Method of determining acceleration of a crankshaft
A method of determining the acceleration of a crankshaft of an internal combustion engine including one or more cylinders, with respect to each combustion event, n, among a plurality of combustion events, includes a) providing a signal indicative of crankshaft speed, with the signal including a series of minima and maxima speeds with respect to each successive combustion event and b) determining the acceleration of the crankshaft of the internal combustion engine with respect to each combustion event, n, among the plurality of combustion events, based on an initial speed value of a minima, Min (n) just before the combustion event, n, and a subsequent speed value of a maximum, Max (n) immediately subsequent to the combustion event, n, in addition to a speed of a minima for a subsequent combustion event, Min (n+1).
1. A method of determining the acceleration of a crankshaft of an internal combustion engine comprising one or more cylinders, with respect to each combustion event, n, among a plurality of combustion events, comprising:
a) providing a signal indicative of crankshaft speed, said signal comprising a series of minima and maxima speeds with respect to each successive combustion event;
b) determining the acceleration of the crankshaft of the internal combustion engine with respect to each combustion event, n, among the plurality of combustion events, based on: an initial speed value of a minima, Min_(n) just before the combustion event, n, and a subsequent speed value of a maximum, Max (n) immediately subsequent to the combustion event, n, as well as a speed of a minima for a subsequent combustion event, Min (n+1).
2. The method as claimed in claim 1 , wherein the determination of the acceleration is used to detect misfire events of the internal combustion engine, the detection occurring based on a comparison of the determination of the acceleration with one or more threshold acceleration values corresponding to the subsequent combustion event.
3. The method as claimed in claim 1 , wherein in step b) said acceleration for the combustion event n, (Acc-n-) acceleration is based on the following equation:
A
c
c
n
=
(
Speed
Max
n
-
(
a
*
Speed
Min
(
n
+
1
)
+
b
*
Speed
Min
n
/
(
a
+
b
)
)
/
t
i
n
t
where Speed Min n is the initial speed at the minima, Min_(n) just before the combustion event, n, and Speed Max n is the speed at the subsequent maximum Max (n) immediately subsequent to the combustion event n, and Speed Min (n+1) is the minima speed for the subsequent combustion event, Min (n+1), and
a and b are factors that can be calibrated in a map function of engine speed and engine brake torque; and t int is the time between the maxima (Max(n)) and the preceding minima (Min (n)).
4. The method as claimed in claim 3 , wherein a equals 0.5 and b equals 0.5.
5. The method as claimed in claim 1 , where said acceleration is additionally based on a minima speed value of a previous combustion event n−1.
6. The method as claimed in claim 5 , wherein in said acceleration for the combustion event n, said (Acc n -) acceleration is based on the following formula:
Acc
n
=
(
Speed
Max
n
-
(
a
*
Speed
Min
(
n
+
1
)
+
b
*
Speed
Min
n
+
c
*
Speed
Min
(
n
-
1
)
/
(
a
+
b
+
c
)
)
/
t
int
,
where Speed Min (n−1) is the minima speed value of the previous combustion event n−1 preceding the combustion event n, and
a, b, and c are factors that can be calibrated in a map function of engine speed and engine brake torque; and t int is the time between the maxima (Max_(n)) and the preceding minima (Min (n)).