Power steering is a system for reducing the steering effort on cars by using an external power source to assist in turning the wheels. Power steering was invented in the 1920s by Francis W. Davis and George Jessup in Waltham, Massachusetts. Chrysler Corporation introduced the first commercially avaliable power steering system on the 1951 Chrysler Imperial under the name Hydraguide.
Hydraulic systems
Most power steering systems work by using a belt driven pump to provide hydraulic pressure to the system.
Electro-hydraulic systems
So called "hybrid" systems use the same hydraulic assist technology as standard systems, with the hydraulic pressure being provided by an electric motor instead of a belt driven one.
Electric systems
More modern systems, such as those found on the Acura NSX, use completely electric components. Sensors detect the motion and torque of the steering collumn and a computer applies assistive power via electric motors. This allows varying amounts of assistance to be applied depending on driving conditions.
