After years on the drawing boards, brake-by-wire technology is about to leap from the laboratory onto the road. Three major brake manufacturers confirm that they have received contracts from European automakers to develop brake-by-wire for future vehicles.
Those companies include Robert Bosch GmbH, Continental-Teves AG and Delphi Automotive Systems.
Bosch appears poised to be first in the market with a brake-by-wire system designed for the Mercedes E-class sedan. Production is scheduled for the 2002 model year.
'The Daimler people are gutsy,' said Robert Oswald, chairman of Robert Bosch Corp. 'When they believe in something, they go for it.'
Former BMW AG product chief Wolfgang Reitzle said BMW was working on one as well when he left the company last year. And Delphi Europe President Jose Maria Alapont said his two customers are European - but not General Motors.
A 'pure' electromechanical brake-by-wire system uses electric motors to activate the brake calipers. This eliminates the need for hydraulic cylinders and lines, which are time-consuming to install and fill.
Brake-by-wire simplifies vehicle design and someday may cut costs. However, the first-generation systems will be hybrids, retaining a hydraulic system as a backup.
Regulators will want to be sure that the technology is reliable before they allow a pure electromechanical brake system.
'We're doing the electrohydraulic approach first,' says Robert Rivard, Bosch's vice president of advanced technology development. 'We don't see a migration to electromechanical systems occurring for eight to 10 years.'
However, the complexity of hybrid systems initially will add cost to conventional brakes. For example, Bosch's system adds valves, a sturdy pump motor, a pressure accumulator and a pedal feedback system to the basic brakes.
'Today it's not cost-neutral, so it's a tough sell,' Rivard said. He declined to estimate the extra cost but predicted that Bosch eventually would eliminate the cost penalty.
Automakers will enjoy a quick payoff from brake-by-wire's flexible packaging. A conventional hydraulic master cylinder must be on the firewall near the brake pedal, but an electronic system can be placed anywhere under the hood.
A brake-by-wire system also simplifies vehicle design. Engineers won't have to design different hydraulic components based on vehicle size. One brake system will serve all vehicle models. Eventually, say suppliers, pure electromechanical systems will be housed entirely in the caliper. Suppliers then could design easy-to-assemble corner modules. To connect the modules to the vehicle, workers simply would bolt in the module and plug in power and data cables.
'You wouldn't have to run all those brake lines,' said Mark Depoyster, chief engineer of Delphi Automotive's chassis customer solutions center.
'If you can have steering, braking and even suspension in one module, the packaging and safety benefits become enormous.'
The switch to brake-by-wire also has safety implications. The elimination of the conventional master cylinder may reduce injuries in frontal crashes. The cylinder and its mounting bracket become ramrods during collisions. They can protrude into the cockpit, causing leg injuries.
In the long run, brake-by-wire could be good news for proponents of collision avoidance technology. Brake-by-wire neatly bundles antilock brake and stability control functions into one mechanism.
Engineers foresee the day when the computer will be linked with sensors that detect surrounding vehicles. In emergencies, a collision avoidance system could activate the brakes before the motorist has time to react. However, those benefits still are years away.
Aaron Robinson can be reached at [email protected]