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Infiniti is First With Steer-by-Wire Technology

August 29, 2013

For a variety of reasons, automobile engineers have long dreamed of eliminating the steering column. Steering mechanisms have always been a major constraint in the packaging of the front end, the underhood components and the dashboard, and the column used to be a safety hazard in a frontal impact. And more fundamentally, because the column provides a fixed mechanical link between the steering wheel in the cabin and the front wheels on the road, there is very little any programmed electronic stability system can do to intervene in the mechanism and rectify the mistakes of a rash or unskilled driver in an emergency situation.

The appeal of a non-mechanical steering system is clear. With a “by-wire” arrangement, the vehicle can be made more compact, more responsive and safer, the steering wheel can be placed wherever it is most convenient or comfortable for the driver, and electronic systems can easily take control whenever required. Yet, these advantages are up against two formidable concerns. First, drivers accustomed to the feeling of security that comes with a direct mechanical link to the wheels fear having no control in the event of an electronic system failure. Secondly, for many drivers the feedback transmitted back up the system to the steering wheel is valuable in the assessment of road conditions and driving the vehicle in a skillful manner. A third anxiety is the uncertain legal position over type approval of a vehicle with a vital safety function accomplished purely electronically.

No steer-by-wire production vehicle has so far been launched, perhaps because of such concerns. Automakers such as BMW and Audi now offer steering systems with variable ratios and assistance maps, but none has yet dared to dispense with the direct mechanical link to the wheels. Until now.

Formula 1 triple world champion Sebastian Vettel and the Infiniti Q50

Infiniti, the premium brand of the Renault-Nissan Alliance, claims its new Q50 mid-size sedan will be the first vehicle to benefit from steer-by-wire technology. Direct Adaptive Steering (DAS), says the company, will “allow the person behind the wheel to choose how that wheel feels in their hands.” To reinforce the credibility of the system, Infiniti says Formula 1 triple world champion Sebastian Vettel was involved in fine-tuning and approving DAS at Infiniti’s proving ground in Japan.

DAS operates on the basic principle that electronic systems work faster than mechanical ones, eliminating mechanical losses which – Infiniti claims − dull the responses of conventional steering. Vibration at the steering wheel is also eliminated, says the company. The system electronically transfers the driver’s movement of the steering wheel to a high-response actuator that drives the steering rack. From the rack onward, the mechanism uses conventional geometry. However, the controllers linking the steering wheel and the actuator are triplicated, for security. And, for absolute security a conventional column system is also present, although it is declutched under normal conditions so that it does not corrupt the response of the electronic system.

The fact that the information flowing between the steering wheel and the road wheels is transferred electronically rather than mechanically means that it can be processed, analyzed, reshaped and, if necessary, overlaid with extra inputs from safety and emergency systems. It also means that everything about the steering, from its weight to its speed of response, can be electronically set. For example, the vehicle’s Drive Mode Selector screen includes a steering menu where the driver can “mix and match” effort and response to suit his or her preferences. Up to four pre-set modes are also available, giving users the ability to switch between, for instance, light and easy steering for maneuvering in a parking lot and a fast-acting wheel for fun driving on twisting roads.

The system’s safety benefits include the ability to automatically compensate for external factors such as road surface cambers, side winds and perhaps even an under-inflated tire. DAS is also able to implement cameras for assisting drivers to stay in-lane.

What Infiniti does not explain is the mechanism by which DAS manages to engineer in what it claims is “the level of feedback that is central to every Infiniti’s performance feel.” Cars that please sports enthusiasts are often characterized by responsive handling and a strong feeling of two-way communication with the road via the steering system. No technical description can possibly predict how satisfying a next-generation steering system such as DAS will prove out on the road. It will take a full test of the Q50 to find out whether Infiniti has indeed succeeded in its bid to change the way we steer our cars.

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© 2013, The Lubrizol Corporation



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