- The Washington Times - Friday, December 28, 2001

The idea of eliminating hydraulic components from a car's power steering system has been tantalizing automotive engineers for years. Hydraulic components are heavy, take up too much space, and cost too much. Now, thanks to modern technology, an alternative is on the market.
The Saturn VUE introduces the world's first application of an Electric Power Steering system in a sport utility vehicle. The EPS system allows easy maneuvering and parking around town, while consuming less fuel than traditional hydraulic systems. Fuel efficiency is improved because no engine power is needed to drive a hydraulic pump. While there is an electrical load on the generator, it is almost negligible in the straight-ahead position in which most driving is done.
In contrast, hydraulic power steering systems still consume considerable power in the straight-ahead driving mode, because the engine is still powering the hydraulic pump. Engineers at Delphi Automotive Systems, the manufacturer of the VUE system, claim their EPS system can result in fuel efficiencies of 1.2 mpg over a traditional hydraulic system.
In addition to fuel economy, other benefits include packaging and performance. Eliminating the hydraulic pump on the engine and the hoses that run to the rack-and-pinion gear cleans up the under-hood environment. On the performance front, the electric control unit can be programmed for just about any desired steering characteristics.
Sensors measure vehicle speed and driver torque (or effort) on the steering wheel. Signals from these sensors are fed into an electronic control module that determines the direction and amount of steering assist. The controller generates a command to the assist motor mounted next to the steering column. Algorithms programmed into the controller make it possible to provide more assist at low speeds for easy parking maneuvers. As road speed rises, the assistance gradually tapers off. However, during a high-speed, rapid-steering maneuver, such as emergency avoidance, the system's torque sensor automatically adjusts assistance so the driver doesn't perceive an undesirable steering effort.
The steering ratio is variable throughout the entire lock-to-lock turning range. A slow on-center ratio was selected to give the VUE optimal steering stability when the wheel is in the center position, and a faster ratio past the center makes it easier to maneuver into tight parking spaces. A side benefit is an improvement in dependability and safety with power steering available even when the engine is off.
Electric steering isn't entirely new. Acura's NSX and the Honda Insight use electric steering for some of the same reasons. Both were designed to be very light vehicles, so they benefit from the weight savings made possible by electric components. And both are compact designs with no room under the hood for old-fashioned hardware. But the compelling reason for electric steering in any small vehicle is fuel economy.
The advent of electric steering didn't happen all at once. Several cars, such as the Mercedes-Benz A-Class and the Mini Cooper, use a hybrid system known as Electro Hydraulic Power Steering. Eliminating belts, pulleys and all direct connection to the engine, EHPS combines an electric motor, pump, electronic control module, and reservoir into a single unit that links to a conventional rack and pinion unit to provide hydraulic power only when the driver needs it.
According to John Plant, president and CEO of TRW Chassis Systems, demand is expected to continue to grow for electric steering technology, eventually increasing to an estimated one out of every two cars built by the year 2010. You can bet that suppliers like Delphi Automotive Systems, Siemens Automotive, and TRW will be scrambling for a share of the market.
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