KR20070029138A - Tensile support strength monitoring system and method - Google Patents

Abstract

A system and method monitoring the health of a support structure for an elevator based on an electrical characteristic, such as resistance, of the support structure and not the temperature of the structure. The resistance of a virgin support structure under the same temperature conditions as the support structure being monitored is calculated and subtracted from the measured resistance of the monitored support structure. The resistance value of the virgin support structure and the monitored support structure may be translated to a reference temperature to simplify calculations and monitoring of the support structure. ® KIPO & WIPO 2007

Description

Tensile Support Strength Monitoring System and Method {TENSILE SUPPORT STRENGTH MONITORING SYSTEM AND METHOD}

TECHNICAL FIELD The present invention relates to an elevator monitoring system, and more particularly, to a system for detecting an amount of wear in an elevator tension support structure.

Tensile support structures, such as coated steel belts or wire ropes, are often used in elevator systems to support elevator cars in hoists. Over time, normal bending of ropes or wires associated with elevator cabs and counterweight motions causes wear. This weakness reduces the cross section of the rope or cord in the tension support structure and weakens the support structure. Therefore, it is desirable to regularly monitor the condition of the supporting structure to detect when the structure is to be replaced.

One way to check the condition of the cord is to monitor electrical characteristics, such as the electrical resistance of the cord within the supporting structure. The reduction in cross section in the cord due to wear increases the resistance of the cord, making it theoretically possible to use the cord resistance measurement as a basis for indicating cord strength or cord condition and to set the resistance threshold at which the support structure must be replaced. do.

However, temperature fluctuations in the elevator hoist will also affect the cord resistance. For example, the temperature at the top of the hoistway may be 10 to 20 degrees Celsius higher than the temperature at the bottom of the hoistway. Since electrical resistance is also a function of temperature, the displacement of the cord resistance due to temperature fluctuations can be quite large, making it impossible to determine how much of the resistance displacement is due to temperature and how much is due to actual cord wear. Do. In other words, the resistance change caused by temperature can mask the resistance change due to wear, so that it is practically impossible to correlate the resistance with the cord condition.

There is a need for an elevator support structure monitoring system that can exclude the effects of temperature changes on the properties to be monitored.

The present invention is directed to a system and method for monitoring the state of a support structure for an elevator based on electrical properties such as resistance of the support structure. One embodiment of the present invention separates the measured electrical properties to compensate for the effect of temperature on the electrical properties, thereby more accurately reflecting the amount of wear in the structure rather than the temperature of the structure.

In one embodiment, the plurality of temperature sensors measure temperature at different points along the elevator hoistway. The resistance of the original support structure is calculated under the same temperature condition as the support structure to be monitored and subtracted from the measured resistance of the monitored support structure. The calculated difference reflects the change in resistance due to wear in the support structure.

In another embodiment, a single temperature sensor is used to isolate the effect of wear on the resistance of the support structure. Using a single temperature sensor in the system simplifies calculating the resistance due to wear. The resistance values of the original support structure and the monitored support structure can be converted to a reference temperature to further simplify the calculation and monitoring of the support structure.

1 is a representative view of an elevator system incorporating one embodiment of the present invention.

2 is a flowchart illustrating a process according to an embodiment of the present invention.

3 is a flowchart illustrating a process according to another embodiment of the present invention.

4 is a flowchart illustrating a process according to another embodiment of the present invention.

1 is a representation of an elevator system 100 incorporating one embodiment of the present invention. System 100 includes an elevator car 102 that is supported by a tension support structure 104, such as a belt, in hoistway 105. The support structure 104 is redirected by one or more pulleys 106. The configuration of the pulley 106 can be any known configuration suitable for the elevator system 100 (eg, one-to-one roping, two-to-one roping, etc.).

One or more temperature sensors 108 are disposed vertically along the hoistway 105. In one embodiment, the temperature sensor 108 is at an equidistant vertical position h _i along the hoistway, and Δh is the distance between the sensors. The spacing between the sensors 108 may vary, but keeping the spacing constant simplifies the calculation of the relationship between resistance and cord health. In another embodiment, the hoistway may have only one sensor 108 in the hoistway 105, such as near the top of the hoistway 105. This temperature sensor 108 is used to compensate for the temperature of any reading of the electrical properties of the support structure 104.

One or more electrical characteristic sensors 110 measure electrical characteristics of the support structure 104, such as resistance or conductivity. Electrical characteristic sensor 110 may be disposed at any point within elevator system 100. In the following example, it is assumed that the electrical characteristic sensor 110 measures the resistance, but other electrical characteristics may also be measured and used for calculation without departing from the scope of the present invention.

Processor 112 receives signals from temperature sensor 108 and resistance sensor 110. Based on the data from the temperature sensor 108, the processor 112 can standardize the data from the resistance sensor 110 to isolate the resistance change due to actual wear in the support structure 104, and the resistance data. It can reduce or eliminate the effects of temperature changes at. User interface 113 provides information about system 100 in a form that can be sensed by any user (eg, visual, audio, or both).

If system 100 includes only one temperature sensor 108, processor 112 indicates that the temperature reading of sensor 108 is the temperature of the entire hoistway or defines a temperature profile or gradient for which the temperature reading is assumed. Will be assumed. Of course, this assumption is approximate, but can yield acceptable results.

2 is a flowchart illustrating a method of standardizing resistance data according to an exemplary embodiment of the present invention. As is known, the resistance of a metal cord typically varies linearly with respect to temperature as well as to the cross-sectional geometry of the cord. The relationship between the resistance of the cord and its cross-sectional area is R = ρL / A, where R is the total cord resistance (Ω), ρ is the bulk resistivity of the code material (Ω-m), and L is the total length of the cord (m ) And A is the cross-sectional area of the cord (m 2).

The embodiment shown in FIG. 2 assumes there are a plurality of temperature sensors 108 spaced along the hoistway 105. Before any processing takes place, various initial values (block 200) are stored in memory 114 coupled to processor 112. These initial values are the resistance per unit length of the virgin cord and its deviation with respect to temperature, the number of temperature sensors 108 in the hoistway 105, the distance between each temperature sensor h _i and the hoistway 105 Ropping configuration of the support structure 104 in the). The resistance of the original cord is ideally approximated by a constant R = ρL / A, where ρ, L, and A are all constant, but the change in temperature along the hoistway 105 and the change in wear along the length in the support structure 104. The resistance reading also changes with the length of the support structure 104. In this case, the total electrical resistance of a given cord in the support structure 104 is most closely expressed by the following equation.

[Equation 1]

Here, the integration takes place along the length L of the support structure 104. Therefore, the estimated total resistance of the original code under the same temperature condition can be expressed as follows.

[Equation 2]

As shown in equation 2, it is assumed that the cross-sectional area A _virgin of the original cord is constant along the length of the support structure 104.

The data sent to the processor 112 at any given time is the temperature reading from the temperature sensor 108 and the current code resistance from the resistance sensor 110. The difference between the resistor R in the monitored cord and the resistor R _{virgin in the} original cord can be expressed as follows.

[Equation 3]

Since Equations 1 and 2 both calculate the total resistance to the same temperature condition, the effect of temperature on the resistance reading R in Equation 3 is eliminated, so that ΔR is reflected to reflect only the resistance change due to the wear of the cord. Leave it.

Equations 1 to 3 assume that the temperature function T (z) is continuous through the hoistway. As a practical matter, however, the hoistway will only contain finite N temperature sensors 108, preferably spaced along points h _j at a uniform distance Δh from each other, as shown in FIG. . The temperature sensors 108 may also be spaced apart from each other at non-uniform distances without departing from the scope of the present invention. Therefore, the integration in Equation 3 can be approximated by the sum and is represented by the following expression. Where c _i is And according to any known mathematical integral approximation, such as Simpson's law or trapezoidal law.

[Equation 4]

As is known, c _i may be 1 or 0.5 depending on the value for i and the law used. (For example, if i = 1 or N, c _i may be 0.5 if the trapezoidal law is used to perform the approximation in Equation 4.) If the spacing between temperature sensors 108 is not uniform, The skilled person will know how to modify Equation 4 to adjust this difference.

The constant K in Equation 4 may be included to account for any excess length of the support structure beyond the height of the hoistway 105. The actual excess length may vary depending on, for example, the roping configuration and / or the elevator height. In most cases, the value of K is negligible and can be ignored because the excess length is a small part of the total support structure length. In one embodiment, K is 1 in a 1: 1 rope configuration and 2 in a 2: 1 rope configuration. Of course other values for K can also be used.

Thus, based on the above equation, processor 112 obtains the temperature value T (h _j ) from each temperature sensor N [block 202], calculates the sum shown in equation 4 [block (204)], then subtract the sum from the measured resistance value R to obtain a value for ΔR (block 206). If necessary, the measured resistance value R is divided by the initial resistance value R _virgin to obtain a percentage change in the resistance value due to the loss of the cross-sectional area (block 208). The change in resistance ΔR and / or percentage change may be compared with a threshold value to evaluate the condition of the support structure (block 210).

To simplify the calculation, the sensing system may include only one temperature sensor 108 in the hoistway 105. In one embodiment, the temperature sensor 108 is located near the top of the hoistway 105. Since there is only one temperature sensor value considered, the resistance calculation can be simplified to obtain the following.

[Equation 5]

Where H is the length of the hoistway, L is the length of the support structure 104, and T (H) is the sensed hoistway temperature. In comparison with Equation 4, H in Equation 5 can be interpreted as corresponding to (N-1) dh, and L can be interpreted as corresponding to KH. If Equation 5 is used to monitor the condition of the supporting structure, the resistance value R _virgin of the original structure at various temperatures T (H) can be stored as a lookup table, so that the processor 112 reads the resistance for a given temperature T (H). You can refer to the exact value of R _virgin to subtract it from the value R.

To convert the measured resistance value R and the original resistance value R _virgin (T (H)) to the selected reference temperature, the measured resistance R and the initial resistance value R (T (H)) are ρ (T ₀ ) / ρ (T (H) Can be divided by the ratio, where T ₀ is the selection reference temperature. The reference temperature T ₀ is preferably chosen close to the room temperature, to facilitate obtaining an initial support structure resistance value R ′ _virgin (T ₀ ) for use by the processor 112. In addition, by converting the resistance values R and R _virgin to their corresponding values at a given reference temperature T ₀ , the support structure state is evaluated using a single value and a single resistance threshold for R _virgin rather than a different value for each temperature. Can be.

After dividing by the above ratio, the resistance difference at the reference temperature T ₀ can be expressed as follows.

 [Equation 6]

식6에서 알 수 있는 바와 같이, 변환된 저항 차 ΔR'은 변환된 측정 저항 R'를 기준 온도에서 최초 저항 R'_virgin로 감하는 것에 의해 근사치를 구할 수 있다.

As can be seen from Equation 6, the converted resistance difference ΔR 'can be approximated by subtracting the converted measurement resistance R' from the reference temperature to the initial resistance R ' _virgin .

Equations 5 and 6 act as approximations, but they are accurate enough to monitor the code state because they reduce the effect of temperature on the resistance reading R to be sufficient to isolate resistance changes due to changes in the code cross-sectional area. Do. In empirical experiments using an embodiment of the present invention, the difference between the calculation using only one temperature sensor 108 and the calculation using a plurality of temperature sensors 108 is about 3%, which means that It is an amount manageable by appropriate choice and acceptable in view of the added complexity of multiple sensors.

3 and 4 show two alternative embodiments that may be practiced if the hoistway has only one temperature sensor 108. In the embodiment shown in Figure 3, the processor obtains a lookup table that includes the total code resistance value for the original code as a function of temperature. Processor 112 then obtains a temperature reading T (H) from temperature sensor 108 and a resistance reading R from electrical characteristic sensor 110 (block 302). In this embodiment, processor 112 treats temperature reading T (H) as the temperature for the entire hoistway.

Processor 112 then selects a value for R _virgin based on temperature reading T (H) (block 304), and then subtracts R _virgin from resistance reading R to obtain ΔR (block 306). )]. If necessary, the resistance difference ΔR can be divided by the initial resistance value R _virgin to obtain a percentage change in resistance due to support structure wear (block 308). The percentage change in ΔR or resistance value may then be compared to the threshold resistance value (block 310).

In the alternative embodiment shown in FIG. 4, the initial value stored in the system 100 includes the initial resistance at the reference temperature R ' _virgin (T ₀ ). In this embodiment, the processor 112 obtains an initial value for R ' _virgin (T ₀ ) (block 311). After acquiring the temperature value T (H) and the resistance value R [block 312], the processor 112 converts the measured resistance value R to the equivalent measured resistance value R 'at the reference temperature T ₀ before any evaluation is made. can do. In this case, a lookup table for the initial resistance value R ' _virgin (T ₀ ) is not necessary, since for a given T ₀ R' _virgin (T ₀ ) will always be the same. Once the converted measured resistance value R 'is obtained, the initial resistance value at the reference temperature R' _virgin (T ₀ ) is subtracted from the converted value R 'to obtain the converted resistance difference ΔR' (block 316). This converted resistance difference ΔR ′ is then compared with a threshold value to evaluate the support structure condition (block 318).

In all the foregoing embodiments, the change from the detected temperature to the new temperature may initiate a recalculation of the converted resistance to reflect the new temperature. In addition, although the above examples focus on converting the initial resistance to reflect the temperature measured in the hoistway, both the initial resistance and / or the measured resistance as long as the initial resistance and the measured resistance are evaluated based on the same reference temperature. Can be converted.

By compensating the effect of temperature changes on the monitored electrical properties, the present invention ensures that the changes reflected in the electrical properties are due to wear in the support structure. Thus, the electrical properties are directly correlated with the state of the supporting structure and can be used as a method of monitoring and evaluating the remaining strength in the structure. This allows a single threshold to be set, for example indicating that the structure needs to be replaced, regardless of any temperature change in the hoistway.

While practicing the invention it should be understood that various alternatives to the embodiments of the invention described herein may be applied. The following claims define the scope of the invention, and methods and apparatus within the scope of these claims and their equivalents are intended to be included thereby.

Claims (19)

At least one temperature sensor disposed in the hoistway, A characteristic sensor to obtain measured electrical characteristics of at least a portion of the support structure; For a lift comprising a processor converting at least one of the measured electrical characteristics and the electrical characteristics of at least a portion of the original support structure to conform to a reference temperature to reflect the effect of temperature in the hoistway as indicated by the at least one temperature sensor. Support structure monitoring system, The value corresponding to the measured electrical characteristics is the measured value and the value corresponding to the electrical characteristics of the original supporting structure is the reference value, The processor calculates a difference between the measured value and the reference value, and compares the value corresponding to the difference with a predetermined threshold to determine the state of the support structure. The apparatus of claim 1, wherein the processor calculates a reference value by converting electrical characteristics of the at least a portion of the original support structure, wherein the reference temperature is equal to the temperature in the hoistway indicated by the at least one temperature sensor, and the measured value is Lifting structure monitoring system for elevators with the same measured electrical characteristics. The system of claim 1, wherein the processor detects a change in temperature at the at least one sensor for a new temperature and recalculates a reference value based on the new temperature. The processor of claim 1, wherein the processor divides the difference between the measured value and the reference value by a reference value to obtain a percentage change value that acts as a value corresponding to the difference, and supports the wear of the processor when the percentage change value exceeds a predetermined threshold. Support structure monitoring system for elevators directing structures. 2. The support structure monitoring system for an elevator according to claim 1, wherein the value corresponding to the difference is the difference between the measured value and the reference value itself and the processor indicates the worn support structure when the difference exceeds a predetermined threshold. The system of claim 1, wherein the at least one temperature sensor comprises a plurality of temperature sensors and the processor calculates a reference value based on temperature readings obtained from the plurality of temperature sensors. 7. The system of claim 6, wherein the plurality of temperature sensors are spaced at a uniform distance from each other along the hoistway. At least one temperature sensor, A characteristic sensor to obtain measured electrical characteristics of at least a portion of the elevator support structure; An elevator support structure assembly comprising a processor, The processor determines a temperature associated with at least a portion of the elevator support structure from the at least one temperature sensor, The processor converts at least one of the electrical and measured electrical properties of at least a portion of the original support structure to conform to the reference temperature to reflect the effect of temperature as indicated by the at least one temperature sensor, The corresponding value is the measured value and the value corresponding to the electrical characteristics of the original supporting structure is the reference value, And the processor calculates a difference between the measured value and the reference value and compares the value corresponding to the difference with a predetermined threshold to determine the state of the support structure. 9. The elevator support structure assembly of claim 8, further comprising a user interface indicating that the elevator support structure is worn when the vehicle exceeds a predetermined threshold. The apparatus of claim 8, wherein the processor calculates a reference value by converting electrical characteristics of the at least a portion of the original support structure, the reference temperature being equal to the temperature in the hoistway indicated by the at least one temperature sensor, and the measured value. Elevator support structure assembly having the same electrical characteristics as the measurement. 9. The processor of claim 8, wherein the processor divides the difference between the measured value and the reference value by a reference value to obtain a percentage change that acts as a value corresponding to the difference, wherein the processor wears support when the percentage change exceeds a predetermined threshold. An elevator support structure assembly indicative of the structure. 10. The elevator support structure assembly of claim 8, wherein the at least one temperature sensor comprises a plurality of temperature sensors spaced at a uniform distance from each other along the hoistway. Measuring a temperature associated with at least a portion of the support structure; Obtaining measured electrical characteristics of at least a portion of the support structure; Converting at least one of the electrical and measured electrical properties of at least a portion of the original support structure to reflect the effect of the measured temperature, wherein a value corresponding to the measured electrical property is a measured value and is dependent upon the electrical properties of the original support structure. The matching value is the reference value, Calculating a difference between the measured value and the reference value, And comparing a value corresponding to the difference with a predetermined threshold to determine a condition of the support structure. The method of claim 13, wherein the support structure comprises a plurality of portions, wherein determining the temperature comprises obtaining a plurality of temperature values, each temperature value associated with a different portion within the support structure, Determining the reference value includes monitoring the elevator support structure status, including converting electrical characteristics of each portion of the original support structure based on the temperature of the portion, and summing transformed electrical characteristics of the portions of the original support structure. Way. 15. The condition of the lift support structure of claim 13, wherein the converting step determines a reference value by converting electrical characteristics of the at least a portion of the original support structure, the reference temperature equals the measured temperature and the measured value equals the measured electrical property. Way. 14. The method of claim 13, further comprising obtaining a percentage change based on a reference value, wherein the indicating step indicates the worn support structure if the percentage change exceeds a predetermined threshold. The method of claim 13, wherein determining the reference value comprises determining electrical characteristics of at least a portion of the support structure at a known state at a plurality of temperatures. 18. The method of claim 17, wherein the known state is an initial support structure state. The method of claim 13, wherein the electrical property is resistance.

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