About Fly-By-Wire Steering, A Recent Automotive Industry Advancement
Back in the 1950s, many aviation contractors were experimenting with ways to control larger aircraft that did not need the long metal control cables that traveled all the way from the cockpit back to flight surfaces, such as rudders and flaps. A far better system would be to have a pedal, for example, send a signal to a motor that moved the rudders or flaps. This would allow a pilot to move huge control surfaces easily. Although acceptance came slowly, after several years, fly-by-wire became the way that modern aircrafts were all designed. You might be guessing already that the term "Fly-By-Wire" comes from the aviation industry!
Back in the day, cars had metal throttle cables that ran right from the gas pedal to the engine throttle. These are gone now as gas pedals send electric signals to motors that control the engine's throttle assembly. However, electronic throttles are everywhere these days, and this is because of the "Fly-By-Wire" concept!
Steering systems would be the next application to go fly-by-wire, one would think, but they haven't for reasons that don't have to do with safety but rather acceptance. Basically, most drivers are concerned when they hear that the steering wheel isn't actually connected directly to the front wheels by a metal shaft. Even modern day "power-assist" steering systems are physically connected. If the assist part fails, you may still steer your vehicle because your steering wheel connects directly to your front tires. It's just a little difficult to do.
But a newly-available steer-by-wire (SBW) system sort of eliminates the mechanical shaft. Long term, they are almost definitely going to be the technology of choice, and this is why: for safety, it comes with a "fail-safe clutch" in its metal steering column. In typical driving situations, this clutch is disengaged, but if one of the three steering control units "suspects" a fault, the clutch snaps shut and the steering behaves as your usual, electrically assisted rack-and-pinion system. The clutch engages when the engine shuts off, too, so if one of the first SBW-equipped cars doesn't start, the owner can still steer the vehicle while pushing it.
There are significant benefits to this new SBW system: Steer-by-wire erases steering system tactile feedback. If you hit a pothole, for example, you won't feel it in your steering wheel. No wiggle, no shimmy, not even a bump. Steering kickback, a common mid-corner occurrence on imperfect pavement, is also non-existent with this system. A SBW column can vary the steering ratio as well during use, whereas conventional racks have fixed variability. Increased safety is a possible benefit.
While SBW increases driver's comfort, SBW's steering feedback redefines what the "feel" of a steering wheel should be like. There have been acceptance factor issues as more and more manufacturers have gone the SBW route and it will remain to be seen if this is a problem with short term acceptance.
Thank you very much to the sales team at Reedman-Toll Nissan of North Bethesda, MD, for chatting with us about the benefits that steer-by-wire systems can provide!
Image Source: wired.com