Method and system for measuring shape of advancing three-dimensional path based on optical fiber shape sensing

Abstract

The invention relates to the technical field of optical fiber sensing, in particular to a marching type three-dimensional path shape measuring method and system based on optical fiber shape sensing. The system comprises an optical fiber shape sensing device, a speedometer, a propelling mechanism, a computer and an optical fiber, the optical fiber is propelled forwards through the propelling mechanism, the speedometer records the forward advancing distance of the optical fiber, and the optical fiber shape sensing device measures strain information of the optical fiber in a three-dimensional path and sends the strain information to the computer; the position of the front end of the optical fiber in the three-dimensional path and the shape of the optical fiber are obtained, the advancing process of the optical fiber is repeated till the tail of the three-dimensional path, and finally the shape of the whole three-dimensional path is obtained. The optical fiber strain sensing device is characterized in that the optical fiber is measured in a marching mode and is not fixed in position, the sensing length is not limited by the length of a sensing strain part of the optical fiber and the measurement performance of the optical fiber strain sensing device, and long-distance three-dimensional path shape measurement can be achieved through the short sensing strain length.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to a method and system for measuring the shape of a three-dimensional path based on optical fiber shape sensing. Background Art

[0002] Fiber optic sensing technology is a technology that obtains sensing information by detecting changes in light in optical fibers caused by changes in a certain physical quantity, such as sensing magnetic fields, temperature, pressure, strain, acceleration and other physical quantities. Compared with traditional sensing technology, fiber optic sensing technology has many advantages such as strong anti-electromagnetic interference ability, high sensitivity and high safety, and has been widely used in aerospace, bridges and tunnels, medical health and other fields.

[0003] Fiber optic shape sensing technology is a technology that uses optical fiber to sense the three-dimensional shape of an object. It can measure the three-dimensional shape of an object in real time without visual contact. It is a technology based on strain measurement. Common strain measurement methods include fiber grating sensor strain measurement, Brillouin optical time domain analyzer (BOTDA) strain measurement, etc., as described in the invention patents CN201210008145.7 and CN201710195526.3.

[0004] Fiber optic shape sensors can be composed of multi-core optical fibers or array-packaged with multiple single-core optical fibers. Fiber optic shape sensors can be used in the field of flexible structure measurement, and play a key role in monitoring the deformation of aircraft structures in aerospace, detecting underground pipelines, tracking catheters in minimally invasive surgeries in the medical industry, and tracking robot positions.

[0005] However, in the current research on optical fiber sensing technology, the position of the optical fiber is fixed, and only the three-dimensional shape of the optical fiber itself is reconstructed, as described in the invention patents CN201510777343.3 and CN202010320486.2. The sensing length of this method is the length of the sensing strain part of the optical fiber itself. It is limited by the measurement performance of the optical fiber strain sensor device, and the sensing length is short, which cannot meet the needs of long-distance measurement. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention proposes a method and system for measuring the shape of a three-dimensional path based on optical fiber shape sensing. The feature of the invention is that the optical fiber is measured in a moving manner in the three-dimensional path, and is not stationary. The advantage of the moving three-dimensional path shape measurement is that the sensing length is not limited by the length of the sensing variable part of the optical fiber itself, and a shorter sensing variable length can be used to achieve long-distance three-dimensional path shape measurement.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: a moving three-dimensional path shape measurement system based on optical fiber shape sensing, comprising:

[0008] An optical fiber shape sensing device, used for demodulating strain information at an optical fiber sensing point and transmitting the strain information to a computer;

[0009] An odometer, used to record the travel length information of the optical fiber, and transmit the travel length information to the calculation;

[0010] A propulsion mechanism, used for providing power for the optical fiber to move forward;

[0011] A computer is used to reconstruct the shape of a three-dimensional path by utilizing the strain information of the optical fiber shape sensing device and the optical fiber travel length information recorded by the odometer.

[0012] Furthermore, the optical fiber includes at least one of a multi-core optical fiber and an optical fiber in which multiple single-core optical fibers are packaged in an array.

[0013] Furthermore, the multi-core optical fiber is a seven-core optical fiber consisting of a central core and six surrounding cores distributed in a regular hexagon; and the diameter of each core is 8 μm, and the distance between adjacent cores is 41.5 μm.

[0014] Furthermore, it also includes a fiber grating sensor, which is engraved on the front end of the multi-core optical fiber.

[0015] Furthermore, the fiber grating sensor comprises two groups, the Bragg center wavelengths of the two groups of fiber grating sensors are 1539 nm and 1541 nm respectively; the length of each fiber grating sensor is 10 mm, and the axial distance between the two groups of fiber grating sensors is 3 cm.

[0016] Furthermore, the optical fiber shape sensing device includes at least one of an optical fiber grating demodulator and a Brillouin optical time domain analyzer.

[0017] Furthermore, the multi-core optical fiber is connected to a fiber grating demodulator through a fan-in and fan-out module, and the fiber grating demodulator can demodulate the Bragg center wavelength of the central core and three surrounding cores of the multi-core optical fiber, thereby obtaining strain information at the sensing point and sending it to a computer.

[0018] Furthermore, it also includes a three-dimensional mold, on which two spiral grooves with different parameters are milled, a rubber tube is arranged in the spiral groove, and the optical fiber is inserted into the rubber tube.

[0019] Furthermore, the pushing mechanism includes a displacement platform, and the displacement platform is provided with a handle for rotating the displacement platform to drive the optical fiber to move.

[0020] The traveling three-dimensional path shape measurement method based on optical fiber shape sensing uses the above-mentioned traveling three-dimensional path shape measurement system based on optical fiber shape sensing, and the method is as follows:

[0021] S1, at the initial time t1, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the initial shape of the optical fiber and the initial position S1 of the front end of the optical fiber in the three-dimensional path;

[0022] S2, the propulsion mechanism pushes the optical fiber forward, and the odometer records the distance Δl1 that the optical fiber moves forward. At time t2, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the shape of the optical fiber and the position S2 of the front end of the optical fiber in the three-dimensional path;

[0023] S3, the propulsion mechanism continues to push the optical fiber forward, the strain information of the optical fiber sensing point is updated, and the odometer records the distance the optical fiber moves forward. At time t3, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the shape of the optical fiber and the position of the front end of the optical fiber in the three-dimensional path S3;

[0024] The above process is repeated until the optical fiber reaches the end of the three-dimensional path, and the position Sn of the front end of the optical fiber in the three-dimensional path and the shape of the entire three-dimensional path can be obtained.

[0025] Beneficial effects of the invention: It can be seen from the above description of the invention that, compared with the prior art, the traveling three-dimensional path shape measurement system based on optical fiber shape sensing of the invention comprises an optical fiber shape sensing device, which is used to demodulate the strain information at the optical fiber sensing point and transmit the strain information to a computer; an odometer, which is used to record the travel length information of the optical fiber and transmit the travel length information to a computer; a propulsion mechanism, which is used to provide power for the optical fiber to move forward; and a computer, which is used to reconstruct the shape of the three-dimensional path by utilizing the strain information of the optical fiber shape sensing device and the optical fiber travel length information recorded by the odometer, so as to realize that the sensing length is not limited by the length of the sensing strain part of the optical fiber itself and the measurement performance of the optical fiber strain sensing device, and that a shorter sensing strain length can be used to realize long-distance three-dimensional path shape measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a traveling three-dimensional path shape measurement system based on optical fiber shape sensing provided by the present invention;

[0027] Figure 2 It is a flow chart of the method for measuring the shape of a three-dimensional path based on optical fiber shape sensing provided by the present invention;

[0028] Figure 3is a physical diagram of a moving three-dimensional path shape measurement system in an embodiment of the present invention;

[0029] Figure 4 is the shape measurement result of the traveling three-dimensional path 1 in the embodiment of the present invention;

[0030] Figure 5 It is the shape measurement result of the traveling three-dimensional path 2 in the embodiment of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] Reference Figure 1 As shown, a preferred embodiment of the present invention is a moving three-dimensional path shape measurement system based on fiber optic shape sensing, including a fiber optic shape sensing device, an odometer, a propulsion mechanism, a computer and an optical fiber. Among them, the optical fiber can be optionally a multi-core optical fiber, or an optical fiber in which multiple single-core optical fibers are packaged in an array, etc., and its function is to measure the strain information at the sensing point of the three-dimensional path. The function of the propulsion mechanism is to provide power for the optical fiber to move forward. The fiber optic shape sensing device can be optionally a fiber grating demodulator, a Brillouin optical time domain analyzer (BOTDA), etc., and its function is to demodulate the strain information at the optical fiber sensing point. The function of the odometer is to record the length of the optical fiber travel. The function of the computer is to reconstruct the shape of the three-dimensional path using the strain information of the fiber optic shape sensing device and the travel length information of the odometer.

[0034] like Figure 2As shown, the present invention also proposes a moving three-dimensional path shape measurement method based on fiber optic shape sensing. First, at the initial moment t1, the fiber optic shape sensing device measures the strain information of the fiber in the three-dimensional path and sends it to the computer to obtain the initial shape of the fiber and the initial position S1 of the front end of the fiber in the three-dimensional path. Then, the propulsion mechanism propels the fiber forward, and the odometer records the distance Δl1 that the fiber travels forward. At moment t2, the fiber optic shape sensing device measures the strain information of the fiber in the three-dimensional path and sends it to the computer to obtain the shape of the fiber and the position S2 of the front end of the fiber in the three-dimensional path. Next, the propulsion mechanism continues to propel the fiber forward, the strain information of the fiber optic sensing point is updated, and the odometer records the distance that the fiber travels forward. At moment t3, the fiber optic shape sensing device measures the strain information of the fiber in the three-dimensional path and sends it to the computer to obtain the shape of the fiber and the position S3 of the front end of the fiber in the three-dimensional path. Repeat the above process until the fiber travels to the end of the three-dimensional path, and the position S of the front end of the fiber in the three-dimensional path can be obtained. n and the shape of the entire 3D path.

[0035] The present invention also built a moving three-dimensional path shape measurement system and conducted a moving three-dimensional path shape measurement experiment. The system uses a multi-core fiber grating sensor as a sensing point and a fiber grating demodulator as a fiber shape sensing device. The actual picture of the system is as follows: Figure 3 shown.

[0036] The optical fiber used in the experiment is a multi-core optical fiber, specifically a seven-core optical fiber consisting of a central core and six surrounding cores distributed in a regular hexagon. The diameter of each core is 8μm, and the distance between adjacent cores is 41.5μm. Two groups of fiber grating sensors are engraved on the front end of the multi-core optical fiber. The Bragg center wavelengths of these two groups of fiber grating sensors are 1539nm and 1541nm respectively. The length of each fiber grating sensor is 10mm, and the axial distance between the two groups of fiber grating sensors is 3cm. The multi-core optical fiber is connected to the fiber grating demodulator through a fan-in fan-out module. The fiber grating demodulator can demodulate the Bragg center wavelengths of the central core and three surrounding cores of the multi-core optical fiber, and then obtain the strain information at the sensing point and send it to the computer.

[0037] In the experiment, a cylindrical three-dimensional mold with a height of 0.5m and a bottom radius of 0.05m was designed. Two spiral grooves with different parameters were milled on the mold. There were black rubber tubes with a diameter of 0.9mm on the spiral grooves. The black rubber tubes on these two spiral grooves served as the three-dimensional paths 1 and 3D paths 2 of the experiment.

[0038] In the moving three-dimensional path shape measurement, the multi-core optical fiber is inserted into the black rubber tube, and the fiber grating demodulator records the strain information of the fiber grating sensor at the initial moment and sends it to the computer to obtain the initial shape of the optical fiber and the initial position of the front end of the optical fiber in the three-dimensional path. The multi-core optical fiber is glued to the displacement table, and the handle of the displacement table is turned to make the displacement table drive the multi-core optical fiber to move. This not only realizes the propulsion function of the propulsion mechanism, but also realizes the function of the odometer to record the travel length by reading the moving distance of the displacement table. At two adjacent measurement moments, the moving distance of the displacement table is 3cm. A total of 11 measurements were made, and the multi-core optical fiber traveled 33cm. At each measurement moment, the fiber grating demodulator measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the shape of the optical fiber and the position of the front end of the optical fiber in the three-dimensional path. Finally, the shape of the entire three-dimensional path is obtained in the computer.

[0039] The shape measurement results of the moving three-dimensional path 1 are as follows Figure 4 As shown in Figure 1, the shape measurement error of 3D path 1 is 3.64%. The shape measurement results of the moving 3D path 2 are shown in Figure 1. Figure 5 As shown, the shape measurement error of the three-dimensional path 2 is 4.68%. The measurement results of the shapes of two different paths show that the measurement method and system provided by the present invention can effectively reconstruct the shape of the three-dimensional path. The error in the measurement may come from the cumulative error in the calculation, the measurement error caused by vibration or friction when the optical fiber travels, the manufacturing error of the fiber grating sensor, etc.

[0040] The present invention aims at the disadvantage that the sensing length in the existing optical fiber sensing technology is limited by the measurement performance of the optical fiber strain sensing device and the length of the optical fiber's own sensing and variable part, and the sensing length is short, and proposes a moving three-dimensional path shape measurement method and system based on optical fiber shape sensing. The feature of the invention is that the optical fiber is measured in a moving manner in the three-dimensional path, and the advantage is that the sensing length is not limited by the length of the optical fiber's own sensing and variable part, and a short sensing and variable length can be used to achieve long-distance three-dimensional path shape measurement.

[0041] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0042] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A traveling three-dimensional path shape measurement system based on optical fiber shape sensing, characterized in that: include An optical fiber shape sensing device, used for demodulating strain information at an optical fiber sensing point and transmitting the strain information to a computer; An odometer, used to record the travel length information of the optical fiber, and transmit the travel length information to the calculation; A propulsion mechanism, used for providing power for the optical fiber to move forward; A computer is used to reconstruct the shape of a three-dimensional path by utilizing the strain information of the optical fiber shape sensing device and the optical fiber travel length information recorded by the odometer.

2. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 1, characterized in that: The optical fiber includes at least one of a multi-core optical fiber and an optical fiber in which multiple single-core optical fibers are packaged in an array.

3. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 2, characterized in that: The multi-core optical fiber is a seven-core optical fiber consisting of a central core and six surrounding cores distributed in a regular hexagon; the diameter of each core is 8 μm, and the distance between adjacent cores is 41.5 μm.

4. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 2, characterized in that: It also includes a fiber grating sensor, which is engraved on the front end of the multi-core optical fiber.

5. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 4, characterized in that: The fiber grating sensors include two groups, and the Bragg center wavelengths of the two groups of fiber grating sensors are 1539nm and 1541nm respectively; the length of each fiber grating sensor is 10mm, and the axial distance between the two groups of fiber grating sensors is 3cm.

6. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 5, characterized in that: The optical fiber shape sensing device includes at least one of an optical fiber grating demodulator and a Brillouin optical time domain analyzer.

7. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 6, characterized in that: The multi-core optical fiber is connected to a fiber grating demodulator through a fan-in and fan-out module. The fiber grating demodulator can demodulate the Bragg center wavelengths of the central core and three surrounding cores of the multi-core optical fiber, thereby obtaining strain information at the sensing point and sending it to a computer.

8. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 1, characterized in that: It also comprises a three-dimensional mould, on which two spiral grooves with different parameters are milled, a rubber tube is arranged in the spiral groove, and the optical fiber is inserted into the rubber tube.

9. The advancing three-dimensional path shape measurement system based on optical fiber shape sensing according to claim 1, characterized in that: The pushing mechanism comprises a displacement platform, and the displacement platform is provided with a handle for rotating the displacement platform to drive the optical fiber to move.

10. A method for measuring a three-dimensional path shape based on optical fiber shape sensing, characterized in that: Using the traveling three-dimensional path shape measurement system based on optical fiber shape sensing as described in any one of claims 1 to 9, the method is as follows: S1, at the initial time t1, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the initial shape of the optical fiber and the initial position S1 of the front end of the optical fiber in the three-dimensional path; S2, the propulsion mechanism pushes the optical fiber forward, and the odometer records the distance Δl1 that the optical fiber moves forward. At time t2, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the shape of the optical fiber and the position S2 of the front end of the optical fiber in the three-dimensional path; S3, the propulsion mechanism continues to push the optical fiber forward, the strain information of the optical fiber sensing point is updated, and the odometer records the distance the optical fiber moves forward. At time t3, the optical fiber shape sensing device measures the strain information of the optical fiber in the three-dimensional path and sends it to the computer to obtain the shape of the optical fiber and the position of the front end of the optical fiber in the three-dimensional path S3; The above process is repeated until the optical fiber reaches the end of the three-dimensional path, and the position Sn of the front end of the optical fiber in the three-dimensional path and the shape of the entire three-dimensional path can be obtained.

Images