Autonomous cars have many hurdles to clear before reaching
consumers, but they're coming. Nissan, Volvo and Mercedes Benz have pledged to
bring self-driving cars to showrooms by 2020. This year, Nissan's Infiniti Q50
luxury sedan debuted one of the biggest steps yet towards that goal: the first
consumer steer-by-wire system.
Another major function of the Direct Adaptive Steering is
the newly developed straight-line stability system. If the vehicle’s line of
travel deviates from a straight path, the Direct Adaptive Steering enhances the
car’s handling characteristics by producing fractional sensations of resistance
as feedback from the steering, helping the driver keep a straight line of
travel and reducing the need for course corrections in a smooth and natural
way. The feedback is so subtle that a driver may not notice it.
Direct adaptive steering bypasses the mechanical connection between the steering wheel and the wheels that meet the road. Sensors measure how a driver turns the wheel and send that data through an electronic controller to actuators, which, in turn, pivot the steering rack. (For safety, two backup controllers provide redundancy.) Because there’s no physical link between the road and the steering wheel, drivers don’t feel jarring bumps or vibrations, but the system does electrically simulate natural steering resistance. Computers vary steering ratio and power assist for easier low-speed maneuvers and high-speed stability.
