US-12618663-B2 - Torsion compensation system and compensation method for fiber Bragg grating curvature sensor

US12618663B2US 12618663 B2US12618663 B2US 12618663B2US-12618663-B2

Abstract

The provided is a torsion compensation system and a compensation method for a FBG curvature sensor. The compensation system includes a FBG curvature sensor, installed on a scraper conveyor; angle sensors, including two and installed on both sides of the FBG curvature sensor, are configured to obtain the torsion angle of the FBG curvature sensor by monitoring the difference between the two ends of the FBG curvature sensor; a FBG string, arranged on the FBG curvature sensor to form a plurality of grating measuring points, is configured to perceive the center wavelength of the FBG curvature sensor; a FBG demodulator, coupled with the FBG string, is configured to convert the optical signal of the center wavelength perceived by the FBG string into an electrical signal; a computer, respectively coupled with the angle sensors and the FBG demodulator, is configured to eliminate the FBG wavelength variation caused by torsion.

Inventors

Xinqiu FANG
Yang Song
Ningning Chen
Haotian Feng
Dexing HE
Minfu LIANG
Gang Wu
Yang Wu

Assignees

CHINA UNIVERSITY OF MINING AND TECHNOLOGY

Dates

Publication Date: 20260505
Application Date: 20240920

Claims (20)

1 . A torsion compensation system of a fiber Bragg grating (FBG) curvature sensor, comprising: a FBG curvature sensor, installed on a scraper conveyor; two angle sensors, one installed on each side of the FBG curvature sensor, that are configured to obtain a torsion angle of the FBG curvature sensor by monitoring a difference between two ends of the FBG curvature sensor; a FBG string, arranged on the FBG curvature sensor to form a plurality of grating measuring points, wherein the FBG string is configured to perceive a center wavelength of the FBG curvature sensor; a FBG demodulator, coupled with the FBG string, wherein the FBG demodulator is configured to convert an optical signal of the center wavelength perceived by the FBG string into an electrical signal; and a computer, respectively coupled with the angle sensors and the FBG demodulator, wherein the computer is configured to eliminate an FBG wavelength variation caused by torsion based on a received torsion angle and the center wavelength to obtain a curvature of a position where the grating measuring point is located after torsion compensation; wherein the computer comprises: a first correction module, wherein the first correction module is configured to correct a positive strain ε a perceived by the FBG string based on the FBG wavelength variation; and a second correction module, wherein the second correction module is configured to correct a curvature of the FBG curvature sensor under a superposition of bending and torsion based on a positive strain ε a perceived by a corrected FBG string to obtain a curvature K of a position of the grating measuring point after the torsion compensation.
2 . The torsion compensation system of the FBG curvature sensor according to claim 1 , wherein the FBG string comprises: a first FBG string arranged along an extended direction of the FBG curvature sensor; and a second FBG string arranged along the extended direction of the FBG curvature sensor; wherein the first FBG string and the second FBG string are separated by 90 degrees in a circumferential direction of the FBG curvature sensor.
3 . The torsion compensation system of the FBG curvature sensor according to claim 1 , wherein a correction formula for the positive strain of an FBG caused by the bending of the FBG curvature sensor is: ε a = [ ( 1 + Δλ λ B ( 1 - p e ) ) 2 - ( r ⁢ φ l ) 2 ] 1 2 - 1 wherein r is a distance between the FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and P e is an effective elastic-optical coefficient of a fiber.
4 . The torsion compensation system of the FBG curvature sensor according to claim 1 , wherein a modified expression of the curvature K at the position of the grating measuring point after the torsion compensation is: K = [ ( 1 r + Δλ M ) 2 - ( φ l ) 2 ] 1 2 - 1 r wherein r is a distance between an FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and M is a curvature sensitivity coefficient of the FBG.
5 . The torsion compensation system of the FBG curvature sensor according to claim 1 , wherein the computer further comprises: a visualization module, the visualization module is configured to realize a visualization of a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm based on compensated curvature information.
6 . The torsion compensation system of the FBG curvature sensor according to claim 1 , wherein the torsion compensation system further comprises: a server, a first end of the server is coupled with the angle sensors and the FBG demodulator, respectively, and a second end of the server is coupled with the computer, the second end is configured to receive and store the torsion angle and the center wavelength, wherein the torsion angle and the center wavelength stored in the server are allowed to be called by the computer.
7 . A compensation method for the torsion compensation system of the FBG curvature sensor according to claim 1 , comprising the following steps: S 10 : obtaining the torsion angle φ of the FBG curvature sensor by monitoring the difference between the two ends of the FBG curvature sensor by the angle sensors; monitoring the center wavelength of each of the plurality of grating measuring points on the FBG curvature sensor by the FBG string; S 20 : correcting the positive strain ε a perceived by the FBG string by the computer based on the FBG wavelength variation; S 30 : correcting the curvature of the FBG curvature sensor subjected to the superposition of bending and torsion by the computer based on the positive strain ε a perceived by the corrected FBG string, and obtaining the curvature K of the position of the grating measuring point after the torsion compensation.
8 . The compensation method according to claim 7 , wherein after S 30 , the compensation method further comprises: based on compensated curvature information, visualizing with the computer a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm.
9 . The compensation method according to claim 7 , wherein in S 20 , a correction formula for the positive strain of an FBG caused by the bending of the FBG curvature sensor is: ε a = [ ( 1 + Δλ λ B ( 1 - p e ) ) 2 - ( r ⁢ φ l ) 2 ] 1 2 - 1 wherein r is a distance between the FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and P e is an effective elastic-optical coefficient of a fiber.
10 . The compensation method according to claim 7 , wherein in S 30 , a modified expression of the curvature K at the position of the grating measuring point after the torsion compensation is: K = [ ( 1 r + Δλ M ) 2 - ( φ l ) 2 ] 1 2 - 1 r wherein r is a distance between an FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and M is a curvature sensitivity coefficient of the FBG.
11 . The compensation method according to claim 7 , wherein in the torsion compensation system, the FBG string comprises: a first FBG string arranged along an extended direction of the FBG curvature sensor; and a second FBG string arranged along the extended direction of the FBG curvature sensor; wherein the first FBG string and the second FBG string are separated by 90 degrees in a circumferential direction of the FBG curvature sensor.
12 . The compensation method according to claim 7 , wherein in the torsion compensation system, a correction formula for the positive strain of an FBG caused by the bending of the FBG curvature sensor is: ε a = [ ( 1 + Δλ λ B ( 1 - p e ) ) 2 - ( r ⁢ φ l ) 2 ] 1 2 - 1 wherein r is a distance between the FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and P e is an effective elastic-optical coefficient of a fiber.
13 . The compensation method according to claim 7 , wherein in the torsion compensation system, a modified expression of the curvature K at the position of the grating measuring point after the torsion compensation is: K = [ ( 1 r + Δλ M ) 2 - ( φ l ) 2 ] 1 2 - 1 r wherein r is a distance between an FBG and a centroid, φ is a torsion error angle of the FBG curvature sensor of the scraper conveyor, l is a length of the FBG curvature sensor of the scraper conveyor, Δλ is the FBG wavelength variation, λ B is an initial wavelength of the FBG, and M is a curvature sensitivity coefficient of the FBG.
14 . The compensation method according to claim 7 , wherein in the torsion compensation system, the computer further comprises: a visualization module, the visualization module is configured to visualize a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm based on compensated curvature information.
15 . The compensation method according to claim 7 , wherein the torsion compensation system further comprises: a server, a first end of the server is coupled with the angle sensors and the FBG demodulator, respectively, and a second end of the server is coupled with the computer, the second end is configured to receive and store the torsion angle and the center wavelength, wherein the torsion angle and the center wavelength stored in the server are allowed to be called by the computer.
16 . The compensation method according to claim 11 , wherein after S 30 , the compensation method further comprises: based on compensated curvature information, visualizing with the computer a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm.
17 . The compensation method according to claim 12 , wherein after S 30 , the compensation method further comprises: based on compensated curvature information, visualizing with the computer a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm.
18 . The compensation method according to claim 13 , wherein after S 30 , the compensation method further comprises: based on compensated curvature information, visualizing with the computer a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm.
19 . The compensation method according to claim 14 , wherein after S 30 , the compensation method further comprises: based on the compensated curvature information, visualizing with the computer the two-dimensional curve and the three-dimensional curve of the scraper conveyor through the discrete curvature continuous algorithm.
20 . The compensation method according to claim 15 , wherein after S 30 , the compensation method further comprises: based on compensated curvature information, visualizing with the computer a two-dimensional curve and a three-dimensional curve of the scraper conveyor through a discrete curvature continuous algorithm.

Description

CROSS-REFERENCE TO THE RELATED APPLICATIONS This application is based upon and claims priority to Chinese Patent Application No. 202310801288.1, filed on Jul. 1, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The invention relates to the field of mine fiber sensing, in particular to a torsion compensation system and a compensation method for a fiber Bragg grating (FBG) curvature sensor. BACKGROUND The accurate perception of the straightness of the scraper conveyor is of great significance for the construction of an intelligent working face, through the accurate perception of the straightness of the scraper conveyor, can provide data support for the realization of three straight and two flat technology in intelligent working face and the construction of unmanned working face. At present, the mainstream technology is to install inertial navigation in the shearer fuselage and invert the straightness of the scraper conveyor through the running track of the shearer, however, this technology has the disadvantages of cumulative error, indirect error, perceived lag, and high cost, which is difficult to effectively guide the long-term non-stop operation of the unmanned working face. Compared with the traditional electromagnetic sensor, the FBG curvature sensor has the advantages of easy bending, passivity, and anti-electromagnetic interference, in recent years, the FBG curvature sensor has been used to sense the straightness of the scraper conveyor in the coal mine, but the ultra-long distance arrangement of the FBG curvature sensor along the scraper conveyor makes this kind of sensor easy to produce torsion, which leads to the superposition of the FBG wavelength drift from the bending and torsion of the sensor. As a result, error is generated in the shape monitoring, and it is difficult to meet the requirements of the straightness perception accuracy of the underground scraper conveyor. Therefore, the invention of a torsion compensation system and method for the FBG curvature sensor of scraper conveyor is beneficial to improve the straightness perception accuracy of scraper conveyor based on FBG, and lay a foundation for the popularization and application of FBG curvature sensor in coal mine. SUMMARY Aiming at the problems and requirements mentioned above, this scheme proposes a torsion compensation system and a compensation method for a FBG curvature sensor, because the following technical characteristics are adopted, the above technical purposes can be realized, and many other technical effects can be brought. One purpose of the invention is to propose a torsion compensation system of a FBG curvature sensor, comprising: a FBG curvature sensor, installed on a scraper conveyor;angle sensors, comprising two and installed on both sides of the FBG curvature sensor, are configured to obtain a torsion angle of the FBG curvature sensor by monitoring a difference between two ends of the FBG curvature sensor;a FBG string, arranged on the FBG curvature sensor to form a plurality of grating measuring points, is configured to perceive a center wavelength of the FBG curvature sensor;a FBG demodulator, coupled with the FBG string, is configured to convert an optical signal of the center wavelength perceived by the FBG string into an electrical signal;a computer, respectively coupled with the angle sensors and the FBG demodulator, is configured to eliminate a FBG wavelength variation caused by torsion based on a received torsion angle and the center wavelength, so as to obtain a curvature of a position where the grating measuring point is located after torsion compensation. In this technical scheme, the torsion angle φ of the FBG curvature sensor is obtained by monitoring the difference between the two ends of the FBG curvature sensor by the angle sensors, and the center wavelength of each grating measuring point on the FBG curvature sensor is monitored by the FBG string, the optical signal of the center wavelength perceived by the FBG string is converted into an electrical signal by the FBG demodulator; after the torsion angle and center wavelength are obtained by the computer, the positive strain εa perceived by the sensor FBG string is corrected by the computer based on the grating wavelength variation; then, the curvature of the FBG curvature sensor subjected to the superposition of bending and torsion is corrected by the computer based on a modified sensor FBG string sensing strain εa, and the curvature K of the position of the grating measuring point is obtained. The compensation system separates the wavelength drift of the FBG of the sensitive element into the bending and torsion of the sensor, by eliminating the wavelength drift induced by the torsion of the sensor, the torsion compensation of the FBG curvature sensor of the scraper conveyor is realized, which can solve the curvature characteristics of the sensor more accurately and realize the straightness perception of the scra