US2002010533A1PendingUtilityA1
Method and apparatus for detecting shock absorber damage
Assignee: BAYERISCHE MOTOREN WERKE AGPriority: Jun 10, 2000Filed: Jun 5, 2001Published: Jan 24, 2002
Est. expiryJun 10, 2020(expired)· nominal 20-yr term from priority
G01M 17/04
32
PatentIndex Score
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Cited by
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Claims
Abstract
In a method and apparatus for detecting shock absorber damage, features of a shock absorber are determined by analyzing a signal of an antilock braking system rotational wheel speed sensor.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A method for detecting shock absorber damage, comprising:
detecting wheel speed signals of an antilock braking system rotational wheel speed sensor; and determining a condition of said shock absorber by analyzing said wheel speed signals.
2 . The method according to claim 1 , wherein the step of analyzing said wheel speed signals includes one of determining a temporal course of a radius change Ar of a vehicle tire, and determining a temporal course of a rotational speed change Δn of a wheel rim, based on said wheel speed signals.
3 . The method according to claim 2 , further comprising computing at least one of an auto power density spectrum φ Δr for the temporal course of the radius change Δr, and an auto power density spectrum φ Δn for the temporal course of the rotational speed change Δn.
4 . The method according to claim 3 , further comprising computing a quotient DSKW Δr or DSKW Δn from the auto power density spectra for first and second frequency ranges, the computed quotient corresponding to a characteristic shock absorber damage value.
5 . The method according to claim 4 , wherein the quotient DSKW Δr or DSKW Δn is computed according to one of the two equations
Φ
x
(
ω
)
=
lim
T
→
∞
X
(
j
ω
)
2
2
T
(
A
)
wherein
ω 1,i =discrete frequency values of the first frequency range,
ω 2,i =discrete frequency values of the second frequency range,
w=bumpiness, preferably approximately 2, and
k:=number of discrete frequency points.
6 . The method according to claim 4 , wherein the first frequency range corresponds to an analysis interval and the second frequency range corresponds to a reference interval.
7 . The method according to claim 4 , wherein the second frequency range has higher frequencies than the first frequency range.
8 . The method according to claim 4 , wherein the first frequency range has frequencies ω 1,i of approximately 12 to 15 Hz and/or the second frequency range has frequencies ω 2,i of approximately 19 to 22 Hz or approximately 30 to 33 Hz.
9 . The method according to claim 1 , further comprising high-pass filtering of the wheel speed signal.
10 . The method according to claim 3 , further comprising:
computing a quotient DSKW′ Δr or DSKW′ Δn from a quotient of the auto power density spectrum for first and second frequency ranges, and a quotient of the auto power density spectrum for the second frequency range and third frequency range, the computed quotient DSKW′ Δr or DSKW′ Δn corresponding to a characteristic shock absorber damage value.
11 . The method according to claim 10 , wherein the quotient DSKW′ Δr or DSKW′ Δn is computed according to one of the two equations
DSKW
Δ
r
=
∑
i
=
1
k
Φ
Δ
r
(
ω
1
,
i
,
d
)
Φ
Δ
r
(
ω
2
,
i
)
·
(
ω
1
,
i
ω
2
,
i
)
w
DSKW
Δ
n
=
∑
i
=
1
k
Φ
Δ
n
(
ω
1
,
i
,
d
)
Φ
Δ
r
(
ω
2
,
i
)
·
(
ω
1
,
i
ω
2
,
i
)
w
wherein
ω 1,i =discrete frequency values of the first frequency range,
ω 2,i =discrete frequency values of the second frequency range,
ω 3,i =discrete frequency values of the third frequency range,
and
k=number of discrete frequency points.
12 . The method according to claim 10 , wherein the first frequency range corresponds to an analysis interval, the second frequency range corresponds to a first reference interval, and the third frequency range corresponds to a second reference interval.
13 . The method according to claim 10 , wherein the second frequency range has higher frequencies than the first frequency range, and the third frequency range has higher frequencies than the second frequency range.
14 . The method according to claim 10 , wherein at least one of the following is true:
the first frequency range has frequencies ω 1,i of approximately 12 to 15 Hz; the second frequency range has frequencies ω 2,i of approximately 19 to 22 Hz; and the third frequency range has frequencies ω 3,i of approximately 30 to 33 Hz.
15 . The method according to claim 4 , further comprising:
correcting the characteristic shock absorber damage value by means of at least one driving condition signal.
16 . The method according to claim 15 , wherein the driving condition signal is selected from the group consisting of driving speed, throttle valve angle, torque, rotational engine speed, gear position, operating condition of a converter clutch and position of a clutch switch group.
17 . The method according to claim 4 , further comprising:
comparing the characteristic shock absorber damage value with a threshold value to determine shock absorber condition.
18 . The method according to claim 17 , wherein shock absorber damage is present when the characteristic shock absorber damage value exceeds the threshold value.
19 . Apparatus for detecting shock absorber damage, comprising a processing unit for determining characteristics of a shock absorber by analyzing wheel speed signals of an antilock system rotational wheel speed sensor.
20 . The apparatus according to claim 19 , wherein said processing unit includes a component for determining one of a temporal sequence of a radius change Δr of a vehicle tire, and a temporal course of a rotational speed change Δn of a wheel rim, based on said wheel speed signals.
21 . The apparatus according to claim 20 , wherein said processing unit comprises a component for computing at least one of an auto power density spectrum φ Δr for the temporal course of the radius change Δr, and an auto power density spectrum φ Δn for the temporal course of the rotational speed change Δn.
22 . The apparatus according to claim 21 , wherein said processing unit further comprises a component for computing a quotient DSKW Δr or DSKW Δn from the auto power density spectra for first and second frequency ranges, the computed quotient corresponding to a characteristic shock absorber damage value.
23 . The apparatus according to claim 22 , wherein the quotient DSKW Δr or DSKW Δn is computed according to one of the two equations
DSKW
Δ
r
′
=
∑
i
=
1
k
(
Φ
Δ
r
(
ω
1
,
i
,
d
)
Φ
Δ
r
(
ω
2
,
i
)
Φ
Δ
r
(
ω
2
,
i
)
Φ
Δ
r
(
ω
3
,
i
)
)
DSKW
Δ
n
′
=
∑
i
=
1
k
(
Φ
Δ
n
(
ω
1
,
i
,
d
)
Φ
Δ
n
(
ω
2
,
i
)
Φ
Δ
n
(
ω
2
,
i
)
Φ
Δ
n
(
ω
3
,
i
)
)
wherein
ω 1,i =discrete frequency values of the first frequency range,
ω 2,i =discrete frequency values of the second frequency range,
w=bumpiness, preferably approximately 2, and
k:=number of discrete frequency points.
24 . The apparatus according to claim 21 , wherein said processing unit further comprises a component for computing a quotient DSKW′ Δr or DSKW′ Δn from a quotient of the auto power density spectra for first and second frequency ranges, and a quotient of the auto power density spectrum for the second frequency range and a third frequency range, the computed quotient DSKW′ Δr or DSKW′ Δn corresponding to a characteristic shock absorber damage value.
25 . The apparatus according to claim 24 , wherein the quotient DSKW′ Δr or DSKW′ Δn is computed according to one of the two equations
DSKW
Δ
r
′
=
∑
i
=
1
k
(
Φ
Δ
r
(
ω
1
,
i
,
d
)
Φ
Δ
r
(
ω
2
,
i
)
Φ
Δ
r
(
ω
2
,
i
)
Φ
Δ
r
(
ω
3
,
i
)
)
DSKW
Δ
n
′
=
∑
i
=
1
k
(
Φ
Δ
n
(
ω
1
,
i
,
d
)
Φ
Δ
n
(
ω
2
,
i
)
Φ
Δ
n
(
ω
2
,
i
)
Φ
Δ
n
(
ω
3
,
i
)
)
wherein
ω 1,i =discrete frequency values of the first frequency range,
ω 2,i =discrete frequency values of the second frequency range,
ω 3,i =discrete frequency values of the third frequency range,
and
k=number of discrete frequency points.
26 . The apparatus according to claim 22 , wherein said processing unit further comprises a correction component for correcting characteristic shock absorber damage value by means of at least one driving condition signal.
27 . The apparatus according to claim 26 , wherein the driving condition signal is selected from the group consisting of driving speed, throttle valve angle, torque, rotational engine speed, gear position, operating condition of a converter clutch, and position of a clutch switch group.
28 . The apparatus according to claim 22 , wherein said processing unit further comprises a component for comparing the characteristic shock absorber damage value with a threshold value to determine shock absorber condition.
29 . The apparatus according to claim 28 , wherein shock absorber damage is present as soon as the characteristic shock absorber value exceeds the threshold value.Join the waitlist — get patent alerts
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