

In the next 12 months, Infiniti, a Nissan brand, will deliver steer-by-wire cars; cars that employ an electronic, not mechanical, connection between the steering wheel and the front wheels. There will also be a camera-based straight-line stability system to help keep the car dead-center in the lane, effectively the next step in lane departure warning and lane keep assist. The Infinitis will have backup mechanical steering to avoid steer-into-ditch moments should steer-by-wire go haywire. Infiniti says the system allows for faster driver inputs and better road surface feedback, although it also says the system “insulates the vehicle from unnecessary road-generated disturbances.” That terminology may give pause to serious drivers who don’t like the lack of road feel from some current power steering systems.

For more than a century, the steering wheel has been connected by a long shaft to a gear in the front of the car that turned the wheels left and right. As cars get heavier, power-assisted steering evolved, first hydraulically and then electrically assisted power steering. Most cars sold in the past generation have power steering. Electrical power steering (EPS) is gaining favor because it’s more compact and works with hybrids or stop-start cars when the engine isn’t running. But it’s still assisting the steering effort of a mechanical linkage. In cars, the Infiniti steer-by-wire concept breaks new ground because the driver’s wheel motions are transmitted electronically to the front wheels. Infiniti calls it “independent control steering technology” rather than steer-by-wire.

According to Nissan, the parent company of the Infiniti luxury brand, the steer-by-wire system employs multiple electronic control units (Nissan doesn’t say how many) and if the primary ECU malfunctions, another ECU takes over. “In extreme circumstances such as the power supply being disrupted,” Nissan says, “the backup clutch will act to connect the steering wheel and wheels mechanically.” On aircraft, once they go fully electronic (aka fly-by-wire), they remove the heavy cables or hydraulic lines that run the length of the plane (after doing a lot of testing). For now, Nissan is going belt-and-suspenders.

The control wires in a Boeing 727, before fly-by-wire was implemented

Nissan and Infiniti cite lots of advantages. The system sends driver inputs more quickly to the road wheels more quickly (Nissan says). Nissan also says steer-by-wire “increases the direct driving performance feel by quickly and intelligently communicating road surface feedback to the driver.” Nissan says the system “insulates the vehicle from unnecessary road-generated disturbances to deliver only the necessary performance feel to the driver.” It gives the example of minor ridges or furrows in the road that can be handled by the car automatically and the driver no longer has to make multiple adjustments or grip the wheel so tightly. Driving enthusiasts may be skeptical at first because power steering, especially EPS, can mask road feel. A good driver might notice slide-inducing gravel in a corner from the steering feel.

Camera-based straight-line stability system

Hand-in-hand with steer-by-wire comes a steering-assist camera mounted in the rear-view mirror cluster (only pointing forward), the same as the location for cameras that serve as a lane departure warning system (LDW) or lane keep assist systems that also nudge the car back into lane. What Infiniti is talking about here is keeping the car centered in the lane all the time, not correcting only when the car drifts across the lane. With ECUs controlling the steering rather than a mechanical linkage, it’s easier to make adjustments. Infiniti notes, quite correctly, that this could be a real benefit on road trips: “By reducing the frequency of detailed steering input adjustments, which are a cause of fatigue on long drives, the driver’s workload is greatly reduced.”

A simple, mechanical (not steer-by-wire) steering systemInfiniti hasn’t announced which models get steer-by-wire first, only that it will happen “on select Infiniti models on sale within one year.” Over time, steer-by-wire will make it easier to center the car in the driving lane; possibly swerve to avoid potential hazards, obviously in concert with blind spot warnings so you don’t avoid one accident and cause another; and ultimately as a component of future self-driving cars. With electronic steering, it would be a simple matter to change the steering ratio for slow speed maneuvering: If a car needs four steering wheel turns to go full left to full right, it could be modified to go two turns lock-to-lock in parking lots and six turns lock-to-lock on straight highways.

Steer-by-wire is part of a larger grouping of drive-by-wire (DBW or DxW) technologies such as throttle-by-wire and brake-by-wire. In each case, the mechanical linkage is replaced by a smaller, lighter, more reliable (except when it all goes wrong) electronic control. Throttle-by-wire is the least difficult to implement and least problematic if there are problems, and steer-by-wire is the most difficult, whether to implement technically or to defend in court.

Infiniti with an asterisk notes its steer-by-wire system is an industry first, the asterisks being matters of terminology: “world-first development of an independent control steering technology that controls tire and steering angles inputs independently” and “world-first development of an accurate tracing technology that enables a driver to continue driving as planned in the lane with small steering angle adjustments (depending on road conditions).” In practical terms, except for prototypes and show cars, this will be the first wide-scale implementation of steer-by-wire. May the force be with you.

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