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BWI is refining a brake-by-wire system that eliminates the hydraulic connection between the driver’s pedal and the individual wheel brakes, providing what the company claims will be an improved level of active safety achievable through faster, more controllable responses.
Anti-lock, traction control, stability control and collision-avoidance functions can all be integrated seamlessly and more effectively using an all-electronic system, it said.
At the heart of the system is its electrically operated ball-screw driven brake caliper that uses a low inertia motor being driven from a standard 14-volt supply. Electric caliper actuation is the key to integrating the range of active safety features since braking is available and adjustable at all times in a transparent manner independent of driver input.
“BWI is continuing to develop brake by-wire technology in order to help the industry’s drive to produce safer, greener vehicles at affordable prices,” said Alan Lee, global director, sales and engineering: brake systems, for BWI. “Having produced several generations and a number of prototype electric calipers and tested them in a range of vehicles under a wide variety of conditions, confidence in the technology is growing.”
A pragmatic approach to the introduction of brake-by-wire will most likely involve the application of electric calipers on the rear brakes only, said BWI. This could simplify vehicle design changes, removing the need to work around the constraints of the braking system hydraulic hardware. Brake-by-wire could also allow vehicle assembly to be re-examined. It enables brakes to become a bolt-on and plug-in assembly operation without the hydraulic brake line and mechanical parking brake connections. It could also eliminate the vacuum booster and integration of brake modulation into the calipers.
“Carmakers usually prefer incremental changes in technology to major architecture changes,” said Lee. “Electric calipers are not yet in the market from any supplier but increases in electric park brake penetration are leading toward the full electrification of the rear caliper.”
On hybrid vehicle applications brake-by-wire supports energy recovery, responding to total braking demand by blending the instantaneous potential for regenerative braking with the additional friction braking required. “Electric brakes are still a few years away from volume production,” said Lee. “But as demand for powertrains with energy recovery systems grows, and increasingly crowded road space requires better safety measures, the electronic integration of all the systems that aid the driver to control the vehicle is both desirable and inevitable.”
Brake-by-wire systems must still overcome many hurdles before reaching volume production, not least legislative restrictions and the cost of manufacture. “As we progress, we must keep government regulators fully aware of the pace of change and participate in the adjustment of various regulations to embrace the new technology,” said Lee. “We have to show the legislators that fail-safe electronic processes can replace fail-safe mechanical ones.”
BWI said its research and investment into brake-by-wire has been considerable. The company employs 300 engineers and technicians on brake engineering and holds over 800 brake patents.