New cars are giving drivers new information on what they are doing with the assistance of new high-speed processors, lots of sensors, and redundant data to make sure the right information is being seen. These include advanced driver-assist radar systems, and they are all part of an informational network. While active safety systems are good in defensive roles and warning systems, they are now making their way into proactive roles and enhancing the driver's skills and intentions.
These systems have made their way into adaptive cruise control systems, automated parking systems, and even "launch mode" for accelerated shifting on high-performance cars. One of the new systems making its way from the racing and performance fields is four-wheel steering.
The benefits of four-wheel steering are obvious: more control in turns, a tighter drive path, reduced response time, and less vehicle slide from the non-powered wheels. The challenge has been the ability and cost of getting the control to the wheels with a mechanical system. The new solutions solve this by moving to a "drive-by-wire" (DBW) system, which decouples the actual driver motions from a direct mechanical coupling to an electronic system that drives actuators.
New systems like those from Nissan (see figure below) use dual actuators controlled from a central ECU to help guide the wheel control for both the front and rear of the car. This system even improves control over traditional four-wheel steering systems. The dynamic of these new systems is the full independent control of speed, direction, and traction control through the high-speed sensor networks.
With this feedback, the full steering solution works well and with control at all speeds. The historic systems worked for parking systems and freeway speed situations, but they provided a more challenging driving environment at in-town start-and-stop driving. The new "smart" systems not only adjust for speed and road conditions, but can vary the amount of "steer" available by the wheels as the situation needs.
Since the DBW systems are a "portable design" -- meaning they are not a custom mechanical design for each car, but can be a standardized component system over a vehicle product line -- they are making their way from premium cars to mid-range and entry level in the near future. This will bring tighter parking and turning radiuses, improved control in bad weather, higher maneuverability and control in evasive action for accident avoidance, and a more directed driving path for the vehicle.
The issue will be the learning curve and the driver's acceptance of the loss of the mechanical control and feel of the road, along with a reliance on needing power to the vehicle to enable the steering function. Current cars will move (being pushed or pulled) and steer without power. It is unclear if the default on these DBW vehicles will be to have a separate high-voltage power system to allow for the actuator control, or a mechanical bypass to traditional steering in times of non-powered use.
This article was originally published on EDN.