Taking a page from the world of aviation, Nissan Motor Co. plans to enter the "by-wire" world and control the steering of a future Infiniti vehicle with electronic signals.
The decision to bring steer-by-wire to a production vehicle is a major one for the automobile industry because it lays the foundation for eventual elimination of the mechanical components that now connect the driver to a vehicle's tires.
"There are a lot of advantages to this," Infiniti spokesman Kyle Bazemore told Design News. "It enhances the driving experience. And in the future, after consumer acceptance of the technology, we could theoretically do away with the mechanicals and save the weight."
Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's "steering feel."
The next-generation steering system, as Nissan calls it, works by endowing the steering wheel with sensors that read the desired steering angle. Data from the sensors is sent to one of three electronic control units (ECUs), which activate electric motors on the vehicle's steering rack. In contrast, conventional steering uses a direct mechanical connection to the rack-and-pinion.
In truth, the new Nissan system won't eliminate the mechanical connection to the driver. Instead, it will use the mechanical connection as a redundant system, only in cases of extreme emergency. If, for example, a power supply conks out or all of the ECUs fail, it will employ a back-up clutch to mechanically connect the steering wheel to the tires. "The clutch is disengaged 999,999 times out of a million," Bazemore told us. "But the steering shaft is still there, just in case."
Nissan said steer-by-wire will enhance the driving experience. When it reaches the market late next year, it will eliminate some of the vibration from rough road surfaces and it will minutely adjust tire angles to compensate for crosswinds and sloped surfaces. At the same time, it will enable drivers to "feel" the road. Grip information, such as slipperiness, will be transferred back to a steering force actuator that will allow the steering wheel to retain some of its original feel. "Theoretically, you could have no steering feel at all, but that would not be good for drivers," Bazemore said. "That's why we dialed some -- but not all -- of the steering feel back into the system."
When I was in college, one the professors was working with Saginaw Steering Gear to put steer by wire on cars back in the early 90's. People wondered how it would all work.
Why is it car makers do not understand that buyers don't want to eliminate the mechanical systems. They don't want the accelerator, steering, or brakes to be fly by wire. If you actually told customers the truth, they would refuse to buy any of the cars with these systems. Andt that is because we all know these systems are bound to fail eventually, so are unacceptible in a car.
Didn't Nissan also give us the one big button to both start the engine and to stop it? Or at least go along with those who started that fad? Since they demonstrated poor judgement by doing that, why should I believe that their drive by wire is any smarter? An electrically assisted power steering system would be different, and they have been around in various applications since around 1980, or thereabouts.
Don't compare this idea with aircraft fly-by-wire systems because there is no comparison. The number one directive for aviation systems is safety, followed by longevity of service, also called reliability. The number one directive in the automotive industry is PROFIT from initial sales, and next is cheapness to manufacture. We all know that it is true, at least those with any automotive engineering experience. Aside from that, only qualified people are legally allowed to service aircraft, while anybody who can grasp a wrench is allowed to service cars.
In addition, as pointed out already, how can we expect that a cheapo electronic controller in an environment nastier than the navy salt spray test, will be more reliable than the present power steering systems. Ask your self: "When was the last time that you heard about a power steering system failing"? And when the do fail it is usually the loss of assistance rather than a loss of steering control. While that failure mode may make driving difficult for the weak and feeble, it is merely quite inconvenient for most of us.
When it comes to making it happen without a mechanical back-up, you can count me as one of those skeptical customers, ChasChas. Obviously, though, Nissan agrees with you, not me. Here's what they told me: "The mechanicals are there for driver confidence. In reality, it doesn't need to be there. But in the future, after consumer acceptance of this, the mechanicals could go away, saving us the extra weight." If I fully understood how the back-up system would work in the absence of the mechanicals, I might feel more confident. But they're not explaining that yet.
Soooo... You compare 2000 microscopic surface mount components some of which contain a million transistors with 100 mechanical components (guestimate) and say that the electronic version is simpler because the 2000 parts are in only THREE boxes.
I LOVE the Infinity styling but I think they have lost their minds in Tokyo.
Note to Nissan: Give the stylists a raise with the money saved by firing the guys that came up with this Idea.
The article suggests that S-B-W needs a lot of electrical power. If the end goal is improved fuel economy, a comparison of power required by S-B-W verus hydraulically boosed power steering would be interesting, maybe HP imposed at the crankshaft output. The comparison could include effects of weight of the system components but I speculate that ends up being a minor effect.
From a FMEA perspective there are two requirements. The first is to get to the side of the road safely (high severity). The second is to be able to drive maybe an hour home, to a dealer, or to a town (low-high severity depending on the situation). If the vehicle charging system fails, it sounds like the battery can't support S-B-W for more than a few minutes. So the mechanical backup will always be necessary unless being stranded at the roadside is acceptable from a safety and marketing perspective.
"Big, Bulky, and complex"? I think not. The complexity is in the electronics, not the mechanicals. And aircraft have multiple backup systems in their fly by wire systems. I don't see that happening in automobiles unless you want a price tag similar to a 747.
Not necessarily. We build airplanes today that are completely dependent on fly-by-wire systems, and would fall right out of the air if those computers were to fail. And making those systems "fail safe" is essentially a solved problem.
On a normal car, the steering column is a major structural limiting factor, driving a large number of constraints for the surrounding vehicle. And it's a big, bulky, complex assembly. Electrically driven steering would make the steering system more modular, more flexible in physical layout, and allow things that are currently not practical, like swapable bodies on common frames, or handing the steering wheel to the passenger without having to pull over or swap seats (anyone remember the GM Hy-X?).
Over the past few decades, we've been steadily finding ways to move complexity from mechanicals to electronics, software, and firmware. It's been demonstrated that this can be done while also increasing reliability and decreasing cost. There's no reason to assume that automobiles are an exception to this.
That having been said, I don't think I'll be lining up to buy the first model year with drive-by-wire steering. :)
God forbid that we get "Windows" for Cars. To reboot the system you would have to turn on and hold the wipers and lights while beeping the horn with your nose!
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