Method and system for knock detection
This invention relates to a method for knock detection in a combustion engine, in which combustion is controlled by a control unit ( 2 ), which comprises the steps of, a) obtaining at least one sensor signal ( 4, 4 ′) carrying information of knock intensity related within a combustion chamber of the combustion engine ( 1 ); (b) processing the sensor signal ( 4, 4 ′) to obtain a knock intensity related detection variable (z 1 ), (c) using said detection variable (z 1 ) in said control unit ( 2 ) arranged to avoid a knocking condition in said combustion engine ( 1 ), if the value (z 1 ) of said detection variable indicates knock when compared with a threshold value (T) wherein using two different computations/processes for said processing ( 5, 6 ) of the at least one sensor signal ( 4, 4 ′) to obtain two separate sub-values (y 1 , y 2 ), and thereafter combining said sub-values (y 1 , y 2 ) to obtain said detection variable (z 1 ).
1. A method for knock detection in a combustion engine, in which combustion is controlled by a control unit, which comprises the steps of,
(a) obtaining at least one sensor signal carrying information of knock intensity within a combustion chamber of the combustion engine;
(b) using different computations for processing the sensor signal to obtain at least two separate sub-values and thereafter combining said sub-values to obtain a knock intensity related detection variable,
(c) comparing said detection variable with a threshold value, and
(d) indicating knock if the value of said detection variable exceeds the threshold value.
2. The method according to claim 1 , wherein said processing relates to computations correlated to knock intensity from one and the same sensor.
3. The method according to claim 2 , wherein said sensor is an ion-sensor and said sub-values relate to the energy of a characteristic frequency and the integral of the ion current respectively.
4. The method according to claim 2 , wherein said sensor is a pressure sensor and said sub-values relate to the energy of a characteristic frequency and the integral of the pressure trace respectively.
5. The method according to claim 1 , wherein said processing relates to computation of sensor signals from different sensors.
6. The method according to claim 5 , wherein said sensors comprise a combination of at least two of the following:
a. an ion-sensor
b. an accelerometer
c. a pressure sensor.
7. The method according to claim 1 , wherein said processing relates to computations of information from different combustion cycles.
8. The method according to claim 7 , wherein said information related to knock intensity at cycle k is combined with information from cycle k+1.
9. The method according to claim 8 , wherein said information related to knock intensity at cycle k is combined with information from cycle k+2.
10. The method according to claim 1 , wherein said control includes comparing said detection variable with a threshold value and said threshold depends on the working point of the engine.
11. The method according to claim 10 , wherein said control includes comparing said detection variable with a threshold value and said threshold depends on the sub-values.
12. A system for knock detection in a combustion engine, in which combustion is controlled by a control unit, comprising,
at least one sensor arranged to deliver a sensor signal carrying information of knock intensity within a combustion chamber of the combustion engine,
at least one processing unit arranged to deliver at least two sub-values from the at least one sensor signal and to combine said sub-values to deliver a knock intensity related detection variable,
a comparison unit for comparing the detection variable with a threshold value, and
a control actuation unit for indicating knock if the value of said detection variable exceeds the threshold value.
13. The system according to claim 12 , wherein a signal from one sensor is used to deliver said at least two sub-values.
14. The system according to claim 12 , wherein at least two signals from at least two sensors are used to deliver at least said two sub-values.
15. The system according to claim 14 , wherein said sensors comprise a combination of at least two of the following:
a) an ion-sensor,
b) an accelerometer,
c) a pressure sensor.
16. A method for knock detection in a combustion engine, in which combustion is controlled by a control unit, which comprises the steps of:
(a) obtaining at least one sensor signal carrying information of knock intensity within a combustion chamber of the combustion engine;
(b) using different computations for processing the sensor signal to obtain at least two separate sub-values and thereafter mathematically combining said sub-values in the form
z
(
k
)
=
∑
l
=
1
L
(
λ
l
·
y
l
(
k
)
)
,
with weighting factors λ l , l=1, . . . L being between 0-1, to obtain a knock intensity related detection variable,
(c) comparing said detection variable with a threshold value, and
(d) indicating knock if the value of said detection variable exceeds the threshold value.
17. A system for knock detection in a combustion engine, in which combustion is controlled by a control unit, comprising,
at least one sensor arranged to deliver a sensor signal carrying information of knock intensity within a combustion chamber of the combustion engine,
at least one processing unit is arranged to deliver at least two sub-values from the at least one sensor signal and to mathematically combine said sub-values in the form
z
(
k
)
=
∑
l
=
1
L
(
λ
l
·
y
l
(
k
)
)
,
with weighting factors λ l , l=1, . . . L being between 0-1, to deliver a knock intensity related detection variable,
a comparison unit for comparing the detection variable with a threshold value, and
a control actuation unit for indicating knock if the value of said detection variable exceeds the threshold value.