Cable force sensor

Abstract

The invention relates to the field of tension sensors, and particularly discloses a cable force sensor. By arranging the cable hoop, the bobbin, the stay wire type displacement sensor and the displacement sensor stay wire, a user can install the cable hoop on a tested steel cable, when the cable force of the tested steel cable is changed, the length of the steel cable changes, and the steel cable with the changed length drives the cable hoop to move; the moving cable hoop drives the displacement sensor stay wire to move, the stay wire type displacement sensor records the moving distance of the displacement sensor stay wire, the moving distance of the cable hoop is calculated through the moving distance of the displacement sensor stay wire, the moving distance of the measured steel cable is reflected, then the cable force change of the steel cable is measured, and the prestress of the steel cable is combined. And the total cable force value of the measured steel cable can be calculated.

Description

Technical Field

[0001] The present invention belongs to the technical field of tensile sensors, and particularly relates to a cable force sensor. Background Art

[0002] With the development of modern construction industry, a green and low-carbon building component - prestressed cable component appears. Due to its characteristics of high strength, small volume, light weight and good corrosion resistance, it is widely used in large bridges, airport terminals, airport buildings, high-speed railway stations and large commercial buildings. Because of the above characteristics, prestressed cables generally play an extremely important role in the above building structures. For example, in a prestressed cable-stayed bridge where the tower column and the bridge body are connected by prestressed cables, it can be said that the prestressed cables almost bear 60% - 80% of the dead load of the bridge body and the loads of vehicles and pedestrians moving on it. Its importance is self-evident. In the building structure safety system, due to its important "status", people need to timely and accurately master the cable force of the prestressed cables during the construction process and the use process of the building.

[0003] Currently, the relatively mature prestressed cable measurement methods include the oil gauge reading method, the frequency method, the load cell method, the magnetic flux sensor method, etc. The oil gauge reading method reads the cable force at the tension end of the prestressed cable through the tensioning equipment - jack and oil gauge used in the prestressed cable construction tensioning process. However, after the building is completed and the equipment is removed, cable force measurement becomes extremely difficult and costly. In addition, since this method can only measure the cable end where the tensioning equipment can be installed and cannot measure the cable force at any part of the cable body, this method is only limitedly used in the measurement of the end cable force during the construction process. The frequency method is developed into a cable force detection method by utilizing the physical relationship between the cable force and its frequency in the prestressed cable. However, this method is only accurate in measuring simply supported cables without other interfering objects on the cable body. If other building components, such as other cables, steel beams, struts, etc., are connected to the cable body, the natural frequency of the cable to be detected will be "interfered" by other components and distorted, so this method becomes infeasible. The load cell method refers to burying a tension or pressure sensor at the end of the prestressed cable and measuring the cable force of the prestressed cable through its structure to transfer the cable force. Like the oil gauge reading method, because this method is buried at the fixed part of the cable and participates in the cable force, it is limited to the cable force measurement at the buried part, with high costs and the risk of sensor failure and irreparable damage, so it is not widely used. The magnetic flux method utilizes the magnetostrictive effect of the object to be detected - the prestressed cable, that is, the change in the cable stress will cause the change in the magnetic permeability of the cable, thereby causing the change in the physical quantity of the external magnetic field. By measuring the changed physical quantity of the magnetic field and using the monotonic relationship between the cable stress and the physical quantity of the magnetic field, the corresponding cable stress (cable force) is obtained. However, the environmental temperature will affect the magnetic permeability of the cable, and the cable force measurement results may be different under the same external force but different temperatures. Especially, the magnetic flux sensor itself will generate heat, which will cause the temperature of the measurement coil to change, and this temperature change of the measurement coil will also lead to different measurement results. Therefore, it is necessary to redesign a sensor with a simple structure that can avoid the influence of factors such as temperature and accurately measure the cable force. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a cable force sensor to solve the problems that the applicable range of traditional cable force measurement devices is limited and the measurement results are affected by environmental factors, resulting in inaccurate measurement results.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A cable force sensor, comprising:

[0007] Cable clamps, at least two are provided, and both of the cable clamps are connected to the cable to be measured;

[0008] Spools are provided in multiple numbers, and the multiple spools are evenly connected to the cable clamp in an annular array, and wire grooves are provided on the spools;

[0009] A pull-wire displacement sensor is connected to one of the cable clamps;

[0010] A displacement sensor pull-wire is wound in the wire grooves of multiple spools, and one end of the displacement sensor pull-wire is connected to the pull-wire displacement sensor, and the other end is connected to the cable clamp.

[0011] Preferably, a filling layer is provided between the cable clamp and the steel cable to be measured, and the filling layer is a soft metal filler.

[0012] Preferably, the cable clamp includes a first half-ring and a second half-ring. An installation hole is provided on the second half-ring, and a locking bolt is provided inside the installation hole. The first half-ring and the second half-ring are spliced by the locking bolt, and the first half-ring and the second half-ring are spliced into a circular ring, and the spool is connected to the first half-ring and the second half-ring.

[0013] Preferably, the displacement sensing pull-wire is tensioned between adjacent spools.

[0014] Preferably, the cable force calculation formula of the steel cable to be measured is:

[0015]

[0016] Where:

[0017] F - The change value of the cable force of the steel cable to be measured;

[0018] A - The effective cross-sectional area of the steel cable to be measured;

[0019] E S - The elastic modulus of the steel cable to be measured;

[0020] a - The measured value of the pull-wire displacement sensor (9);

[0021] N - The number of windings of the displacement sensor pull-wire (8);

[0022] L - The distance between the spools corresponding to the upper and lower cable clamps.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] In the present invention, by providing a cable clamp, a spool, a wire-pulling displacement sensor and a displacement sensor wire, the user can install the cable clamp on the steel cable to be measured. When the tension of the steel cable to be measured changes, the length of the steel cable will change. The steel cable with the length change will drive the cable clamp to move, and the moving cable clamp will drive the displacement sensor wire to move. The wire-pulling displacement sensor records the moving distance of the displacement sensor wire. By calculating the moving distance of the displacement sensor wire, the moving distance of the cable clamp can be obtained, reflecting the moving distance of the steel cable to be measured, and then the change in the tension of the steel cable can be measured. Combining with the prestress of the steel cable, the total tension value of the steel cable to be measured can be calculated;

[0025] By measuring the total elongation near the measurement point of the prestressed steel cable and combining with the mechanical properties of the steel cable, the tension of the steel cable can be obtained. The measurement method is relatively direct, and the measurement result is the absolute value of the tension or the absolute value of the tension increment. There is no intermediate physical quantity of other measurement methods, such as the magnetic field and magnetic flux in the magnetic flux method, the measurement frequency in the frequency method, etc. Because having an intermediate physical quantity means introducing more measurement uncertainties and errors, the tension measurement error can be reduced;

[0026] This sensor measurement device can avoid the influence of temperature on the measurement result to the greatest extent. Because the temperature change itself will cause the deformation of the steel cable, and then cause the change in the tension, and this change will be measured by the wire-pulling displacement sensor. This application uses a wire-pulling displacement sensor, which measures displacement by pulse counting, and the measurement result is more stable and reliable;

[0027] The measurement device of the present invention is separated from the stress system of the prestressed steel cable, that is, the measurement part does not participate in the stress of the structure. Therefore, the requirements for the use of the measurement device are greatly reduced. By streamlining the structure of the measurement part, the economic benefits can be greatly improved, and the measurement range can be maximized;

[0028] The present invention can achieve high measurement accuracy and resolution, and can also be adjusted according to different needs. From the working principle, the micro-deformation of the steel cable is amplified by N times and then read by the wire-pulling displacement sensor. The amplification factor is the number of turns of the wire-pulling displacement sensor. The larger N is, the higher the measurement accuracy and the smaller the resolution. Therefore, the measurement accuracy and resolution can be adjusted according to different needs, which is also difficult to achieve by other sensors;

[0029] The present invention has relatively low requirements for the calibration of the sensor. Since it obtains the tension by measuring the strain of the steel cable, and the strain-stress of the prestressed steel cable is almost linear during the working stage, that is to say, only one calibration point is needed to determine its curve equation. This is different from other measurement methods with intermediate physical quantities, and the stress change of the steel cable to be measured can be obtained more directly through the strain of the prestressed steel cable;

[0030] The present invention can be used for measuring the cable force of existing prestressed steel cables. From the structure and installation method of the sensor, it can be seen that the sensor is fixed on the steel cable to be measured through two semi-circular cable clamps, that is, it can be measured post-positionally, and can be used for measuring the cable force increment of the existing cables that have been built and put into use or for measuring the total cable force by adding the initial force value when installing the device, without performing other operations on the prestressed steel cables in use;

[0031] The device of the present invention is convenient for installation and disassembly, and the maintenance and replacement costs are extremely low, greatly improving the economic benefits in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 is a schematic cross-sectional view of an installation structure of a cable force sensor disclosed by the present invention;

[0034] In the figure: 1. First semi-ring; 2. Second semi-ring; 3. Installation hole; 4. Locking bolt; 5. Spool; 6. Wire groove; 7. Filling layer; 8. Displacement sensor wire; 9. Pull-wire type displacement sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment:

[0037] Please refer to Figure 1 - Figure 2 As shown in the figure, a cable force sensor includes:

[0038] Cable clamps, at least two are provided, and both of the cable clamps are connected to the steel cable to be measured;

[0039] Spools 5, a plurality of spools 5 are provided, and the plurality of spools 5 are connected to the cable clamps at equal intervals in a circular array, and wire grooves 6 are formed in the spools 5;

[0040] Pull-wire type displacement sensor 9, connected to one of the cable clamps;

[0041] Displacement sensor wire 8 is wound in the wire grooves 6 of the plurality of spools 5, and one end of the displacement sensor wire 8 is connected to the pull-wire type displacement sensor 9, and the other end is connected to the cable clamp.

[0042] As can be seen from the above, in the present invention, by providing a cable clamp, a spool 5, a pull-wire displacement sensor 9, and a displacement sensor pull wire 8, the user can install the cable clamp on the steel cable to be measured. When the cable force of the steel cable to be measured changes, the length of the steel cable will change. The steel cable with the length change will drive the cable clamp to move, and the moving cable clamp will drive the displacement sensor pull wire 8 to move. The pull-wire displacement sensor 9 records the moving distance of the displacement sensor pull wire 8, calculates the moving distance of the cable clamp through the moving distance of the displacement sensor pull wire 8, reflects the moving distance of the steel cable to be measured, and further measures the change in the cable force of the steel cable. Combining with the prestress of the steel cable, the total cable force value of the steel cable to be measured can be calculated.

[0043] A filling layer 7 is provided between the cable clamp and the steel cable to be measured. The filling layer 7 is a soft metal filler, and some softer metal alloys can be used to fill the gap between the steel cable to be measured and the cable clamp, increase the friction between the cable clamp and the steel cable to be measured, so that the stretched steel cable can drive the cable clamp to move in time, and then stretch the displacement sensor pull wire 8 through the cable clamp, and the elongation of the displacement sensor pull wire 8 accurately reflects the elongation of the steel cable to be measured.

[0044] The cable clamp includes a first half-ring 1 and a second half-ring 2. An installation hole 3 is provided on the second half-ring 2, and a locking bolt 4 is arranged inside the installation hole 3. The first half-ring 1 and the second half-ring 2 are spliced through the locking bolt 4. The first half-ring 1 and the second half-ring 2 are spliced into a circular ring, and the spool 5 is connected to the first half-ring 1 and the second half-ring 2. The user can clamp the first half-ring 1 and the second half-ring 2 on the steel cable to be measured, and then combine the first half-ring 1 and the second half-ring 2 together through the locking bolt 4. At this time, the first half-ring 1 and the second half-ring 2 will be clamped on the steel cable to be measured. As mentioned above, the user can adjust the locking force of the locking bolt 4 to firmly clamp the half-ring on the steel cable to be measured. When measuring some relatively thin steel cables, a filling layer 7 can be provided between the half-ring and the steel cable to ensure that the stretched steel cable can drive the first half-ring 1 and the second half-ring 2 to displace.

[0045] To enable the pull-wire displacement sensor 9 to accurately measure the displacement value of the displacement sensor pull wire 8, the displacement sensor pull wire 8 is tightly arranged between adjacent spools 5. At this time, the stretching amount of the steel cable to be measured can be accurately reflected on the displacement sensor pull wire 8.

[0046] Under the action of external force, the prestressed steel cable elongates. If the distance between the cable clamps is L, actually the center distance between the upper and lower wire grooves 6 is L, the number of winding turns of the pull-wire displacement sensor 9 is N, and the steel cable to be measured elongates by ΔL under the action of external force, then the single-end displacement value measured by the pull-wire displacement sensor 9 is NΔL. According to the formula of material mechanics, the cable force value of the steel cable can be obtained. The calculation process is as follows:

[0047]

[0048] If the displacement reading of the wire-pulling type displacement sensor 9 is a and the number of turns of wire winding is N, then

[0049] Furthermore, the calculation formula for the cable force of the measured steel cable is obtained as follows:

[0050]

[0051] Where:

[0052] ε - the strain value of the steel cable;

[0053] F - the change value of the cable force of the measured steel cable;

[0054] A - the effective cross-sectional area of the measured steel cable;

[0055] E S - the elastic modulus of the measured steel cable;

[0056] a - the measured value of the wire-pulling type displacement sensor 9;

[0057] N - the number of turns of the wire of the displacement sensor wire-pulling 8;

[0058] L - the distance between the spools 5 corresponding to the upper and lower cable clamps.

[0059] The present invention measures the total elongation near the measurement point of the prestressed steel cable, that is, the method of total strain, and obtains the cable force of the steel cable according to the mechanical properties of the steel cable. The measurement method is the most direct, and the measurement result is the absolute value of the cable force or the absolute value of the cable force increment. There is no intermediate transition physical quantity of other measurement methods, such as the magnetic field and magnetic flux in the magnetic flux method, the measurement frequency in the frequency method, etc., because passing through the intermediate physical quantity means introducing more measurement uncertainty factors and errors.

[0060] The present invention maximally avoids the influence of temperature on the measurement result. Since temperature change itself can cause the deformation of the steel cable and even lead to the change of cable force, and exactly this change is measured by the wire-pulling displacement sensor. In other measurement methods, large deviations in the measurement result often occur due to improper handling of the temperature effect. For example, in the cable force measurement using a magnetic flux sensor, temperature can affect the magnetic permeability of the steel cable, that is, the measurement results may be different under the same external force but different temperatures, especially because the magnetic flux sensor itself generates heat, causing the temperature of the measurement coil to change, and this change in the temperature of the measurement coil will also lead to different measurement results. Another example is that load cells generally use the resistance strain gauge method for measurement. The measurement circuit itself and the strain gauges, etc. will vary due to different temperatures, as well as the temperature drift problem, so that the temperature effect is relatively difficult to handle; in the frequency method measurement, there are also temperature problems because the temperature effects of the vibrating string of the sensor and the cable body are not the same. And this solution uses an encoder wire-pulling displacement sensor, which measures displacement by pulse counting. For example, when the encoder rotates one week, a fixed number of pulses will be generated, generally 1024 - 4096. That is, for a specific sensor, the displacement value represented by one pulse is stable. Therefore, this sensor converts the measured displacement into more reliable pulse counting, and the measurement result is more stable and reliable.

[0061] The measuring device of the present invention is separated from the stress system of the prestressed steel cable, that is, the measuring system does not participate in the stress of the structure. Therefore, the requirements for the measuring device are greatly reduced, which can greatly improve the economic benefits and can also maximize the measuring range. Taking the load cell as an example, the measurement process of the load cell is that the prestressed steel cable transfers the cable force to the load cell, and the bearing device of the sensor undergoes micro-deformation, which is sensed by the measurement circuit in the sensor to obtain the processing result. This method has very high requirements for the sensor itself. For example, for the cable force of a large prestressed steel cable, it is generally from dozens of tons to hundreds of tons or even higher. Therefore, the bearing capacity of the sensor itself also needs to match, otherwise it will be damaged due to insufficient bearing capacity; while the present invention only measures the micro-deformation amount of the prestress and does not participate in the stress of the prestressed steel cable.

[0062] The present invention can achieve very high measurement accuracy and resolution, and can also be adjusted according to different requirements. From the above working principle, it can be seen that the micro-deformation of the steel cable is amplified by N times and then read by the wire-pulling displacement sensor. The amplification factor is the number of turns of the wire-pulling displacement sensor. The larger N is, the higher the measurement accuracy and the finer the resolution. Furthermore, the measurement accuracy and resolution can be adjusted according to different requirements, which is also difficult for other sensors to achieve.

[0063] The calibration requirements for the sensor in the present invention are relatively low. Since the cable force is obtained by measuring the strain of the steel cable, and the strain-stress of the prestressed steel cable is almost linear during the working stage, that is to say, only one calibration point is needed to determine its curve equation. This is different from other measurement methods with intermediate physical quantities. For example, in the magnetic flux sensor method, due to the different magnetic permeabilities between different measurement points on the same cable, calibration needs to be carried out for different measurement points, and temperature calibration is also required; the same is true for load cells, and different load cells need to be calibrated according to their different principles and the characteristics of the measurement circuits.

[0064] The present invention can be used for measuring the cable force of existing prestressed steel cables. From the structure and installation of the above-mentioned sensor, it can be seen that the present invention uses two semi-circular cable clamps to be fixed on the steel cable to be measured, that is, it can be measured retroactively, and can be used for measuring the cable force increment or the total cable force of the already built and put into use. The absolute value of the total cable force is the sum of the initial force value when the installation device is added, and no other operations need to be performed on the prestressed steel cable in use. For example, the closed magnetic flux sensor needs to remove the steel cable and even replace the steel cable to install the sensor, and the same is true for load cells.

[0065] The device of the present invention is convenient to install and disassemble, and the maintenance and replacement costs are extremely low, which greatly improves the economic benefits in the later stage.

[0066] The standard parts used in the present invention can all be purchased from the market. The special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part all adopt conventional means such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts, and equipment all adopt conventional models in the prior art. Coupled with the circuit connection adopting the conventional connection method in the prior art, it will not be elaborated here. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0067] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. The meaning of "plural" is two or more unless otherwise specifically defined.

[0068] In the present invention, unless otherwise clearly defined or limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0069] In the present invention, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature has a lower horizontal height than the second feature.

[0070] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not have to be directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0071] In the drawings of the disclosed embodiments of the present invention, only the structures related to the disclosed embodiments are involved, and other structures can refer to the general design. Without conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

Claims

1. A cable force sensor, characterized in that: include: There are at least two cable hoops, and both of the cable hoops are connected to the steel cable to be tested; A plurality of bobbins (5) are provided, and the plurality of bobbins (5) are connected to the cable clamp at equal intervals in a ring array, and a wire groove (6) is provided on the bobbins (5); A wire-type displacement sensor (9) connected to one of the cable clamps; The displacement sensor pull wire (8) is wound in the wire grooves (6) of the plurality of spools (5), and one end of the displacement sensor pull wire (8) is connected to the pull wire displacement sensor (9), and the other end is connected to the cable clamp.

2. A cable force sensor according to claim 1, characterized in that: A filling layer (7) is provided between the cable hoop and the steel cable to be measured, and the filling layer (7) is a soft metal filler.

3. A cable force sensor according to claim 1, characterized in that: The cable clamp comprises a first half ring (1) and a second half ring (2); a mounting hole (3) is provided on the second half ring (2); a locking bolt (4) is arranged inside the mounting hole (3); the first half ring (1) and the second half ring (2) are spliced ​​together by the locking bolt (4); the first half ring (1) and the second half ring (2) are spliced ​​together into a circular ring; the spool (5) is connected to the first half ring (1) and the second half ring (2).

4. A cable force sensor according to claim 1, characterized in that: The displacement sensing pull wire (8) is tensioned and arranged between adjacent bobbins (5).

5. A cable force sensor according to claim 1, characterized in that: The calculation formula of the cable force of the measured steel cable is: in: F-the change value of the measured steel cable force; A-effective cross-sectional area of ​​the measured wire rope; E S - Elastic modulus of the tested cable; a-measurement value of the wire-type displacement sensor (9); N - the number of windings of the displacement sensor cable (8); L - the distance between the wire spools (5) corresponding to the upper and lower cable hoops.

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