A reflective optical fiber two-dimensional radial force measurement pin without inter-dimensional coupling

Abstract

The present invention discloses a reflective optical fiber two-dimensional radial force measuring pin shaft without inter-dimensional coupling, and relates to the technical field of two-dimensional force measurement and reflective optical fiber sensing. The present invention innovatively designs an elastic element of a multi-dimensional force sensor with the same stiffness in any radial direction. The elastic element is specifically a drum-shaped elastic ring structure, which is geometrically symmetrical at 360° in the circumferential direction, and lays a mechanical structural foundation for simplifying the conversion relationship between the sensor output signal and the input load and realizing algorithm decoupling. The displacement of the elastic element is innovatively used as the measurement object of the conversion element, and the conversion relationship between its deformation displacement and the input load is simple, and the deformation size of the elastic element is obtained by a non-contact measurement method. The method specifically selects a reflective intensity modulation type transceiver integrated optical fiber probe, which has the advantages of non-contact measurement, high measurement accuracy, insensitivity to temperature, and no electromagnetic interference.

Description

Technical Field

[0001] The invention relates to the technical field of two-dimensional force measurement and reflective optical fiber sensing, and in particular to a reflective optical fiber two-dimensional radial force measurement pin shaft without inter-dimensional coupling. Background Art

[0002] The two-dimensional radial force measuring pin is both a force sensor with sensing function and a pin with connecting function. For example, by using this force measuring pin to replace the traditional pin to connect the train shoe support and the brake beam, the positive pressure and friction of the brake shoe can be obtained in real time, providing the necessary data basis for the intelligent operation and maintenance of the train. Force sensors are usually composed of elastic elements and conversion elements. Among them, the elastic element directly bears the action of force and produces elastic deformation or elastic strain response, and the conversion element converts the response of the elastic element into a signal suitable for transmission or measurement, such as an electrical signal, an optical signal, etc. Elastic elements can be divided into two categories: integral type and assembled type;

[0003] Integral elastic bodies often use structures such as horizontal beams and vertical ribs, including the following:

[0004] The FBG two-dimensional force sensor with a cross beam structure proposed by Sun Shizheng, Liao Chao, Li Jie, etc. in Design and Experimental Study of Two-Dimensional Force Sensor Based on Fiber Bragg Grating [J]. Journal of Scientific Instrumentation;

[0005] A resistive strain type three-dimensional force sensor with four vertical ribs was proposed by Liu Changjian in the research and implementation of a three-dimensional force sensor and controller based on force feedback equipment;

[0006] Flexible planar 3-RRR type three-dimensional force sensor proposed by Yang Zhenzhen in the paper Development of planar parallel flexible hinge three-dimensional force sensor[D]. Yanshan University, 2016.

[0007] The three-dimensional force sensor proposed by Li Yongming in Optimization design and decoupling of a new three-dimensional force sensor based on flexible structure [D]. Jiangxi University of Science and Technology, 2018.

[0008] Assembled elastomers often use parallel mechanisms, including the following:

[0009] The parallel three-dimensional force sensor proposed by Yang Wei in Design and Experimental Research of Rigid-Flexible Hybrid Large Deformation Parallel Three-Dimensional Force Sensor[D]. Yanshan University, 2020.

[0010] The sliding three-dimensional force sensor proposed by Sun Zhuanghu in Design of three-dimensional force sensor based on axial force and radial force measurement of water pump[D]. Shenyang University of Technology, 2023.

[0011] The twelve-branch mechanical decoupling parallel three-dimensional force sensor proposed by Weng Dacheng in Design and Development of Mechanical Decoupling Parallel Three-Dimensional Force Sensor [D]. Yanshan University, 2017.

[0012] The above technology has the following technical deficiencies:

[0013] (1) Interdimensional coupling problem. Interdimensional coupling is the main factor restricting the measurement accuracy of multi-dimensional force sensors. Domestic and foreign scholars have conducted a lot of research to reduce the interdimensional coupling of multi-dimensional force sensors. Generally speaking, it is as follows:

[0014] The integral elastic body has no gaps and friction pairs, so the repeatability and linearity are good, but the disadvantage is that the inter-dimensional coupling is large;

[0015] The assembled elastic body reduces the inter-dimensional coupling by designing appropriate kinematic pairs, but due to the existence of friction, it does not achieve zero inter-dimensional coupling and also reduces the repeatability and linearity of the sensor.

[0016] (2) Temperature sensitivity. Existing multi-dimensional force sensors often use resistance strain gauges or fiber Bragg gratings as conversion elements to calculate the load on the elastic element by measuring the strain of the elastic element. However, both strain measuring elements are sensitive to temperature and require specially designed temperature compensation devices. In addition, the manufacture of fiber Bragg gratings requires the use of complex lithography and etching processes, which has a high manufacturing cost.

[0017] Therefore, a new solution to the above problems needs to be proposed. Summary of the invention

[0018] The object of the present invention is to provide a reflective optical fiber two-dimensional radial force measuring pin without inter-dimensional coupling to solve the problems raised in the background technology.

[0019] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a reflective optical fiber two-dimensional radial force measuring pin shaft without inter-dimensional coupling, comprising a mounting base, a positioning sleeve and a loading device, wherein a hole is opened at the loading device, and further comprising a core shaft, a bearing sleeve, a clamping nut, an axial positioning sleeve with a hole, an axial positioning sleeve, a metal hollow O-ring and a reflector;

[0020] Both ends of the mandrel are fixedly connected to the mounting base via external threads;

[0021] A bearing sleeve is arranged on the outer side of the core shaft, and the bearing sleeve is used to bear the two-dimensional radial load of the loading device;

[0022] The left end of the mandrel is provided with a clamping nut, and the outer surface of the mandrel is provided with an axial positioning sleeve with a hole and an axial positioning sleeve, and the clamping nut is used to cooperate with the shaft shoulder at the right end of the mandrel to axially compress the axial positioning sleeve with a hole and the axial positioning sleeve;

[0023] A metal hollow O-shaped sealing ring is arranged between the core shaft and the bearing sleeve, and the metal hollow O-shaped sealing ring has a certain elastic deformation ability;

[0024] Four reflectors are also arranged on the outer side of the core shaft.

[0025] Furthermore, the bearing sleeve includes an outer cylindrical surface and a drum-shaped elastic ring, the outer cylindrical surface is connected to the inner cylindrical surface of the hole of the loading device, the bearing sleeve is interference fit with the core shaft in the radial direction through the drum-shaped elastic ring, and the inner wall of the bearing sleeve is provided with a drum-shaped elastic ring, and the drum-shaped elastic ring is used to withstand two-dimensional radial force.

[0026] Furthermore, the drum-shaped elastic ring is positioned in the axial direction by means of an axial positioning sleeve with a hole and an axial positioning sleeve.

[0027] Furthermore, four reflective intensity modulated transceiver integrated optical fiber probes are installed inside the bearing sleeve, and the reflective intensity modulated transceiver integrated optical fiber probes are arranged in a group of two and at a 90° circumferential interval.

[0028] Furthermore, the four reflective intensity modulated integrated transceiver optical fiber probes are divided into a first optical fiber probe, a second optical fiber probe, a third optical fiber probe and a fourth optical fiber probe according to their applications. The first optical fiber probe and the second optical fiber probe respectively measure the center offset components x1 and y1 of the cross section on the left side of the core shaft, and the third optical fiber probe and the fourth optical fiber probe respectively measure the center offset components x2 and y2 of the cross section on the right side of the core shaft.

[0029] Furthermore, the first optical fiber probe, the second optical fiber probe, the third optical fiber probe and the fourth optical fiber probe are all composed of an input optical fiber, an output optical fiber and a metal steel pipe, and the input optical fiber and the output optical fiber are arranged on the inner side of the metal steel pipe.

[0030] Furthermore, the four reflectors are all metal blocks coated with a reflective film, and the reflectors are fixedly connected to the core shaft through the notch on the perforated axial positioning sleeve. The four reflectors are numbered as a first reflector, a second reflector, a third reflector and a fourth reflector respectively.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention realizes two-dimensional radial force measurement without inter-dimensional coupling through two aspects of technical innovation;

[0033] One aspect is: the elastic element of the present invention (the drum-shaped elastic ring inside the bearing sleeve) is a 360° symmetrical structure in the circumferential direction, and its radial stiffness is the same in all directions. Therefore, the offset of the center of the core shaft section corresponds to the amplitude of the radial load, and the offset direction is consistent with the direction of the radial load, that is, the conversion relationship between the sensor output signal and the input load is simple, which lays the foundation for inter-dimensional decoupling from the perspective of mechanical structure. However, the traditional elastic element composed of ribs and beam structures has different stiffness in all directions, and the conversion relationship between the output signal and the input load is complex. In theory, the elements in the decoupling matrix are not constants, which brings great difficulties to the realization of algorithm decoupling;

[0034] Another aspect is that the present invention adopts non-contact displacement measurement to obtain the deformation size of the elastic element, directly realizing inter-dimensional decoupling from the perspective of the conversion element. Non-contact measurement can avoid the influence of friction on the measurement results, and displacement measurement can avoid the inter-dimensional coupling caused by traditional (strain) measurement.

[0035] 2. The reflective intensity modulated transceiver optical fiber probe used in the present invention uses the principle of light reflection for distance measurement. The measurement result of the conversion element is not sensitive to temperature, and there is no need to specially design a temperature compensation device, which reduces the introduction of measurement errors, thereby solving the problem that the resistance strain gauges or optical fiber Bragg gratings used in existing multi-dimensional force sensors to measure strain are sensitive to temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0037] Figure 1 It is a schematic structural diagram of a reflective optical fiber two-dimensional radial force measuring pin shaft without inter-dimensional coupling of the present invention;

[0038] Figure 2 It is a schematic diagram of a bearing sleeve with a drum-shaped elastic ring structure according to the present invention;

[0039] Figure 3 This is a diagram of the reflective intensity modulated transceiver integrated optical fiber probe;

[0040] In the figure: 1. core shaft; 2. bearing sleeve; 3. locking nut; 4. axial positioning sleeve with hole; 5. axial positioning sleeve; 6. metal hollow O-ring; 7. reflective intensity modulated transceiver optical fiber probe; 8. reflector; 201. outer cylindrical surface; 202. drum-shaped elastic ring; 71. first optical fiber probe; 72. second optical fiber probe; 711. input optical fiber; 712. output optical fiber; 713. metal steel pipe; 81. first reflector; 82. second reflector. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of 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.

[0042] See also Figure 1 - Figure 2 A reflective optical fiber two-dimensional radial force measuring pin shaft without inter-dimensional coupling, comprising a mounting base, a positioning sleeve and a loading device, wherein a hole is provided at the loading device, and further comprising a core shaft 1, a bearing sleeve 2, a clamping nut 3, an axial positioning sleeve with a hole 4, an axial positioning sleeve 5, a metal hollow O-ring 6 and a reflector 8;

[0043] Both ends of the mandrel 1 are fixedly connected to the mounting base through external threads;

[0044] A bearing sleeve 2 is arranged on the outer side of the core shaft 1, and the bearing sleeve 2 is used to bear the two-dimensional radial load of the loading device;

[0045] A clamping nut 3 is provided at the left end of the mandrel 1, and an axial positioning sleeve 4 with a hole and an axial positioning sleeve 5 are provided on the outer surface of the mandrel 1. The clamping nut 3 is used to cooperate with the shaft shoulder at the right end of the mandrel 1 to axially compress the axial positioning sleeve 4 with a hole and the axial positioning sleeve 5;

[0046] A metal hollow O-shaped sealing ring 6 is provided between the core shaft 1 and the bearing sleeve 2. The metal hollow O-shaped sealing ring 6 has a certain elastic deformation ability, and can still provide reliable sealing when a small amount of radial relative displacement occurs between the core shaft 1 and the bearing sleeve 2. The metal hollow O-shaped sealing ring 6 is used to protect the reflective intensity modulated transceiver integrated optical fiber probe 7 from interference from external light and dust;

[0047] Four reflectors 8 are also arranged on the outer side of the core shaft 1 .

[0048] The bearing sleeve 2 includes an outer cylindrical surface 201 and a drum-shaped elastic ring 202. The outer cylindrical surface 201 is connected to the inner cylindrical surface of the hole of the loading device. The bearing sleeve 2 is interference fit with the core shaft 1 in the radial direction through the drum-shaped elastic ring 202. The inner wall of the bearing sleeve 2 is provided with a drum-shaped elastic ring 202, and the drum-shaped elastic ring 202 is used to withstand two-dimensional radial force.

[0049] The drum-shaped elastic ring 202 is positioned in the axial direction by means of an axial positioning sleeve 4 with a hole and an axial positioning sleeve 5 .

[0050] Four reflective intensity modulated transceiver integrated optical fiber probes 7 are installed inside the bearing sleeve 2. The reflective intensity modulated transceiver integrated optical fiber probes 7 are arranged in groups of two and at 90° circumferential intervals.

[0051] The four reflective intensity modulated transceiver integrated optical fiber probes 7 are divided into a first optical fiber probe 71, a second optical fiber probe 72, a third optical fiber probe and a fourth optical fiber probe according to their applications. The first optical fiber probe 71 and the second optical fiber probe 72 measure the center deviation components x1 and y1 of the cross section on the left side of the core shaft respectively, and the third optical fiber probe ( Figure 1 The optical fiber probe (not shown) and the fourth optical fiber probe respectively measure the center offset components x2 and y2 of the cross section on the right side of the core shaft.

[0052] The first optical fiber probe 71, the second optical fiber probe 72, the third optical fiber probe and the fourth optical fiber probe are all composed of an input optical fiber 711, an output optical fiber 712 and a metal steel pipe 713, and the input optical fiber 711 and the output optical fiber 712 are arranged inside the metal steel pipe 713;

[0053] The four reflectors 8 are all metal blocks coated with a reflective film. The reflectors 8 are fixedly connected to the core shaft 1 through the notch on the axial positioning sleeve 4 with a hole. The four reflectors 8 are numbered as the first reflector 81, the second reflector 82, the third reflector 83 and the fourth reflector 84. Figure 1 not shown) and a fourth reflector ( Figure 1 not indicated);

[0054] It should be noted that the first optical fiber probe 71, the second optical fiber probe 72, the third optical fiber probe and the fourth optical fiber probe correspond to the first reflector 81, the second reflector 82, the third reflector and the fourth reflector in sequence, so that light is injected from the input optical fiber 711 and emitted from the output optical fiber 712 after being reflected by the reflector 8, see Figure 3 ,The intensity of the reflected light from the fiber optic probe is affected by the distance s between the probe and the reflector, and the measurement accuracy of s is as high as 1μm.

[0055] The working principle of the two-dimensional radial force measuring pin is:

[0056] The two-dimensional radial force is applied to the outer cylindrical surface 201 of the bearing sleeve through the hole on the loading device, and the drum-shaped elastic ring 202 on the inner wall of the bearing sleeve produces radial deformation corresponding to the radial force, so that the concentricity of the core shaft 1 and the bearing sleeve 2 changes. Four reflective intensity modulation transceiver integrated optical fiber probes 7 measure the center offset vectors x1, y1 and x2, y2 of the left and right sections of the core shaft 1. The x component and y component of the two-dimensional radial force on the bearing sleeve 2 can be obtained by sensor calibration. Figure 1It can be seen that the first optical fiber probe 71 only outputs the displacement load component in the x direction, and is not affected by the displacement load component in the y direction; the second optical fiber probe 72 only outputs the displacement load component in the y direction, and is not affected by the displacement load component in the x direction; therefore, there is no inter-dimensional coupling between the first optical fiber probe 71 and the second optical fiber probe 72. Similarly, it can be seen that there is no inter-dimensional coupling between the third optical fiber probe and the fourth optical fiber probe. This is fundamentally different from the inter-dimensional coupling phenomenon in which the strain measuring elements in each direction produce outputs when the traditional strain-type multi-dimensional force sensor is subjected to a unidirectional force.

[0057] like Figure 1 The first optical fiber probe 71 in the prior art only outputs the displacement component in the x direction, and is not affected by the displacement component in the y direction. However, in the prior art, the FBG1 of the cross-beam structured FBG two-dimensional force sensor for measuring strain proposed by Sun Shizheng, Liao Chao, Li Jie, et al. in Design and Experimental Research of Two-Dimensional Force Sensor Based on Fiber Bragg Grating [J]. Journal of Scientific Instrumentation not only outputs the displacement component in the x direction, but also outputs the displacement component in the y direction, that is, the output signal of the conversion element has inter-dimensional coupling. Therefore, it is better to conclude that "the present invention adopts non-contact displacement measurement to obtain the deformation size of the elastic element, directly realizes inter-dimensional decoupling from the perspective of the conversion element, non-contact measurement can avoid the influence of friction on the measurement result, and displacement measurement can avoid the inter-dimensional coupling caused by traditional (strain) measurement".

[0058] In summary, the present invention has the following necessary technical innovations:

[0059] The present invention innovatively designs an elastic element of a multi-dimensional force sensor with the same stiffness in any radial direction. The elastic element is specifically a drum-shaped elastic ring structure, which is geometrically symmetrical at 360° in the circumferential direction, and lays a mechanical structural foundation for simplifying the conversion relationship between the sensor output signal and the input load and realizing algorithm decoupling.

[0060] Furthermore, the present invention innovatively uses the displacement of the elastic element rather than the strain as the measurement object of the conversion element, and the conversion relationship between the deformation displacement and the input load is simple and clear;

[0061] The present invention adopts a non-contact measurement method to obtain the deformation size of the elastic element. This method specifically selects a reflective intensity modulation transceiver integrated optical fiber probe, which has the advantages of non-contact measurement, high measurement accuracy, insensitivity to temperature, and no electromagnetic interference.

[0062] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A reflective optical fiber two-dimensional radial force measuring pin without inter-dimensional coupling, comprising a mounting base, a positioning sleeve and a loading device, wherein a hole is provided at the loading device, and characterized in that: It also includes a core shaft (1), a bearing sleeve (2), a clamping nut (3), an axial positioning sleeve with a hole (4), an axial positioning sleeve (5), a metal hollow O-ring sealing ring (6) and a reflector (8); Both ends of the core shaft (1) are fixedly connected to the installation base via external threads; A bearing sleeve (2) is arranged on the outer side of the core shaft (1), and the bearing sleeve (2) is used to bear the two-dimensional radial load of the loading device; The left end of the core shaft (1) is provided with a clamping nut (3), and the outer surface of the core shaft (1) is provided with an axial positioning sleeve with a hole (4) and an axial positioning sleeve (5), and the clamping nut (3) is used to cooperate with the shaft shoulder at the right end of the core shaft (1) to axially clamp the axial positioning sleeve with a hole (4) and the axial positioning sleeve (5); A metal hollow O-shaped sealing ring (6) is arranged between the core shaft (1) and the bearing sleeve (2), and the metal hollow O-shaped sealing ring (6) has a certain elastic deformation capability; Four reflectors (8) are also arranged on the outer side of the core shaft (1); The bearing sleeve (2) comprises an outer cylindrical surface (201) and a drum-shaped elastic ring (202); the outer cylindrical surface (201) is connected to the inner cylindrical surface of the hole of the loading device; the bearing sleeve (2) is interference-fitted with the core shaft (1) in the radial direction through the drum-shaped elastic ring (202); the inner wall of the bearing sleeve (2) is provided with a drum-shaped elastic ring (202); the drum-shaped elastic ring (202) is used to bear a two-dimensional radial force; the drum-shaped elastic ring (202) is a 360° symmetrical structure in the circumferential direction, and its radial stiffness is the same in all directions; The drum-shaped elastic ring (202) is positioned in the axial direction by means of an axial positioning sleeve (4) with a hole and an axial positioning sleeve (5).

2. The reflective optical fiber two-dimensional radial force measuring pin without inter-dimensional coupling according to claim 1, characterized in that: Four reflective intensity modulated transceiver integrated optical fiber probes (7) are installed inside the bearing sleeve (2), and the reflective intensity modulated transceiver integrated optical fiber probes (7) are arranged in groups of two at 90° circumferential intervals.

3. The reflective optical fiber two-dimensional radial force measuring pin without inter-dimensional coupling according to claim 2, characterized in that: The four reflective intensity modulated transceiver integrated optical fiber probes (7) are divided into a first optical fiber probe (71), a second optical fiber probe (72), a third optical fiber probe and a fourth optical fiber probe according to their applications. The first optical fiber probe (71) and the second optical fiber probe (72) respectively measure the center deviation components x1 and y1 of the cross section on the left side of the core shaft, and the third optical fiber probe and the fourth optical fiber probe respectively measure the center deviation components x2 and y2 of the cross section on the right side of the core shaft.

4. The reflective optical fiber two-dimensional radial force measuring pin without inter-dimensional coupling according to claim 3, characterized in that: The first optical fiber probe (71), the second optical fiber probe (72), the third optical fiber probe and the fourth optical fiber probe are all composed of an input optical fiber (711), an output optical fiber (712) and a metal steel pipe (713), and the input optical fiber (711) and the output optical fiber (712) are arranged on the inner side of the metal steel pipe (713).

5. The reflective optical fiber two-dimensional radial force measurement pin without inter-dimensional coupling according to claim 1, characterized in that: The four reflectors (8) are all metal blocks coated with a reflective film. The reflectors (8) are fixedly connected to the core shaft (1) through the notch on the perforated axial positioning sleeve (4). The four reflectors (8) are numbered as a first reflector (81), a second reflector (82), a third reflector and a fourth reflector.

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