Electronically controlled power steering system

A method for controlling a power steering system of the type used in motor vehicles for steering a pair of dirigible wheels, said method comprising the steps of:

• applying an input torque to a power steering unit by applying a steering torque to a steering wheel coupled thereto;
• generating a mechanically derived steering force in response to said input torque;
• generating a hydraulically derived steering force in response to said input torque for augmenting said mechanically derived steering force;
• summing said mechanically derived steering force and said hydraulically derived steering force to define a total steering force which is applied to the dirigible wheels;
• sensing a first signal indicative of said input torque;
• amplifying and modifying said first signal to generate an output signal which is a function of said input torque applied to said steering wheel;
• applying said output signal to a control valve assembly;
• and
• selectively actuating said control valve assembly in response to said output signal for regulating said hydraulically derived steering force as a function of said input torque.

An electronically controlled power steering system for motor vehicles of the type used for steering dirigible wheels in response to an input torque applied to a steering wheel, comprising:

• mechanical steering gear means coupled to said steering wheel for generating a mechanically derived steering force in response to said input torque;
• a power cylinder coupled to said mechanical steering gear means for producing a hydraulically derived steering force for augmenting said mechanically derived steering force;
• first transducer means for generating a first signal indicative of said input torque applied to said steering wheel;
• control valve means in fluid communication with said power cylinder for generating a differential pressure applied to said power cylinder;
• means for supplying fluid to said control valve means;
• a source of pressurized hydraulic fluid adapted to supply hydraulic fluid to said control valve means;
• signal processing means for generating an output signal in response to said first signal, said signal processing means operable to selectively actuate said control valve means in response to said output signal for selectively regulating said hydraulically derived steering force generated by said power cylinder;
• and
• second transducer means for generating a rate signal indicative of the velocity of an output motion of said mechanical steering gear means, said rate signal being fed back to said signal processing means for selectively modifying said output signal said signal processing means being adapted to amplify and selectively manipulate said first signal such that said output signal is a function of said input torque applied to said steering wheel.