Patent ID: 7555402

Claim:
A method for determining the angular position of the steering wheel ( 2 ) of an automobile vehicle electric power-assisted steering system, the steering system comprising an assistance electric motor ( 8 ) controlled by an on-board electronic processor ( 10 ), the assistance electric motor ( 8 ) comprising a plurality (n) of stator poles distributed around its circumference, a measurement of the instantaneous angular position (θ) between two successive poles of the assistance electric motor ( 8 ) being carried out by a sensor, notably of the resolver type ( 13 ) or using the Hall effect, characterized in that it consists in determining in which current sector (tr_motor), a sector of the assistance motor ( 8 ) being bounded by two successive poles, the assistance motor ( 8 ) is situated, the passage from one sector to another, preceding or following respectively, being identified when the separation between two measurements from the sensor ( 13 ) of the instantaneous angular position (θ) of the assistance motor ( 8 ) is, respectively, less than a first predetermined value or greater than a second predetermined value; determining a relative angular position (Angle_steer_rel) of the steering wheel ( 2 ), with respect to the assistance motor ( 8 ), as a function of a reduction ratio (reduction_ratio) between the assistance motor ( 8 ) and the steering column ( 3 ), and of a reference instantaneous angular position (θ 0 ) of the assistance motor ( 8 ) within one sector, in particular by the formula: Angle_steer ⁢ _rel = 1 reduction_ratio × ( tr_motor n × 360 + ( θ - θ 0 ) ) identifying a sector, referred to as neutral sector (tr_motor_neutral), in which the assistance motor ( 8 ) is situated when the rotation speeds of the right-hand rear wheel (v rear R) and left-hand rear wheel (v rear L) of the vehicle are equal; determining an angular offset (Angle_offset) of the steering wheel ( 2 ), corresponding to a neutral angular position of the steering wheel, as a function of the current sector (tr_motor), of the neutral sector (tr_motor_neutral), and of the reduction ratio (reduction_ratio) between the assistance motor ( 8 ) and the steering column ( 3 ), in particular by the formula: Angle_Offset = 360 n × ( tr_motor - tr_motor ⁢ _neutral reduction_ratio ) ; determining an absolute angular position (Angle_steer_absolute) of the steering wheel ( 2 ), which is equal to the difference between the relative angular position (Angle_steer_rel) of the steering wheel ( 2 ) and its angular offset (Angle_offset).