Is Drive By Wire the Future?
21st Nov 2013
It’s not news that cars are becoming more and more technologically advanced every year. The discerning Kahn customer’s car will have satnav, traction control, power-assisted steering, automatic electronic suspension adjustment, climate control and various other driver aids to comfort, safety and quality of ride.
Japanese car maker Infinti, the luxury division of Nissan, have gone a step further by introducing Direct Adaptive Steering into the higher-end models of the Q50. This comes after 15 years of development.
“DAS replaces the mechanical linkage with an electronic linkage,” says chassis engineer, Takeshi Kimura. “We have a steering rack with two motors, which we call steering angle actuators. There is a steering column with one motor, called the steering force actuator. When the driver turns the steering wheel, an ECU calculates what angle the front wheels should turn to and the steering angle actuators then turn the wheels. The system replicates steering feel by decreasing resistance as grip levels change. It’s much better than electric power steering.”
Kimura went on to stress that speed of response is probably the most significant advantage of the new system: “On a conventional system the torsional compliance of the steering shaft and of the steering gear mounts means there is a delay between turning the steering wheel and the front wheels actually turning,” he explains. “The DAS system doesn’t have that compliance, so the response is much faster.”
The system has fuel efficiency benefits over hydraulic-based power steering systems and can reduce road noise from uneven surfaces. It also means lane departure warnings can be implemented.
At the moment, there is no weight-saving, since a clutch-actuated mechanical rack-and-pinion system is fitted as a failsafe. If anything, the extra electronics make the system a weight penalty. In time Kimura hopes to eliminate the failsafe, which will increase car safety by removing the large metal pin pointing at the driver’s chest.
The main drawback of DAS is the feel. You, as the driver, have no direct contact with the road. According to Dan Prosser at Pistonheads who has driven the car, the programming creates an inconsistency in the weighting, which changes while you’re cornering, so you never really fully trust that the feedback you’re getting is accurate.
Infiniti, though, are pressing ahead, as they believe it is the future of driving.
“As engineers we want to use the system on all of our cars. We are discussing the implementation of DAS right now,” Kimura confirmed. “Other manufacturers have looked at steer-by-wire, but they gave up because of the difficulties. After driving our car I think it is possible they will be encouraged to develop their own systems.”
There are obvious advantages to Infiniti’s DAS system. For one thing, from the point of view of Kahn Design, with placing of the steering wheel no longer being dictated by the position of the steering column, it will allow a total restyle of the interior, possibly even doing away with the steering wheel completely.
Interesting times, indeed.