FBG type spiral beam high-sensitivity parallel six-dimensional force sensor

Abstract

The invention discloses an FBG type spiral beam high-sensitivity parallel six-dimensional force sensor which comprises a fixed platform, a measuring platform and a plurality of elastic connecting beams. The fixed platform and the measuring platform are hollow cylinders, and the measuring platform is concentrically arranged in the fixed platform; the far ends of the plurality of elastic connecting beams are uniformly distributed and fixed on a central circular ring on the outer side surface of the measuring platform; the near ends of the elastic connecting beams are fixed to the upper end face and the lower end face of the inner side face of the fixed platform at intervals. An optical fiber is arranged in each elastic connecting beam, the two ends of each optical fiber are fixed to the corresponding side faces of the measuring platform and the fixed platform respectively, and each optical fiber is led out from the outer side face of the fixed platform. The force / torque is transmitted to the elastic connecting beam when the measuring platform is subjected to the force / torque, and the grating central wavelength of the internal optical fiber drifts due to the deformation of the elastic connecting beam, so that a six-dimensional force value is obtained through the drifting of the central wavelength. According to the invention, higher sensitivity and higher resolution can be obtained.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, and in particular to an FBG type spiral beam high-sensitivity parallel six-dimensional force sensor. Background Art

[0002] As a core component for robots to achieve safe and efficient operation, six-dimensional force sensors provide force and torque information in three directions when the robot performs tasks. They have been widely used in collision testing, aerospace, medical rehabilitation, industrial manufacturing and other fields.

[0003] The basic principle of the six-dimensional force sensor is to transfer the deformation generated by the external load to the detection element through the elastic element, and measure the magnitude of the applied force and torque. The design of the elastic element is the core issue. The shape and size of the elastic element determine the performance of the sensor, such as sensitivity, stiffness and reliability. The existing force sensor structure design mainly includes cross beams and derivative structures, Y-beam structures, T-beams and parallel structures. Chinese patent ZL201811367523.4 discloses a six-dimensional force sensor, which uses a cross beam and a T-beam to apply strain gauges as detection elements to achieve structural decoupling. Chinese patent ZL202210280781.1 discloses a six-dimensional force sensor that uses a cross beam derivative structure as an elastic element and uses a capacitive detection method to achieve a compact six-dimensional force sensor structure. Chinese patent ZL202010411837.0 discloses a spherical six-dimensional force sensor that uses six Y-beams combined with strain gauges to achieve six-dimensional force detection. Chinese patent 201610534836.9 discloses a shunt-type three-plane branch parallel six-dimensional force sensor, which has the advantage of large-range measurement. The above structure has problems such as poor isotropy or large inter-dimensional coupling to varying degrees. Its detection elements are strain gauges, capacitors, etc. Such elements are susceptible to electromagnetic interference, poor linearity, and serious zero drift, making them difficult to be used in industrial or medical scenarios requiring high precision and high sensitivity. Summary of the invention

[0004] The invention provides a FBG type spiral beam high-sensitivity parallel six-dimensional force sensor, which adopts FBG type spiral beam parallel distribution, has high measurement sensitivity, small size, light weight and is not subject to electromagnetic interference.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A FBG type spiral beam high-sensitivity parallel six-dimensional force sensor, comprising: a fixed platform, a measuring platform and a plurality of elastic connecting beams, wherein the number of the elastic connecting beams is an even number; The fixed platform is a hollow cylinder; The measuring platform is a cylinder, the diameter of the measuring platform is smaller than the inner diameter of the fixed platform, and the measuring platform is concentrically arranged inside the fixed platform; The distal ends of the plurality of elastic connecting beams are evenly distributed and fixed on the central circular ring on the outer side of the measuring platform; The proximal ends of the plurality of elastic connection beams are fixed at intervals on the upper and lower end surfaces of the inner side surface of the fixed platform; the plurality of elastic connection beams are distributed in a spiral shape between the inner side surface of the fixed platform and the outer side surface of the measuring platform; The elastic connecting beam has two end connecting parts which are hollow cylindrical, and the middle section is a hollow spiral beam, and the cross section of the spiral beam is rectangular; An optical fiber is arranged inside each elastic connecting beam, and two ends of each optical fiber are respectively fixed to the outer side surface of the measuring platform and the inner side surface of the fixed platform, and each optical fiber is led out from the outer side surface of the fixed platform; The measuring platform is deformed when subjected to force / torque and the deformation is transmitted to the elastic connecting beam. The deformation of the elastic connecting beam causes the central wavelength of the grating of the internal optical fiber to drift, so that the six-dimensional force value is obtained from the drift of the central wavelength.

[0006] Further, the number of the plurality of elastic connecting beams is set to 6; the distal positions of all the elastic connecting beams are set to b1 to b6 in counterclockwise order, and the corresponding proximal positions are a1 to a6, and a1 to a6 are distributed in counterclockwise order, and the positions of a1 to a6 projected on the distal center circular ring plane are A1 to A6, then a1, a3, a5 are spaced 120° apart in pairs, and a2, a4, a6 are spaced 120° apart in pairs; A three-dimensional Cartesian coordinate system is established with the center of the far-end central ring as the origin, and the far-end and near-end positions of all elastic connecting beams meet the conditions: ; ; ; ; ; in, is the Jacobian matrix of the six-dimensional force, , , , , , , , are all intermediate variables; The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, is the length of the elastic connecting beam, is the height of the proximal end relative to the plane of the distal central ring, To measure the outer diameter of the platform, is the inner diameter of the fixed platform.

[0007] Furthermore, optical fiber arrangement grooves are provided on both end surfaces of the fixed platform, and optical fiber concentrated outlets are provided on the sides of the fixed platform; optical fiber arrangement grooves on both end surfaces are provided with optical fiber guide outlets connected to the optical fiber concentrated outlets at the positions of the optical fiber concentrated outlets; the optical fiber arrangement grooves are used to place optical fibers led out from the inner side surfaces of the fixed platform, and the optical fibers in the optical fiber arrangement grooves are led out of the sensor through the optical fiber guide outlets and the optical fiber concentrated outlets.

[0008] Furthermore, a plurality of optical fiber limiting beams are evenly arranged on the top surface of the optical fiber arrangement groove.

[0009] Furthermore, the sensor further comprises an upper cover located on the first end surface of the fixed platform and a base located on the second end surface side; The upper cover is fixedly connected to the measuring platform, and there is a gap of a first preset distance between the upper cover and the fixed platform; The base is fixedly connected to the fixed platform, and there is a gap of a second preset distance between the base and the measuring platform.

[0010] Furthermore, the measuring platform is a hollow cylinder.

[0011] Furthermore, all optical fibers use Bragg gratings.

[0012] Furthermore, the sensor also includes a data decoupling module, which adopts a KAN model; the KAN model outputs the six-dimensional force applied to the measurement platform according to the central wavelength drift value obtained from each optical fiber of the sensor.

[0013] Furthermore, the KAN model includes an input layer, a single hidden layer and an output layer, and the method for learning the model parameters is: applying a known six-dimensional force on the sensor, and collecting the central wavelength obtained by each optical fiber of the sensor to construct a training sample; then training the parameters in the KAN model based on the training sample.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a FBG type spiral beam high-sensitivity parallel six-dimensional force sensor, which uses a spiral structure with high sensitivity as an elastic beam of the sensor, and combines the advantages of FBG's anti-electromagnetic interference, sensitive response, and small size, so as to quickly sense the force changes on the measurement platform. The change in force causes the elastic beam to deform, thereby generating a corresponding FBG wavelength drift. Through the six-dimensional force decoupling processing by the KAN model, the force components in each direction can be accurately measured, and the accuracy and stability of the six-dimensional force measurement can be improved. In addition, the sensor is manufactured by metal 3D printing, and the main structure of the sensor is made in one piece, which enhances the compactness of the structure, reduces the sensor assembly error, and improves the sensor reliability and measurement accuracy. The combined application of these technologies can enable the sensor to obtain higher sensitivity and resolution, and expand its application range to industrial and medical scenarios with higher precision and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the overall explosion structure of an FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to an embodiment of the present invention.

[0016] Figure 2 This is a schematic structural diagram of a FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to an embodiment of the present invention.

[0017] Figure 3 The top view and optical fiber distribution diagram of an FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to an embodiment of the present invention; (a) is a top view, and (b) is a schematic diagram of optical fiber distribution.

[0018] Figure 4 This is a schematic diagram of a FBG type spiral beam high-sensitivity parallel six-axis force sensor spiral beam according to an embodiment of the present invention; wherein (a) is a detailed schematic diagram, and (b) is a cross-sectional view.

[0019] Figure 5 This is a schematic diagram of the spiral beam structure and a schematic diagram of the spiral beam endpoint coordinates of an FBG type spiral beam high-sensitivity parallel six-axis force sensor according to an embodiment of the present invention; (a) is a schematic diagram of the beam structure, and (b) is a schematic diagram of the spiral beam endpoint coordinates.

[0020] Explanation of the numbers in the figure: 1 is the upper cover, 2 is the sensor body, 3 is the base, 201 is the fixed platform, 202 is the optical fiber concentrated outlet, 203 is the optical fiber guide outlet, 204 is the optical fiber limiting beam, 205 is the optical fiber arrangement groove, 206 is the optical fiber far end glue groove, 207 is the fixed platform nut hole, 208 is the measuring platform, 209 is the optical fiber proximal end glue groove, 210 is the measuring platform nut hole, 211 is the elastic connecting beam, 211-1 is spiral beam one, 211-2 is spiral beam two, 211-3 is spiral beam three, 211-4 is spiral beam four, 211-5 is spiral beam five, 211-6 is spiral beam six, 212-1 is optical fiber one, 212-2 is optical fiber two, 212-3 is optical fiber three, 212-4 is optical fiber four, 212-5 is optical fiber five, 212-6 is optical fiber six. DETAILED DESCRIPTION

[0021] The following is a detailed description of an embodiment of the present invention. This embodiment is based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process to further explain the technical solution of the present invention.

[0022] This embodiment provides a FBG type spiral beam high sensitivity parallel six-dimensional force sensor, such as Figure 1 As shown, it includes an upper cover 1, a base 3 and a sensor body 2, wherein the upper cover 1 is located on a first end surface of the sensor body 2, and the base 3 is located on a second end surface of the sensor. Figure 2 As shown, the sensor body 2 includes a fixing platform 201, a measuring platform 208, a plurality of elastic connecting beams 211 and a data decoupling module, and the number of the elastic connecting beams 211 is an even number.

[0023] The fixed platform 201 is a hollow cylinder, the measuring platform 208 is a hollow cylinder, the diameter of the measuring platform 208 is smaller than the inner diameter of the fixed platform 201 , the height of the measuring platform 208 is smaller than the height of the fixed platform 201 , and the measuring platform 208 is concentrically arranged inside the fixed platform 201 .

[0024] like Figure 3 As shown, the distal ends of the plurality of elastic connection beams 211 are evenly distributed and fixed on the central circular ring of the outer side surface of the measuring platform 208; the proximal ends of the plurality of elastic connection beams 211 are fixed at intervals on the upper and lower end surfaces of the inner side surface of the fixed platform 201; the plurality of elastic connection beams 211 are distributed in a spiral shape between the inner side surface of the fixed platform 201 and the outer side surface of the measuring platform 208.

[0025] like Figure 4As shown, the elastic connecting beam 211 has a hollow cylindrical connection at both ends, a hollow spiral beam in the middle, and a rectangular cross section. Each elastic connecting beam 211 is provided with a fiber distal end glue groove 206 at the connection with the measuring platform 208, and each elastic connecting beam 211 is provided with a fiber proximal end glue groove 209 at the connection with the fixed platform 201. An optical fiber is arranged inside each elastic connecting beam 211, and the two ends of each optical fiber are respectively fixed to the glue grooves on the outer side of the measuring platform 208 and the inner side of the fixed platform 201 by glue. In this embodiment, all optical fibers use Bragg gratings.

[0026] The same annular fiber arrangement grooves 205 are arranged on both end surfaces of the fixed platform 201, and a plurality of fiber limiting beams 204 are evenly arranged on the top surface of the fiber arrangement grooves 205 (between the top circles of the inner side surface and the outer side surface of the fixed platform 201), and a fiber concentration outlet 202 is arranged on the outer side surface of the fixed platform 201. The fiber arrangement grooves 205 on both end surfaces of the fixed platform 201 are provided with fiber guide outlets 203 connected to the fiber concentration outlets 202 at the positions of the fiber concentration outlets 202. The fiber arrangement grooves 205 are used to place the optical fibers led out from the inner side surface of the fixed platform 201, and the optical fibers in the optical fiber arrangement grooves 205 are limited in the optical fiber arrangement grooves 205, and finally the sensor is led out through the optical fiber guide outlets 203 and the optical fiber concentration outlets 202.

[0027] In this embodiment, the number of the elastic connecting beams 211 is set to 6, and the six elastic connecting beams are numbered 211-1 to 211-6. Figure 4 As shown, the corresponding numbers of the internal optical fibers are 212-1 to 212-6; the distal positions of all elastic connecting beams 211 are set to b1~b6 in counterclockwise order, and the corresponding proximal positions are a1~a6, and a1~a6 are distributed in counterclockwise order, and the positions of a1~a6 projected on the plane of the distal center ring are A1~A6, then a1, a3, a5 are spaced 120° apart, and a2, a4, a6 are spaced 120° apart. A three-dimensional Cartesian coordinate system is established with the center of the distal center ring as the origin, then the distal and proximal positions of all elastic connecting beams 211 meet the conditions: ; ; ; ; ; in, is the Jacobian matrix of the six-dimensional force, , , , , , , , are all intermediate variables; The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, is the length of the elastic connecting beam 211, is the height of the proximal end relative to the plane of the distal central ring, To measure the outer diameter of the platform 208, is the inner diameter of the fixed platform 201.

[0028] The upper cover 1 is fixedly connected to the measuring platform 208, and there is a gap of a first preset distance between the upper cover 1 and the fixed platform 201; the base 3 is fixedly connected to the fixed platform 201, and there is a gap of a second preset distance between the upper cover 1 and the fixed platform 201. When the measuring platform 208 receives the force / torque transmitted by the upper cover 1, it can avoid the measuring platform 208 and the base 3 from contacting each other to affect the measurement accuracy, and avoid the upper cover 1 and the fixed platform 201 from contacting each other to affect the measurement accuracy.

[0029] In this embodiment, on the connection surface between the fixed platform 201 and the base 3, a fixed platform nut hole 207 is provided at the position where the limiting beam 204 extends inwardly, for fixedly connecting the fixed platform 201 and the base 3. On the connection surface between the measuring platform 208 and the upper cover 1, a plurality of measuring platform nut holes 210 are evenly provided, for fixedly connecting the measuring platform 208 and the upper cover 1.

[0030] The data decoupling module adopts the KAN model, and outputs the six-dimensional force applied to the measurement platform 208 according to the center wavelength drift value obtained by each optical fiber of the sensor. Specifically, the KAN model includes an input layer, a single hidden layer and an output layer, and the learning method of the model parameters is: applying a known six-dimensional force on the sensor, and collecting the center wavelength obtained by each optical fiber of the sensor, constructing a training sample; and then training the parameters in the KAN model based on the training sample.

[0031] The measuring platform 208 is deformed when subjected to force / torque and the deformation is transmitted to the elastic connecting beam 211. The deformation of the elastic connecting beam 211 causes the grating center wavelength of the internal optical fiber to drift, so that the KAN model adopted by the data decoupling module obtains the six-dimensional force value according to the output of the center wavelength drift of the optical fiber.

[0032] The structural arrangement principle of the FBG type spiral beam high-sensitivity parallel six-axis force sensor of this embodiment is as follows: According to the screw theory, the force balance equation is established: ; in For the The axial force acting on the elastic beam; Indicates The unit line vector of the elastic beam relative to the reference coordinate system; and Respectively represent the force and moment acting on the measuring platform; It is a dual conformity.

[0033] The above equation can be rewritten in matrix form: ; in is the force Jacobian matrix, which can be expressed as: ; is a The first three rows are the force vectors, and the last three rows are the moment vectors. For clarity, the matrix It can be expressed as: ; in, is the force vector mapping matrix, is the moment vector mapping matrix.

[0034] When studying the isotropy of sensors, the matrix is ​​usually Expressed as a force vector mapping matrix and the moment vector mapping matrix The form is as shown below: ;

[0035] In terms of sensor structure design, it is generally believed that and When all are zero matrices, it indicates that the sensor meets the decoupling performance. Furthermore, when and When it is a diagonal matrix, the sensor is considered to be isotropic in force and torque.

[0036] According to the above conditions and the spiral theory, the first-order static coefficient matrix of the six-dimensional force sensor structure of the present invention is obtained: ; ; Among them, Figure 5 As shown, is the coordinate of the connection point between the sensor elastic connecting beam and the inner side of the fixed platform, is the coordinate of the connection point between the sensor elastic connecting beam and the outer side of the measuring platform, for The angle between the connection points with the sensor center as the coordinate origin is for The angle between the connection points with the sensor center as the coordinate origin is is the length of the elastic connecting beam, and the lengths of the elastic connecting beams of the present invention are the same.

[0037] Can get The expression is: ; .

[0038] Therefore, the FBG type spiral beam high-sensitivity parallel six-dimensional force sensor of this embodiment satisfies the decoupling performance and isotropy, so the sensor structure design satisfies the following formula: .

[0039] In addition, the data decoupling module of this embodiment adopts the KAN model, which specifically includes: (1) Apply a given numerical six-dimensional force to the measurement platform to obtain the central wavelength drift of optical fibers 1 to 6, and construct training samples and prediction samples respectively.

[0040] (2) Construct a KAN model with an input layer, a single hidden layer, and an output layer; the input signal is the center wavelength drift of the six optical fibers. , the output is a six-dimensional force (three-dimensional force and three-dimensional moment) of a given value , its hidden layer elements can be expressed as: ; in, The input layer nodes to the hidden layer The activation function of each node, represents the number of input layer nodes, Indicates the number of hidden layer nodes.

[0041] Then, each node of its output layer can be expressed as: ; in, For hidden layer Nodes to the output layer The activation function of each node, is the number of nodes in the output layer.

[0042] (3) The parameters of the KAN model are optimized and learned using training samples to obtain the data decoupling module of the six-dimensional force sensor based on the KAN model, which is expressed as: .in, , .

[0043] (4) Input the newly obtained central wavelength drift of all six optical fiber outputs into the data decoupling module , and the corresponding six-dimensional force is output.

[0044] The above embodiments are preferred embodiments of the present application. Ordinary technicians in this field can also make various changes or improvements on this basis. Without departing from the overall concept of the present application, these changes or improvements should fall within the scope of protection required by the present application.

Claims

1. A FBG type spiral beam high sensitivity parallel six-dimensional force sensor, characterized in that: include: A fixed platform, a measuring platform and a plurality of elastic connecting beams, wherein the number of the elastic connecting beams is an even number; The fixed platform is a hollow cylinder; The measuring platform is a cylinder, the diameter of the measuring platform is smaller than the inner diameter of the fixed platform, and the measuring platform is concentrically arranged inside the fixed platform; The distal ends of the plurality of elastic connecting beams are evenly distributed and fixed on the central circular ring on the outer side of the measuring platform; The proximal ends of the plurality of elastic connection beams are fixed at intervals on the upper and lower end surfaces of the inner side surface of the fixed platform; the plurality of elastic connection beams are distributed in a spiral shape between the inner side surface of the fixed platform and the outer side surface of the measuring platform; The elastic connecting beam has two end connecting parts which are hollow cylindrical, and the middle section is a hollow spiral beam, and the cross section of the spiral beam is rectangular; An optical fiber is arranged inside each elastic connecting beam, and two ends of each optical fiber are respectively fixed to the outer side surface of the measuring platform and the inner side surface of the fixed platform, and each optical fiber is led out from the outer side surface of the fixed platform; The measuring platform is deformed when subjected to force / torque and the deformation is transmitted to the elastic connecting beam. The deformation of the elastic connecting beam causes the central wavelength of the grating of the internal optical fiber to drift, so that the six-dimensional force value is obtained from the drift of the central wavelength.

2. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: The number of the plurality of elastic connecting beams is set to 6; the distal positions of all the elastic connecting beams are set to b1 to b6 in counterclockwise order, and the corresponding proximal positions are a1 to a6, and a1 to a6 are distributed in counterclockwise order, and the positions of a1 to a6 projected on the distal center circular ring plane are A1 to A6, then a1, a3, a5 are spaced 120° apart in pairs, and a2, a4, a6 are spaced 120° apart in pairs; A three-dimensional Cartesian coordinate system is established with the center of the far-end central ring as the origin, and the far-end and near-end positions of all elastic connecting beams meet the conditions: ； ； ； ； ； in, is the Jacobian matrix of the six-dimensional force, , , , , , , , are all intermediate variables; The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, The projection point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, For point The angle of the line connecting the origin of the coordinate system with respect to the x-axis, is the length of the elastic connecting beam, is the height of the proximal end relative to the plane of the distal central ring, To measure the outer diameter of the platform, is the inner diameter of the fixed platform.

3. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: Optical fiber arrangement grooves are arranged on both end surfaces of the fixed platform, and optical fiber concentrated outlets are arranged on the side of the fixed platform; optical fiber arrangement grooves on both end surfaces are arranged at the positions of the optical fiber concentrated outlets, and optical fiber guide outlets connected to the optical fiber concentrated outlets are arranged; The optical fiber arrangement groove is used to place the optical fiber led out from the inner side of the fixed platform, and the optical fiber in the optical fiber arrangement groove is led out of the sensor through the optical fiber guide outlet and the optical fiber concentration outlet.

4. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 3 is characterized in that: A plurality of optical fiber limiting beams are evenly arranged on the top surface of the optical fiber arrangement groove.

5. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: The sensor also includes an upper cover located on the first end surface of the fixed platform and a base located on the second end surface side; The upper cover is fixedly connected to the measuring platform, and there is a gap of a first preset distance between the upper cover and the fixed platform; The base is fixedly connected to the fixed platform, and there is a gap of a second preset distance between the base and the measuring platform.

6. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: The measuring platform is a hollow cylinder.

7. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: All optical fibers use Bragg gratings.

8. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 1 is characterized in that: The sensor also includes a data decoupling module, which adopts a KAN model; the KAN model outputs the six-dimensional force applied to the measurement platform according to the central wavelength drift value obtained by each optical fiber of the sensor.

9. The FBG type spiral beam high-sensitivity parallel six-dimensional force sensor according to claim 8, characterized in that: The KAN model includes an input layer, a single hidden layer and an output layer. The method for learning the model parameters is: applying a known six-dimensional force on the sensor, collecting the central wavelength obtained by each optical fiber of the sensor, and constructing a training sample; then training the parameters in the KAN model based on the training sample.

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