EPAS prospects, pros and cons

EPAS technology is new to Europe but has been available on small (600 to 800 cc) Japanese cars for more than 10 years. First systems to arrive in Europe were adaptations of Japanese park-assist units, such as the one incorporated in the 1996 Renault Twingo.

Developed in collaboration with the Japanese company Koyo, the Twingo EPAS provides assisted steering up to a speed of 65 km/hr. "EPAS know-how is now being transferred from Japan to France where production of EPAS systems will start within six months," claims Yannick Lacour, director of strategic planning at SMI, the Koyo subsidiary in Irigny (near Lyon, France).

Another Japanese manufacturer bringing EPAS into Europe is NSK. Its systems have been fitted into 1-(liter) Opel Corsas since 1997. NSK EPAS is also likely to be introduced on the 1.2-(liter) version of the Corsa, and is offered as an option on the new Fiat Seicento.

For more powerful vehicles, some manufacturers are starting to develop a hybrid approach to EPAS technology. These are electro-hydraulic steering systems, which use an electric motor to drive the hydraulic pump, rather than driving it off the engine.

As a result, the hydraulic pump runs independently from the engine, and needs only run when power support is required at the steering wheel. It gives a fuel savings of 0.2 litre per 100 km, claims Karl Mauer, Opel spokesman, whose company is adopting a hybrid system on the new Astra being released this year. The suppliers are TRW and Delphi Saginaw.

Many vehicle manufacturers are, however, not satisfied with current EPAS performance. "Right now they don't give the comfort and safety we want to provide our customers with," remarks Marc Boucque, R&D spokesman at PSA. He talks of a "sticking" phenomenon, meaning that the steering wheel does not go naturally back to its original position after it has been turned. However, Boucque expects EPAS performance and cost to reach an acceptable level by 2000 when PSA will incorporate it widely into their models.

Ford, like PSA, is not satisfied with current EPAS performance. "We are not dismissing the technology, but we have evaluated 12 of the systems that are currently being developed or in production and none provided a satisfactory dynamics performance," reports Ulrich Eichhorn, manager, vehicle dynamics, advanced vehicle technology and small and medium car vehicle center, Ford Automotive Operations.

"They feel artificial because they suppress feedback from the road. Vehicle response is not what we would like it to be," he adds. Ford will probably use electro-hydraulic technology as a first step towards EPAS because it works with existing hydraulic systems, Eichhorn indicates.