Steer-By-Wire to Reach Production Vehicles

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."