It's not surprising that advanced "by-wire" technologies have started to make their way into ordinary cars. These systems promise improvements in fuel economy, safety, handling, and design flexibility. "Complete longitudinal control is available today," notes Rainer Kallenbach, general manager of semiconductors and control systems for Bosch. As examples, he cites systems that accelerate, shift, and brake by wire. Next up, and perhaps the most difficult, are systems that steer by wire. "Lateral control of the vehicle needs more time," Kallenbach says.
Many technical hurdles still stand in the way of steer-by-wire systems—particularly ones without a mechanical back-up. During a panel discussion at the recent SAE World Congress, Kallenbach and engineering leaders from other companies working on steer-by-wire systems outlined a technology wish list. These technologies will have to be:
The reliability of embedded systems from other industries just won't do. "Drive-by-wire systems will have to prove that they are fail-safe," says Chuck Heine, president of technology development and diversified products for Dana Corp. This need for reliability will play out in the need for better data transmission networks and energy sources, according to Kallenbach. "Today's supplies aren't reliable enough without a mechanical or hybrid backup," he says.
More intelligent actuators—with on-board sensors, electronics, and sub-system software—will also be needed. Some of these are in the works. Dana, for example, has developed actuators for steer-by-wire. An electrohydraulic power steering actuator will appear at the end of this year on a new hybrid truck, Heine reports. Dana also has out an electric power steering actuator for steering-assist applications—a more transitional implementation than full-fledged steer-by-wire. It consists of a brushless dc motor with an electronics control module and integrated position sensor.
One big challenge in creating any by-wire system is the tasks associated with the embedded system development, especially the software component. "Software is going to be our major challenge," says Craig Stephens, Ford Motor Company's manager of powertrain controls research and advanced engineering. "One thing we badly need are techniques to bridge the gap between functional requirements and finished designs."
Stephens argues that the adoption of industry-wide standards could help ease the development of embedded software. Kallenbach agrees, calling for more open system architectures. Also important will be improved CAD tools, according to Don Winter, director of Network Centric Operations for Boeing Phantom Works. He gave an outsider's perspective on automotive by-wire technologies from his years of work on fly-by-wire systems, and he notes that Boeing had to create its own computer-aided design tools. "Embedded systems are still underserved by the tools industry," he says.