METHOD FOR IDENTIFYING THE EDGES ON A CAMSHAFT TARGET

摘要

Process for identifying edges on a camshaft target (30) having a plurality of teeth on the periphery thereof, the plurality of teeth forming a series of M edges when the camshaft rotates through one revolution, the process including the following steps:
calculating, for each of the M edges, the characteristic:;CP(j)=[∑i=1NP(j-i+1)+∑i=3N4N-1P(j-i)∑i=N3N-1P(j-i)]N≥1;P(i) denoting the angular distance between the edge i and the preceding edge,
during the movement of the camshaft target, calculating, during an edge detection, an index:;CT(k)=[∑i=1NT(k-i+1)+∑i=3N4N-1T(k-i)∑i=N3N-1T(k-i)]N≥1;T(i) denoting the time elapsed since the appearance of the edge i−1 to the edge i,
comparing the index CT(k) with each of the CP(j),determining the position of the camshaft.

主权项

1. A process for identifying edges on a camshaft target (30) of an internal combustion engine rotating in a normal direction of rotation and controlled by a control unit (40), said camshaft target (30) having a plurality of teeth on the periphery thereof, the plurality of teeth forming, for a position sensor (20) facing said teeth, a series of M significant edges when the camshaft rotates through one revolution, the process comprising the following steps:
a) calculating, for each of the M significant edges, a characteristic relating to the position of the edges preceding said edge in accordance with the normal direction of rotation, said characteristic being defined by the formulaCP(j)=[∑i=1NP(j-i+1)+∑i=3N4N-1P(j-i)∑i=N3N-1P(j-i)]N≥1  P(i) denoting the angular distance between the significant edge i and the preceding edge, and storing at least these M values CP(j), j ranging from 1 to M, in a memory of the control unit (40), b) defining a sub-list of significant edges and initializing this sub-list with all significant edges, c) during the movement of the camshaft target (30), calculating as soon as possible, during a significant edge detection, an index relating to the time intervals elapsed since the preceding edges, by the formula:CT(k)=[∑i=1NT(k-i+1)+∑i=3N4N-1T(k-i)∑i=N3N-1T(k-i)]N≥1  T(i) denoting the time elapsed since the appearance of the edge i−1 until the edge i, d) comparing the index CT(k) with each of the intervals INT(j) defined by[CP(j)Coeff,Coeff×CP(j)]  and eliminating from the sub-list the edges j for which the index CT(k) is outside the interval INT(j), where Coeff is a margin coefficient, e) awaiting the appearance of a new significant edge, replacing each edge j in the sub-list by its immediate successor j+1 modulo M, then repeating steps c) to d) until at most one edge is obtained in the sub-list in step d), f) identifying the position of the camshaft once a single edge has been obtained in the sub-list.