Motor Driven Power Steering—For the Maximum Steering Sensation in Every Driving Situation

This paper describes the first commercialized motor driven hydraulic power steering system which is installed in Subaru XT from May,1987 in Japan. This electronic-controlled Motor Driven Power Steering (MDPS) has been completed for improvement of the steering sensation and fuel efficiency.

The MDPS system is a speed sensing power steering which produces heavier steering effort depending on the increase of the vehicle speed, Driving situations are automatically divided by the vehicle speed and steering frequency into four modes such as high speed driving, city areas, suburban and winding roads. Power assist can be controlled for the optimum steering sensation in each mode. The motor is not activated for improvement of fuel consumption when steering signals are not input below a given vehicle speed.

Performance data of the steering effort and fuel efficiency on the MDPS system are included and also the specific working fluid, the motor specifications and other components are described in the appropriate section.