The first power steering system on a vehicle was apparently installed in 1876 by a man named Fitts, though little else is known about him. In 1903, a separate electric motor was used to assist steering on a Columbia 5-ton truck. Robert E. Twyford included a mechanical power steering mechanism as part of his 1900 patent for a four-wheel drive system.
Francis W. Davis, an engineer at Pierce-Arrow, invented and demonstrated the first practical power steering system in 1926. He then refined the hydraulic-assisted system at General Motors, but the automaker deemed it too expensive to produce. Davis subsequently signed with Bendix, a parts manufacturer, and military needs during World War II for easier steering on heavy vehicles increased the demand for power assistance on armored cars and tank-recovery vehicles for both British and American armies.
Chrysler Corporation introduced the first commercially available passenger car power steering system on the 1951 Chrysler Imperial, named "Hydraguide," based on some of Davis’ expired patents. General Motors followed in 1952 with a power steering system on the Cadillac, utilizing Davis’ earlier work for the company. Charles F. Hammond filed several patents for improvements to power steering with the Canadian Intellectual Property Office in 1958.
Hydraulic power steering systems augment steering effort via a hydraulic cylinder within a servo system. These systems maintain a direct mechanical connection between the steering wheel and the steering linkage, ensuring the vehicle can still be steered manually if the power-steering system fails. One design measures torque applied to the steering wheel using a torsion bar at the lower end of the steering column; the bar's twist controls a valve regulating fluid flow to the cylinder. Hydraulic pumps deliver flow proportional to engine speed, requiring restricting orifices and flow-control valves to prevent excessively fast steering at high engine speeds, alongside pressure relief valves to prevent pressure build-up.
DIRAVI innovated speed-sensitive steering, where force steering the wheels remains constant regardless of road speed. Introduced by Citroën of France, the system uses a hydraulic cylinder to move the wheels in proportion to steering wheel angle, with a separate hydraulic system applying pressure proportional to road speed to return the wheel to centre. This system was known as 'VariPower' in the UK and 'SpeedFeel' in the U.S. when first introduced in the Citroën SM in 1970.
Electro-hydraulic power steering (EHPS) systems use an electric motor to drive the hydraulic pump, rather than a drive belt connected to the engine. In 1965, Ford experimented with a fleet of Mercury Park Lanes equipped with "wrist-twist instant steering," featuring a fast 15:1 gear ratio and an electric hydraulic pump. Subaru fitted the XT6 with a Cybrid adaptive electro-hydraulic system in 1988, adjusting assistance based on vehicle speed. Toyota introduced electro-hydraulic power steering on its second-generation MR2 in 1990, avoiding the need for hydraulic lines running from the engine. Volkswagen produced the Golf Mk3 Ecomatic in 1994 with an electric pump, allowing the power steering to operate even with the engine stopped to save fuel.
Electric power steering (EPS) or motor-driven power steering (MDPS) replaces the hydraulic system with an electric motor and electronic control unit (ECU). Sensors detect steering column position and torque, and the ECU applies assistive torque via the motor, connected to the steering gear or column. This allows engineers to tailor steering response and add driver assistance features like lane assist and wind drift correction. In 1986, NSK put the world’s first electric power steering system for battery forklifts into practical use, and in 1988, Koyo Seiko and NSK co-developed a column system for minicars in Japan. The Suzuki Cervo featured the first electric power steering system for mass-produced passenger cars in 1988. Honda introduced the first electric power variable gear ratio steering (VGS) system on the S2000 Type V in 2000, and Toyota followed with the "Variable Gear Ratio Steering" (VGRS) system on the Lexus LX 470 and Landcruiser Cygnus in 2002.
Electric systems offer fuel efficiency advantages by eliminating the continuously running belt-driven hydraulic pump, and simplify manufacturing and maintenance by removing several hydraulic hoses. They can also instantly vary torque assist levels with electronic stability control. In 2023, Lexus introduced the RZ 450e featuring a steer-by-wire system, eliminating the mechanical linkage between the steering wheel and wheels.