U.S. patent application number 10/901577 was filed with the patent office on 2006-02-02 for method and system for identifying damage to a wire.
Invention is credited to Martin W. Kendig, Daniel N. Rogovin.
Application Number | 20060025939 10/901577 |
Document ID | / |
Family ID | 35733447 |
Filed Date | 2006-02-02 |
United States Patent
Application |
20060025939 |
Kind Code |
A1 |
Rogovin; Daniel N. ; et
al. |
February 2, 2006 |
Method and system for identifying damage to a wire
Abstract
Methods, systems, and articles of manufacture consistent with
the present invention determine the type of damage to a wire, the
amount of damage, and the location of the damage based on the
wire's broadband impedance measured from a single measurement
point. The type of damage is determined by comparing the wire's
calculated dielectric function, resistance and inductance to known
values that correspond to types of wire damage. The amount of
damage is determined by comparing the wire's low-frequency
impedance phase to known low-frequency impedance phase information
that corresponds to a known amount of wire damage. The location of
damage is determined by comparing the wire's high-frequency
impedance phase to known high-frequency impedance phase information
that corresponds to a known location of wire damage.
Inventors: |
Rogovin; Daniel N.; (Newbury
Park, CA) ; Kendig; Martin W.; (Thousand Oaks,
CA) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL LLP
Wacker Drive Station
P.O. Box 061080
Chicago
IL
60606-1080
US
|
Family ID: |
35733447 |
Appl. No.: |
10/901577 |
Filed: |
July 29, 2004 |
Current U.S.
Class: |
702/58 |
Current CPC
Class: |
H04B 5/00 20130101; G01R
31/088 20130101; G01R 31/52 20200101; G01R 31/58 20200101 |
Class at
Publication: |
702/058 |
International
Class: |
G06F 19/00 20060101
G06F019/00 |
Goverment Interests
GOVERNMENT CONTRACT
[0001] This invention was made with Government support under
Contract No. DTFA-03-C-00014 awarded by the FAA. The Government has
certain rights in this invention.
Claims
1. A method in a data processing system having a program for
identifying damage to a wire, the method comprising the steps of:
obtaining a broadband impedance information for the wire from a
single measurement point; determining a type of damage to the wire
based on the broadband impedance information; and determining a
location of damage along the wire by comparing a high-frequency
phase information of the obtained broadband impedance information
to at least one known high-frequency phase information
corresponding to a known location of damage.
2. A method of claim 1 wherein the broadband impedance information
is obtained from a single measurement point on the wire.
3. A method of claim 1 wherein the step of determining the type of
damage comprises: calculating a frequency-dependent dielectric
function of the wire based on the obtained broadband impedance
information; and comparing the calculated frequency-dependent
dielectric function to at least one known frequency-dependent
dielectric function corresponding to a known type of damage.
4. A method of claim 1 wherein the step of determining the type of
damage comprises: calculating a frequency-dependent resistance of
the wire based on the obtained broadband impedance information; and
comparing the calculated frequency-dependent resistance to at least
one known frequency-dependent resistance corresponding to a known
type of damage.
5. A method of claim 1 wherein the step of determining the type of
damage comprises: calculating a frequency-dependent inductance of
the wire based on the obtained broadband impedance information; and
comparing the calculated frequency-dependent inductance to at least
one known frequency-dependent inductance corresponding to a known
type of damage.
6. A method of claim 1 further comprising the step of determining
an amount of damage to the wire by comparing a low-frequency phase
information of the obtained broadband impedance information to at
least one known low-frequency phase information corresponding to a
known amount of damage.
7. (canceled)
8. A computer-readable medium containing instructions that cause a
data processing system having a program to perform a method for
identifying damage to a wire, the method comprising the steps of:
obtaining a broadband impedance information for the wire from a
single measurement point; determining a type of damage to the wire
based on the broadband impedance information; and determining a
location of damage along the wire by comparing a high-frequency
phase information of the obtained broadband impedance information
to at least one known high-frequency phase information
corresponding to a known location of damage.
9. A computer-readable medium of claim 8 wherein the broadband
impedance information is obtained from a single measurement point
on the wire.
10. A computer-readable medium of claim 8 wherein the step of
determining the type of damage comprises: calculating a
frequency-dependent dielectric function of the wire based on the
obtained broadband impedance information; and comparing the
calculated frequency-dependent dielectric function to at least one
known frequency-dependent dielectric function corresponding to a
known type of damage.
11. A computer-readable medium of claim 8 wherein the step of
determining the type of damage comprises: calculating a
frequency-dependent resistance of the wire based on the obtained
broadband impedance information; and comparing the calculated
frequency-dependent resistance to at least one known
frequency-dependent resistance corresponding to a known type of
damage.
12. A computer-readable medium of claim 8 wherein the step of
determining the type of damage comprises: calculating a
frequency-dependent inductance of the wire based on the obtained
broadband impedance information; and comparing the calculated
frequency-dependent inductance to at least one known
frequency-dependent inductance corresponding to a known type of
damage.
13. A computer-readable medium of claim 8 further comprising the
step of determining an amount of damage to the wire by comparing a
low-frequency phase information of the obtained broadband impedance
information to at least one known low-frequency phase information
corresponding to a known amount of damage.
14. (canceled)
15. A data processing system for identifying damage to a wire, the
data processing system comprising: a memory having a program that
obtains a broadband impedance information for the wire from a
single measurement point, determines a type of damage to the wire
based on the broadband impedance information, and determines a
location of damage along the wire by comparing a high-frequency
phase information of the obtained broadband impedance information
to at least one known high-frequency phase information
corresponding to a known location of damage; and a processing unit
that runs the program.
16. A data processing system of claim 15 wherein the broadband
impedance information is obtained from a single measurement point
on the wire.
17. A data processing system of claim 15 wherein the program
determines an amount of damage to the wire by comparing a
low-frequency phase information of the obtained broadband impedance
information to at least one known low-frequency phase information
corresponding to a known amount of damage.
18. (canceled)
19. A wire analyzer for identifying damage to a wire, the wire
analyzer comprising: means for obtaining a broadband impedance
information for the wire from a single measurement point; means for
determining a type of damage to the wire based on the broadband
impedance information; and means for determining a location of
damage along the wire by comparing a high-frequency phase
information of the obtained broadband impedance information to at
least one known high-frequency phase information corresponding to a
known location of damage.
Description
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to the field of
electrical wire testing and, more particularly, to methods and
systems for determining the type of damage, the amount of damage,
and the location of damage to a wire using broadband impedance.
[0003] Damaged wiring can lead to detrimental conditions, such as
short circuits. When the damaged wiring is located in, for example,
commercial or military aircraft, space vehicles, or nuclear power
plants, the damaged wiring can lead to serious problems.
[0004] Conventional approaches for determining whether a wire is
damaged include hi-pot and wire insulation tests. Although these
conventional methods are effective to detect damage in a wire, such
as short circuits using the hi-pot test or damaged insulation using
the wire insulation test, the conventional tests can break or
damage the wire. For example, during a hi-pot test, a high voltage
of 500V is typically applied to the wire. Such voltage can damage a
delicate wire or thin conductor. Further, conventional approaches
determine whether a wire is damaged, but fail to provide the type
of damage, the location of the damage, or the amount of damage.
SUMMARY OF THE INVENTION
[0005] Methods, systems, and articles of manufacture consistent
with the present invention determine the type of damage, the amount
of damage, and/or the location of damage to a wire using broadband
impedance measured from a single measurement point on the wire.
[0006] In accordance with methods consistent with the present
invention, a method in a data processing system having a program
for identifying damage to a wire is provided. The method comprises
the steps of obtaining a broadband impedance information for the
wire from a single measurement point, and determining a type of
damage to the wire based on the broadband impedance
information.
[0007] In accordance with articles of manufacture consistent with
the present invention, a computer-readable medium containing
instructions that cause a data processing system having a program
to perform a method for identifying damage to a wire is provided.
The method comprises the steps of obtaining a broadband impedance
information for the wire from a single measurement point, and
determining a type of damage to the wire based on the broadband
impedance information.
[0008] In accordance with systems consistent with the present
invention, a data processing system for identifying damage to a
wire is provided. The data processing system comprises: a memory
having a program that obtains a broadband impedance information for
the wire from a single measurement point, and determines a type of
damage to the wire based on the broadband impedance information;
and a processing unit that runs the program.
[0009] In accordance with systems consistent with the present
invention, a wire analyzer for identifying damage to a wire is
provided. The wire analyzer comprises means for obtaining a
broadband impedance information for the wire from a single
measurement point, and means for determining a type of damage to
the wire based on the broadband impedance information.
[0010] Other features of the invention will become apparent to one
with skill in the art upon examination of the following figures and
detailed description. It is intended that all such additional
systems, methods, features, and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in an
constitute a part of this specification, illustrate an
implementation of the invention and, together with the description,
serve to explain the advantages and principles of the invention. In
the drawings,
[0012] FIG. 1 is a schematic diagram of a system for analyzing a
wire for damage consistent with the present invention;
[0013] FIG. 2 is a block diagram of a data analysis system
consistent with the present invention;
[0014] FIG. 3 is a detail of the wire in FIG. 1;
[0015] FIG. 4 is a flow diagram of the exemplary steps for
determining a type of wire damage, the amount of damage, and the
location of the damage consistent with the present invention;
[0016] FIG. 5 is a measured frequency-dependent magnitude spectrum
of the wire of FIG. 1 for a case in which the wire is in an
open-circuit configuration;
[0017] FIG. 6 is a measured frequency-dependent phase spectrum of
the wire of FIG. 1 for a case in which the wire is in an
open-circuit configuration;
[0018] FIG. 7 is a measured frequency-dependent magnitude spectrum
of the wire of FIG. 1 for a case in which the wire is in a
closed-circuit configuration;
[0019] FIG. 8 is a measured frequency-dependent phase spectrum of
the wire of FIG. 1 for a case in which the wire is in a
closed-circuit configuration;
[0020] FIG. 9 is a flow diagram of the exemplary steps for
determining the type of wire damage consistent with the present
invention;
[0021] FIG. 10 is a calculated frequency-dependent real dielectric
function spectrum; and
[0022] FIG. 11 is a calculated frequency-dependent imaginary
dielectric function spectrum.
[0023] Corresponding reference characters indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Reference will now be made in detail to an implementation in
accordance with methods, systems, and articles of manufacture
consistent with the present invention as illustrated in the
accompanying drawings.
[0025] Methods, systems, and articles of manufacture consistent
with the present invention determine the type of damage, the amount
of damage, and/or the location of damage to a wire using broadband
impedance measured from a single measurement point on the wire.
[0026] FIG. 1 depicts a block diagram of a system 100 for detecting
and locating wire damage in a wire consistent with the present
invention. As illustrated, the system 100 generally comprises a
wire 102, which may be damaged, for example, by a short-circuit or
degraded insulation. A data analysis system 104 is connected to a
measurement point 106 of wire 102 via a cable 108. Cable 108
electrically connects to wire 102 via one or more connectors 110,
such as a banana clip or other type of connector. Data analysis
system 104 measures the broadband impedance of wire 102, determines
whether there is damage along the wire, determines the amount of
damage, and locates the damage based on the measured broadband
impedance. Further, data analysis system 104 determines the
location of the damage at any point along the wire using the
measured broadband impedance obtained from the single measurement
point 106.
[0027] FIG. 2 depicts data analysis system 104 in more detail. Data
analysis system 104 comprises an impedance measurement device 202
and a data processing system 204. Impedance measurement device 202
measures the magnitude and phase of the broadband impedance of wire
102, and can be a suitable off-the-shelf impedance measurement
device. For example, the impedance measurement device can be, but
is not limited to, the 4294A Precision Impedance Analyzer
manufactured by Agilent Technologies, Inc. of Palo Alto, Calif.,
U.S.A. As impedance measurement devices are known to those skilled
in the art, the impedance measurement device will not be described
in further detail.
[0028] During operation, the impedance measurement device outputs a
low-voltage output signal, which is transmitted through wire 102
via cable 108. The frequency of the output signal is adjusted so
impedance measurement device 202 measures the frequency-dependant
impedance of wire 102 across a range of frequencies, such as from
about 0 Hz to about 100 MHz. The measured impedance information is
converted to a digital signal by an analog-to-digital converter 206
and output from the impedance measurement device. Once the signal
is in a digital form, it can be processed by data processing system
204. Collected impedance information may be archived in a memory
208 or a secondary storage 210 of data processing system 204.
[0029] One having skill in the art will appreciate that the data
acquisition and data collection functionality of data analysis
system 102 can be included in a device separate from data
processing system 204. The separate device would comprise an
impedance measurement system having an analog-to-digital converter,
a processing unit, and a memory. The collected data would be stored
on the separate device during data acquisition and transferred to
the data processing system 204 for processing.
[0030] Data processing system 204 comprises a central processing
unit (CPU) or processor 212, a display device 214, an input/output
(I/O) unit 216, secondary storage device 210, and memory 208. The
data processing system may further comprise standard input devices
such as a keyboard, a mouse or a speech processor (each not
illustrated).
[0031] Memory 208 comprises a program 220 for identifying the type,
amount, and location of damage to a wire, such as wire 102. In an
illustrative example, program 220 is implemented using MATLAB.RTM.
software, however, the program can be implemented using another
application program or another programming language. As will be
described in more detail below, the program determines the type of
damage to a wire by analyzing the wire's dielectric function,
resistance and inductance, analyzes the low-frequency portion of
the phase of the wire's broadband impedance information to
determine the amount of the wire damage, and analyzes the
high-frequency portion of the phase of the wire's broadband
impedance information to locate the damage. MATLAB is a United
States registered trademark of The MathWorks, Inc. of Natick,
Mass.
[0032] One having skill in the art will appreciate that the program
can reside in memory on a system other than data processing system
204. Program 220 may comprise or may be included in one or more
code sections containing instructions for performing their
respective operations. Although program 220 is described as being
implemented as software, the program may be implemented as a
combination of hardware and software or hardware alone. Also, one
having skill in the art will appreciate that program 220 may
comprise or may be included in a data processing device, which may
be a client or a server, communicating with data processing system
204. Further, data analysis system 104 can itself be an impedance
measurement device.
[0033] Although aspects of methods, systems, and articles of
manufacture consistent with the present invention are depicted as
being stored in memory, one having skill in the art will appreciate
that these aspects may be stored on or read from other
computer-readable media, such as secondary storage devices, like
hard disks, floppy disks, and CD-ROM; a carrier wave received from
a network such as the Internet; or other forms of ROM or RAM either
currently known or later developed. Further, although specific
components of data processing system 204 have been described, one
having skill in the art will appreciate that a data processing
system suitable for use with methods, systems, and articles of
manufacture consistent with the present invention may contain
additional or different components.
[0034] Data processing system 204 can itself also be implemented as
a client-server data processing system. In that case, program 220
can be stored on the data processing system as a client, and some
or all of the steps of the processing described below can be
carried out on a remote server, which is accessed by the client
over a network. The remote server can comprise components similar
to those described above with respect to the data processing
system, such as a CPU, an I/O, a memory, a secondary storage, and a
display device.
[0035] FIG. 3 depicts the illustrative wire 102 in more detail. As
shown, the illustrative wire comprises two conductors 302 and 304,
which are illustratively arranged in a twisted-pair configuration.
Alternatively, conductors 302 and 304 can be arranged in a
different configuration, such as a coaxial or parallel-spaced
conductor configuration. Conductors 302 and 304 are preferably
insulated. The wire has a length (LT), which is 10 meters in the
illustrative example. Wire damage 306 is present along the wire
from location L.sub.1 to location L.sub.2 and represents, for
example, a short circuit, damaged insulation, or another type of
defect. In the illustrative example, the wire damage is damaged
insulation in conductor 304 from L.sub.1=5 meters to L.sub.2=6
meters. The damage represents damage, for example, from humidity or
exposure to hydraulic fluid.
[0036] Impedance measurement device 202 transmits the low-voltage
signal to wire 102 via conductors 108a and 108b of cable 108. As
shown, conductors 108a and 108b of cable 108 connect to the
conductors of wire 102 via respective connectors 110a and 110b. The
low-voltage signal from the impedance measurement device has a
potential of, for example, a few volts. Thus, there is a lower risk
of damaging the wire with low-voltage signal consistent with the
present invention than with conventional test signals that
typically have a potential of around 500 volts.
[0037] FIG. 4 depicts a flow diagram illustrating the exemplary
steps performed by program 220 for detecting and identifying the
type, amount, and location of damage to a wire, such as wire damage
306, on a wire. As will be described in more detail below, the
program determines the type of damage to a wire by analyzing the
wire's dielectric function, resistance and inductance, analyzes the
low-frequency portion of the phase of the wire's measured broadband
impedance information to determine the amount of wire damage, and
analyzes the high-frequency portion of the phase of the wire's
measured broadband impedance information to locate the damage.
First, the program receives the measured impedance information for
the wire (step 402). The measured impedance information can be
received, for example, as a data file in the memory or in the
secondary storage. Alternatively, the program can measure the
measured impedance over a predetermined range of frequencies and
store the frequency-dependent impedance magnitude and phase
spectra, for example, in the memory or the secondary storage. In
the illustrative example, the impedance measurement device measures
the frequency-dependent impedance magnitude and phase spectra and
transfers the information to the data processing system, where the
information is saved in a measured-data data file 222 in the
secondary storage. The broadband impedance data is measured for
cases in which the wire is in an open-circuit configuration and a
closed-circuit configuration at the end of the wire opposite the
measurement point.
[0038] The data for the measured impedance magnitude spectrum for
the illustrative example, wherein the wire is in an open-circuit
configuration, is shown in FIG. 5. The phase spectrum for the
measured impedance data, wherein the wire is in an open-circuit
configuration, is depicted in FIG. 6.
[0039] Further, the data for the measured impedance magnitude
spectrum for the illustrative example, wherein the wire is in a
short-circuit configuration, is shown in FIG. 7. The phase spectrum
for the measured impedance data, wherein the wire is in a
short-circuit configuration, is depicted in FIG. 8.
[0040] Then, the program determines whether the wire is damaged by
a known type of damage (step 404). To determine whether the wire is
damaged, the program calculates the wires frequency-dependent
dielectric function (.epsilon.(.omega.)), resistance (R(.omega.)),
and inductance (L(.omega.)) based on the measured broadband
impedance of the wire and compares these calculated values to known
values corresponding to various types of damage. Through extensive
experimentation, the inventors have discovered the
frequency-dependent dielectric function, resistance, and inductance
contribute to the electrical properties of the wire and correspond
to the state of the insulation and conductor. For example, the skin
effect, which results from an oxide layer or other type of layer
contacting the surface of the conductor, manifests itself in the
conductor's resistance. Also, when the wire's insulation is
affected by various environmental stresses, the wire's dielectric
function exhibits two microscopic processes: a relatively slow
ionic process that is nearly Debye and a relatively fast electronic
process that is nearly independent of frequency.
[0041] FIG. 9 depicts a flow diagram of the process performed in
step 404 in more detail. As shown in FIG. 9, to determine the type
of damage, the program extracts the real (.epsilon..sub.1(.omega.))
and imaginary (.epsilon..sub.2(.omega.)) components of the wire's
dielectric function (.epsilon.(.omega.)) from the measured
impedance data (step 902). A cable, such as the insulated
twisted-pair wire of the illustrative example, has a
frequency-dependent resistance (R(.omega.)) per meter, conductance
(C(.omega.)) per meter, inductance (L(.omega.)) per meter, and
conductance (G(.omega.)) per meter. The capacitance and conductance
are related to the dielectric function .epsilon.(.omega.) of the
cable as shown below in Equation (1).
G(.omega.)+i.omega.C(.omega.)=.LAMBDA..omega..epsilon.(.omega.)
Equation (1) In Equation (1), ".LAMBDA." is a structure factor that
depends on the configuration of the insulated wire (e.g., twisted
pair) and is independent of frequency. For the insulated wire of
the illustrative example, the structure factor .LAMBDA. can be
computed as shown below in Equation (2). .LAMBDA. = .pi. cosh - 1
.function. ( s d ) Equation .times. .times. ( 2 ) ##EQU1## In
Equation (2), "d" represents the diameter of each wire of the
twisted pair of the insulated wire and "s" represents a
center-to-center distance between the conductors of the wires of
the insulated wire.
[0042] When the impedance measurement device affects a voltage
between the wires of the twisted-pair insulated wire, the voltage
and current can be computed by Equations (3) and (4).
.differential. .differential. x .times. V .function. ( x , t ) = -
I .function. ( x , t ) .times. .times. R - .differential.
.differential. t .times. LI .function. ( x , t ) Equation .times.
.times. ( 3 ) .differential. .differential. x .times. I .function.
( x , t ) = - GV .function. ( x , t ) - .differential.
.differential. t .times. CV .function. ( x , t ) Equation .times.
.times. ( 4 ) ##EQU2##
[0043] The voltage of Equation (3) and the current of Equation (4)
define a set of normal node waves A.sub..+-.(x,t) propagating
through the insulated wire. A.sub..+-.(x,t) is further shown below
in Equation (5).
A.sub..+-.(x,t)=exp[.+-..gamma.(.omega.)x-i.omega.t] Equation (5)
In Equation (5), ".gamma." is a propagation function, which can be
defined by Equation (6). .gamma. .function. ( .omega. ) = ( R
.function. ( .omega. ) + I .times. .times. .omega. .times. .times.
L .function. ( .omega. ) ) .times. ( G .function. ( .omega. ) + I
.times. .times. .omega. .times. .times. C .function. ( .omega. ) )
= ( .alpha. .function. ( .omega. ) + I .times. .times. .beta.
.function. ( .omega. ) ) Equation .times. .times. ( 6 ) ##EQU3## In
Equation (6), .alpha.(.omega.) is the dissipation coefficient per
meter of the insulated wire. 2.pi./.beta.(.omega.) represents the
wavelength of the normal mode wave A.sub..+-.(x,t) propagating
through the insulated wire. v(.omega.)=.omega./.beta.(.omega.)
represents the speed (v(.omega.)) at which the signals can
propagate on the insulated wire. The propagation function can be
rewritten as shown below in Equation (7). .gamma.(.omega.)= {square
root over
((R(.omega.)+i.omega.L(.omega.))i.LAMBDA..omega..epsilon.(.omega.))}
Equation (7)
[0044] Knowing the propagation function, the frequency-dependent
open-circuit and short-circuit impedances are shown by Equations
(8) and (9). Z.sub.open(.omega.)=Z.sub.0(.omega.)cot
h[.gamma.(.omega.)l] Equation (8)
Z.sub.short(.omega.)=Z.sub.0(.omega.)tan h[.gamma.(.omega.)l]
Equation (9)
[0045] In the illustrative example, the length "l" of the insulated
wire (i.e., L.sub.T) is 10 meters and yields the characteristic
impedance Z.sub.0(.omega.) shown below in Equation (10). Z 0
.function. ( .omega. ) = R .function. ( .omega. ) + I .times.
.times. .omega. .times. .times. L .function. ( .omega. ) G
.function. ( .omega. ) + I .times. .times. .omega. .times. .times.
C .function. ( .omega. ) Equation .times. .times. ( 10 )
##EQU4##
[0046] The characteristic impedance can also be computed as the
product of the measured open-circuit and short-circuit impedances
as shown below in Equation (11).
Z.sub.0.sup.2Z.sub.short(.omega.)Z.sub.open(.omega.) Equation
(11)
[0047] Further, the propagation function can be found from the
ratio of the measured open-circuit and short-circuit impedances as
shown in Equation (12). .gamma. .function. ( .omega. ) .times. l =
tanh - 1 .times. Z short .function. ( .omega. ) Z open .function. (
.omega. ) Equation .times. .times. ( 12 ) ##EQU5##
[0048] Having obtained the characteristic impedance and the
propagation function from the measured open-circuit and
short-circuit impedance (i.e., using Equations (11) and (12)), the
program can calculate the real and imaginary components of the
dielectric function. Equations (7), (10), (11) and (12) yield the
following relationships shown in Equations (13) and (14). .gamma.
.function. ( .omega. ) .times. Z 0 .function. ( .omega. ) = R
.function. ( .omega. ) + I .times. .times. .omega. .times. .times.
L .function. ( .omega. ) Equation .times. .times. ( 13 ) .gamma.
.function. ( .omega. ) Z 0 .function. ( .omega. ) = I .times.
.times. .LAMBDA. .times. .times. .omega. .times. .times. .function.
( .omega. ) Equation .times. .times. ( 14 ) ##EQU6##
[0049] Accordingly, the frequency-dependent resistance (R(.omega.))
per meter, inductance (L(.omega.)) per meter, real component of the
dielectric function (.epsilon.(.omega.)), and imaginary component
of the dielectric function (.epsilon.(.omega.)) can be calculated
based on the characteristic impedance Z.sub.0(.omega.) and
propagation function .gamma.(.omega.) as shown below in Equations
(15), (16), (17) and (18). R .function. ( .omega. ) = Re .function.
[ .gamma. .function. ( .omega. ) .times. Z 0 .function. ( .omega. )
] Equation .times. .times. ( 15 ) L .function. ( .omega. ) = Im
.function. [ .gamma. .function. ( .omega. ) .times. .times. Z 0
.function. ( .omega. ) / .omega. ] Equation .times. .times. ( 16 )
1 .function. ( .omega. ) = - Re .function. [ .gamma. .function. (
.omega. ) .omega. .times. .times. .LAMBDA. .times. .times. Z 0
.function. ( .omega. ) ] Equation .times. .times. ( 17 ) 2
.function. ( .omega. ) = Im .function. [ .gamma. .function. (
.omega. ) .omega. .times. .times. .LAMBDA. .times. .times. Z 0
.function. ( .omega. ) ] Equation .times. .times. ( 18 )
##EQU7##
[0050] Therefore, having obtained the characteristic impedance and
the propagation function from the measured open-circuit and
short-circuit impedance (i.e., using Equations (11) and (12)), the
program then uses Equations (17) and (18) to calculate the real
(.epsilon..sub.1(.omega.)) and imaginary (.epsilon..sub.2(.omega.))
components of the dielectric function (.epsilon.(.omega.)). In the
illustrative example, the structure factor (.LAMBDA.) of the
insulated wire is calculated using the known illustrative diameter
(d)=1 mm and known illustrative center-to-center distance (s)=2
mm.
[0051] The real and imaginary components of the dielectric function
for the impedance data, as calculated by the program, are shown in
FIGS. 10 and 11, respectively.
[0052] Then, the program compares the calculated dielectric
function to known dielectric function values exhibiting various
types of damage in a wire (step 904). The dielectric function of
the wire exhibits two microscopic processes: a relatively slow
ionic process (.epsilon..sub.ionic(.omega.)) that is on the order
of tens of milliseconds or longer, and a relatively fast electronic
process (.epsilon..sub.e(.omega.)) that is on the order of
nanoseconds and is nearly independent of frequency. The dielectric
function (.epsilon.(.omega.)) including its components is shown in
Equation (19), and the components .epsilon..sub.ionic(.omega.) and
.epsilon..sub.e(.omega.) are shown in Equations (20) and (21),
respectively. .function. ( .omega. ) = ionic .function. ( .omega. )
+ e .function. ( .omega. ) Equation .times. .times. ( 19 ) ionic
.function. ( .omega. ) = A s .times. 0 1 + ( I .times. .times.
.omega. .times. .times. .tau. ionic ) n ionic Equation .times.
.times. ( 20 ) e .function. ( .omega. ) = B s .times. 0 1 + ( I
.times. .times. .omega. .times. .times. .tau. e ) n e Equation
.times. .times. ( 21 ) ##EQU8##
[0053] In Equations (19) and (20), .epsilon..sub.0 is the
dielectric constant of vacuum, A.sub.s is a geometric factor that
is <<1, B.sub.s is a geometric factor that is .apprxeq.3-10,
n.sub.ionic.apprxeq.1, n.sub.e.ltoreq.1, and .tau. is a time
response. Thus, as the ionic process is a slower process, the ionic
process influences the low frequency portion of the dielectric
function's spectra, and the faster electronic process influences a
wider range of frequencies in that it is larger than the ionic
process.
[0054] A damage type database 228 contains frequency-dependent real
and imaginary dielectric function data for combinations of known
wire types, wire lengths, and damage types. The program compares
the calculated frequency-dependant real and imaginary dielectric
function values to the damage type database entries to determine
whether the wire is damaged. For each wire type, the damage type
database contains frequency-dependent real and imaginary dielectric
function data for each wire length and each damage type. For
example, the damage type database can include entries for the wire
types twisted-pair, coaxial, and parallel-conductor wire. The wire
types can further be designated by their conductor and insulation
materials. The wire lengths can be delimited, for example, from 1
meter to 100 meters in 0.5 meter increments. The types of damage
can include exposure to hydraulic fluid, humidity, and mechanical
wear. One having skill in the art will appreciate that damage type
database can include alternative or additional values. Further, the
damage type database can be in a form other than a database, such
as a multi-dimensional array.
[0055] A user of the data processing system can enter the wire type
and wire length as values, which are received by the program, to
narrow the database search to damage type database entries
corresponding to the relevant wire type and wire length. If the
calculated frequency-dependant real and imaginary dielectric
function values correspond to the values of one or more of the
relevant dielectric function data in the damage type database, then
the program determines there is damage along the wire of the
relevant damage type.
[0056] As shown in step 906, the program then calculates the
frequency-dependent resistance of the wire. The frequency-dependent
resistance of the wire can be affected by the skin effect, that is
by an oxide layer or other type of layer contacting the conductor.
In general, the resistance of the wire becomes frequency dependant
when the skin depth in Equation (22) is satisfied. .omega. .gtoreq.
2 .sigma. .times. .times. .mu. .times. .times. r 0 2 Equation
.times. .times. ( 22 ) ##EQU9## In Equation (22), .omega.
represents the frequency, .sigma. represents conductivity of the
conductor, .mu. is the magnetic permeability and is around
4.pi..times.10.sup.-7, and r.sub.0 is the radius of the wire. Thus,
the resistance increases with frequency as .omega..sup.1/2.
[0057] Using Equation (15), the program calculates the
frequency-dependent resistance for the wire and compares the
calculated values to known values in the damage type database (step
908). Therefore, in addition to the entries described above for
each wire type, the damage type database also contains
frequency-dependent resistance values. The program compares the
calculated frequency-dependent resistance to database entries for
frequency-dependent resistance values corresponding to the same or
similar wire type and wire length. If the program determines the
values match or substantially match, then the program determines
the wire has damage of the relevant damage type.
[0058] Then, the program calculates the frequency-dependent
inductance of the wire (step 910). The frequency-dependent
inductance of the wire can also be affected by the skin effect. For
example, the low frequency inductance for a twisted pair wire is
given by Equation (23). L = .mu. .pi. .times. .times. Cosh - 1
.function. [ s d ] Equation .times. .times. ( 23 ) ##EQU10##
[0059] In Equation (23), the magnetic permeability (.mu.) is about
4.pi..times.10.sup.-7. For the frequency range of around 100 kHz to
around 1 MHz, the inductance decreases gradually. This behavior is
due to the inductance depending on the magnetic field between the
two conductors of the twisted-pair wire. When the skin effect is
exhibited in one or both of the conductors of the twisted-pair
wire, the inductance decreases more rapidly.
[0060] Using Equation (16), the program calculates the
frequency-dependent inductance for the wire and compares the
calculated values to known values in the damage type database (step
912). Therefore, in addition to the entries described above for
each wire type, the damage type database also contains
frequency-dependent inductance values. The program compares the
calculated frequency-dependent inductance to database entries for
frequency-dependent inductance values corresponding to the same or
similar wire type and wire length. If the program determines the
values match or substantially match, then the program determines
the wire damage is of the relevant damage type.
[0061] Referring back to FIG. 4, if the program determines there is
wire damage in step 406, then the program determines the amount of
wire damage (step 408). Through extensive experimentation, the
inventors have discovered that the low-frequency portion of the
phase of the measured broadband impedance spectrum of the wire is
sensitive to damage along the wire. If the wire is undamaged, the
measured impedance phase spectrum is relatively flat at around
-90.degree. over a range of low frequencies, such as from about 100
Hz to about 1 MHz. However, if the wire is damaged, then the
measured impedance phase deviates from -90.degree. in the
low-frequency range, such as from about 1 kHz to about 100 kHz.
Further, the greater the amount of damage, the greater the
impedance phase generally deviates from -90.degree. to
0.degree..
[0062] FIG. 12 depicts illustrative frequency-dependent impedance
phase spectra for the wire for cases in which the wire has been
damaged in various amounts by exposure to hydraulic fluid. As
shown, the wire damage impresses its signature on the low-frequency
portion (e.g., about 5 kHz to about 500 kHz) of the impedance phase
spectrum. The greater the amount of damage, the greater the
impedance phase generally deviates from -90.degree. to 0.degree. at
around 50 kHz. As shown, at 50 kHz, when there is no damage (i.e.,
baseline) the impedance phase is around -90.degree., when there is
0.5 meter of damage the impedance phase is around -89.degree., when
there is 1.0 meter of damage the impedance phase is around
-88.degree., when there is 1.5 meters of damage the impedance phase
is around -87.degree., and when there is 2.0 meters of damage the
impedance phase is around -86.degree..
[0063] The frequency-dependent impedance phase spectrum for the
wire in the illustrative example is thus depicted in FIG. 12 as the
case in which there is 1.0 meter of wire damage. The program
determines the amount of wire damage by calculating the average
impedance phase of the wire over a range of frequencies (e.g.,
about 0 Hz to about 1 MHz or higher) and comparing the average
impedance phase to values in a damage amount table 224. Damage
amount table 224 includes amount of damage values for known wire
types, wire lengths, types of damage, and average impedance phase
values. As each of these variables impresses a signature on a wire,
the amount of damage is determined by identifying a match
corresponding to the measured wire. In the illustrative example,
damage amount table 224 includes values for: wire types including
twisted pair, coaxial, and parallel-conductor wires; wire lengths
from 1 meter to 100 meters in 0.5 meter increments; amounts of
damage from 0 meters to 100 meters (limited to the wire length) in
0.5 meter increments; and types of damage including exposure to
hydraulic fluid, humidity, and mechanical wear. One having skill in
the art will appreciate that damage amount table 224 can include
alternative or additional values. Further, damage amount table 224
can be in the form of a data structure other than a table, such as
a multi-dimensional array.
[0064] Knowing the wire type, the wire length and the type of
damage, the program compares the calculated average impedance phase
to the average impedance phase values of corresponding wire type,
wire length, and damage type entries in damage amount table 224. In
the illustrative example, to determine the amount of damage, the
program compares the calculated average impedance phase of the
measured impedance to the known average impedance phase values for
a 10 meter twisted-pair wire that has been exposed to hydraulic
fluid. Based on the known average impedance phase values in the
damage amount table, the program would determine that there is 1
meter of damage to the wire.
[0065] Alternatively, the program can analyze an impedance phase
value other than the calculated average impedance phase value. For
example, the program can analyze the measured impedance phase of
the wire at a particular frequency, such as 10 kHz, or determine
whether the measured impedance phase has a value within a
predetermined range (e.g., less than -90.degree.) at a
predetermined frequency (e.g., 10 kHz).
[0066] After determining the amount of wire damage in step 408, the
program then determines the location of the wire damage (step 410).
Through extensive experimentation, the inventors have discovered
that the high-frequency portion of the phase of the measured
broadband impedance spectrum of the wire is sensitive to the
distance from the measurement point to the location of the damage
along the wire. As the distance from the measurement point to the
location of the damage to the wire increases, the zero-crossing of
the phase at high frequency shifts toward a lower frequency.
[0067] FIG. 13 depicts illustrative frequency-dependent impedance
phase spectra for the wire for cases in which the wire has been
damaged at various locations by exposure to hydraulic fluid. As
shown, the illustrative wire damage impresses its signature on the
high-frequency portion (e.g., about 5.7 MHz to about 6.45 MHz) of
the impedance phase spectrum, with the phase spectrum for the case
in which there is no damage (i.e., baseline) having a zero crossing
at about 6.45 MHz). The greater the distance from the measurement
point to the location of the damage, the more the zero-crossing of
the phase spectrum deviates toward a lower frequency. The
frequencies of the zero-crossings of the phase spectra of FIG. 13
are summarized below in Table 1. TABLE-US-00001 TABLE 1 Distance
from measurement Frequency of zero-crossing point to damage (m)
(MHz) No damage .about.6.45 0-1 .about.6.40 1-2 .about.6.35 2-3
.about.6.30 3-4 .about.6.20 4-5 .about.6.10 5-6 .about.5.93 6-7
.about.5.90 7-8 .about.5.80 8-9 .about.5.75 9-10 .about.5.70
[0068] Referring to the illustrative example, the
frequency-dependent impedance phase spectrum for the illustrative
wire is thus depicted in FIG. 13 as the case in which the damage is
located 5-6 meters from the measurement point. The program
determines the location of the wire damage by comparing the
zero-crossing of the phase of the measured impedance to known
zero-crossings of phases over a range of frequencies (e.g., about 1
MHz to about 100 MHz or higher) that are stored in a data
structure, such as a zero-crossing table 226. Zero-crossing table
226 includes zero-crossing values for known wire types, wire
lengths, types of damage, and distances from measurement points to
damage locations. As each of these variables impresses a signature
on a wire, the location of damage is determined by identifying a
match corresponding to the measured wire. In the illustrative
example, zero-crossing table 226 includes values for: wire types
including twisted pair, coaxial, and parallel-conductor wires; wire
lengths from 1 meter to 100 meters in 0.5 meter increments; types
of damage including exposure to hydraulic fluid, humidity, and
mechanical wear; and distances from the measurement point to the
damage from 0 meters to 100 meters (limited to the wire length) in
1.0 meter increments. One having skill in the art will appreciate
that zero-crossing table 226 can include alternative or additional
values. Further, zero-crossing table 226 can be in the form of a
data structure other than a table, such as a multi-dimensional
array.
[0069] Knowing the wire type, the wire length and the type of
damage, the program compares the measured high-frequency impedance
phase zero-crossing to the zero-crossing values corresponding to
the same or similar wire type, wire length, and damage type entries
in zero-crossing table 226. In the illustrative example, to
determine the location of the damage, the program compares the
measured impedance phase zero-crossing to the known zero-crossing
values for a 10 meter twisted-pair wire that has been exposed to
hydraulic fluid. Based on the known zero-crossing values in the
zero-crossing table, the program would determine that the damage is
located from 5-6 meters from the measurement point.
[0070] If the program determines in step 406 that there is no wire
damage or after the program locates the wire damage in step 410,
then the program displays the results of the analysis, for example,
on the display device (step 412). The results include, for example,
the type of damage, the amount of damage, and the location of the
damage. In the illustrative example, the program displays that, at
5-6 meters from the measurement point, a 1 meter segment of the
wire has been damaged by exposure to hydraulic fluid.
Alternatively, the program can display additional or alternative
results.
[0071] Therefore, methods, systems, and articles of manufacture
consistent with the present invention determine the type of damage
to a wire, the amount of damage, and/or the location of the damage
from a single measurement point on the wire. Further, the methods,
systems, and articles of manufacture consistent with the present
invention provide beneficial improvements over conventional
approaches, in that: wire prognosis can be performed; impedance is
measured from a single measurement point; and/or as the impedance
is measured from a single measurement point, there is a reduced
risk of damaging the wire.
[0072] The foregoing description of an implementation of the
invention has been presented for purposes of illustration and
description. It is not exhaustive and does not limit the invention
to the precise form disclosed. Modifications and variations are
possible in light of the above teachings or may be acquired from
practicing the invention. For example, the described implementation
includes software but the present implementation may be implemented
as a combination of hardware and software or hardware alone.
Further, the illustrative processing steps performed by the program
can be executed in an different order than described above, and
additional processing steps can be incorporated. For example, the
program can locate the wire damage prior to determining the amount
of damage, and the program can calculate the inductance of the wire
prior to calculating the wire's resistance. The invention may be
implemented with both object-oriented and non-object-oriented
programming systems. The scope of the invention is defined by the
claims and their equivalents.
[0073] When introducing elements of the present invention or the
preferred embodiment(s) thereof, the articles "a", "an", "the" and
"said" are intended to mean that there are one or more of the
elements. The terms "comprising", "including" and "having" are
intended to be inclusive and mean that there may be additional
elements other than the listed elements.
[0074] As various changes could be made in the above constructions
without departing from the scope of the invention, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *