Steering tasks consisting of steady turns and fast passing manoeuvres were performed by five drivers using an automobile with a variable-steering system. The experiment employed subjective evaluation methods to investigate the influence of (1) steering-force gradient and (2) artificial steering system torques (with the force gradient held fixed) on driver opinion of vehicle handling in the selected manoeuvres. The experiment indicate that both the steering force gradient and the damping of the steering system through its influence on the free control oscillatory mode of motion of the over-all vehicle have a first order effect on driver evaluation of the handling qualities of an automobile. A steering-force gradient of 17-ft-lb/g of lateral acceleration was found to be near optimum for the specific conditions investigated.
Abstract