Method for determining the location of an impact on a surface of an object
The invention relates to a method for determining the location of an impact on a surface of an object based on the analysis of an acoustic signal generated by the impact. This method further comprises a signal treatment step of weighting the acoustic signal to take into account spurious contributions in particular due to reflections at the border of the object.
1. Method for determining the location of an impact on a surface of an object based on the analysis of an acoustic signal generated by the impact comprising:
a signal treatment step of weighting the acoustic signal to thereby take into account spurious contributions in particular due to reflections at the border of the object,
wherein the signal treatment step of weighting comprises a step of identifying a first wave front of the acoustic signal and a step of applying a damping window,
wherein the step of applying a damping window comprises using multiplying the acoustic signal with an exponential damping window:
w
(
t
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{
=
0
,
for
0
<
t
<
t
i
-
Δ
t
=
exp
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(
t
i
-
Δ
t
-
t
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for
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<=
t
wherein t i corresponds to the time of arrival of the first wave front and Δt a time delay and T is the exponential time constant.
2. Method according to claim 1 , wherein the weighting is carried out in the time domain.
3. Method according to claim 1 , wherein the step of identifying a first wave front comprises identifying the maximum signal amplitude.
4. Method according to claim 3 , wherein the step of identifying furthermore comprises determining the arrival of the first wave front as the time when the acoustic signal passes a threshold value which is based on the maximum signal amplitude.
5. Method according to claim 1 , wherein the acoustic signal is sensed by at least two transforming means and wherein the first wave front is identified for one, in particular only one, transforming means such that the same time origin of the damping window is applied for all transforming means.
6. Method according to claim 1 , wherein the acoustic signal is sensed by at least two transforming means and the weighting of the acoustic signal is carried out using inter-correlation products of the signals sensed by the at least two transforming means.
7. Method according to claim 6 , wherein the step of identifying the first wave fronts contribution comprises determining the maximum value of the inter-correlation product.
8. Method according to claim 6 , wherein the step of applying a damping window comprises applying a symmetrical window function, in particular a Gaussian, Hamming, Hanning or Blackman window.
9. Method according to claim 1 further comprising applying low and/or high pass filtering to the acoustic signal.
10. Computer program product comprising one or more computer readable media having computer-executable instructions for performing:
a signal treatment step of weighting the acoustic signal to thereby take into account spurious contributions in particular due to reflections at the border of the object,
wherein the signal treatment step of weighting comprises a step of identifying a first wave front of the acoustic signal and a step of applying a damping window,
wherein the step of applying a damping window comprises multiplying the acoustic signal with an exponential damping window:
w
(
t
)
{
=
0
,
for
0
<
t
<
t
i
-
Δ
t
=
exp
(
(
t
i
-
Δ
t
-
t
)
/
T
)
,
for
t
i
-
Δ
t
<=
t
wherein t i corresponds to the time of arrival of the first wave front and Δt a time delay and T is the exponential time constant.
11. Device for determining the location of an impact on a surface of an object, said device arranged and configured to perform:
a signal treatment step of weighting the acoustic signal to thereby take into account spurious contributions in particular due to reflections at the border of the object,
wherein the signal treatment step of weighting comprises a step of identifying a first wave front of the acoustic signal and a step of applying a damping window,
wherein the step of applying a damping window comprises multiplying the acoustic signal with an exponential damping window:
w
(
t
)
{
=
0
,
for
0
<
t
<
t
i
-
Δ
t
=
exp
(
(
t
i
-
Δ
t
-
t
)
/
T
)
,
for
t
i
-
Δ
t
≤
t
wherein t i corresponds to the time of arrival of the first wave front and Δt a time delay and T is the exponential time constant.
12. The computer program product according to claim 10 , wherein the step of identifying a first wave front comprises identifying the maximum signal amplitude.
13. The computer program product according to claim 12 , wherein the step of identifying furthermore comprises determining the arrival of the first wave front as the time when the acoustic signal passes a threshold value which is based on the maximum signal amplitude.
14. The device according to claim 11 , wherein the step of identifying a first wave front comprises identifying the maximum signal amplitude.
15. The device according to claim 11 , wherein the step of identifying furthermore comprises determining the arrival of the first wave front as the time when the acoustic signal passes a threshold value which is based on the maximum signal amplitude.