CN116294954A - Conductor strain evaluation method and device and cable life prediction method - Google Patents

Abstract

The present invention provides a conductor strain evaluation method and device capable of life prediction in a short time, and a cable life prediction method. A method for evaluating strain imparted to a conductor (11a) when a bending and/or twisting action is applied to a cable (10) having a conductor (11a) composed of twisted wire conductors formed by twisting a plurality of wires The method, wherein measuring the resistance value of the conductor (11a) which changes in time series when an action is periodically applied to the cable (10), based on the range of variation of the measured resistance value of the conductor (11a) which changes in time series to evaluate strain.

Description

Conductor strain evaluation method and device, cable life prediction method

technical field

The invention relates to a conductor strain evaluation method and device, and a cable life prediction method.

Background technique

For example, there is known a cable that is repeatedly bent and/or twisted to a cable that is laid on a movable part of an industrial robot. For example, in cables used for industrial robots, a sudden disconnection may cause a great inconvenience such as stopping of a production line. Therefore, it is desirable to replace the cable before most of the conductors arranged in the cable are disconnected (that is, before the cable reaches the end of its life). Furthermore, in order to judge the replacement timing of the cable, it is necessary to evaluate the disconnection of the conductor included in the cable with high accuracy.

At present, in order to evaluate the life of the cable, tests are carried out in which the operation of repeatedly bending and twisting is applied to the cable, and the number of operations at which the conductor resistance rises above a predetermined ratio due to disconnection of a plurality of wires constituting the conductor is set as the life of the cable.

In addition, there is Patent Document 1 as prior art document information related to the invention of the present application.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2007-139488

Contents of the invention

The problem to be solved by the invention

Regarding the existing methods of evaluating the life of cables, for cables in recent years that have greatly improved the durability against bending and twisting, for example, the evaluation time sometimes takes several months, which is very long, so that the evaluation is too expensive. The subject of time. Therefore, there is a demand for a method capable of predicting the lifetime of cables in a shorter period of time.

Therefore, an object of the present invention is to provide a conductor strain evaluation method and device, and a cable life prediction method capable of predicting the life of a cable in a short time.

Solution to the problem

The present invention aims at solving the above-mentioned problems, and provides a conductor strain evaluation method, which is a method of evaluating the strain imparted to the above-mentioned conductor after bending and/or twisting is applied to the cable having the conductor. The above-mentioned conductor is composed of A stranded wire conductor composed of a plurality of wires twisted, wherein the resistance value of the above-mentioned conductor that changes in time series when the above-mentioned action is periodically applied to the above-mentioned cable is measured, based on the measured resistance value of the above-mentioned conductor that changes in the above-mentioned time series The range of variation of the resistance value was used to evaluate the above-mentioned strain.

Furthermore, the present invention aims at solving the above-mentioned problems, and provides a conductor strain evaluation device, which is a device for evaluating the strain applied to the above-mentioned conductor after bending and/or twisting is applied to the cable having the conductor. A stranded conductor is composed of a plurality of wires twisted, and the conductor strain evaluation device includes: a resistance value measuring unit that measures the resistance value of the conductor that changes in time series when the above-mentioned operation is periodically applied to the cable; and strain An evaluation unit that evaluates the strain based on a variation range of the resistance value of the conductor that changes in the time series measured by the resistance value measurement unit.

In addition, the present invention provides a cable life prediction method for the purpose of solving the above-mentioned problems, wherein the variation range of the above-mentioned resistance value is obtained by using a conductor strain evaluation method, and the relationship between the variation range of the above-mentioned resistance value and the attained life of the above-mentioned cable is obtained in advance. The relationship between the number of times of operation of the above-mentioned cable is based on the obtained fluctuation range of the above-mentioned resistance value and the above-mentioned relationship, and the number of times of operation of the above-mentioned cable before the end of the life of the cable is predicted.

The effects of the invention are as follows.

According to the present invention, it is possible to provide a conductor strain evaluation method and device, and a cable life prediction method capable of life prediction in a short time.

Description of drawings

FIG. 1 is a schematic diagram of a cable life prediction device using a conductor strain evaluation device according to an embodiment of the present invention.

Fig. 2 is a sectional view showing a section perpendicular to the longitudinal direction of the cable.

FIG. 3 is a diagram illustrating a resistance value of a conductor measured when the operating part is operated.

FIG. 4 is a diagram illustrating estimation of an operating frequency.

FIG. 5 is a diagram illustrating setting of a start point of a period.

FIG. 6 is a diagram illustrating a method of obtaining an equivalent amount of strain.

Fig. 7 is a graph showing the relationship between the equivalent amount of strain and the number of operations until the cable reaches its lifetime.

FIG. 8 is a flowchart of a conductor strain evaluation method according to one embodiment of the present invention.

Symbol Description

1—conductor strain evaluation device, 10—cable, 11—wire, 11a—conductor, 11b—insulator, 20—action part, 30—resistance value measurement part, 32—operation frequency estimation part, 33—cycle starting point setting part, 34—Strain Evaluation Department.

Detailed ways

[implementation mode]

Embodiments of the present invention will be described below with reference to the drawings.

The inventors considered the following: when predicting the life of a cable when bending and/or twisting operations are repeatedly applied to the cable, the strain applied to the conductor in one operation is considered, and the number of operations at which the cable reaches its life is estimated based on the strain. . That is, the cable life prediction method of the present embodiment is a method of predicting the number of operations at which the cable reaches its life (referred to as cable life) based on the strain applied to the conductor when the cable is bent and/or twisted. In addition, as the life of the cable, for example, when the cable is repeatedly subjected to bending and/or twisting operations, the ratio of how many wires among all the wires constituting the conductor are broken is a predetermined ratio or more (for example, 80% or more). In this case, it is assumed that the cable life has been reached.

In addition, as the bending action applied to the cable, there are, for example, a U-shaped bending action and a left-right bending action. The conductor cable is bent into a U-shape, and one end of the cable is periodically slid and moved along the cable length direction of the one end with a predetermined stroke. During the left and right bending action, as shown in Figure 3 below , to apply a constant force to the cable at a constant cycle in a reciprocating manner between the state where the cable is bent either clockwise or counterclockwise and the state where the cable is bent either clockwise or counterclockwise . And, as the action of twisting that is applied to the cable, for example, there is a twisting action, that is, one end of the cable having a conductor made of a twisted wire conductor twisted with a plurality of wires is fixed. The torsion section at a predetermined torsion length (for example, 10 mm or more) in the cable length direction repeatedly twists the cable at a constant cycle in the cable circumferential direction at a predetermined torsion angle (for example, ±180° to ±360°).

In order to predict the life of the cable with high precision using this method, it is necessary to measure the strain applied to the conductor when bending and/or twisting is applied to the cable with high precision. However, it is difficult to obtain sufficient accuracy and it takes labor and time to measure the strain of the strain gauges generally used today. Therefore, the inventors considered measuring the change in the resistance value of the conductor itself, which is the measurement target of the strain. However, the change in the resistance value after strain is applied to the conductor is small and buried in noise, making it difficult to measure with high precision. Therefore, the inventors completed the present invention as a result of intensive studies to measure minute changes in resistance value after strain is applied to conductors with high precision.

(Conductor Strain Evaluation Device 1 and Cable Life Prediction Device 100)

FIG. 1 is a schematic diagram of a cable life prediction device 10 using a conductor strain evaluation device 1 according to the present embodiment. In addition, FIG. 2 is a cross-sectional view showing a cross section of the cable 10 perpendicular to the longitudinal direction.

The cable 10 shown in FIG. 2 is configured such that a crimping tape 14 is helically wound around a cable core 13 twisted with six electric wires 11 and a filamentary clamping member 12, and the crimping tape 14 is covered. Set the sheath 15 in a surrounding manner. The electric wire 11 has the conductor 11a which consists of the twisted wire conductor which twisted a some wire rod, and the insulator 11b provided so that the periphery of the conductor 11a may be covered. The conductor 11 a is constituted by, for example, a multi-strand wire formed by twisting 26 wires composed of annealed copper wires with an outer diameter of 0.16 mm. In addition, the wire rod used for the conductor 11a is not limited to 26 wires. The interposition material 12 is, for example, a filament made of jute or staple fiber. The insulator 11b is made of, for example, a fluororesin such as ETFE (tetrafluoroethylene-ethylene copolymer). Although not shown in FIG. 2 , a central interposition member made of a polyethylene linear body or the like may be arranged in the center of the cable. The outer diameter of each electric wire 11 is, for example, 1.74 mm, and the outer diameter of the cable 10 is, for example, 6.8 mm.

In addition, the number of electric wires 11 used for the cable 10 is not limited to six. That is, the number of electric wires 11 may be one, several, or several tens or more. Moreover, when the electric wire 11 is one, the interposer 12, the crimping tape 14, and the sheath 15 are not included in many cases. In this case the cable 10 and the wire 11 are shown identical. The pinch belt 14 is comprised by the belt member which consists of nonwoven fabrics, paper, resin, etc., for example. The sheath 15 is made of, for example, PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), or the like. In addition, the cable 10 is not limited to the structure shown in figure, What is necessary is just to include at least the conductor 11a which consists of several wires, and can have various structures.

As shown in FIG. 1 , the conductor strain evaluation device 1 evaluates the strain applied to the conductor 11a when bending and/or twisting is applied to the cable 10 having a conductor 11a composed of a stranded conductor twisted with a plurality of wires. The device for strain includes an operating unit 20 , a resistance value measuring unit 30 , and an arithmetic unit 31 .

The operation unit 20 repeats the operation of bending and/or twisting the cable 10 at a constant cycle. Here, the case where the action part 20 is a member that imparts left and right bending actions to the cable 10 will be described. Folding and twisting movements. Furthermore, when evaluating the cable 10 already mounted in a device such as an industrial robot, the device such as an industrial robot can also be used as the operating unit 20 .

In the example of FIG. 1 , the action unit 20 has a disc-shaped base 21 rotatably provided on a base not shown, and a pair of cylinders provided opposite to each other on the base 21 with the central axis of the base 21 interposed therebetween. Shaped mandrel 22, and fixing portion 23 for fixing cable 10 on pedestal 21. When the pedestal 21 is turned left and right about the central axis, the cable 10 arranged to pass between the mandrels 22 is bent to the left and right along the mandrels 22 . In addition, the operation part 20 shown in FIG. 1 is just an example, and can be changed suitably.

The resistance value measurement unit 30 measures the resistance value of the conductor 11 a that changes in time series when the operation unit 20 periodically applies an operation such as bending to the cable 10 . The resistance value measurement unit 30 measures the resistance value between both ends of the conductor 11 a in the cable 10 placed on the operation unit 20 over time. The data (=resistance value data 50 ) of the resistance value of the conductor 11 a that changes in time series measured by the resistance value measuring unit 30 is input to the arithmetic unit 31 and stored in the storage unit 31 b. In addition, although the case where the resistance value measurement part 30 is provided separately from the calculation device 31 was shown here, the resistance value measurement part 30 may be built in the calculation device 31. Furthermore, when an apparatus such as an industrial robot is used as the operating unit 20, the resistance value measuring unit 30 may be mounted on a control device of the apparatus such as the industrial robot.

Here, the resistance value of the conductor 11 a measured when the cable 10 is bent from side to side by the operation unit 20 will be described. As shown in FIG. 3 , from the state in which the cable 10 is straight (called the basic state C), the pedestal 21 is rotated 90° clockwise to bend the cable 10 by 90° (called the first state A), and the pedestal 21 is reversed. A 90° clockwise rotation returns the cable 10 to a straight line (basic state C). Thereafter, the base 21 is rotated 90° counterclockwise to bend the cable 10 by −90° (referred to as the second state B), and the base 21 is rotated 90° clockwise to return the cable 10 to a straight line (basic state C). In this way, the pedestal 21 is sequentially rotated from the basic state C to the first state A, the basic state C, the second state B, and the basic state C, which constitutes one (one cycle) operation. The time taken for one movement, that is, the movement period is 2 seconds (the frequency (=movement frequency) at the time of one movement is 0.5 Hz).

In the cable 10, since a plurality of electric wires 11 are twisted, the strain applied to the conductor 11a changes according to the twisted state. In the example of FIG. 3 , in the first state A in which the cable 10 is bent by 90°, the conductor 11a passes outside the bend, so the conductor 11a is stretched compared to the basic state C, and the resistance value increases. However, in the second state B in which the cable 10 is bent at -90°, the conductor 11a passes inside the bend, so the stretching of the conductor 11a does not occur, and the resistance value of the conductor 11a becomes almost zero from the basic state C. state of change. Therefore, as shown in the lower part of Fig. 3, in one cycle of operation, the change of the resistance value becomes an asymmetric waveform, and it becomes a waveform containing a large number of high-order frequency components n times (n is a natural number greater than 2) of the operating frequency. waveform.

The computing device 31 has a control unit 31a and a storage unit 31b. An operating frequency estimation unit 32 , a cycle start point setting unit 33 , and a strain evaluation unit 34 are mounted on the control unit 31 a. The operating frequency estimation unit 32 , cycle start point setting unit 33 , and strain evaluation unit 34 are realized by appropriately combining computing elements such as CPU, memories such as RAM and ROM, software, interfaces, storage devices, and the like. A display 60 is connected to the computing device 31 , and various data stored in the storage unit 31 b such as strain equivalent data 55 and predicted life data 57 described below can be displayed on the display 60 . In addition, although not shown, an input device such as a keyboard is provided in the computing device 31 , and various settings and operations on the display content of the display 60 can be performed through input from the input device. In addition, the display 60 may be constituted by a touch panel display, and the display 60 may also be configured as an input device. In addition, the display 60 may be connected to the computing device 31 not by wire, but may also be connected wirelessly. In this case, the display 60 may be, for example, a display of a smartphone or a tablet.

The computing device 31 is constituted by, for example, a personal computer. In addition, without being limited thereto, the computing device 31 may be, for example, a server device. In this case, the resistance value data 50 measured by the resistance value measuring unit 30 is transmitted to the computing device 31 as a server device via a network. When the computing device 31 is configured as a server device, it can be configured to be able to share the following strain evaluation results and cable life prediction results with users of devices such as industrial robots and device manufacturers, for example. In addition, the control unit 31a and the storage unit 31b may be constituted by different devices. For example, the control unit 31a installed in another server device, personal computer, etc. can also be configured to download the resistance value data 50 stored in the storage unit 31a of the server device, and perform evaluation of strain and prediction of cable life.

The operating frequency estimation unit 32 is used to estimate the operating frequency based on the resistance value data 50 measured by the resistance value measuring unit 30 when the operating frequency is unknown. Therefore, when the operating frequency (or operating period) is known or obtained from information such as position information of the pedestal 21 or time associated with the position information of the pedestal 21 , the operating frequency estimation unit 32 can be omitted.

The operating frequency estimation unit 32 performs frequency analysis on the resistance value data 50 measured by the resistance value measuring unit 30 , that is, the resistance value data of the conductor 11 a that changes in time series, and estimates the operating frequency based on the result of the frequency analysis. Specifically, as shown in FIG. 4, the frequency analysis of the resistance value data 50 measured by the resistance value measuring unit 30 is performed, and the magnitude of the signal (that is, the amplitude of the resistance value fluctuation or the resistance value) is obtained for each component of each frequency. range of value change). In the present embodiment, since the load is applied to the cable 10 at a constant cycle (operating frequency), in the analysis result 51 of the frequency analysis, the operating frequency component and n-fold higher frequency components are larger than other frequency components. Therefore, it is preferable to extract a frequency with a large signal magnitude from the analysis result 51 of the frequency analysis, and to estimate the smallest (lowest order) frequency among the extracted frequencies as the operating frequency. In addition, it is preferable to exclude frequency components near 0 Hz (for example, below 0.2 Hz) where the influence of noise is large. Furthermore, even at a frequency with a large signal magnitude, if the signal magnitude at a frequency n times the frequency is small and high-order frequency components do not occur, the frequency may be excluded as noise. In the example of FIG. 4 , if the frequency components near 0 Hz are excluded, the frequency components of 0.5 Hz and 1.0 Hz surrounded by the dotted line become larger, and it can be inferred that the minimum 0.5 Hz is the operating frequency. The operating frequency estimated by the operating frequency estimation unit 32 is stored in the storage unit 31 b as operating frequency data 50 a.

The cycle starting point setting unit 33 is used to set the starting point of an operation cycle in operations such as bending. Therefore, when the starting point of the cycle is known (for example, when the position information of the pedestal 21 is obtained in relation to the resistance value data 50 or information such as time associated with the position information of the pedestal 21), the setting of the starting point of the cycle can be omitted. Section 33.

As shown in FIG. 5 , in this embodiment, in order to eliminate the influence of noise, the cycle start point setting unit 33 extracts the operating frequency estimated by the operating frequency estimating unit 32 from the resistance value data 50 of the conductor 11 a which changes in time series. (here, 0.5 Hz), and set the starting point of the cycle based on the time-series change 52 of the extracted operating frequency component. For example, the cycle starting point setting unit 33 can set the resistance value of the conductor 11a to be equal to the resistance value of the conductor 11a (indicated by the dotted line in FIG. On the other hand, the time when the resistance value becomes maximum (the first state A in FIG. 3 is reached) is set as the start point of the cycle. From the starting point set here to the time when the operation cycle corresponding to the operation frequency passes is a section corresponding to one operation. In addition, the specific method of setting the starting point of the cycle is not particularly limited, and the basic state C may not be set as the starting point of the cycle. That is to say, if the time of the same state can be specified in each operation cycle, any time can also be set as the starting point of the cycle, for example, the time when the resistance value becomes maximum (first state A), The time when it becomes extremely small (the second state) is set as the starting point of the cycle. The start point of the cycle set by the cycle start point setting unit 33 is stored in the storage unit 31b as the cycle start point data 50b.

The strain evaluation unit 34 evaluates the strain based on the variation range of the resistance value of the conductor 11 a that changes in time series measured by the resistance value measurement unit 30 . However, when the variation width of the resistance value only in a section corresponding to one operation is used, it is considered that the influence of noise becomes large and sufficient evaluation accuracy cannot be obtained. Therefore, in the present embodiment, the strain evaluation unit 34 divides the resistance value of the conductor 11 a that changes in time series for each operation cycle, and divides the resistance value of each divided cycle for each elapsed time from the start point of the cycle. The change in resistance value was averaged, the change in resistance value for one cycle after averaging was obtained, and the strain was evaluated based on the range of variation in resistance value in the change in resistance value for one cycle after averaging.

More specifically, as shown in FIG. 6 , the strain evaluation unit 34 firstly, based on the operating frequency estimated by the operating frequency estimating unit 32 and the starting point of the cycle set by the cycle starting point setting unit 33, each corresponds to one movement. The resistance value data 50 is divided into intervals (that is, the resistance value data 50 is divided for each operation cycle). Hereinafter, the divided resistance value data 50 is referred to as divided resistance value data 53 . The obtained divided resistance value data 53 is stored in the storage unit 31b.

Here, it can be said that it is desirable to use as many divided resistance value data 53 as possible in order to further suppress the influence of noise and further improve the evaluation accuracy. Therefore, when measuring the resistance value data 50, it can be said that it is desirable to perform measurement for a somewhat longer time. Specifically, it is more desirable to set the period for measuring the resistance value so as to include an operation cycle of 300 or more.

Then, the strain evaluation unit 34 superimposes and averages a plurality of divided resistance value data 53 , and obtains the averaged resistance value data of one section (one period). Hereinafter, the averaged resistance value data of one section (one cycle) is referred to as averaged resistance value data 54 . When performing averaging, all the resistance values at the same time (elapsed time from the start point of the cycle) in each section are added, and the average is performed by dividing by the number of added sections. The obtained averaged resistance value data 54 is stored in the storage unit 31b.

Then, the strain evaluation unit 34 obtains the variation range of the resistance value in the obtained averaged resistance value data 54 , that is, the value obtained by subtracting the minimum value from the maximum value of the resistance value in the averaged resistance value data 54 as the strain equivalent. quantity. This equivalent amount of strain is an amount proportional to the strain applied to the conductor 11a. The strain applied to the conductor 11a can also be calculated from the equivalent amount of strain, but in this embodiment, the equivalent amount of strain is used as it is as a parameter indicating the degree of strain applied to the conductor 11a. The obtained equivalent strain is stored in the storage unit 31 b as equivalent strain data 55 .

The cable life prediction device 100 includes the conductor strain evaluation device 1 of the present embodiment and a device for predicting the cable 10's life expectancy based on the equivalent amount of strain (the variation range of the resistance value in the averaged resistance value data 54) obtained by the conductor strain evaluation device. The life prediction unit 35 of the number of operations of the cable 10 . The life expectancy unit 35 is mounted on the control unit 31a of the arithmetic device 31, and is realized by appropriately combining arithmetic elements such as CPU, memories such as RAM and ROM, software, interfaces, storage devices, and the like.

The life predicting unit 35 obtains in advance the relationship between the equivalent amount of strain (the variation range of the resistance value of the averaged resistance value data 54 ) and the number of operations of the cable 10 at which the cable 10 reaches its life by actually measuring, and predicts the life of the cable 10 based on this relationship. The number of actions of the cable 10. FIG. 7 is a graph showing the relationship between the measured amount of equivalent strain and the number of operations at which the cable 10 reaches its lifetime (the number of lifetime operations). As shown in FIG. 7 , the equivalent amount of strain is approximately proportional to the number of times the cable 10 operates to reach its lifetime. The relationship in FIG. 7 is obtained in advance through experiments or the like, and is stored in the storage unit 31 b in advance as relational data 56 for life prediction. The life predicting unit 35 uses the life predicting relational data 56 stored in the storage unit 31 b to find the number of operations for the cable 10 to reach its life corresponding to the equivalent amount of strain calculated by the conductor strain evaluating device 1 . The obtained number of operations at which the life of the cable 10 is reached is stored in the storage unit 31b as predicted life data 57 .

(Conductor Strain Evaluation Method and Cable Life Prediction Method)

FIG. 8 is a flowchart of a conductor strain evaluation method according to this embodiment. As shown in FIG. 8, in the conductor strain evaluation method of the present embodiment, first, in step S10, the cable 10 to be measured is mounted on the operating part 20, and connected to both ends of the conductor 11a to be measured. Resistance value measuring part 30. Thereafter, in step S11 , the operation of the operation unit 20 is started, and the measurement of the resistance value of the conductor 11 a by the resistance value measurement unit 30 is started. Then, the operation of the operation unit 20 and the measurement of the resistance value measurement unit 30 are continued for a predetermined period (step S12). Thereafter, in step S13, the operation of the operation unit 20 and the measurement of the resistance value measurement unit 30 are stopped, and the obtained resistance value data 50 is stored in the storage unit 31b. The resistance value data 50 obtained here corresponds to the "resistance value of the conductor 11a that changes in time series after an action is periodically applied to the cable 10" in the present invention.

Thereafter, in step S14 , the operating frequency is estimated from the resistance value data 50 . Specifically, as described in FIG. 4 , the frequency analysis is performed on the resistance value data 50, and based on the analysis result 51 of the frequency analysis, the lowest frequency among the frequencies at which the magnitude of the signal becomes large (wherein 0 Hz is appropriately excluded) Noisy frequencies such as nearby frequencies) are used to infer the action frequency equivalent to the action cycle. The operating frequency estimated by the operating frequency estimation unit 32 is stored in the storage unit 31 b as operating frequency data 50 a. In addition, when the operating frequency is known, or the operating frequency is obtained from information such as the position information of the pedestal 21 or the time associated with the position information of the pedestal 21 , step S14 can be omitted.

After that, in step S15, the start point of the period is set. Specifically, as described in FIG. 5 , the operating frequency component stored as operating frequency data 50a is extracted from the resistance value data 50, and is set based on the time-series change 52 of the extracted operating frequency component. The start of the action cycle. The start point of the cycle set by the cycle start point setting unit 33 is stored in the storage unit 31b as the cycle start point data 50b. In addition, when the starting point of the period is known, step S15 can be omitted.

Thereafter, in step S16 , the resistance value data 50 is divided to obtain divided resistance value data 53 . Specifically, as illustrated in FIG. 6 , each interval determined based on the operating frequency (operation cycle) stored as the operation frequency data 50a and the start point of the cycle stored as the cycle start data 50b (that is, each operation period) to divide the resistance value data 50 to obtain a plurality of divided resistance value data 53 . The obtained divided resistance value data 53 is stored in the storage unit 31b.

Then, in step S17 , the plurality of divided resistance value data 53 obtained in step S16 are superimposed and averaged to obtain averaged resistance value data 54 . Specifically, as illustrated in FIG. 6 , a plurality of divided resistance value data 53 is averaged for each elapsed time from the beginning of the cycle, and the averaged resistance value change for one cycle after averaging is obtained. resistor value data 54. The obtained averaged resistance value data 54 is stored in the storage unit 31b.

Thereafter, in step S18, the equivalent amount of strain is obtained from the variation range of the resistance value in the averaged resistance value data 54 obtained in step S17. The obtained equivalent amount of strain is an amount proportional to the strain applied to the conductor 11 a in one operation, and the equivalent amount of strain can be used to evaluate the strain applied to the conductor 11 a. In this way, in the conductor strain evaluation method of the present embodiment, the strain is evaluated based on the averaged variation range of the resistance value of the conductor 11 a per operation. The obtained equivalent strain is stored in the storage unit 31 b as equivalent strain data 55 .

In the cable life prediction method of the present embodiment, an experiment is performed in advance to obtain the relationship shown in FIG. It is stored in advance in the storage unit 31b as the relational data 56 for life prediction. Moreover, the operating conditions (such as the number of times of bending, bending radius, bending angle, twisting times, length of the twisted portion, twisting angle, twisting speed, etc.) and structural conditions (such as the size of the conductor, the structure of the stranded conductor) , the size of the insulator, the number of wires, the twisting distance of the wire, etc.) or material conditions (such as the material of the conductor, the material of the insulator, the material of the crimping tape, the material of the sheath, etc.), the cable 10 is based on In the evaluation of strain in the conductor strain evaluation method described above, an equivalent amount of strain (=updated equivalent amount of strain) obtained by updating the operating conditions of the cable 10 and the like is obtained. The updated equivalent strain calculated here is stored in the storage unit 31 b as equivalent strain data (=updated equivalent strain data) 55 obtained by updating the operating conditions of the cable 10 . The life predicting unit 35 predicts that the cable 10 after the operating condition has been updated will reach the end of its life based on the relational data 56 for life prediction and the updated equivalent strain (variation range of the resistance value) stored as the updated equivalent strain data 55 . the number of actions. The predicted number of operations at which the cable 10 reaches its lifetime is stored in the storage unit 31 b as predicted lifetime data 57 . The operating conditions, structural conditions, and material conditions of the cable 10 are stored in the storage unit 31b as condition data for obtaining the strain equivalent data 55 and predicted life data 57 stored in the storage unit 31b.

In addition, the predicted life data 57 stored in the storage unit 31 b can also be used as the relational data 56 for life prediction. For example, it may also be configured such that the predicted life data 57 within a predetermined period (for example, a period of several days, months, or years) from when it is stored in the storage unit 31b is directly used as the predicted life data 57, and after the predetermined period The predicted life data 57 after the period transitions to the relational data 56 for life prediction. In addition, the estimated lifetime data 57 stored in the storage unit 31b may be configured to transition to the lifetime prediction relational data 56 when the updated strain equivalent amount data 55 is stored in the storage unit 31b. The condition data may also contain information about the time of day the strain was evaluated.

(Functions and Effects of Embodiments)

As described above, in the conductor strain evaluation method of the present embodiment, the resistance value of the conductor 11a that changes in time series is measured when an action is periodically applied to the cable 10, and the measured resistance value of the conductor 11a that changes in time series is measured. The strain was evaluated based on the variation range of the resistance value.

Accordingly, the strain of the conductor 11 a can be easily evaluated, and the number of operations until the life of the cable 10 reaches its lifetime can be evaluated in a short time based on the estimated strain. Currently, it is necessary to conduct a test until the conductor 11a is disconnected (the resistance value of the conductor 11a rises above a predetermined ratio), which requires a very long test time such as several months. The life of the cable 10 can be predicted in a short period of time, such as several tens of minutes, for example. In addition, although the change in the resistance value of the conductor 11a due to strain is small, the measured resistance value data 50 is divided for each section to obtain divided resistance value data 53, and the divided resistance value data 53 is averaged. Then, the averaged resistance value data 54 is obtained, and the variation range of the resistance value in the averaged resistance value data 54 is obtained as an equivalent amount of strain, so that the influence of noise can be suppressed, and the evaluation of strain can be performed with high accuracy (that is, , the measurement of the equivalent amount of strain).

In addition, for example, it is also possible to predict the life of the cable 10 by simulation, but in order to predict the life with high accuracy, it is necessary to take into account the friction between the electric wire 11 and the surrounding parts, the movement of the electric wire 11 formed by bending, and the movement of the electric wire 11 caused by bending. Various behaviors such as changes in the twisted state of the electric wire 11 caused by bending or the like are simulated. Therefore, it is very difficult to accurately predict the lifetime of the cable 10 by simulation. According to the present invention, since the life of the cable 10 can be predicted using the strain when the cable 10 is actually operated, it is possible to perform highly accurate life prediction.

Furthermore, according to the present embodiment, since life prediction can be performed in a short time, strain evaluation and cable 10 The life prediction of the cable 10 is easy to obtain the operating conditions and the like that impose the least burden on the conductor 11a and maximize the life of the cable 10, that is, optimize the operating conditions and the like. For example, changes in the life of the cable 10 when the radius of curvature of the cable 10 is changed when the cable 10 is bent, changes in the life of the cable 10 when the excess length of the cable 10 in the movable part for bending or the like is changed, etc. It is easy to predict the life of the cable 10 under various operating conditions, etc., and it is easy to optimize the structure of the cable 10, the material conditions used for the cable 10, and the like.

(summary of embodiment)

Next, technical ideas grasped from the embodiments described above will be described by citing symbols and the like in the embodiments. In addition, each code|symbol etc. in the following description does not limit the component in a claim to the member etc. which are specifically shown in embodiment.

[1] A conductor strain evaluation method, which is a method of evaluating the strain applied to the above-mentioned conductor 11a when bending and/or twisting is applied to the cable 10 having the conductor 11a, the above-mentioned conductor 11a is formed by twisting a plurality of wires. The twisted wire conductor configuration, wherein the resistance value of the above-mentioned conductor 11a that changes in time series when the above-mentioned action is periodically applied to the above-mentioned cable 10 is measured, based on the measured resistance value of the above-mentioned conductor 11a that changes in the above-mentioned time series The range of variation of the value is used to evaluate the above-mentioned strain.

[2] The conductor strain evaluation method according to [1], wherein the resistance value of the conductor 11a that changes in the time series is divided for each operation cycle, that is, the operation cycle, and the resistance value of the conductor 11a that changes in the time series is divided for each operation cycle from the start point of the cycle. The change in the resistance value of each divided cycle is averaged, and the change in the resistance value of one cycle after the average is obtained. Based on the above-mentioned change in the resistance value of one cycle after the average The above-mentioned strain was evaluated by the variation range of the resistance value.

[3] The conductor strain evaluation method according to [2], wherein a frequency analysis is performed on the resistance value of the conductor 11a that changes in the time series, and an operating frequency corresponding to the operating cycle is estimated based on the result of the frequency analysis. .

[4] The conductor strain evaluation method according to [3], wherein the component of the operating frequency estimated is extracted from the resistance value of the conductor 11a that changes in the time series, and based on the extracted operating frequency The time-series change of the composition sets the starting point of the above cycle.

[5] A conductor strain evaluation device 1 that evaluates the strain applied to the conductor 11a when bending and/or twisting is applied to the cable 10 having the conductor 11a made of a plurality of wires A stranded wire conductor configuration, wherein: a resistance value measurement unit 30 that measures the resistance value of the conductor 11a that changes in time series when the above-mentioned motion is periodically applied to the cable 10; and a strain evaluation unit 34 , which evaluates the strain based on the variation range of the resistance value of the conductor 11 a measured by the resistance value measuring unit 30 in the time series.

[6] A cable life prediction method, which uses the conductor strain evaluation method described in any one of [1] to [3] to obtain the variation range of the above-mentioned resistance value, and obtains in advance the difference between the above-mentioned variation range of the resistance value and the above-mentioned The relationship between the number of operations of the cable 10 at which the cable 10 reaches its lifetime is predicted based on the obtained variation range of the resistance value and the above relationship, and the number of operations of the cable 10 at which the cable 10 reaches its lifetime is predicted.

(Note)

As mentioned above, although embodiment of this invention was described, the embodiment described above does not limit the invention of a claim. In addition, it should be noted that combinations of all the features described in the embodiments are not necessarily essential for solving the problems of the invention.

The present invention can be appropriately modified and implemented within a range not departing from the gist. For example, in the above-described embodiment, the cable 10 is operated at a constant cycle, but the operation cycle is not strictly constant, and a slight deviation (for example, a deviation of 10% or less from the reference operation cycle) is allowed.

In addition, in the above-mentioned embodiment, the case of evaluating the strain of one conductor 11a in the cable 10 has been described, but it is also possible to measure the resistance value of a plurality of conductors 11a in the cable 10 and evaluate the strain of the plurality of conductors 11a. .

Furthermore, it is also possible to extract in advance a frequency band with particularly large noise such as a frequency near 0 Hz by frequency analysis, create resistance value data after removing the extracted frequency band with large noise, and use the created resistance value data to derive Strain equivalent. Thereby, the influence of noise can be further suppressed, and the equivalent strain can be calculated|required more accurately.

Claims (6)

1. A method for evaluating a strain applied to a conductor when bending and/or twisting is applied to a cable having the conductor, the conductor being constituted by a stranded conductor formed by stranding a plurality of wires, the method comprising the steps of,

measuring a resistance value of the conductor which changes in time series when the operation is periodically applied to the cable,

the strain is evaluated based on a measured fluctuation range of the resistance value of the conductor which changes in the time series.

2. The method for evaluating a conductor strain according to claim 1, wherein,

dividing the resistance value of the conductor changed in the time series for each operation period, that is, for each operation period, averaging the divided changes in the resistance value for each period with the lapse of time from the start of the period, obtaining the averaged changes in the resistance value for one period,

the strain is evaluated based on the fluctuation range of the resistance value in the change of the resistance value of the one cycle amount after the averaging.

3. The method for evaluating a conductor strain according to claim 2, wherein,

frequency analysis is performed on the resistance value of the conductor which changes in the time series, and an operation frequency corresponding to the operation cycle is estimated based on the result of the frequency analysis.

4. The method for evaluating a conductor strain according to claim 3, wherein,

the estimated component of the operation frequency is extracted from the resistance value of the conductor which changes in time series, and the start point of the cycle is set based on the time series change of the extracted component of the operation frequency.

5. A conductor strain evaluation device for evaluating a strain applied to a conductor when bending and/or twisting is applied to a cable having the conductor, the conductor being made of a twisted wire conductor obtained by twisting a plurality of wires, the conductor strain evaluation device comprising:

a resistance value measuring unit that measures a resistance value of the conductor that changes in time series when the operation is periodically applied to the cable; and

and a strain evaluation unit configured to evaluate the strain based on the fluctuation range of the resistance value of the conductor that is changed in the time series measured by the resistance value measurement unit.

6. A cable life prediction method is characterized in that,

the method for evaluating a conductor strain according to any one of claims 1 to 3, wherein the fluctuation range of the resistance value is obtained,

the relation between the fluctuation range of the resistance value and the operation frequency of the cable reaching the service life of the cable is obtained in advance,

the number of operations of the cable for which the service life of the cable is achieved is predicted based on the obtained fluctuation range of the resistance value and the relationship.

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