THE IMPACT OF NONLINEAR STEERING SYSTEMS ON OBJECTIVE AND SUBJECTIVE STEERING EVALUATION

Traditionally, vehicle steering systems had a linear relation between steering wheel rotation and road wheel angle. Nonlinear steering racks arrived in the last decades of the 20th century with the aim to achieve better parking characteristics. In the current century, the development of variable steering ratios has become more and more important and not only for parking. The aim of these steering systems is to combine a low speed agility increase with safe high speed behaviour. Both mechanical solutions (variable rack) and mechatronic solutions (active front steering) have been implemented in production cars. FEV has investigated the impact of these two approaches on the experienced steering behaviour. Actual production vehicles with both systems have been tested to confirm the targeted improvement of agility whilst maintaining safety at high speed, including the feeling of linearity and transitional behaviour.