Basically, nothing has changed since the birth of the automobile: cars have been steered for more than a century with a steering wheel (or steering wheel) connected to the wheels via a metal column. But a new revolution will change the situation. Marketing of systems fully electronic steering, where the steering wheel no longer has a physical connection with the wheels, is imminent. The advantages are many. The most obvious concerns the disappearance of the steering column, which frees up space on board to reorganize the cabin. This also makes it possible to dispense with a metal element and thus save weight. Above all, this leaves much greater adjustment latitude than a traditional system, while isolating the steering wheel from road vibrations.
Conventional power steering, whether electric or hydraulic, does nothing more than reduce the effort required to turn the steering wheel, variable depending on speed. This greatly facilitates the task in the city, but there is still a physical limit: the gear ratio between the pinion and the rack is fixed. And this one is based on a compromise. At low speed, we would like to have the most direct and most assisted steering possible, so as not to have to “mill” with the steering wheel, for example during a parallel manoeuvre. On the motorway, on the contrary, we prefer a significant reduction, so that the small, imperceptible movements of the hands do not result in deviations from the lane.
There are already tricks to vary the gear ratio
In order to vary the transmission angle depending on the driving situation, there are already several solutions. The simplest is one stand with variable pitch. This type of component, notably used by Volkswagen on their Golf GTI, consists of progressively tighter teeth on the rack as the steering wheel is turned. In short, the response is less lively around the center point, at the low steering angles used at high speed. On the contrary, when you turn the steering wheel, the effect is amplified. This gives a feeling of increased responsiveness in tight turns.
In the house of Ford, it’s an electric motor system with a worm gear mounted on the steering wheel hub which is offered on some high-end models, such as the Edge, S-Max and Galaxy. At low speed, this comes into play at the same time as the driver turns the steering wheel, to reinforce the steering. Which in this precise case corresponds to reducing the perceived reduction angle.
BMW Active Steering