Method for identifying the edges on a camshaft target
View Patent ↗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 = 1 N P ( j - i + 1 ) + ∑ i = 3 N 4 N - 1 P ( j - i ) ∑ i = N 3 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 = 1 N T ( k - i + 1 ) + ∑ i = 3 N 4 N - 1 T ( k - i ) ∑ i = N 3 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.
1. A process for identifying edges on a camshaft target of an internal combustion engine rotating in a normal direction of rotation and controlled by a control unit, said camshaft target having a plurality of teeth on the periphery thereof, the plurality of teeth forming, for a position sensor facing said teeth, a series of significant edges when the camshaft rotates through one revolution, the significant edges being edges that are processed by identification logic, the process comprising the following steps:
a) calculating, for each of the significant edges, a characteristic relating to a position of the significant edges preceding said significant edge in accordance with the normal direction of rotation, said characteristic being defined by formula
CP
(
j
)
=
[
∑
i
=
1
N
P
(
j
-
i
+
1
)
+
∑
i
=
3
N
4
N
-
1
P
(
j
-
i
)
∑
i
=
N
3
N
-
1
P
(
j
-
i
)
]
N
≥
1
P(i) denoting the angular distance between the significant edge i and the preceding significant edge on the camshaft,
and storing at least these values CP(j), j ranging from 1 to the number of the significant edges, in a memory of the control unit,
b) defining a sub-list of significant edges and initializing the sub-list with all significant edges,
c) during the movement of the camshaft target, calculating, during a significant edge detection, an index relating to time intervals elapsed since the preceding significant edges, by the formula:
CT
(
k
)
=
[
∑
i
=
1
N
T
(
k
-
i
+
1
)
+
∑
i
=
3
N
4
N
-
1
T
(
k
-
i
)
∑
i
=
N
3
N
-
1
T
(
k
-
i
)
]
N
≥
1
T(i) denoting time elapsed since an appearance of significant edge i−1 until the significant edge i,
d) comparing the index CT(k) with each of intervals INT(j) defined by
[
CP
(
j
)
Coeff
,
Coeff
×
CP
(
j
)
]
and eliminating from the sub-list the significant edges j for which the index CT(k) is outside the interval INT(j), where Coeff is a margin coefficient of uncertainty,
e) awaiting an appearance of a new significant edge, replacing each edge j in the sub-list by its immediate successor j+1 modulo, then repeating steps c) to d) until at most one significant edge is obtained in the sub-list in step d),
f) identifying the position of the camshaft once a single significant edge has been obtained in the sub-list.
2. The process as claimed in claim 1 , wherein N=1, and the expressions of CP(j) and CT(k) become:
CP
(
j
)
=
[
P
(
j
)
+
P
(
j
-
3
)
P
(
j
-
2
)
+
P
(
j
-
1
)
]
N
=
1
and
and
CT
(
k
)
=
[
T
(
K
)
+
T
(
k
-
3
)
T
(
k
-
2
)
+
T
(
k
-
1
)
]
N
=
1
.
3. The process as claimed in claim 2 , wherein the margin coefficient Coeff is between 1.05 and 4.
4. The process as claimed in claim 2 , wherein, after initialization, 4N+1 edges are awaited before starting the calculations defined in c).
5. The process as claimed in claim 2 , wherein the significant edges are falling or rising edges.
6. The process as claimed in claim 2 , wherein the significant edges are solely rising edges.
7. The process as claimed in claim 2 , wherein the significant edges are solely falling edges.
8. The process as claimed in claim 1 , wherein the margin coefficient of uncertainty Coeff is between 1.05 and 4.
9. The process as claimed in claim 1 , wherein, after initialization, 4N+1 significant edges are awaited before starting the calculations defined in c).
10. The process as claimed in claim 1 , wherein the significant edges are falling or rising edges.
11. The process as claimed in claim 10 , wherein the target comprises teeth generating regularly spaced rising edges.
12. The process as claimed in claim 10 , wherein the target comprises teeth generating regularly spaced falling edges.
13. The process as claimed in claim 1 , wherein the significant edges are solely rising edges.
14. The process as claimed in claim 13 , wherein the camshaft target comprises teeth generating regularly spaced rising edges.
15. The process as claimed in claim 13 , wherein the camshaft target comprises teeth generating regularly spaced falling edges.
16. The process as claimed in claim 1 , wherein the significant edges are solely falling edges.
17. The process as claimed in claim 16 , wherein the camshaft target comprises teeth generating regularly spaced falling edges.
18. The process as claimed in claim 1 , wherein calculations of the index CT(k) are used in order to detect a conformity fault of the camshaft target.