Picture this: you're driving down the highway on a gray and rainy day when you hit a puddle and start to skid, veering into the adjacent lane. Automatically, the brakes on each wheel adjust to stabilize the car as you and the car steer in the direction of the skid. Dampers and roll sensors feed information back to a computer that returns optimum damping levels for the car's suspension, helping to stabilize the car and keep the wheels firmly on the pavement.
Better fuel economy, too, can be attributed in part to the car's by-wire electronics, specifically throttle-by-wire. An electronically controlled throttle can maintain optimal airflows for all driving conditions. One controlled by your foot on the accelerator, however, doesn't deliver the same performance.
Carmakers, according to Joe Ziomek of JFZ & Associates, an automotive consulting firm in Islamorada, Fla., see reductions in the number of traffic fatalities and injuries with the use of by-wire systems. Industry experts believe such systems may prevent up to 30 percent of traffic fatalities, the same percentage as airbags.
Someday, by-wire systems will automatically steer the car and reduce its speed from 80 km/h to 40 km/h to 0 km/h without specific action on the driver's part. Instead, input will come from a built-in positioning system, road-condition sensors, and nearby cars to determine the safest path for vehicles likely to collide. The necessary calculations will be made by powerful on-board computers. But that is a decade or more away and requires more computing and control than by-wire systems are initially expected to have.
"Fundamentally, though," said Brian Murray, manager of safety systems engineering for Delphi Automotive Systems Corp., Saginaw, Mich., "this is what [near-term] by-wire systems are all about--putting a computer between the driver and whatever is being controlled with the intention of making the driver or the car's performance better, not [taking complete control of the car from] the driver."
The basic concept of by-wire sounds simple enough: replace the car's mechanically linked hydraulic systems--steering and braking, for example--with electronic ones. By-wire systems began to be installed well over a decade ago, first in military and then in commercial aircraft.
In a "true" by-wire system, there would be no hydraulic backup to the electronic system; therein lies a cause for carmakers' concern. Drivers count on the fact that the brakes and steering work when and how they are supposed to, thanks to hydraulic systems. Carmakers just don't know how drivers will react to the wires, computers, and microcontrollers. They see drivers asking "Will I need to reboot my brakes instead of adding brake fluid?" and walking away from by-wire cars.
Another basic hurdle automakers face is that no industrywide standard exists for a by-wire system. There is no set specification for the electronic control of a safety-critical system like braking or steering. While automakers agree that having such a standard will help both in winning public confidence in by-wire systems and in designing and implementing such systems, they have yet to agree on one. What's more, this standard needs to work for all safety-critical functions under the by-wire umbrella [see illustration] like steer-by-wire (for front and rear steer), throttle-by-wire, and brake-by-wire.