Determination of the absolute angular position of a steering wheel by incremental measurement and measuring the differential speed of the wheels

A method for determining the absolute angular position θ of the steering wheel of a motor vehicle with respect to the chassis of said vehicle,

• said method comprising using a system including:
• a device for incremental measurement of the relative angular position δ of the steering wheel, including:
• an encoder positioned to rotate together with the steering wheel, said encoder including a main multipolar track;
• a fixed sensor arranged with respect to and at a gap distance from the encoder, including at least two sensitive elements positioned with respect to the main track so as to deliver two periodic electrical signals S1, S2, in quadrature, the sensor including a suitable electronic circuit, so as to deliver the relative angular position δ of the steering wheel based on the signals S1, S2;
• a device for measuring the differential speed ΔV/V of the wheels on a same axle;
• a processing device sampling, in a period t, the angular positions δ(ti) and the differential speeds ΔV/V(ti), said device including calculation means for determining, at every tn instant, an estimate θ*(tn) of the absolute angular position θ(tn) according to the differential speed ΔV/V(tn), the average offset(tn) difference between the angular positions θ*(ti) and δ(ti), where i varies from 0 to n;
• and the absolute angular position θ(tn);
• said method further including the following repeated steps:
• measuring the angular position δ(ti) and the differential speed ΔV/V(ti);
• determining an estimate θ*(tn) of the absolute angular position θ(tn) according to the differential speed ΔV/V(tn);
• determining the difference in the average of the vectors {circumflex over (θ)}*(tn)=[θ*(t0), . . . , θ*(tn)] and {circumflex over (δ)}*(tn)=[(t0), . . . , δ(tn)] so as to obtain the average offset(tn) difference;
• determining the absolute angular position θ(tn) by adding the average offset(tn) difference and the angular position δ(tn).