All-fiber mechanical vibration sensor for sensing mechanical vibration by optical technology

Abstract

According to the scheme, the all-fiber mechanical vibration sensor which is based on the magneto-optical effect and senses vibration motion through the optical technology is provided, the modern optical fiber technology and the optical interferometer principle are utilized, optical fibers are adopted as sensing materials and optical transmission materials, and sensing of mechanical vibration to be detected is achieved through light beams in the optical fibers. Sensing parts do not contain devices which are susceptible to external electromagnetic interference and damage the insulation degree, such as conductive wires, and optical sensing vibration information can be accurately and safely completed in a passive, non-contact and loss-free manner at a high speed. The optical fiber sensing device has the advantages of simple optical fiber sensing structure, small size, high reliability, high response speed, wide signal frequency band, high safety and the like. The all-fiber mechanical vibration sensor can be used for sensing and monitoring vibration states and vibration characteristics of various rotating machines, and can also be used for optically sensing and monitoring vibration states of non-rotating machines, so that the mechanical equipment can realize intelligent and safe operation.

Description

Technical Field

[0001] Fiber optic sensors and mechanical vibration optical sensors belong to the field of optoelectronics.

[0002] Keywords: All-fiber sensing of mechanical vibration; Background Technology

[0003] Using optical technology to sense and measure various mechanical vibrations in order to ensure the safe and reliable operation of equipment, and further realize intelligent operation monitoring and control, is an important new technology in modern industry and a crucial field in many key industries.

[0004] Existing technologies for sensing and monitoring mechanical vibrations, such as those that use various mechanical transmission technologies and devices to convert mechanical vibrations into corresponding electrical signals, have relatively complex structures, poor reliability, stability, and consistency, slow response, narrow bandwidth, and require mechanical contact to achieve sensing. Furthermore, due to their large size, they are difficult to embed inside devices to sense and monitor vibrations and obtain signals.

[0005] An existing vibration sensing device, the Hall effect vibration sensor, suffers from the inherent risk of magnetic saturation due to the iron core it requires. Furthermore, the iron core results in a relatively slow response to mechanical vibrations, leading to a slow response speed for the corresponding electrical signal and limiting the response bandwidth. Additionally, the sensor requires electrical conductors to connect to it, making it susceptible to external electromagnetic interference. Moreover, its large size prevents it from being embedded inside a device to sense vibrations.

[0006] Some optical vibration testing and sensing technologies based on the principle of optical interference, such as fiber optic vibration interferometry based on Mark-Zehnder interferometers, have some inherent advantages of optical interference technology, such as high precision, resistance to electromagnetic interference, environmental friendliness, small size, and light weight. However, their weaknesses are also prominent, such as being highly sensitive to mechanical interference, generating more noise, having poor stability, and poor anti-interference ability, making it difficult to become an industrial product.

[0007] Therefore, the present invention cleverly utilizes the optical path reciprocity of the fiber optic structure and uses the optical differential effect to provide an all-fiber mechanical vibration sensor that senses vibration using optical fiber technology. It provides an excellent technology and product that can take advantage of the principles of fiber optic technology and optical interferometers and overcome the weaknesses of the aforementioned optical interferometers. Summary of the Invention

[0008] The all-fiber mechanical vibration sensor (FVS) proposed in this invention utilizes optical technology and the principle of optical interferometers. It employs modern optical fiber technology and typically uses a sensing fiber (or sensing optical device) and a transmission fiber as the sensing material and transmission device. By using the beam propagating in the sensing fiber (or sensing optical device) to sense the mechanical vibration under test, it achieves passive, contactless, lossless, high-speed, and accurate optical technology sensing.

[0009] The all-fiber mechanical vibration sensor technology proposed in this invention utilizes the Faraday magneto-optical effect and sensing optical fiber (or sensing optical device) to sense mechanical vibration using modern optical fiber technology.

[0010] All-fiber optic sensing technology products for mechanical vibration can be used for optical sensing and monitoring of vibration spectra in steam turbines, gas turbines, internal combustion engines, external combustion engines, generators, electric motors, and various rotating machinery, enabling these mechanical devices to achieve intelligent and safe operation.

[0011] For non-rotating mechanical vibration, all-fiber optic sensing technology can be used for optical sensing and monitoring of vibration information in various vehicles, electromechanical equipment, and various non-rotating mechanical equipment, enabling these machines to operate safely and reliably. When combined with specialized equipment, it can also be used for optical sensing and monitoring of vibration in equipment operating in gaseous or fluid media, achieving intelligent and safe operation.

[0012] The advantages of all-fiber mechanical vibration sensors include: high-speed and broad-spectrum rapid response to mechanical vibrations (up to 10). -10 (seconds); achieves passive, contactless, and lossless optical sensing and measurement; contains no conductive wires or other components susceptible to external electromagnetic interference and potential insulation damage; and due to the absence of electromagnetic interference, it boasts excellent electromagnetic compatibility; has a very large dynamic measurement range; and because it lacks an iron core, it eliminates safety hazards such as saturation in sensing and measuring rapidly changing mechanical vibrations, resulting in high reliability; the sensor's small size facilitates easy placement; it can directly convert mechanical parameters of object vibration amplitude, acceleration, frequency, phase, and period into digital and / or analog electrical signals; and its simple, robust, and long-lasting structure, requiring no maintenance, among other unique advantages, make it a powerful sensing technology for achieving intelligent control of various thermodynamic, electrical, and mechanical equipment, as well as modern industrial facilities that involve mechanical vibrations.

[0013] The all-fiber mechanical vibration sensor provided by this invention includes: a photoelectric unit, a sensing unit, and a signal processing unit; the photoelectric unit includes: a light source, a polarization-maintaining fiber circulator (or a polarization-maintaining fiber coupler), an online fiber polarizer, an optical phase modulator, a fiber delayer, an online quarter-wave plate, and a photoelectric converter; the sensing unit includes: a vibration conversion device, a sensing fiber (or a sensing optical device), and a fiber optic mirror; the signal processing unit includes: a signal processor; an analog-to-digital converter (AD), and a digital-to-analog converter (DA).

[0014] The light beam transmitted through the optical fiber in the photoelectric unit enters from the polarization-maintaining fiber circulator (or polarization-maintaining fiber coupler) and enters the online polarizer at its output port to obtain the output linearly polarized beam. After being split at 45 degrees in the fiber, the orthogonally linearly polarized beams with equal amplitude enter the optical phase modulator for modulation to obtain a phase difference. Then, they enter the online quarter-wave plate of the fiber and are converted into two circularly polarized beams rotating in opposite directions before entering the sensing fiber (or sensing optics). At its end, they are reflected by the fiber optic mirror and return along the same path. As these two circularly polarized beams propagate back and forth in the sensing fiber (or sensing optics), they sense the vibration to be measured based on the magneto-optic effect and use the vibration conversion device to sense the vibration information. The beam then returns along the same path as it came from the fiber and enters the photoelectric converter from the other outlet of the polarization-maintaining fiber circulator (or polarization-maintaining fiber coupler) to be converted into an electrical signal. After the signal processing unit decomposes the vibration information, it is output.

[0015] Its features

[0016] The vibration conversion device and the sensing fiber (or sensing optical device) work together to convert the vibration characteristic information of the mechanical object under test into optical information sensed by the beam propagating in the sensing fiber (or sensing optical device). After processing by the photoelectric unit and the signal processing unit, the vibration information of the mechanical object under test is solved and output through the optical fiber.

[0017] The sensing unit includes at least one of the following types of sensor devices: either a sensing fiber or a sensing optics device with a high magneto-optical coefficient.

[0018] The sensing fiber of the sensing unit is one of the following types of optical fiber: either communication optical fiber, low birefringence optical fiber, circularly polarized cycloid optical fiber, or high magneto-optical coefficient sensing fiber with high sensing efficiency.

[0019] The sensing fiber (or sensing optical device) of the sensing unit is characterized in that: the sensing fiber (or sensing optical device) is an optical fiber (or optical device) that can acquire the vibration characteristic information to be measured given by the vibration transformation device after transformation by using optical sensing technology.

[0020] The vibration conversion device of the sensing unit is characterized in that: the vibration conversion device converts the characteristic information of vibration motion into a form that can be sensed by optical sensing technology, thereby obtaining vibration information through sensing by sensing optical fiber (or sensing optical device).

[0021] The sensing fiber (or sensing optical device) and vibration conversion device of the sensing unit are characterized in that: the structural shape, mechanical size, placement orientation, and placement location of the vibration conversion device of the sensing unit shall provide sensing information of the vibration to be sensed.

[0022] The sensing fiber (or sensing optics) of the sensing unit is installed in a relatively fixed position, while the vibration conversion device is placed on the vibrating machinery under test at a position where it is in a vibrating state; or, conversely, the vibration conversion device is placed in a fixed state, while the sensing fiber (or sensing optics) of the sensing unit is installed on the vibrating machinery under test at a position where it is in a relatively vibrating state.

[0023] The sensing fiber (or sensing optics) of the sensing unit and the vibration conversion device realize non-contact sensing. The optical sensing and sensing process does not affect the original characteristics and operating state of the vibrating machinery under test.

[0024] The vibrations sensed by all-fiber vibration conversion devices include mechanical vibrations generated in rotational states and mechanical vibrations generated in translational states; or mechanical vibrations generated in a combined state of these two types of mechanical motion.

[0025] The vibration conversion device of the sensing unit is characterized in that: its constituent materials should be constructed by using ferromagnetic materials alone or in combination with polymers, or non-magnetic materials such as aluminum, copper, glass, ceramics, wood, and cardboard.

[0026] Attached Figure

[0027] Figure 1 Schematic diagram of the overall principle of the all-fiber mechanical vibration sensor FVS

[0028] Figure 2 A schematic diagram of the sensing unit components when the all-fiber mechanical vibration sensor FVS is used in a translational mechanical system.

[0029] Figure 3 A schematic diagram of the sensing unit components of an all-fiber mechanical vibration sensor (FVS) used in a rotating system.

[0030] Explanation of the meaning of the attached diagram

[0031] Figure 1The overall optical path principle, structure, and interrelationships of the all-fiber mechanical vibration sensor (FVS): A light source emits a beam of light, which is input into the optical fiber. Optical devices modulate, process, and delay the beam in the fiber before transmitting it to the sensing fiber (or sensing optics). In the sensing fiber (or sensing optics), the optical sensing device acquires the vibration signal, which, after transformation, is given by the vibration transformation device and can be optically sensed. The beam carrying this signal then returns to the photodetector. The photodetector converts the optical signal in the beam into an electrical signal. The signal processing circuit processes the electrical signal and outputs the vibration value.

[0032] Figure 2 A schematic diagram of the sensing unit components of an all-fiber optic mechanical vibration sensor (FVS) used in a translational (or non-rotational) mechanical vibration system: When an FVS is used in a translational mechanical vibration system (e.g., a microphone), the sensing fiber (or sensing optics) is fixed to the non-vibrating structural part (e.g., the base on which the vibration transducer is mounted) to realize the sensing of the translational vibration signal of the vibrating machinery.

[0033] Figure 3 A schematic diagram of the sensing unit components of an all-fiber optic mechanical vibration sensor (FVS) used in a rotating mechanical vibration system: When an FVS is used in a rotating mechanical vibration system (e.g., a steam turbine in a power plant), the sensing fiber (or sensing optics) is placed on the non-vibrating structure of the mechanical system (e.g., the turbine base) to sense the vibration motion signals of the rotating components (e.g., the turbine rotor). Alternatively: The sensing fiber (or sensing optics) is placed on the vibrating structure of the mechanical system (e.g., the turbine rotor) to sense the vibration motion signals of the rotating components (e.g., the turbine rotor).

[0034] The sensor values ​​of vibration in a rotating mechanical system are manifested in the changes in amplitude and frequency of the waveform obtained from the sensing of rotational motion, since vibration can be coupled with the rotational motion of the rotating mechanical system. Detailed Implementation Plan

[0035] Vibration conversion device structure of the sensing unit

[0036] *Materials for constructing vibration conversion devices

[0037] The vibration conversion device of the sensing unit should be constructed using ferromagnetic materials alone or in combination with polymers, or non-magnetic materials such as aluminum, copper, glass, ceramics, wood, and cardboard.

[0038] The construction and placement of vibration transducers are determined based on the structural characteristics of the mechanical equipment whose vibrations are being sensed.

[0039] *Structure selection of vibration conversion devices

[0040] FVS vibration information source device: It usually uses the above-mentioned appropriate materials and is installed in the appropriate position of the vibrating machinery under test, so that the vibration conversion device, together with the sensing fiber (or sensing optical device), can realize the function of acquiring and sensing the vibration information of the machinery under test.

[0041] Placement of the vibration conversion device of the sensing unit and the sensing fiber (or sensing optics)

[0042] *Coordinated operation of vibration transducers and sensing optical fibers (or sensing optics)

[0043] During FVS sensing operation, the vibration conversion device and the sensing fiber (or sensing optics) move independently in their respective spaces. They need to keep the distance between them as close as possible without being disturbed by each other's mechanical vibrations in order to sense as much vibration information as possible.

[0044] * Installation of vibration conversion devices and sensing optical fibers (or sensing optics) and acquisition of vibration information

[0045] The installation requirements of vibration transducers and sensing optical fibers (or sensing optics) dictate that their presence should allow for the sensing of the original vibrations of the measured mechanical components with minimal interference. Therefore, they must be fixed to different objects or mechanical parts.

[0046] The construction and installation of the vibration conversion device and sensing fiber (or sensing optics) should ensure that their presence does not interfere with or affect the original vibration of the machine under test. Therefore, both must be small in size and light in weight, and fixed in positions that do not affect the original vibration of the object under test or its mechanical parts. At the same time, the FVS should be able to acquire vibration information of sufficient intensity using optical technology.

[0047] Therefore, the choice of the installation method of the vibration conversion device and the sensing fiber (or sensing optical device) on the machine under test should ensure that this requirement is met.

[0048] Operating conditions of all-fiber mechanical vibration sensor FVS

[0049] *When the all-fiber optic mechanical vibration sensor (FVS) is used to sense mechanical vibration, the ambient temperature of the mechanical vibration being sensed should not exceed the limit temperature of ~1000℃.

[0050] *When the all-fiber optic mechanical vibration sensor (FVS) senses mechanical vibration, it requires that there be no strong external electromagnetic field in the operating environment of the mechanical vibration being sensed.

[0051] *When the all-fiber optic mechanical vibration sensor (FVS) senses mechanical vibration, it requires that there be no earthquakes perceptible to humans in the operating environment of the mechanical vibration being sensed, i.e., an earthquake magnitude below 3 on the Richter scale.

[0052] In order to use the all-fiber mechanical vibration sensor FVS for earthquake sensing and testing, a specially designed and manufactured all-fiber seismic sensor is required.

Claims

1. Claim 1, the all-fiber mechanical vibration sensor, comprising: Optoelectronic unit, sensing unit, signal processing unit; The optoelectronic unit includes: a light source, an optical fiber circulator (or optical fiber coupler), an online optical fiber polarizer, an optical phase modulator, an optical fiber delayer, an online quarter-wave plate, and an optoelectronic converter; the sensing unit includes: a vibration transducer, a sensing optical fiber (or sensing optical device), and an optical fiber mirror; the signal processing unit includes: a signal processor; an analog-to-digital converter (AD), and a digital-to-analog converter (DA). The light beam transmitted through the optical fiber in the photoelectric unit enters from the optical fiber circulator (or the optical fiber coupler) and enters the online optical fiber polarizer at its output port to obtain a linearly polarized beam. After being split at 45 degrees by the optical fiber, the orthogonally linearly polarized beams with equal amplitudes enter the optical phase modulator for modulation to obtain a phase difference. Then, they enter the online 1 / 4 waveplate of the optical fiber and are converted into two circularly polarized beams rotating in opposite directions before entering the sensing optical fiber (or the sensing optical device). At its end, they are reflected by the optical fiber mirror and return along the same path. When these two circularly polarized beams propagate back and forth in the sensing optical fiber (or the sensing optical device), they sense the information of the vibration to be measured based on the magneto-optical effect and use the vibration conversion device to sense the information of the vibration to be measured. The beam then returns along the same path as it came from the optical fiber and enters the photoelectric converter from the other outlet of the polarization-maintaining optical fiber circulator (or the optical fiber coupler) to be converted into an electrical signal. After being processed by the signal processing unit, the vibration information is deciphered and output. Its features The vibration conversion device and the sensing optical fiber (or the sensing optical device) work together to convert the vibration characteristic information of the mechanical object to be measured into optical information sensed by the beam propagating in the sensing optical fiber (or the sensing optical device). After processing by the photoelectric unit and the signal processing unit, the vibration information of the mechanical object to be measured is deciphered and output through the optical fiber.

2. According to claim 1, the sensing unit comprises at least one of the following types of sensor devices: either a sensing optical fiber or a sensing optical device with a high magneto-optical coefficient.

3. According to claim 1, the sensing fiber of the sensing unit is one of the following types of optical fiber: either a communication optical fiber, or a low birefringence optical fiber, or a circularly polarized cycloid optical fiber, or a high magneto-optical coefficient sensing fiber with high sensing efficiency.

4. According to claim 1, the sensing fiber (or the sensing optics) of the sensing unit is characterized in that: The sensing optical fiber (or the sensing optical device) is an optical fiber (or optical device) that can acquire the vibration characteristic information of the test device after transformation by optical sensing technology.

5. The vibration conversion device of the sensing unit according to claim 1, characterized in that: The vibration transformation device transforms the characteristic information of vibration motion into a form that can be sensed using optical sensing technology, thereby obtaining vibration information through the sensing optical fiber (or the sensing optical device).

6. According to claim 1 or claim 5, the sensing optical fiber (or the sensing optics) and vibration transducer of the sensing unit are characterized in that: The determination of the structure, mechanical dimensions, placement orientation, and placement location of the vibration conversion device of the sensing unit should provide the sensing information of the vibration to be sensed.

7. According to claim 1 or claim 6, the sensing fiber (or the sensing optics) of the sensing unit is installed in a relatively fixed position, while the vibration conversion device is placed on the vibrating machinery under test at a position in a vibrating state; or, in the opposite manner, the vibration conversion device is placed in a fixed state, while the sensing fiber (or the sensing optics) of the sensing unit is installed on the vibrating machinery under test at a position in a relatively vibrating state.

8. According to claim 1 or claim 7, the sensing optical fiber (or the sensing optical device) of the sensing unit and the vibration conversion device realize the sensing is non-contact, and the optical sensing and sensing process does not affect the original characteristics and operating state of the vibrating machinery under test.

9. According to claim 1 or claim 5, the vibration sensed by the all-fiber vibration conversion device includes mechanically generated vibration in a rotational state and mechanically generated vibration in a translational state; or mechanically generated vibration in a combined state of these two types of mechanical motion.

10. The vibration conversion device of the sensing unit according to claim 1, characterized in that: Its constituent materials should be constructed either alone with ferromagnetic materials or in combination with polymers, or with non-magnetic materials such as aluminum, copper, glass, ceramics, wood, and cardboard.

Images