Method for measuring friction force of cable support by using strain gauge and displacement sensor

Abstract

The invention provides a method for measuring the friction force of a cable support by using strain gauges and a displacement sensor, and the method comprises the following steps: respectively arranging the strain gauges at the positions, close to column feet, of left and right columns of the cable support for collecting the strain of the cable support at the positions; displacement sensors are arranged at the tops of the cable supports and used for measuring the displacement of the tops of the cable supports and judging the bending directions of the cable supports; deducing a strain-bending moment formula of the cable bracket according to a strain value measured by the strain gauge by using a relationship between material mechanical strain and bending moment, and calculating a received horizontal bending moment; the friction force borne by the cable support is calculated through the bending moment average value of the left and right stand columns and the distance from the cable to the strain measurement point. Compared with a traditional method for measuring the stress of the support through a force sensor, the method has the advantages that the measurement precision is higher, the measurement result is more accurate, and the cost is lower; the strain gauges and the displacement sensor are very simple in arrangement and use mode, the measurement process is convenient, and a result can be directly obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural engineering, and particularly relates to a method for measuring the friction force of a cable support using strain gauges and displacement sensors. Background Art

[0002] With the increasing urban power consumption, the construction demand for urban high-voltage power lines is increasing day by day. The application of heavy cables such as 500 kV and 1000 kV is becoming more and more extensive, and the laying of cables is gradually transferred underground. Compared with overhead laying, underground cable laying is restricted by the environment.

[0003] At present, underground cables are mostly laid section by section by manual control. During the laying process, it is necessary to manually lift and bend the cable according to the position of the cable support, and then start to make cable joints after the cable is completely laid. The entire cable laying process has defects such as low mechanization level, high safety risk, and labor-intensive, and is only suitable for short-distance cable laying. However, with the increase in the scale of the power grid, the scope of cable laying is getting larger and larger. Taking the Jiangdi Tunnel of the Shanghai Liuhekou Line as an example, the total length of the cable is 16.5 km, and the working conditions in the tunnel are poor. There are only working wells that can enter and exit the tunnel at both ends. The traditional laying method is inefficient and risky. Therefore, a more mechanized intelligent conveyor construction method needs to be adopted for laying.

[0004] Compared with traditional conveyors, intelligent conveyors can adaptively adjust the conveying direction and driving force, enabling the cable to be automatically laid forward on the cable support, greatly saving manpower. However, different from traditional laying construction, intelligent conveyors place the cable on the rollers of the cable support and push the cable forward for laying, rather than the traditional section-by-section laying. This causes the cable to exert a thrust on the support during the conveying process. Considering the relatively high speed of the conveyor and various transportation conditions such as turning and climbing during the entire cable transportation, the influencing factors of the force on the cable support will be more complex. In order to reasonably design the cable support and ensure that the cable support meets the bearing capacity requirements and can resist friction, it is necessary to use a reasonable method to measure the magnitude of the friction force generated by the cable on the support during cable transportation. Since the cable runs on the rollers of the support as a coupling of rolling friction and sliding friction, the stress state is very complex, and traditional force sensors are difficult to directly and accurately measure.

[0005] Therefore, it is very important to find a method that can accurately measure the force on the cable support during cable laying. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for measuring the friction force of a cable support using strain gauges and displacement sensors.

[0007] The method disclosed by the present invention measures the response of the bracket using strain gauges and displacement sensors, and converts the frictional force received by the bracket through mechanical derivation, greatly reducing the error generated by measurement and making the measurement result more accurate. Compared with the traditional method of directly testing the force on the cable bracket using a mechanical sensor, this method has a smaller measurement error, solves the problem that the force at the contact between the cable bracket and the cable is complex and difficult to measure, greatly improves the accuracy and convenience of measuring the frictional force, and thus provides more accurate data support for the design of the cable bracket.

[0008] A method for measuring the frictional force of a cable bracket using strain gauges and displacement sensors, wherein the cable bracket includes left and right columns and a top cross beam, and the top cross beam is erected in the upper middle part of the left and right columns, and the method includes the following steps:

[0009] (1) Arrange strain gauges at positions close to the column feet of the left and right columns of the cable bracket respectively to collect the strain of the cable bracket at this position;

[0010] (2) Arrange displacement sensors at the top of the cable bracket respectively to measure the displacement at the top of the cable bracket and judge its bending direction;

[0011] (3) According to the strain value measured by the strain gauge, use the relationship between strain and bending moment in material mechanics to derive the strain-bending moment formula of the cable bracket and calculate the horizontal bending moment received;

[0012] (4) Calculate the frictional force received by the cable bracket through the average value of the horizontal bending moments of the left and right columns and in combination with the distance from the cable to the strain measurement point.

[0013] Preferably, in the step (2), the displacement sensor is a laser displacement sensor or a contact displacement sensor, and the measurement accuracy is not less than 0.01 mm. The function of the displacement sensor is to measure the displacement at the top of the bracket and is used to judge the bending direction of the two brackets.

[0014] Preferably, in the step (3), the bending moment of a single left column in the cable bracket is obtained from the strain value, and the average value of the two is taken to obtain where M is the bending moment of a single column; each ε is the strain value measured by the strain gauge; E is the elastic modulus of the cable bracket material; W x is the flexural section modulus of a single column of the cable bracket along the cable traveling direction.

[0015] Preferably, in the step (3), the horizontal bending moment of a single right column in the cable bracket is where M is the bending moment of a single column; each ε is the strain value measured by the strain gauge; E is the elastic modulus of the cable bracket material; W x is the flexural section modulus of a single column of the cable bracket along the cable traveling direction.

[0016] Preferably, in the step (4), the horizontal force on the cable support is: F = (M letf + M right ) / l, where M is the bending moment of a single column and l is the distance from the cable to the strain measurement point; the frictional force is the horizontal force.

[0017] Preferably, in the step (1), the material of the cable support is steel or aluminum alloy.

[0018] To ensure the accuracy of the measurement data, the strain gauges need to be arranged as close to the column base as possible, that is, to make l as large as possible.

[0019] Due to the adoption of the above - mentioned scheme, the beneficial effects of the present invention are as follows:

[0020] 1. Compared with the traditional method of measuring the force on the support using a force sensor, this method has higher measurement accuracy, more accurate measurement results, a more convenient operation method, smaller errors, and lower costs.

[0021] 2. It improves the accuracy and convenience of measuring the frictional force, reduces the measurement difficulty and measurement cost, and thus provides more accurate data support for the design of the cable support.

[0022] 3. The arrangement and use method of the strain gauges and displacement sensors are very simple, the whole measurement process is convenient, and the result can be obtained directly.

[0023] 4. The strain gauges and displacement sensors have low costs and can be used repeatedly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the front view of the cable support frictional force test device of the present invention.

[0025] Figure 2 It is the top view of the cable support frictional force test device of the present invention.

[0026] Number description: 1 - strain gauge, 2 - displacement sensor, 3 - cable support;

[0027] 1 - 1, 1 - 2, 1 - 3, 1 - 4, 1 - 5 respectively correspond to the readings of the strain gauges. For example, 1 - 1 is the reading ε1 of the strain gauge, and 1 - 5 is the reading ε5 of the strain gauge. DETAILED DESCRIPTION OF THE INVENTION

[0028] To further elaborate on the technical means and effects adopted by the present invention, the following further illustrates the technical solution of the present invention in conjunction with the drawings and through specific embodiments, but the present invention is not limited to the scope of the embodiments.

[0029] Example 1: Frictional Force of Cable Support

[0030] As Figure 1 and Figure 2 shown, take a steel cable support 3 with a column height of 1.2 m, a material elastic modulus E of 200 GPa, and a flexural section modulus Wx of 1.5×10 -5 m 3 . Strain gauges 1 (model: BX120-3AA) are respectively pasted at 5 cm from the bottom of the left and right columns (about 4% of the column height), and a displacement sensor 2 (a laser displacement sensor) (accuracy 0.01 mm) is installed on the top crossbeam of the cable support 3.

[0031] Use an intelligent conveyor to lay a 500 kV cable at a speed of 1 m / s. The cable weighs 20 kg / m, and the rollers are in contact with the cable. The strain difference measured by the strain gauge 1 for the left column is 1.2×10 -4 , and for the right column is 1.1×10 -4 . The displacement sensor shows a 0.5 mm displacement to the right at the top, and the stress direction of the column is confirmed.

[0032] According to the formula, calculate the bending moment of the left column: M1 = (1.2×10 -4 )×(200×10 9 )×(1.5×10 -5 ) = 360 N·m.

[0033] Horizontal force of the left column: F1 = 360 / 1.15 = 313 N (l = 1.15 m).

[0034] Similarly, the bending moment of the right column M2 = 330 N·m, and the horizontal force F2 = 287 N.

[0035] Friction force of the entire support: F = (313 + 287) / 2 = 300 N.

[0036] The test results show that the friction force of the cable support is 300 N, the measurement error is less than 5%, far lower than 10 - 15% of the traditional force sensor method.

[0037] Example 2: Tests under different working conditions

[0038] Under the turning working condition, repeat the method of Example 1 for testing, and adjust the conveyor speed to 0.5 m / s. The strain differences measured by the strain gauges are 1.5×10 -4 and 1.4×10 -4 respectively, and the displacement sensor shows a 0.7 mm displacement at the top. It is calculated that the friction force is 380 N, proving that this method still has high precision under complex working conditions.

[0039] The above description of the embodiments is intended to enable those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for measuring the frictional force of a cable support using a strain gauge and a displacement sensor, the cable support (3) comprising left and right columns and a top cross beam, the top cross beam being installed in the upper middle part of the left and right columns, characterized in that: It includes the following steps: (1) Strain gauges (1) are respectively arranged at positions near the column feet of the left and right columns of the cable support (3) to collect the strain of the cable support (3) at this position; (2) Displacement sensors (2) are respectively arranged at the top of the cable support (3) to measure the displacement at the top of the cable support (3) and judge its bending direction; (3) According to the strain value measured by the strain gauge (1), using the relationship between strain and bending moment in material mechanics, the strain-bending moment formula of the cable support (3) is derived to calculate the horizontal bending moment received; (4) Through the average value of the horizontal bending moments of the left and right columns, combined with the distance from the cable to the strain measurement point, the friction force received by the cable support (3) is calculated.

2. A method for measuring the friction force of a cable support using strain gauges and displacement sensors according to claim 1, characterized in that: In the step (2), the displacement sensor is a laser displacement sensor or a contact displacement sensor.

3. A method for measuring the friction force of a cable support using strain gauges and displacement sensors according to claim 1, characterized in that: In the step (3), the horizontal bending moment of the single column on the left side of the cable support (3) is obtained by the strain value, and the two are averaged to obtain Where M is the bending moment of a single column; each ε is the strain value measured by the strain gauge (1); E is the elastic modulus of the cable support (3); W x It is the bending section modulus of a single column of the cable support (3) along the direction of cable travel.

4. A method for measuring the friction force of a cable support using strain gauges and displacement sensors according to claim 1, characterized in that: In the said step (3), the moment in the horizontal direction of the single right-side column in the cable support (3) is where M is the moment of a single column; each ε is the strain value measured by the strain gauge (1); E is the elastic modulus of the material of the cable support (3); W x is the flexural section modulus of a single column of the cable support (3) in the cable running direction.

5. A method for measuring the friction force of a cable support using strain gauges and displacement sensors according to claim 1, characterized in that: In the step (4), the horizontal force received by the cable support (3) is: F = (M letf + M right ) / l, where M is the bending moment of a single column and l is the distance from the cable to the strain measurement point.

6. A method for measuring the friction force of a cable support using strain gauges and displacement sensors according to claim 1, characterized in that: In the step (1), the material of the cable support (3) is steel or aluminum alloy.

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