed U,,, equation (3), and understeerloversteer gradient KO, equation (5). Again, there is some uncertainty as to which specification of understeer is the most meaningful for driver control.…”

“…Similarly, the side-slip velocity response to steering wheel inputs is given by the transfer function However, as will be shown, very little experimental work has been done to investigate the closed-loop effects of sideslip response parameters, despite evidence that sideslipping motions may be an important cue for driver steering control [5,25,45, 531.…”

“…According to Bergman [5], variations of understeer within the range encountered in normal production vehicles do not influence subjective evaluations. Only by modifying vehicles to extremes could he find measurable effects.…”