Technology news: September 2006
Siemens plans to cram everything into wheel hubs
Engineers at Siemens VDO are planning to integrate the drive train, steering, shock absorbers and brakes into the wheels of future cars. They believe that this concept, which they are calling eCorner, will form the basis for "drive-by-wire" cars that will be common within 15 years.
The new system, based on four independent electric wheel hub motors, will replace the conventional suspension, mechanical steering, hydraulic brakes and engines. For drivers, it will mean lower fuel bills, increased safety, and improved reliability, Siemens VDO suggests.
Eliminating the large central engine and the transmission system will also allow new vehicle designs. It will be possible, for example, to park cars sideways using pivoting wheels, or to control the acceleration of each wheel individually for better stability in dangerous situations. Fewer components and elimination of the hydraulic systems will reduce wear and breakdowns, and make servicing easier, Siemens predicts.
The diagram above shows the eCorner`s key components. The hub motor (2) is located inside the wheel rim (1). The electronic wedge brake (3) uses pads driven by electric motors. An active suspension (4) and electronic steering (5) replace conventional hydraulic systems.
"Hybrid drives are only an intermediate step along the path to future propulsion solutions," says Dr Klaus Egger, Siemens VDO Automotive`s group vice-president. "We consider the electric motor to be the actual long-term drive solution for fulfilling the most stringent emission laws of the future."
Compared to today`s petrol and diesel engines which operate with an overall efficiency of less than 50%, the wheel hub motors are expected to operate at efficiencies of up to 96%.
The motors will ensure contact between the wheel and the road, and each wheel could be moved to its own steering angle. During braking, the motors will act as generators, to recover energy and charge the vehicle battery.
The first step towards making the eCorner concept a reality will happen later this decade when electrically driven "electronic wedge brakes" (shown above) start to be used commercially. EWBs will allow each wheel to be decelerated separately and precisely.
Siemens VDO expects all of the component systems except for electronic shock absorbers and electronic steering to be integrated into car wheels within a decade. It adds, however, that the combustion engine won`t disappear for a while.