U.S. patent application number 12/885803 was filed with the patent office on 2011-05-26 for tensile support strength measurement system and method.
Invention is credited to Norbert Hootsmans, William Veronesi.
Application Number | 20110125474 12/885803 |
Document ID | / |
Family ID | 35063648 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110125474 |
Kind Code |
A1 |
Veronesi; William ; et
al. |
May 26, 2011 |
TENSILE SUPPORT STRENGTH MEASUREMENT SYSTEM AND METHOD
Abstract
A method and system determines probable strength degradation in
a tensile support in an elevator system by monitoring an electrical
characteristic of the tensile support as a whole, such as the total
electrical resistance of the tensile support, that varies as the
remaining strength in the tensile support varies. As the
degradation of strength in a typical tensile support varies along
the support, and as the relationship between strength and the
electrical characteristic generally exhibits an inherent
uncertainty, the overall relationship between strength and the
electrical characteristic of the whole tensile support will vary as
well. Quantifying the probable strength degradation indicated for
each value in a range of a measurable electrical characteristic
allows monitoring the strength degradation of the tensile support.
The method and system also quantifies the relationship between
tensile support degradation and a measurable electrical
characteristic to monitor degradation.
Inventors: |
Veronesi; William;
(Hartford, CT) ; Hootsmans; Norbert; (South
Glastonbury, CT) |
Family ID: |
35063648 |
Appl. No.: |
12/885803 |
Filed: |
September 20, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10589479 |
Aug 14, 2006 |
7801690 |
|
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PCT/US04/08192 |
Mar 16, 2004 |
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12885803 |
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Current U.S.
Class: |
703/7 ;
702/43 |
Current CPC
Class: |
B66B 7/1223
20130101 |
Class at
Publication: |
703/7 ;
702/43 |
International
Class: |
G06G 7/48 20060101
G06G007/48; G01L 1/00 20060101 G01L001/00; G06F 19/00 20110101
G06F019/00 |
Claims
1. A method of modeling a condition of an elevator tensile support,
comprising; determining a rate of degradation of the tensile
support for a selected load; modeling a configuration of at least
one selected elevator system; estimating an elevator traffic
pattern; determining sheave contact and load information using the
determined rate of degradation, the modeled configuration and the
estimated traffic pattern; and determining a mean degradation of
the tensile support from the determined sheave contact and load
information.
2. The method of claim 1, including determining a plurality of mean
degradation values by varying at least one of the modeled
configuration or the estimated elevator traffic pattern.
3. The method of claim 1, including determining a relationship
between an electrical characteristic and a selected condition of
the tensile support and using the determined relationship and the
determined mean degradation for determining an apparent electrical
characteristic value corresponding to the selected condition of the
tensile support.
4. The method of claim 3, including repeatedly performing the steps
of claim 3 to determine a plurality of the apparent electrical
characteristic values and using the values to determine a
relationship between a corresponding measured electrical
characteristic and a condition of a tensile support.
5. The method of claim 4, wherein the electrical characteristic is
resistance.
6. The method of claim 5, including subsequently measuring a
resistance of a tensile support and using the determined
relationship between resistance and the selected condition of the
tensile support to determine a current condition of the tensile
support.
7. The method of claim 1, including generating a first map from the
determined mean degradation; generating a second map correlating an
electrical characteristic with a selected degree of strength
degradation; combining the first and second maps to generate a
third map correlating the electrical characteristic with the
remaining strength in the tensile support.
8. The method of claim 7, wherein the step of generating the first
map comprises incorporating at least one tensile support
operational factor with the strength loss model.
9. The method of claim 8, wherein said at least one tensile support
operational factor is selected from the group consisting of an
elevator system configuration, estimated elevator traffic, actual
elevator usage, and sheave contact.
10. The method of claim 9, wherein said at least one tensile
support operational factor is the actual elevator usage, and
wherein the step of generating the first map further comprises
repeating the correlating step based on an updated actual elevator
usage.
11. The method of claim 7, wherein the combining step comprises:
generating an intermediate map that correlates the electrical
characteristic with remaining strength in a segment of the tensile
support, wherein the tensile support comprises a plurality of
segments; and summing the remaining strengths of the plurality of
segments to generate the third map.
12. The method of claim 7, comprising incorporating a degradation
rate variance factor in the first map.
13. The method of claim 7, comprising incorporating an electrical
characteristic variance factor in the second map.
14. The method of claim 7, comprising incorporating at least one of
a temperature-induced variance factor and an electronic device
variance factor to generate the third map.
15. The method of claim 7, wherein the electrical characteristic is
resistance.
16. A system for determining a condition of an elevator tensile
support, comprising: a device for measuring an electrical
characteristic of at least a portion of the tensile support; and a
controller that relates the measured characteristic to a
predetermined data set indicating a relationship between
corresponding apparent characteristic values and conditions of the
tensile support and determines a current condition of the tensile
support.
17. The system of claim 16, wherein the controller determines a
rate of degradation of the tensile support for a selected load;
models a configuration of at least one selected elevator system;
estimates an elevator traffic pattern; determines sheave contact
and load information using the determined rate of degradation, the
modeled configuration and the estimated traffic pattern; and
determines a mean degradation of the tensile support from the
determined sheave contact and load information.
18. The system of claim 17, wherein the controller determines a
relationship between an electrical characteristic and a selected
condition of the tensile support and uses the determined
relationship and the determined mean degradation for determining an
apparent electrical characteristic value corresponding to the
selected condition of the tensile support.
19. The system of claim 18, wherein the controller determines a
plurality of the apparent electrical characteristic values and uses
those values to determine a relationship between a corresponding
measured electrical characteristic and a condition of a tensile
support.
20. The system of claim 16, wherein the electrical characteristic
is resistance.
21. A controller useful for determining a condition of an elevator
tensile support, comprising: programming for determining a rate of
degradation of the tensile support for a selected load; modeling a
configuration of at least one selected elevator system; estimating
an elevator traffic pattern; determining sheave contact and load
information using the determined rate of degradation, the modeled
configuration and the estimated traffic pattern; and determining a
mean degradation of the tensile support from the determined sheave
contact and load information.
22. The controller of claim 21, including programming for
determining a plurality of mean degradation values by varying at
least one of the modeled configuration or the estimated elevator
traffic pattern.
23. The controller of claim 21, including programming for
determining a relationship between an electrical characteristic and
a selected condition of the tensile support and using the
determined relationship and the determined mean degradation for
determining an apparent electrical characteristic value
corresponding to the selected condition of the tensile support.
24. The controller of claim 23, including programming for
determining a plurality of the apparent electrical characteristic
values and using the values to determine a relationship between a
corresponding measured electrical characteristic and a condition of
a tensile support.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/589,479 filed Aug. 14, 2006, which is the
national phase of International application No. PCT/US04/08192
filed Mar. 16, 2004, now U.S. Pat. No. 7,801,600, which issued Sep.
21, 2010.
TECHNICAL FIELD
[0002] The present invention relates to evaluating strength in a
tensile support, and more particularly to a system and method that
monitors tensile support strength based on electrical
characteristics of the tensile support.
BACKGROUND OF THE INVENTION
[0003] Tensile supports, such as coated steel belts or wire ropes
containing metal cords, are used to move an elevator car up and
down within an elevator shaft. Because the condition of the tensile
support is critical to safe operation of the elevator, there is a
need to determine the remaining strength level of the tensile
support and detect if the remaining strength level falls below a
minimum threshold.
[0004] Tensile support strength can be reduced by normal operation
of the elevator. The primary source of tensile support strength
degradation is the cyclic bending of the tensile support around
sheaves as the elevator is moved up and down in an elevator shaft.
Tensile support degradation is normally not uniform along the
length of the tensile support; instead, areas of the tensile
support subjected to high levels or severities of bending cycles
will degrade faster than areas experiencing fewer bend cycles.
[0005] Some electrical characteristics, such as electrical
resistance or impedance, of the cords in the tensile support will
vary as the cross-sectional area of the cords decrease. Thus, it is
theoretically possible to determine the remaining support strength
of the tensile support based on the cords' electrical
characteristics. However, as noted above, weaker spots in the
tensile support are usually distributed over the tensile support in
varying fashions depending on elevator usage (e.g., speed,
acceleration, jerk, etc.), elevator system layout, the cord
material, manufacturing variables, and other factors, making it
difficult to determine exactly when and where the tensile support
may have reached its minimum remaining strength. Without a
quantitative method relating an electrical characteristic of the
tensile support with the remaining tensile support strength,
electrical monitoring of the tensile support can only reveal
whether the tensile support is intact or broken.
[0006] There is a desire for a system and method that can
quantitatively indicate a remaining strength level of cords in a
tensile support based on electrical characteristics of the cords,
and therefore the electrical characteristic of the tensile
support.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a method and system
that can determine strength degradation in a tensile support based
on an electrical characteristic, such as electrical resistance. One
example system determines a relationship between strength
degradation and various physical factors, such as the rate of
degradation for a given load, operating environment information for
the tensile support, and estimated or actual usage data, to obtain
a map of mean degradation. This map of mean degradation is then
used to generate one or more maps linking the strength degradation
(i.e., in the form of a remaining strength percentage) and an
electrical characteristic, such as resistance, that varies as the
remaining tensile support strength varies. Based on these
electrical characteristic maps, it is possible to detect when the
tensile support has lost a given level of strength by measuring the
electrical characteristic.
[0008] In one embodiment, variances in the degradation rate of the
tensile support, the relationships between the electrical
characteristic and strength degradation, temperature, and/or
electrical devices used to measure the electrical characteristic
are taken into account to generate the electrical characteristic
maps.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a block diagram of a process for generating a map
of mean degradation according to one embodiment of the
invention;
[0010] FIG. 2 is a block diagram of a process for determining an
apparent resistance according to one embodiment of the
invention;
[0011] FIG. 3 is a plot of remaining strength probabilities for
given increases in apparent resistance according to one embodiment
of the invention;
[0012] FIG. 4 is a plot of remaining strength probabilities for an
estimated usage and for an actual usage according to another
embodiment of the invention;
[0013] FIG. 5 is a block diagram illustrating one possible
implementation of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0014] As noted above, the strength of a tensile support is related
to the cross-sectional area of the cords in the tensile support and
accumulated breaks in the cords as the tensile support is bent and
unbent around one or more sheaves during elevator operation.
Empirical testing can yield a strength loss model linking the loss
in tensile support strength and elevator operation factors, such as
tensile support loading, sheave geometry (e.g., sheave diameter),
and the number of bend cycles. In other words, the model provides a
relationship between a constant load and the rate of strength
degradation caused by the constant load.
[0015] Because different sections of the tensile support lose
strength at different rates, it is desirable to generate a map of
mean degradation to predict the amount of strength degradation for
any section in the tensile support. As a practical matter, it is
virtually impossible to locate the weakest portion of the tensile
support directly. However, because weakened portions of the tensile
support are distributed over the entire tensile support length
during use, the resistance of the entire tensile support can be an
accurate indication of the weakest section in the tensile support,
which dictates the tensile support's remaining strength.
[0016] FIG. 1 illustrates one method of generating the map of mean
degradation 100. In this embodiment, the map 100 is generated based
on a strength loss model 102 for the elevator system being
considered, the elevator configuration 104 and the estimated
elevator traffic 106. Each of these components will be explained in
greater detail below.
[0017] To obtain the strength loss model 102, the rate of
degradation of the tensile support for a given constant load is
obtained empirically. In one embodiment, repeated bend cycles are
applied to a plurality of sample tensile supports until they break.
This can be conducted using any known fatigue machine. From this
information, it is possible to determine a statistical distribution
of the number of bend cycles required to bend a given tensile
support to failure for a known constant load.
[0018] The remaining strength in the tensile support is also
dictated by the elevator configuration 104, such as the number of
sheaves in the elevator system, tensile support routing around the
sheaves, the distance between the sheaves, and the sheave
configuration. The estimated elevator traffic 106, such as
frequency of use, average passenger weight, etc., is also
considered in generating the mean degradation map. Usage details,
such as the number of times the elevator moves between certain
floors, directly affects the location and amount of degradation in
the tensile support. Taking estimated elevator traffic 106 and the
elevator configuration 104 into account keeps track of the number
of times a sheave contacts a particular section of the tensile
support and the tension at that time. This is tracked via a sheave
contact and load tracking algorithm 108. From this information, it
is possible to predict a wear state of a given section of the
tensile support and therefore predict the remaining strength of the
entire tensile support.
[0019] The mean degradation map 100 for a given elevator
configuration 104 can be analyzed statistically by varying the
estimated elevator traffic data 106 and the data on the degradation
rate 102 and data 108 for monitoring the effects of the load at
areas where the sheave contacts the tensile support in different
load and traffic situations. The resulting map of mean degradation
100 provides a statistical distribution of strength degradation for
a particular elevator system for a given constant load. In other
words, the map of mean degradation 100 indicates a range of bend
cycles in which the tensile support is expected to fail for a type
of elevator system.
[0020] To detect remaining strength in the tensile support based on
an electrical characteristic, such as electrical resistance, the
information in the map of mean degradation 100 needs to be linked
with the electrical characteristics of the tensile support,
preferably in the form of electrical characteristic maps. FIG. 2 is
a block diagram illustrating a process 200 according to one
embodiment of the invention to determine the relationship between
electrical resistance and remaining strength.
[0021] To generate the electrical resistance maps in this
embodiment, the degradation map 100 is first considered with a
degradation rate variance 202, which reflects the uncertainty in
the degradation rate reflected by the map 100. Although the map of
mean degradation 100 provides a range of possible values, the range
itself reflected in the map 100 may also vary. The degradation rate
variance 202 takes this into account when determining the
resistance maps. The amount of variance can be determined
empirically.
[0022] Evaluating the degradation map 100 with respect to the
degradation rate variance 202 generates a range of usage patterns
and wear rates of the tensile support and produces a range of
minimum tensile support strength and/or maximum loss in braking
strength (LBS) 204, which reflects the maximum amount that the
tensile support strength can be degraded. More particularly, the
maximum LBS can be determined by detecting the point in the
degradation map at which the tensile support strength is the
lowest, after taking the degradation rate variance 202 into
account, and then using this point as the maximum LBS value 204.
The maximum LBS 204 indicates the point at which the tensile
support would break if placed under extreme load.
[0023] This maximum LBS 204 value that can be linked with an
apparent resistance 205 value, which will be described in greater
detail below. From this link, an operator can be alerted to a weak
tensile support condition when the apparent resistance 205 reaches
a value corresponding to the maximum LBS 204.
[0024] Note that linking the relationship between the resistance
and the LBS for multiple tensile supports only provides a range of
possible resistance values for the maximum LBS. Additional
analysis, which will be explained below, is needed to obtain the
relationship between resistance values and strength characteristics
other than the LBS.
[0025] As noted above, the loss in the cross-sectional area of the
cords in the tensile support and accumulation of breaks in the
cords may affect electrical characteristics of the tensile support,
such as increase the electrical resistance. In the example shown in
FIG. 2, a relationship between the electrical resistance R and the
LBS is developed empirically and analytically to generate an R vs.
LBS map 206. Because the relationship between the resistance R and
the LBS can vary randomly among tensile supports due to
uncontrollable factors, such as manufacturing variables and
differing material properties, the process 200 simulates these
random variations in a variation map 208 and adds them to the R vs.
LBS map 206.
[0026] The modified degradation map 100, 202 and the modified R vs.
LBS map 206, 208 are incorporated together to generate an
electrical resistance map 210, which reflects the electrical
resistance at any given section of the tensile support. As shown in
the Figure, corresponding map points in the modified degradation
map 100, 202 and the modified R vs. LBS map 206, 208 are multiplied
together to obtain the resistance map 210. The total resistance of
the tensile support at any given time can be calculated by summing
212 the resistances of the tensile support sections together.
[0027] Temperature changes and variations among electronic devices
in the elevator system may change the apparent resistance of the
tensile support. In general, the effects of temperature-induced
variances 214 and electronic device variances 216 can be determined
experimentally and/or analytically. For example, the effect of
temperature changes on the tensile support resistance can be
calculated as well as empirically measured, while variances in
electronic devices can be empirically determined through testing.
The process 200 incorporates the effects of temperature-induced
variance 214 and electronic device variances 216 on the resistance
value to generate a resistance map that reflects the possible
values of the apparent resistance 205. Alternatively, if the
temperature along the tensile support is known or simulated, the
temperature variance may be applied to each value in the resistance
map 210 before the summation 212 is performed.
[0028] Thus, the analysis shown in FIGS. 1 and 2 generates a
distribution of minimum remaining tensile support strength
estimates and a corresponding distribution of apparent resistances
corresponding to the strength estimates. These distributions can be
analyzed statistically to produce probability estimates of
remaining tensile support strength for selected electrical
resistances.
[0029] FIG. 3 is a graph illustrating one possible relationship
between changes in the apparent, total tensile support resistance
and the probability estimates of remaining tensile support
strength. As shown in the Figure, the larger the percentage
increase in the apparent resistance (shown in FIG. 3 as "DR"), the
lower the amount of remaining strength in the tensile support. The
distributions shown in FIG. 3 illustrate the percentage of tensile
supports having a given percentage of remaining strength for a
given percent increase in apparent resistance. From this graph, it
is simple to estimate the amount of strength remaining in a tensile
support based on the amount its resistance has increased.
[0030] In another embodiment, the map of mean degradation 100 used
to calculate the apparent resistance and determine the strength
probability map is based on actual elevator usage data instead of
simulated or historical data. To obtain this embodiment, actual
elevator usage data can be substituted for the estimated elevator
traffic 106 in FIG. 1.
[0031] The actual elevator usage data may be continuously fed to
the sheave contact and load tracking algorithm 108 so that the map
of mean degradation 100, and therefore the apparent resistance
values 205 and corresponding resistance maps, can be updated
continuously as more data regarding the elevator usage is obtained.
In addition to the elevator usage factors used to estimate tensile
support degradation, this embodiment also considers how the
elevator is actually used and takes passenger loads and the
severity and number of bend cycles in any section of the tensile
support into account. Because the strength probability estimates
are based on actual elevator usage, the estimates of the remaining
strength levels obtained in this embodiment will likely have a
narrower range than those in the first embodiment, which
encompasses a broad range of possible elevator usage.
[0032] FIG. 4 shows a comparison between an estimate of remaining
tensile support strength based on estimated elevator usage versus
actual elevator usage. The actual elevator usage data provides an
electrical resistance value that improves the estimate of the
remaining tensile support strength for a given elevator system,
making it possible to set action thresholds in an elevator health
monitoring system that are relevant to the particular elevator
system being monitored.
[0033] FIG. 5 is a representative diagram of a system that
evaluates tensile support strength as described above. Generally,
the system 300 should include at least one electrical
characteristic measurement device, such as a resistance meter 302,
that monitors the tensile support and a temperature measurement
device 303 that monitors the tensile support's environment. The
system 300 also includes a processor 304 that generates the maps
described above from the measured electrical and temperature
characteristics and determines the probable remaining strength in
the tensile support. The specific components to be used on the
system 300 can be selected by those of ordinary skill in the
art.
[0034] By measuring the tensile support strength based on an
electrical characteristic, such as electrical resistance, the
invention can monitor the remaining strength level of the tensile
support, detect a minimum remaining strength level and, if desired,
prompt action based on the remaining strength level. Although the
examples described above focus on tensile supports used in elevator
applications, such as coated steel belts, the invention can be used
to monitor the strength of any structure whose electrical
characteristics vary based on tensile support strength. Further,
although the examples above focus on correlating resistance with
remaining strength, other electrical characteristics can be
monitored and used. The invention can be implemented in any known
manner using any desired components; those of ordinary skill in the
art will be able to determine what devices are needed to obtain the
electrical characteristic data, obtain simulation data, and
generate programs that can carry out the invention in a processor,
for example.
[0035] It should be understood that various alternatives to the
embodiments of the invention described herein may be employed in
practicing the invention. It is intended that the following claims
define the scope of the invention and that the method and apparatus
within the scope of these claims and their equivalents be covered
thereby.
* * * * *