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Is ‘steer-by-wire’ ready for prime time?

Published November 1, 2012

Almost every aspect of the modern automobile has changed dramatically over its 125-plus year history. But one of the most basic systems has remained relatively unchanged in principle — until now.

In the very first cars, steering was accomplished by the driver turning a steering tiller or wheel, which was connected to a steering shaft, which was connected to some sort of steering gear, which was connected to linkages that turned the wheels.

And so it remains today.

Of course the geometry has changed over the years, as have the types of steering gear, and various forms of power assist have been added.

But there still remains a mechanical connection all the way through the system from the steering wheel to the vehicle’s front wheels.

Nissan is about to change that paradigm.

The Japanese company has announced plans to introduce a “drive-by-wire” steering system on select Infiniti models within a year, although it doesn’t say in what markets.

Nissan calls the concept “Independent Control Steering Technology,” which allows “independent control of a vehicle’s tire angle and steering inputs.”

In other words, there’s no direct mechanical connection between the steering wheel and the steered wheels (in normal conditions). Rather the new technology replaces that mechanical connection with electronic signals.

When the driver turns the wheel, it sends a signal to an electronic control unit (ECU). The ECU then manipulates the signal and sends it to an electric motor that turn the wheels. (There may be more than one motor.)

If that concept sounds a bit scary, consider that both military and commercial aircraft have been relying on just such technology for decades. There’s no mechanical connection between the cockpit controls and the airplane’s critical control surfaces.

In the automotive context, almost all new vehicles now on the market use electronic throttle controls — not cables, as used in the past.

The idea of extending that principle to the steering system isn’t new. It gained prominence a decade ago when General Motors revealed its fuel cell-powered Autonomy concept car at the 2002 North American International Auto Show in Detroit.

Key to that concept was the replacement of all conventional mechanical links between the passenger compartment and the chassis — accelerator, brake and steering — with “by-wire” controls.

GM built several working prototypes to demonstrate both the fuel cell and by-wire technologies in the ensuing years and I’ve had the opportunity to drive most of them.

Initially, the steer-by-wire systems were diabolical, at least in my hands, but by the last iteration that I tried — the GM Sequel in 2006 — it seemed little different in function and feel from a conventional steering system.

GM didn’t pursue that pioneering work as far as production.

Now Nissan is doing so. The company says its version of this next-generation technology transmits the driver’s intentions to the wheels even faster than a mechanical system and actually increases steering feel.

The system is also said to insulate the vehicle from unnecessary road-generated disturbances — for example, on a road with minor ridges or furrows, the driver no longer has to grip the steering wheel tightly and make detailed adjustments to keep on the intended path.

To go with it, Nissan has developed a world-first camera-based straight-line stability system that is said to enhance on-centre stability.

If the vehicle direction changes due to road surface or crosswinds, the system acts to offset the effect of those conditions, minimizing the need for corrective input from the driver and thus reducing fatigue, particularly on long drives

It uses a camera mounted above the rearview mirror to analyze the road ahead and detect changes in the vehicle’s direction; then it transmits this information to multiple electronic control units. If a discrepancy occurs, it acts to reduce the discrepancy by minutely changing the steering direction.

But what about reliability? What if there’s an electronic malfunction?

That possibility is always a concern with drive-by-wire systems, but Nissan says it duplicates aircraft practice with the use of multiple ECUs. In the event that a single ECU malfunctions, another will instantly take control.

Plus, there’s another level of redundant backup for extreme circumstances, such as disruption of the power supply. There’s still a conventional steering shaft in the car that can be automatically connected via a clutch in the event of by-wire system failure.

It appears that Nissan has covered all the bases, particularly in terms of safety. And the idea of enhanced on-centre stability, in these days of minimal steering feel and feedback, sounds very attractive.

But I’ll reserve final judgment until I’ve driven it for myself.

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