Multi-rod annular structure fiber bragg grating axial force meter

Abstract

The invention provides a multi-rod annular structure fiber bragg grating axial force meter, which comprises a shell, a group of axial force measuring rods uniformly distributed in the shell, at least one temperature compensation rod arranged in the shell, a measuring fiber bragg grating arranged on each axial force measuring rod, a temperature compensation fiber bragg grating arranged on the temperature compensation rod, and a fiber outlet hole arranged on the shell. The device is simple in structure, convenient to use and suitable for engineering environments with different temperatures, the stress unbalance loading phenomenon of the supporting structure can be found in time, timely finding and timely processing are achieved, and construction safety is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber sensing, in particular to a multi-rod annular structure optical fiber Bragg grating axial force meter. Background Art

[0002] Monitoring sensors are instruments that are buried directly in the ground or structures before or during the construction of underground projects to monitor the stress and deformation of the project structure during the construction phase. By monitoring the support axial force, the stress and changes of the steel support can be understood in a timely manner, and the stability and safety of the foundation pit support system can be accurately judged to guide the foundation pit construction procedures and methods to ensure the safety of the foundation pit construction.

[0003] The traditional single-string ordinary axial force gauge is only a single-string coil structure, without a temperature sensor, and lacks temperature data when temperature compensation is required; and most of them are resistance strain type, which is more obviously affected by the environment, cannot work normally in harsh environments, are prone to data overload, and have a low degree of intelligence. Summary of the invention

[0004] The present invention aims to overcome the deficiencies in the prior art and provides a multi-rod annular structure fiber Bragg grating axial force meter.

[0005] This application provides the following technical solutions: A multi-rod annular structure fiber Bragg grating axial force meter, which includes a shell, and is characterized in that: a group of axial force measuring rods are evenly distributed in the shell, at least one temperature compensation rod is provided in the shell, a measuring fiber Bragg grating is provided on each axial force measuring rod, a temperature compensation fiber Bragg grating is provided on the temperature compensation rod, and a fiber outlet hole is provided on the shell.

[0006] On the basis of the above technical solution, there can also be the following further technical solutions: The set of axial force measuring rods comprises three rods distributed on the same circumference, the upper and lower ends of the axial force measuring rods are respectively connected and fixed to the top surface and the bottom surface of the shell, and the axial force measuring rods are vertically distributed to the top surface and the bottom surface.

[0007] A temperature compensation rod is arranged at the center of the inner bottom surface of the shell, a temperature compensation fiber grating is arranged on the temperature compensation rod, and a certain distance is provided between the top end of the temperature compensation rod and the top surface of the shell.

[0008] A mounting groove corresponding to the measuring optical fiber grating is arranged on the rod wall of the axial force measuring rod, and pigtail lead-out grooves are also arranged on the rod walls on both sides above and below the mounting groove.

[0009] Advantages of the invention: The present invention has a simple structure and is easy to use. It adopts multiple axial force measuring rods distributed on the same circumference to directly measure the axial force of the supporting structure, and the data measured by the multiple axial force measuring rods can be mutually verified to ensure the accuracy of the measurement. In addition, the multiple axial force measuring rods distributed on the same circumference can reflect the state of the annular stress of the supporting structure in real time, discover the stress unbalanced load phenomenon of the supporting structure at the first time, and achieve timely discovery and timely processing to ensure construction safety.

[0010] The temperature compensation rod in the technical solution effectively solves the problem of wavelength drift of fiber Bragg grating caused by temperature. Through the reference grating difference method, the influence of temperature on the fiber Bragg grating of the axial force measurement rod is eliminated, and the error caused by temperature is minimized as much as possible, making the axial force meter more flexible in application and suitable for engineering environments with different temperatures.

[0011] The rod-shaped structure adopted in the present invention protects the grating inside the rod body, reducing the interference of external factors on the grating; at the same time, the groove structure will not cause the flow of adhesive, and the glue distribution will be more uniform in a natural state, thereby reducing the error of the sensor caused by human factors as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 AA section view; Figure 3 yes Figure 1 Schematic diagram of the structure of the central axis force measurement rod. DETAILED DESCRIPTION

[0013] like Figure 1-3 As shown, a multi-rod annular structure fiber Bragg grating axial force meter includes a cylindrical hollow shell 1. Three axial force measuring rods 2 distributed on the same circumference are evenly distributed in the shell 1, and the circumference is coaxially distributed with the shell 1. The upper and lower ends of the axial force measuring rod 2 are in contact with the top surface and the bottom surface of the shell 1 respectively, and are connected and fixed by a connecting piece 7 so that the axis of the axial force measuring rod 2 is vertically distributed with the top surface and the bottom surface of the shell 1.

[0014] A vertically distributed temperature compensation rod 3 is connected to the bottom surface of the housing 1 inside the three axial force measuring rods 2 through a connecting piece. There is a certain distance between the upper end of the temperature compensation rod 3 and the top surface of the housing 1.

[0015] A mounting groove 2a is provided on the rod wall of the axial force measuring rod 2, to which a measuring optical fiber grating 5 is connected by bonding, and a pigtail lead-out groove 2b is provided on the rod wall of the axial force measuring rod 2 on the upper and lower sides of the mounting groove 2a for leading out the pigtail.

[0016] A temperature compensating fiber Bragg grating installation groove is provided on the rod wall of the temperature compensating rod 3, a temperature compensating fiber Bragg grating is connected in the temperature compensating fiber Bragg grating installation groove by bonding, and temperature compensating fiber Bragg grating pigtail lead-out grooves are also provided on the rod walls on the upper and lower sides of the temperature compensating fiber Bragg grating installation groove. Since the temperature compensating rod 3 has the same overall structure as the axial force measuring rod 2, except that the height is lower and there is no hole on the top connected to the connecting piece 7, no drawings are provided.

[0017] The housing 1 is provided with an optical fiber outlet hole 6. The optical fiber is arranged in the sensor through the optical fiber outlet hole 6, and is led out of the housing 1 through the optical fiber outlet hole and protected by an armored protective tube, which can be connected to the housing 1 by means of, but not limited to, threads, bolts, interference fit, welding, etc.

[0018] The connecting member 7 is a common screw in the prior art.

[0019] This design adopts a multi-rod annular distribution structure, and three measuring rods are evenly distributed on the pressure-bearing surface of the force-bearing body. When calculating the force value, the weighted average of the square of the difference between the wavelength of the three groups of fiber gratings and the initial wavelength is used for calculation.

[0020] When the supporting structure is normally loaded, the axial force measured by the evenly distributed axial force measuring rod is approximately equal, and the measured result is equal to the axial force of the supporting structure; when the supporting structure is tilted and the axial force deviates from the center line, the axial force measured by the evenly distributed axial force measuring rod will produce obvious differences. By using the sensor of the present invention to obtain data in real time, the stability of the supporting structure can be grasped in time to ensure the safety of the project.

Claims

1. A multi-rod annular fiber Bragg grating axial force meter, comprising a housing (1), Features: A group of axial force measuring rods (2) are evenly distributed in the housing (1), at least one temperature compensation rod (3) is provided in the housing (1), a measuring optical fiber Bragg grating (5) is provided on each axial force measuring rod (2), a temperature compensation optical fiber Bragg grating is provided on the temperature compensation rod (3), and an optical fiber outlet hole (6) is provided on the housing (1).

2. According to the multi-rod annular structure fiber Bragg grating axial force meter described in claim 1, Features: The group of axial force measuring rods (2) are distributed on the same circumference, the upper and lower ends of the axial force measuring rods (2) are respectively connected and fixed to the top surface and the bottom surface of the shell (1), and the axial force measuring rods (2) are distributed perpendicular to the top surface and the bottom surface.

3. According to the multi-rod annular structure fiber Bragg grating axial force meter described in claim 1, Features: A temperature compensation rod (3) is provided at the center of the inner bottom surface of the shell (1), a temperature compensation optical fiber Bragg grating is provided on the temperature compensation rod (3), and a certain distance is spaced between the top end of the temperature compensation rod (3) and the top surface of the shell (1).

4. According to the multi-rod annular structure fiber Bragg grating axial force meter described in claim 1, Features: A mounting groove (2a) corresponding to the measuring optical fiber grating (5) is provided on the rod wall of the axial force measuring rod (2), and pigtail lead-out grooves (2b) are also provided on the rod walls on the upper and lower sides of the mounting groove (2a).

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