RDS uses a hydraulic pump/motor mounted axially in the driveline.
We reported last fall that Ford and Eaton were developing a hydraulic-boost system for light and medium trucks (see “Getting a boost from hydraulics,” CCJ, Sept. 2002, page 70). Now we have learned that Australia-based Permo-Drive has undertaken a similar effort. Called the Regenerative Drive System (RDS), it works very much like the Ford/Eaton system, consisting of a hydraulic pump/ motor, mounted axially in the driveline; two accumulator/ storage tanks – one for high-pressure fluid and one for low – and a controller.
When an RDS-equipped vehicle is braked, the pump/motor becomes a driveshaft-powered pump, forcing low-pressure fluid into the high-pressure accumulator. Because this process absorbs energy, it slows the vehicle.
When it’s time to go, a valve directs high-pressure fluid to the pump/motor, which goes into motor-mode and adds energy to the driveshaft. This helps the vehicle accelerate more quickly, while increasing fuel economy.
Two additional benefits, according to Paul Chandler, vice president of Permo-Drive’s North American operations, are reduced exhaust emissions and reduced brake maintenance.
Permo-Drive expects to make RDS available for all classes of vehicles, because “hydraulics are scaleable,” says Chandler. Moreover, the company plans to offer a kit to retrofit the system to existing vehicles.
Last October, Permo-Drive signed a cooperative research and development agreement with the U.S. Army’s National Automotive Center to evaluate hybrid, hydraulic driveline systems for both military and commercial applications.
“Look for RDS to start appearing on military vehicles around 2005,” says Chandler, “and in the mainstream about six months to a year after that.”