Torque sensor based on optical interference and measuring method

Abstract

The invention discloses a torque sensor based on optical interference and a measuring method. The torque sensor comprises a broadband light source, an optical fiber coupler, a spectrograph, a signal processing device, a first signal detection arm, a second signal detection arm, a first signal reference arm, a second signal reference arm, a first reference mirror, a second reference mirror and a rotating shaft. The rotating shaft comprises a cylindrical shaft part, a first shape machining part and a second shape machining part, and the first shape machining part and the second shape machining part are located at the two ends of the cylindrical shaft part respectively; the radius of the first morphology processing part and the radius of the second morphology processing part change periodically. The broadband light source, the spectrograph, the first signal detection arm, the second signal detection arm, the first signal reference arm and the second signal reference arm are respectively connected with the optical fiber coupler through optical fibers; the spectrometer is connected with the signal processing device. The invention provides a torque sensor based on optical interference and a measuring method, which can realize high-precision, wide-range and quick-response torque measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of torque measurement, and specifically refers to a torque sensor and a measurement method based on optical interference. Background Art

[0002] Torque is a key physical parameter in a mechanical transmission system, and its magnitude and variation reflect the working state and performance characteristics of the mechanical transmission. The ability to accurately detect static torque or monitor dynamic torque in real time has important engineering value and economic significance for the performance optimization, safe operation, fault diagnosis, and maintenance strategy of a mechanical system. The detection of static torque, such as the rated torque check of mechanical components and the calibration of torque load during equipment installation, can provide key basis for the design and manufacture of equipment; the monitoring of dynamic torque, such as the online monitoring of the torque of a wind turbine bearing and the real-time response evaluation of an industrial robotic arm under complex load conditions, poses higher requirements for the safety and reliability of equipment operation.

[0003] Existing torque sensors can be classified into several types according to their working principles, such as strain type, magnetic induction type, surface acoustic wave type, and optical type. The strain type torque sensor mainly transfers the elastic deformation caused by an external load to a sensitive element (such as a strain gauge, fiber Bragg grating, etc.), and measures the torque by detecting the change in the electrical signal or optical signal output by the sensitive element. However, this type of sensor usually requires multiple layers of transfer (elastomer - bonding layer - sensitive element), has a significant hysteresis effect, and is prone to cumulative deformation error under high-frequency alternating loads, resulting in poor dynamic response performance and thus affecting the measurement accuracy.

[0004] The magnetic induction type sensor measures the torque by detecting the magnetic field change of a magnetic element under the action of an external load. Its advantage is fast response speed, but the change in the magnetic field is easily interfered by the external environment (such as temperature, material property change, etc.), resulting in unstable measurement accuracy, and may not work properly under specific conditions. The surface acoustic wave type torque sensor detects the torque through the propagation characteristics of ultrasonic waves in a material, but it requires special treatment of the material surface and the use of a coupling agent. The measurement process is complex and is easily interfered by bending moment or vibration, thus limiting its possibility of wide application.

[0005] Optical torque sensors, including photoelasticity method, Doppler effect method, and fiber optic interference method, etc., utilize the high sensitivity and electromagnetic interference resistance of optical signals and perform excellently in high-precision measurement and dynamic response performance. Among them, although the Doppler effect type sensor has the advantage of non-contact measurement, the Doppler frequency shift is weak or even disappears under low-speed or static conditions, resulting in the system losing its detection ability. In addition, most other optical sensors (such as fiber optic distributed sensors) still adopt a contact measurement method, and the interference to the original system is inevitable, thus affecting the measurement accuracy.

[0006] Chinese Patent Invention 202310323476.8 discloses a non-contact torque sensor that does not design the rotating shaft. It relies on the roughness of the rotating shaft itself, which is uncontrollable and will affect the measurement accuracy.

[0007] In summary, the existing torque measurement technologies have certain limitations in terms of dynamic response ability, anti-interference ability, and measurement accuracy. Summary of the Invention

[0008] One of the technical problems to be solved by the present invention is to provide a torque sensor based on optical interference, which can achieve high-precision, wide-range, and fast-response torque measurement.

[0009] Another technical problem to be solved by the present invention is to provide a measurement method for a torque sensor based on optical interference for static torque measurement.

[0010] The third technical problem to be solved by the present invention is to provide a measurement method for a torque sensor based on optical interference for dynamic torque measurement.

[0011] The present invention is implemented as follows:

[0012] Technical Solution One:

[0013] A torque sensor based on optical interference, comprising: a broadband light source, an optical fiber coupler, a spectrometer, a signal processing device, a first signal detection arm, a second signal detection arm, a first signal reference arm, a second signal reference arm, a first reference mirror, a second reference mirror, and a rotating shaft;

[0014] The rotating shaft includes: a cylindrical shaft portion, a first topography processing portion, and a second topography processing portion. The first topography processing portion and the second topography processing portion are respectively located at both ends of the cylindrical shaft portion; the radii of the first topography processing portion and the second topography processing portion change periodically;

[0015] The broadband light source, the spectrometer, the first signal detection arm, the second signal detection arm, the first signal reference arm, and the second signal reference arm are respectively connected to the optical fiber coupler via optical fibers; the spectrometer is connected to the signal processing device;

[0016] The first signal detection arm is aligned with the first topography processing portion of the rotating shaft, and the first signal reference arm is aligned with the first reference mirror; the first signal detection arm and the first signal reference arm are connected to the optical fiber coupler via the same optical fiber;

[0017] The second signal detection arm is aligned with the second surface machining portion of the rotating shaft, and the second signal reference arm is aligned with the second reference mirror; the second signal detection arm and the second signal reference arm are connected to the fiber optic coupler through the same optical fiber;

[0018] The broadband light source divides the optical signal into four beams of light through the fiber optic coupler:

[0019] The first beam of light is the detection light, which is transmitted to the first surface machining portion of the rotating shaft through the first signal detection arm and returns to the fiber optic coupler after reflection;

[0020] The second beam of light is the reference light, which is transmitted to the first reference mirror through the first signal reference arm and returns to the fiber optic coupler after reflection;

[0021] The third beam of light is the detection light, which is transmitted to the second surface machining portion of the rotating shaft through the second signal detection arm and returns to the fiber optic coupler after reflection;

[0022] The fourth beam of light is the reference light, which is transmitted to the second reference mirror through the second signal reference arm and returns to the fiber optic coupler after reflection;

[0023] When the reference light of the second beam of light is reflected back by the first reference mirror, it interferes with the detection light of the first beam of light scattered back in the same channel and is coupled with the fiber optic coupler into a dual-frequency interference signal and transmitted to the signal processing device;

[0024] When the reference light of the fourth beam of light is reflected back by the second reference mirror, it interferes with the detection light of the third beam of light scattered back in the same channel and is coupled with the fiber optic coupler into a dual-frequency interference signal and transmitted to the signal processing device;

[0025] The signal processing device obtains an accurate torque signal through multi-channel input and output.

[0026] Technical solution two:

[0027] A measurement method of a torque sensor based on optical interference for measuring static torque, including:

[0028] When the rotating shaft is subjected to static torque, the optical signals generated at the left and right ends of the rotating shaft will have a fixed optical path difference due to the design of the surface profile radius change. By collecting the interference signals of the detection light and the reference light at the left and right ends and calculating their phase difference, the torsional angle of the rotating shaft can be obtained;

[0029] The application of torque causes the rotation shaft to undergo rigid body rotation and elastic torsion within the shaft. Intuitively, the torque on the shaft is manifested as a torsional angle generated at one end relative to the other end; when a torque T is applied to a rotation shaft made of an isotropic linearly elastic material, a torsional angle will be generated on the rotation shaft. The relationship between the torsional angle and the torque is described by the following formula:

[0030]

[0031] where l is the distance between the two ends before and after relative torsion, G is the torsional stiffness of the rotation shaft, is the polar moment of inertia of the rotation shaft, and d is the diameter of the rotation shaft.

[0032] Technical solution three:

[0033] A measurement method of a torque sensor based on optical interference, used for the measurement of dynamic torque, includes:

[0034] When the rotation shaft is rotating and working and suddenly receives a torque T, due to the relative torsional angle existing between the front and rear detection surfaces, the influence of this torsional angle is reflected in the signal image as an obvious time difference Δt appearing between the front and rear square wave signals, and this time difference can characterize the torque change;

[0035] When calculating the torsional angle, the rotational speed needs to be calculated first; since the contour radius of the rotation shaft changes periodically, the data collected during the rotation of the rotation shaft also shows periodic changes, and the angle corresponding to each period is related to the number of contour radius periods m 0 within one circle. Therefore, if m periods are collected within the acquisition time t, the rotational speed n is specifically expressed as:

[0036]

[0037] After obtaining the rotational speed n, the torsional angle can be expressed as:

[0038]

[0039] Furthermore, the torque M m can be obtained as:

[0040]

[0041] The advantages of the present invention are as follows:

[0042] 1. The rotation shaft of the torque sensor of the present invention is designed as a cylindrical rotation shaft with topography processing parts at both ends, and has the characteristics of simple structure, high resolution, strong sensitivity, excellent anti-electromagnetic interference ability, high sampling frequency, and fast dynamic response speed, and is suitable for a variety of torque measurement scenarios, especially for applications in high-precision and high-tech fields.

[0043] 2. The present invention provides a non-contact torque sensor, which is based on the principle of optical interference. Utilizing the physical property of the fast propagation response speed of light, it can avoid the drawbacks of response lag brought by the resistance strain type and other physical principles, effectively reducing the creep, forward and return difference, zero drift and hysteresis of the sensor, and featuring fast response. On this basis, combined with the shaft surface profile information, it accurately locates the absolute position of each point on the shaft, thereby realizing accurate static / dynamic measurement. The present invention adopts non-contact measurement and can accurately and quickly obtain the torque received by the object to be measured. Therefore, the present invention has strong practicability and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the accompanying drawings in conjunction with embodiments.

[0045] Figure 1 It is a schematic structural diagram of the torque sensor of the present invention.

[0046] Figure 2 It is a three-dimensional structural diagram of the rotating shaft in the torque sensor of the present invention.

[0047] Figure 3 is Figure 2 front view of

[0048] Figure 4 is Figure 3 top view of DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] As Figures 1 to 4 shown, a torque sensor based on optical interference includes: a broadband light source 1, an optical fiber coupler 3, a spectrometer 4, a signal processing device 11, a first signal detection arm 5, a first signal reference arm 6, a second signal detection arm 7, a second signal reference arm 8, a first reference mirror 9, a second reference mirror 10, and a rotating shaft 12;

[0050] The rotating shaft 12 includes: a cylindrical shaft portion 121, a first profile machining portion 122, and a second profile machining portion 123. The first profile machining portion 122 and the second profile machining portion 123 are respectively located at both ends of the cylindrical shaft portion 121; the radii of the first profile machining portion 122 and the second profile machining portion 123 change periodically;

[0051] The broadband light source 1, the spectrometer 4, the first signal detection arm 5, the first signal reference arm 6, the second signal detection arm 7, and the second signal reference arm 8 are respectively connected to the optical fiber coupler 3 via an optical fiber 2; the spectrometer 4 is connected to the signal processing device 11;

[0052] The first signal detection arm 5 is aligned with the first surface profile processing part 122 of the rotating shaft 12, and the first signal reference arm 6 is aligned with the first reference mirror 9; the first signal detection arm 5 and the first signal reference arm 6 are connected to the fiber optic coupler 3 through the same optical fiber;

[0053] The second signal detection arm 7 is aligned with the second surface profile processing part 123 of the rotating shaft 12, and the second signal reference arm 7 is aligned with the second reference mirror 10; the second signal detection arm 7 and the second signal reference arm 8 are connected to the fiber optic coupler 3 through the same optical fiber;

[0054] The broadband light source 1 divides the optical signal into four beams of light through the fiber optic coupler 3:

[0055] The first beam of light is the detection light, which is transmitted through the first signal detection arm 5 to the first surface profile processing part 121 of the rotating shaft 12 and returns to the fiber optic coupler 3 after reflection;

[0056] The second beam of light is the reference light, which is transmitted through the first signal reference arm 6 to the first reference mirror 9 and returns to the fiber optic coupler 3 after reflection;

[0057] The third beam of light is the detection light, which is transmitted through the second signal detection arm 7 to the second surface profile processing part 122 of the rotating shaft 12 and returns to the fiber optic coupler 3 after reflection;

[0058] The fourth beam of light is the reference light, which is transmitted through the second signal reference arm 8 to the second reference mirror 10 and returns to the fiber optic coupler 3 after reflection;

[0059] When the reference light of the second beam of light is reflected back by the first reference mirror 9, it interferes with the detection light of the first beam of light scattered back in the same channel and is coupled with the fiber optic coupler 3 into a dual-frequency interference signal and transmitted to the signal processing device 11;

[0060] When the reference light of the fourth beam of light is reflected back by the second reference mirror 10, it interferes with the detection light of the third beam of light scattered back in the same channel and is coupled with the fiber optic coupler 3 into a dual-frequency interference signal and transmitted to the signal processing device 11;

[0061] The signal processing device 11 obtains an accurate torque signal through multi-channel input and output.

[0062] When the rotating shaft 12 is subjected to a torque, the surface profile processing areas at its left and right ends will have an optical path difference due to torsion. The two beams of detection light and the corresponding reference light are superimposed at the fiber optic coupler 3 to form an interference fringe signal, and the spectrometer 4 collects the interference signal. The signal processing device 11 combines the fast Fourier transform (FFT) and the Hanning window energy centroid method (HnWECM) algorithms to process the signal for time-frequency conversion and energy leakage problems, and finally realizes high-precision torque measurement.

[0063] According to the stress state of the rotating shaft 12, the present invention can measure the torque in two working modes:

[0064] The first is the static torque measurement mode:

[0065] When the rotating shaft is subjected to static torque, the optical signals generated at the left and right ends of the shaft will have a fixed optical path difference due to the design of the surface profile radius. By collecting the interference signals of the detection light and the reference light at the left and right ends and calculating their phase difference, the torsional angle of the shaft can be obtained. Combining the knowledge of material mechanics, the application of torque will cause the rotating shaft to have rigid body rotation and elastic torsion inside the shaft. The intuitive manifestation of torque on the shaft is that one end generates a torsional angle relative to the other end. If a torque T is applied to a circular shaft made of an isotropic linearly elastic material, it will cause a torsional angle Torsional angle The relationship with the torque can be described by the following formula:

[0066]

[0067] where l is the distance between the two ends before and after relative torsion, G is the torsional stiffness of the rotating shaft, is the polar moment of inertia of the rotating shaft, and d is the diameter of the rotating shaft.

[0068] The second is the dynamic torque measurement mode:

[0069] When the rotating shaft is rotating, when a torque T is suddenly applied to the shaft (in the case of no torque, the two signals generated by the front and rear detection arms completely coincide), due to the relative torsional angle between the front and rear detection surfaces, the influence of this torsional angle is reflected in the signal image as an obvious time difference Δt between the front and rear square wave signals, and this time difference can characterize the torque change. When calculating the torsional angle, the rotational speed needs to be calculated first. Since the profile radius of the rotating shaft changes periodically, the data collected when the rotating shaft rotates also shows periodic changes, and the angle corresponding to each period is related to the number of profile radius periods m 0 within one revolution. Therefore, if m periods are collected within the acquisition time t, the rotational speed n is specifically expressed as:

[0070]

[0071] After obtaining the rotational speed n, the torsional angle can be expressed as:

[0072]

[0073] Furthermore, the torque M m can be obtained as:

[0074]

[0075] It should be noted that when the number and position of the signal detection heads are different, and the number of the channel reference arms and signal reference mirrors are different, the measured torque accuracy, error analysis, and signal processing methods are different.

[0076] When the distances of the components in the optical path are different, the number and position of the signal detection heads are different, the number of the channel reference arms and signal reference mirrors are different, and the signal processing of the signal collection system is different, this torque sensor is used for small / large static torque detection and small / large dynamic torque real-time monitoring.

[0077] The present invention can achieve high-precision, wide-range, and fast-response torque measurement under non-contact conditions, adapt to the complex measurement requirements under static and dynamic working conditions, and at the same time overcome the problems such as hysteresis, creep, and environmental interference in the prior art, promoting the further development and engineering application of torque measurement technology.

[0078] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by those of ordinary skill in the art shall be regarded as not departing from the patent scope of the present invention.

Claims

1. A torque sensor based on optical interferometry, characterized in that: include: A broadband light source, a fiber coupler, a spectrometer, a signal processing device, a first signal detection arm, a second signal detection arm, a first signal reference arm, a second signal reference arm, a first reference mirror, a second reference mirror and a rotating shaft; The rotating shaft comprises: a cylindrical shaft portion, a first topography processing portion and a second topography processing portion, wherein the first topography processing portion and the second topography processing portion are respectively located at two ends of the cylindrical shaft portion; the radii of the first topography processing portion and the second topography processing portion are periodically changed; The broadband light source, the spectrometer, the first signal detection arm, the second signal detection arm, the first signal reference arm and the second signal reference arm are respectively connected to the fiber coupler via optical fibers; the spectrometer is connected to the signal processing device; The first signal detection arm is aligned with the first topographic processing part of the rotating shaft, and the first signal reference arm is aligned with the first reference mirror; the first signal detection arm and the first signal reference arm are connected to the optical fiber coupler via the same optical fiber; The second signal detection arm is aligned with the second topographic processing part of the rotating shaft, and the second signal reference arm is aligned with the second reference mirror; the second signal detection arm and the second signal reference arm are connected to the optical fiber coupler via the same optical fiber; The broadband light source divides the optical signal into four beams through the optical fiber coupler: The first beam of light is a detection light, which is transmitted to the first topography processing part of the rotating shaft through the first signal detection arm, and returns to the optical fiber coupler after reflection; The second beam of light is a reference light, which is transmitted to the first reference mirror through the first signal reference arm and returns to the optical fiber coupler after reflection; The third beam of light is a detection light, which is transmitted to the second topographic processing part of the rotating shaft through the second signal detection arm, and returns to the optical fiber coupler after reflection; The fourth beam of light is a reference light, which is transmitted to the second reference mirror through the second signal reference arm and returns to the optical fiber coupler after reflection; When the reference light of the second light beam is reflected back by the first reference mirror, it interferes with the detection light of the first light beam scattered back in the same channel and is coupled with the optical fiber coupler to form a dual-frequency interference signal which is transmitted to the signal processing device; When the reference light of the fourth light beam is reflected back by the second reference mirror, it interferes with the detection light of the third light beam scattered back in the same channel and is coupled with the optical fiber coupler to form a dual-frequency interference signal which is transmitted to the signal processing device; The signal processing device obtains an accurate torque signal through multi-channel input and output.

2. The method for measuring a torque sensor based on optical interference according to claim 1, characterized in that: For static torque measurement, including: When the shaft is subjected to static torque, the optical signals generated at the left and right ends of the shaft will have a fixed optical path difference due to the design of the change in surface profile radius. The torsion angle of the shaft can be obtained by collecting the interference signals of the detection light and the reference light at the left and right ends and calculating their phase difference. The application of torque will cause the shaft to produce rigid body rotation and elastic torsion in the shaft. The intuitive manifestation of torque on the shaft is that one end produces a torsion angle relative to the other end. Applying torque T on a shaft of an isotropic linear elastic material will produce a torsion angle of the shaft. The relationship between the torsion angle and the torque is described by the following formula: Among them, l is the distance between the two ends before and after the relative torsion, G is the torsional stiffness of the shaft, is the polar moment of inertia of the shaft, and d is the diameter of the shaft.

3. The method for measuring a torque sensor based on optical interference according to claim 1, characterized in that: For dynamic torque measurement, including: When the shaft is rotating and is suddenly subjected to a torque T, due to the relative torsion angle between the front and rear detection surfaces, the influence of this torsion angle is reflected in the signal image as an obvious time difference Δt between the front and rear square wave signals. This time difference can represent the torque change. When calculating the torsion angle, the rotation speed needs to be calculated first. Since the profile radius of the rotating shaft changes periodically, the data collected when the rotating shaft rotates also changes periodically, and the angle corresponding to each cycle is related to the number of profile radius cycles m0 in one circle. Therefore, if m cycles are collected within the collection time t, the rotation speed n is specifically expressed as: After obtaining the speed n, the torsion angle It can be expressed as: Then we can get the torque M m for:

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