For a century the steering wheel has been bolted, through a column and a shaft, to the wheels on the ground. Turn the wheel and a mechanical linkage turns the tires. Steer-by-wire cuts that physical connection. The wheel becomes an input device; sensors read it, a computer decides, and motors actually turn the wheels. The link is now electronic.
Why bother removing a linkage that has worked for a hundred years? Two reasons. First, packaging: without a steering column you can move the wheel, flatten the dash, even stow the wheel in a future autonomous mode. Second, tunability: steering feel becomes software, so the same car can steer light for parking and firm at highway speed. Those are real benefits, and they are why by-wire keeps showing up on concept cars.
But cut the mechanical link and you create a problem that did not exist before: there is no backup. In a conventional car, if the power steering fails you can still physically turn the wheels, just with more effort. In a pure by-wire system, if the motor or its electronics fail, nothing turns the wheels. That is why redundancy is not a nice-to-have in by-wire — it is the whole engineering problem.
Which is the lens for reading ZF's grant. US12651984B2, “Dual motor drive assembly” (ZF Automotive UK Limited, granted June 9, 2026), carries CPC classes B62D 5/006 and B62D 5/0409 — “power-assisted or power-driven steering” — alongside motor-control class H02P 5/753. A dual-motor assembly is one direct answer to the redundancy requirement: two motors so that if one fails, the other can still steer the car. ZF is a tier-1 steering supplier, and this is the kind of component-level IP that by-wire actually rides on.
Read the CPC, not the buzzword, and the picture sharpens. B62D is the motor-vehicle steering class; a grant landing there with two motors is squarely about the actuator layer of steering, not the cabin-design fantasy that usually sells the concept. The glamorous part of steer-by-wire is the stowable wheel; the part that makes it road-legal is redundant actuation like this.
The takeaway for a careful reader: steer-by-wire's headline is freedom — new layouts, software-defined feel — but its engineering is dominated by the unsexy obligation to never lose steering. When you see a by-wire announcement, the question that separates a shipping system from a show car is “where is the redundancy?” Patents like ZF's dual-motor assembly are where that answer gets built.