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Infiniti first to market with 'Steer-by-Wire'

All-new 2014 Infiniti Q50 sedan offers Direct Adaptive Steering as an option

Published: September 23, 2013, 11:00 AM
Updated: April 29, 2018, 12:07 PM

Automakers have been experimenting with 'steer-by-wire' technology for a couple decades, if not longer. But although the technology has now become well developed, none has taken the final step of bringing it to market. Until now.

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The all-new 2014 Infiniti Q50 sedan is the first volume-production car to offer 'steer-by-wire', called Direct Adaptive Steering in Infiniti marketing speak.

With this system, there is no direct mechanical connection between the steering wheel and the steered wheels (under normal conditions). Rather, the new technology replaces that mechanical connection with electronic signals.

Turning the wheel transmits a signal to an electronic control unit (ECU), which manipulates that signal and sends it on to an electric motor on the steering rack, which actually turns the wheels.

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If that concept sounds a bit scary, consider that the commercial aircraft you've been flying on for decades rely on just such technology. With their 'fly-by-wire systems', there's no mechanical connection between the cockpit controls and the airplane's critical control surfaces.

And just in case, there is still a redundant mechanical connection in the Q50 that will engage instantly and automatically in the event of a primary system failure.

This is far from the first use of 'by-wire' technology in automobiles. Electronic throttle controls have been around for years and are now in almost universal use.

'Brake-by-wire' systems that control hydraulic brake application electronically were also used briefly by Mercedes-Benz – although that technology didn't really catch on.

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But 'steer-by-wire' has taken longer to adopt, perhaps because of concerns over customer acceptance. It's also taken some time to develop the systems so they don't feel totally foreign to drivers.

I first drove an experimental car with a rudimentary version of the technology time about a dozen years ago. It was diabolical – at least in my hands.

At that preliminary stage of development, full travel of the steering wheel was about 15 degrees either way off centre, but that limited motion turned the wheels full lock-to-lock.

Add in the fact of zero steering feedback to provide any sense of feel and I was fortunate to keep the car within the bounds of the empty parking lot where I was driving, let alone trying to keep it within a driving lane.

I've since driven several more developmental iterations of 'steer-by-wire', primarily in a series of General Motors fuel-cell concept vehicles that evolved from the company's 2002 Autonomy concept car.

Key to that concept and its 'skateboard' chassis was the replacement of all conventional mechanical links between the passenger compartment and the chassis – accelerator, brake and steering – with 'by-wire' controls.

As the technology evolved, it became almost indistinguishable in terms of driving feel or sensation from today's conventional steering but GM didn't pursue that pioneering work as far as production. Now Nissan is doing so, by way of its Infiniti brand.

The company says its Direct Adaptive Steering can transmit the driver’s intentions to the wheels faster than a mechanical system.

It also enables four different settings that allow drivers to customize steering effort/response to suit their preference or road conditions. Those settings include, in increasing order of driver engagement: standard/casual; standard/standard; heavy/standard; and heavy/quick.

Standard/standard is the default mode, whenever the car is started, but the setting can be readily changed via a centre-stack touch screen or programmed into a personalization mode that matches one's individual key fob.

One of the primary benefits of the system – the capability that may be most important to its success in the future – is that it enables the use of other new technologies, such as Active Lane Control and lane Departure Prevention, which are precursors on the path to fully autonomous driving.

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I had the opportunity to drive two Q50s with Direct Adaptive Steering recently and can report that the technology is indeed ready for prime time – if the intent is to make 'steer-by-wire' seem indistinguishable from a normal steering system, for most drivers. Which is probably necessary to assure market acceptance.

I suspect that few people are likely to notice anything significantly different from what they're used to, at least in the default mode. Venture into the other modes, however, and they'll definitely feel the differences from the standard settings.

Whether they like what they feel will probably be a matter of personal preference.

Because there is no mechanical connection between the road wheels and the steering wheel, there is, in fact, no real feedback or road feel. It has to be electronically induced.

To that end, sensors in the system determine the lateral forces acting on the wheels and feed those force signals back, suitably modified, to a steering force actuator connected to the steering wheel.

One of the Infiniti engineers' goals in developing the system was to filter out what they consider 'dirty noise' from that feedback – things like road-crown effects or pavement ridges and variations that are normally felt in the steering wheel.

They have achieved that goal. And they've given the Q50 a sensation of feel that is the equal of most of today's sometimes assist-numbed steering systems.

To my admittedly critical hands, however, they haven't yet duplicated that almost subliminal sense of steering feel that defines the very best of the breed and rewards the driver accordingly.

But this is just the beginning.