Abstract: A power steering system for a vehicle which has one or more steerable wheels (10) includes a manually operable steering wheel (12), a first angle sensing device (16) connected to the steering wheel (12), a servo motor (13) connected to the steering wheel or wheels (10), associated with the servo motor (13), and a control unit (17) for receiving signals from the first angle sensing device (16) and for energizing the servo motor (13).

Abstract: A power steering system intended for a vehicle having at least one steerable wheel (50) and including an electric servo motor (56), a wheel position related steering control unit (58), and a control unit calibrating device (55,61) for identifying the straight-ahead position of the steerable wheel (50) as the latter is turned within a steering interval defined by a first extreme end position (A) and a second extreme end position (B), wherein the calibrating device comprises a disc shaped element (55) which is rotatable about a central axis (X) in a conjoint relationship with the steerable wheel (50) and provided with a pattern of open and closed portions (64-67,70,71) and a single immobile sensor (61) for producing digital signals in response to its alignment with the open and closed portions (64-67,70,71), wherein a reference point (Y) corresponding to the straight-ahead position of the wheel (50) is defined by the transition from one open portion (64) to one closed portion (65) of the disc shaped element (55