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."
So let me get this straight, we introduce steer by wire so we can remove the feel of rough roads etc. but we dial in the feel electronically because that wouldn't be good for the driver, and were saving weight even though we added 3 ECU's AND a clutch to re-engage the traditional steering column if all 3 ECU's die (which will happen every time an alternator dies)
I think some engineers in the automotive industry have lost the plot, They're putting complexity in for the sake of it.
I don't get it. All I see is a riduculously complex and expensive system which the owner has to pay for but adds little or nothing useful to the operation of the vehicle.
In my view, you had redundancy and tactile feedback with a rod that connects to the gear that moves the wheels. How much more elegant, cost effective and reliable can you get than that? Seems the weight issue is a materials question, not motors and redundant computers.
That is 100% correct. In the aerospace industry there is a massive effort to test and qualify all fly by wire systems to prove that they are fully redundent and fail safe. To incorporate this into a car without a mechanical backup will cause a very complex and expesive system. This is why the aircraft that are relatively inexpesive (single engine puddle jumpers) are still cable and pulley. We may see a day when drive by wire is 100% but I beleive it will be in the high end cars where cost is less of an issue.
I'm going to play teh antagonist here. When it comes to driving, feeling the road is much more important to me than a smooth ride. The feel actually helps me know that a tire has a problem before it is a real problem. I get the whole technology thing for the future, but nothing can replace a solid mechanical system. Removing that is like putting a rocket on the road with no breaks. There always seems to be delay in control system response, and that nanosecond of steering response has saved my life. I embrace technology, but I'm not confident that this is the right way to go.
Anyone remember the accelerating Toyotas? I know GM has been working on this for over 20 years. I think it will ultimately come down to consumers and federal mandates (such as CAFE).
The new 787 Dreamliner is entirely electronic. The difference is the rundundant back-ups are not going to exist in the physical sense on cars (weight, weight, weight). So the development in the automobile has to be sensor/control failsafe that stops the vehicle. It is better to get out of the car that is on the side of the road than trying to parachute out of an airplane with type of failsafe!
Today I drive a car with mechanical linkage and electric power boost (by chance, also a Nissan). Nissan propose to give me the same, with an extra sensor and wire to the steering mechanism. The electrical signal will be the primary mechanism, but so what? It doesn't replace the existing linkage. Its extra - extra weight, extra power, extra complexity. What happened to "keep it simple" ? Keeping the mechanical linkage in place as a backup is Nissans' way of saying "we like the new system - but we don't fully trust it"
I think the only down side is the number of automobiles on the road. The chances of the system failing are far greater than with cars. You cannot guarantee that the car is professionally maintained. However, if this system is fool proof, I mean that with masses in mind, then it is the future.
Right, Rob. For now, the clutch is there, but Nissan told us that if the mechanicals were ever removed, its engineers would incorporate a fail-safe sub-system. At this point however, it's not clear how the fail-safe sub-system would work.
Interesting story, Chuck. It seems that the real gain will come when the redundant mechanical steering is eliminated. Yet that means that you wouldn't have steering if the electrical system failed.
You're not alone, Greg. I think most consumers will feel safer knowing the shaft is there, at least until steer-by-wire has a few years of success behind it.
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