Audi A8 - Dynamic all-wheel steering. Boundaries pushed: dynamic all-wheel steering There is another world first in the suspension of the new A8: dynamic all-wheel steering. It, too, is controlled by the electronic suspension platform (ESP).
Audi Q7 all-wheel steering Audi offers another groundbreaking innovation as an option: all-wheel steering. A steering system with an electric spindle drive turns the rear wheels inward by as much as five degrees depending on the situation.
Electric Power Steering To provide steering assistance, an electric motor mounted to the side of the rack housing drives a ball-screw mechanism via a toothed rubber belt. The screw engages a spiral cut in the outside of the steering rack. A torque sensor attached to the pinion shaft signals a control computer when to provide assistance.
A planetary gearbox determined rear-steering degree based on steering-wheel angle. At small angles, the rear wheels would steer up to 1.5 degrees in phase with the fronts, but at larger angles (more than 246 degrees of steering rotation), the rear wheels would steer up to 5.3 degrees opposite the fronts, trimming the turning radius about 10 percent.
A steering system that is designed to operate with power assistance isn’t meant to be driven without that power, and because of steering gear ratios, other geometrical considerations, and drag in the system, it can be surprisingly hard to turn the wheel when this happens.
Rear wheel steering tends to be unstable because in turns the steering geometry changes hence decreasing the turn radius (over steer), rather than increase it (under steer). Rear wheel steering is meant for slower vehicles that need high-maneuverability in tight spaces, e.g. fork lifts.
Steer by wire European Commissioner Günther Oettinger trying Uniti steer-by-wire system at the 2016 CeBit Edition. This kind of system will provide steering control to a car with fewer mechanical components/linkages between the steering wheel and the wheels.