Method and device for detecting a pulse-type mechanical effect on a system part
A method and a device for detecting a pulse-type mechanical effect at a system component, include continuously recording an operating noise in the system component with a sensor disposed at the system component and converting the operating noise with the sensor into a measured signal subjected to a mathematical transformation. A sliding mean is calculated by determining quantiles from determined transformations and an evaluation function, which displays an application of the pulse-type mechanical effect on the system component, is derived from the sliding mean.
1. In a method for detecting a pulse-type mechanical effect on a system part, which includes continuously detecting an operating noise present in the system part with a sensor disposed at the system part and converting the operating noise with the sensor into a measurement signal (M), the improvement comprising the following steps:
a) determining a magnitude (A(f i ,tj)) of a transform of the measurement signal (M) with prescribed parameters (f i ) of a mathematical transformation rule in time windows (Δt) being temporally sequential in time steps (δt);
b) determining a deviation of the magnitude (A(f i ,t j )) from a mean magnitude (Ā(f i ,t)) for each time step (δt) and each of the prescribed parameters (f i );
c) deriving an evaluation function (K(t)) for each time step (δt) from the deviations determined for each of the prescribed parameters ( fi );
d) comparing the evaluation function (K(t)) with a threshold value (K 0 ), and using an overshooting of the threshold value (K 0 ) as an index for a presence of a pulse-type signal component indicating the mechanical effect; and
e) determining a mean magnitude (Ā(f i ,t j )) in a sliding fashion as a function of time t from a data record (A(f i ,t)) having M magnitudes A(f i ,t m ) with the aid of a relationship:
A ( f i ,t )=( Q α ( f i ,t )+ Q 1−α ( f i ,t ))/2
with Q α and Q 1−α being respective α and (1−α) quantiles of the magnitudes A(f i ,tm) respectively determined in a time segment (T), with t m =t+mδt, and with m being a whole number.
2. The method according to claim 1 , wherein the time segment (T) is disposed symmetrically in relation to the time t.
3. The method according to claim 1 , which further comprises calculating an improved mean magnitude (Ā opt (f i ,t)) from the mean magnitude (Ā(f i ,t)), and eliminating from the data record magnitudes (A(f i ,t)) overshooting the mean magnitude (Ā) by a prescribed difference value to determine the quantiles.
4. The method according to claim 1 , which further comprises determining, for each of the prescribed parameters (f i ), a mean deviation (s(f i ,t)) of the magnitudes (A(f i ,t j )) from the mean magnitude (Ā(f i ,t)) for a plurality of sequential time windows (Δt) with the aid of a relationship:
s
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f
i
,
t
)
=
Q
α
(
f
i
,
t
)
-
Q
1
-
α
(
f
i
,
t
)
2
q
1
-
α
with q 1−α being the (1−α) quantile of a normalized normal distribution, and a normalized deviation of the magnitudes from the mean magnitude (Ā(f i ,t)) being determined with the aid thereof and being used to calculate the evaluation function (K(t)).
5. The method according to claim 4 , which further comprises calculating an improved mean magnitude (Ā opt (f i ,t)) from the mean magnitude (Ā(f i ,t)), eliminating from the data record magnitudes (A(f i ,t)) overshooting the mean magnitude (Ā) by a prescribed difference value to determine the quantiles, and the prescribed difference value being a threefold multiple of the mean deviation (s).
6. The method according to claim 5 , which further comprises for each time window (Δt), forming a sum of the squares of each normalized deviation over each of the prescribed parameters from which the evaluation function (K) is derived.
7. The method according to claim 1 , wherein the mathematical transformation rule is a windowed Fourier transformation, and the parameters are frequencies (f i ) of a frequency spectrum of the measurement signal (M).
8. A device for detecting a pulse-type mechanical effect on a system part, the device comprising:
at least one sensor disposed at the system part for continuously detecting and measuring an operating noise present in the system part and outputting measurement signals (M);
an A/D converter connected downstream of said sensor for digitizing the measurement signals (M) output by said sensor; and
an arithmetic unit for receiving digitized measurement signals from said A/D converter, said arithmetic unit programmed to:
a) determine a magnitude (A(f i ,t j )) of a transform of the measurement signals (M) with prescribed parameters (f i ) of a mathematical transformation rule in time windows (Δt) being temporally sequential in time steps (δt);
b) determine a deviation of the magnitude (A(f i ,t j )) from a mean magnitude (Ā(f i ,t)) for each time step (δt) and each of the prescribed parameters (f i );
c) derive an evaluation function (K(t)) for each time step (δt) from the deviations determined for each of the prescribed parameters (f i );
d) compare the evaluation function (K(t)) with a threshold value (K 0 ), and use an overshooting of the threshold value (K 0 ) as an index for a presence of a pulse-type signal component indicating the mechanical effect; and
e) determine the mean magnitude (Ā(f i ,t j )) in a sliding fashion as a function of time t from a data record (A(t)) having M magnitudes A(t m ) with the aid of a relationship:
A ( f i ,t )=( Q α ( f i ,t )+ Q 1−α ( f i ,t ))/2
with Q α and Q 1−α being respective α and (1−α) quantiles of the magnitudes A(f i ,t m ) respectively determined in a time segment (T), with t m =t+mδt, and with m being a whole number.
9. The device according to claim 8 , wherein the time segment (T) is disposed symmetrically in relation to the time (t).
10. The device according to claim 8 , wherein said arithmetic unit implements an algorithm for calculating an improved mean magnitude (Ā opt (f i ,t)) from the mean magnitude (Ā(f i ,t)), and magnitudes (A(f i ,t m )) overshooting the mean magnitude (Ā(f i ,t)) by a prescribed difference value are eliminated from the data record (A(t)) to determine the quantiles.
11. The device according to claim 8 , wherein said arithmetic unit determines, for each of the prescribed parameters (f i ), the mean deviation (s(f i ,t)) of the magnitudes (A(f i ,t j )) from the mean magnitude (Ā(f i ,t)) for a plurality of sequential time windows (Δt) with the aid of a relationship:
s
(
f
i
,
t
)
=
Q
α
(
f
i
,
t
)
-
Q
1
-
α
(
f
i
,
t
)
2
q
1
-
α
with q 1−α being the (1−α) quantile of a normalized normal distribution, and the normalized deviation of the magnitudes from the mean magnitude (Ā(f i ,t)) being determined with the aid thereof and being used to calculate the evaluation function (K(t)).
12. The device according to claim 11 , wherein said arithmetic unit implements an algorithm for calculating an improved mean magnitude (Ā opt (f i ,t)) from the mean magnitude (Ā(f i ,t)), magnitudes (A(f i ,t m )) overshooting the mean magnitude (Ā(f i ,t)) by a prescribed difference value are eliminated from the data record (A(t)) to determine the quantiles, and the prescribed difference value is a threefold multiple of the mean deviation (s).
13. A device for detecting a pulse-type mechanical effect on a system part, the device comprising:
at least one sensor disposed at the system part for continuously detecting and measuring an operating noise present in the system part and outputting measurement signals (M);
an A/D converter connected downstream of said sensor for digitizing the measurement signals (M) output by said sensor; and
an arithmetic unit for receiving digitized measurement signals from said A/D converter, said arithmetic unit including:
a) means for determining a magnitude (A(f i ,t j )) of a transform of the measurement signals (M) with prescribed parameters (f i ) of a mathematical transformation rule in time windows (Δt) being temporally sequential in time steps (δt);
b) means for determining a deviation of the magnitude (A(f i ,t j )) from a mean magnitude (Ā(f i ,t)) for each time step (δt) and each of the prescribed parameters (f i );
c) means for deriving an evaluation function (K(t)) for each time step (δt) from the deviations determined for each of the prescribed parameters (f i );
d) means for comparing the evaluation function (K(t)) with a threshold value (K 0 ), and using an overshooting of the threshold value (K 0 ) as an index for a presence of a pulse-type signal component indicating the mechanical effect; and
e) means for determining the mean magnitude (Ā(f i ,t j )) in a sliding fashion as a function of time t from a data record (A(t)) having M magnitudes A(t m ) with the aid of a relationship:
A ( f i ,t )=( Q α ( f i ,t )+ Q 1−α ( f i ,t ))/2
with Q α and Q 1−α being respective α and (1−α) quantiles of the magnitudes A(f i ,t m ) respectively determined in a time segment (T), with t m =t+mδt, and with m being a whole number.