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Hybrid Brake-Throughs

Ever looked under the hood of a hybrid vehicle?

Ever looked under the hood of a hybrid vehicle? All those wires, hoses and metal bits take up a vast amount of real estate. With underhood space at a premium, you’d think automakers would embrace any technology that both saves weight and reduces the number of parts. At least that’s what the folks at TRW Automotive (www.trwauto.com) are hoping will take place. TRW has developed two advanced regenerative braking technologies that do just that: Slip Control Boost (SCB) and Active Hydraulic Braking (AHB). SCB is a fully-integrated stability and brake actuation system that replaces the current boosters, master cylinders and vacuum pumps with an electro-hydraulic control unit and brake pedal simulator with integral dual master cylinder that supplies brake pressure.

“This is an integrated device, meaning that you have both a boost and slip control function, all integrated into one,” said Dan Milot, TRW’s chief engineer, new products-North America. “And by removing the booster, you save space. This provides flexibility in terms of the additional space available under the hood.” Another key benefit is weight savings provided by the reduction in the overall number of parts when compared to a traditional system, along with maximum energy recovery through regenerative braking. According to Phil Cunningham, director of Chassis Product Planning, the regenernative function will be imperceptible to the vehicle operator. “One thing you don’t want is the driver to feel the switching between the regenerative braking mode and conventional braking mode and this system does that,” he says. TRW already has signed a contract with a U.S. domestic OEM to supply the SCB system for an upcoming hybrid vehicle due on the market in the 2008 model year.

For those automakers who already have an electronic stability control system supplier, TRW has its AHB system. This works in conjunction with any currently available ESC system, and provides a single full-functionality electro-hydraulic braking solution that can be used across multiple vehicle platforms and powertrain systems, including both conventional and hybrid applications. “What you have is a boost element integrated with the master cylinder that is packaged with a standalone vehicle stability system that can apply brake pressure autonomously,” says Milot. However, getting OEMs to ante up for the AHB system may be a challenge due to the extra cost involved, especially for non-hybrid vehicles. Since AHB requires complex collision mitigation systems to achieve full benefits, it is unlikely the technology will find mass applications anytime soon. That means prices for electronic stability control, anti-lock brakes, and radar or lidar-based collision warning systems will have to drop to bring the combined price to an acceptable level, a process that may take a few more years. “The two technologies together will have to get deployed on vehicles, therefore it will be pulled by the technologies that support it,” Cunningham said. The cost challenges are the reason TRW has set a later launch date for the AHB system. It is expected to arrive on a model year ’09 vehicle.—KMK