Contiguous body mechanism space curvature measurement flexible sensing module and manufacturing method

Abstract

The present application relates to the technical field of flexible strain measurement, and discloses a flexible sensing module for measuring the spatial curvature of a continuum mechanism and a manufacturing method thereof, which comprises a flexible substrate and a sensing array module arranged in the flexible substrate in a determined direction; after the flexible sensing module is wrapped on the surface of the continuum mechanism, the axial tensile strain or the axial 45-degree angle shear strain at different positions on the surface of the continuum mechanism is measured by each strain sensing unit, then the bending deformation and the torsional deformation of the measurement interval covered by the flexible sensing module are calculated by combining the deformation continuity of the continuum mechanism, and the spatial curvature distribution of the continuum mechanism is fitted and reconstructed. Based on the capacitive in-plane strain sensing element of the flexible substrate and combined with the design of the lateral stiffness enhancement structure, the one-directional large tensile strain measurement with low cross-interference of the sensing site is realized, thereby increasing the accuracy and the range of the curvature measurement of the continuum mechanism.

Description

Technical Field

[0001] This invention relates to the field of flexible strain measurement technology, specifically to a flexible sensing module for measuring the spatial curvature of a continuum mechanism and its fabrication method. Background Technology

[0002] Continuum robotic arms and other multi-degree-of-freedom, highly redundant continuum systems exhibit complex curvature distributions and corresponding spatial deformations in their overall operating segments. Depending on the connection method, the deformation along the continuum mechanism may include torsional deformation in addition to bending, further complicating the curvature distribution. Due to the demands of continuum systems in complex and confined spaces, the radial dimension of the continuum operating segment is continuously decreasing, along with the working radius of curvature, significantly increasing the difficulty of measuring its curvature distribution. On one hand, the compact structure of the continuum operating segment places stringent requirements on the size and system of the integrated sensing module; on the other hand, the wide-range strain measurement requirements corresponding to large curvature deformations cannot be met by conventional strain measurement elements.

[0003] Currently, the most commonly studied methods for measuring the curvature of such continuum mechanisms fall into two main categories: one is indirect measurement at the drive end, where the measurement module is not located at the operation end where assembly space is limited, but rather installed in a centralized drive system, such as a rope drive system that indirectly calculates the curvature of the corresponding operation end by measuring changes in rope length. This method is easy to implement and has fewer restrictions on the measurement module, but indirect measurement at a remote end limits the accuracy of measuring the complex spatial bending of the continuum mechanism. The other category utilizes the advantages of a distributed grating fiber optic strain measurement system, integrating micron-diameter optical fibers onto the surface of the operation section of the continuum mechanism. Each grating point can measure the surface strain, and then the spatial deformation can be reconstructed based on the measured strain distribution. The distributed grating fiber optic measurement technology used in this method is relatively mature and can also achieve direct measurement of the operation section. However, due to the small upper limit of fiber strain (tensile strain <0.6%, curvature radius >30mm), its application in large strain and small curvature radius measurement scenarios is limited. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a flexible sensing module for measuring the spatial curvature of a continuum mechanism and its manufacturing method, which can effectively solve the above-mentioned problems.

[0005] The technical solution adopted in this invention is as follows:

[0006] The present invention provides a flexible sensing module for measuring the spatial curvature of a continuum mechanism, comprising a flexible substrate (1) and a sensing array module arranged in a defined direction inside the flexible substrate (1); each sensing module in the sensing array module comprises a strain sensing unit (2) and a ground lead (3) and a signal lead (4) connected to the strain sensing unit (2); the strain sensing unit (2) is a unidirectional strain sensing unit;

[0007] After the flexible sensing module is covered on the surface of the continuum mechanism, the axial tensile strain or axial 45° angle shear strain at different positions on the surface of the continuum mechanism is measured by each strain sensing unit (2). Then, the bending deformation and torsional deformation of the measurement range covered by the flexible sensing module are decoupled by the deformation continuity of the continuum mechanism, and the spatial curvature distribution of the continuum mechanism is fitted and reconstructed.

[0008] Furthermore, the sensor array modules of the flexible sensing module are periodically arranged along the axial direction of the continuum mechanism; each period of the sensor array module includes 8 strain sensing units (2), which are respectively denoted as: strain sensing unit A1t, strain sensing unit A2sc, strain sensing unit B3sa, strain sensing unit B4t, strain sensing unit C1sa, strain sensing unit C2t, strain sensing unit D3t and strain sensing unit D4sc;

[0009] Along the axial direction from top to bottom, strain sensing units A1t and A2sc of equal height are set, strain sensing units B3sa and B4t of equal height are set at a fixed distance, strain sensing units C1sa and C2t of equal height are set at a fixed distance, and strain sensing units D3t and D4sc of equal height are set at a fixed distance.

[0010] In the horizontal projection direction, strain sensing unit A1t is arranged at the 0° position to measure strain along the axial direction; strain sensing unit C1sa is arranged at the 0° position to measure strain along the axial direction at an angle of -45°; strain sensing unit A2sc is arranged at the 90° position to measure strain along the axial direction at an angle of 45°; strain sensing unit C2t is arranged at the 90° position to measure strain along the axial direction; strain sensing unit B3sa is arranged at the 180° position to measure strain along the axial direction at an angle of -45°; strain sensing unit D3t is arranged at the 180° position to measure strain along the axial direction; strain sensing unit B4t is arranged at the 270° position to measure strain along the axial direction; strain sensing unit D4sc is arranged at the 270° position to measure strain along the axial direction at an angle of 45°.

[0011] Furthermore, each strain sensing unit (2) includes an interdigitated capacitor structure (8) consisting of two sets of interdigitated electrodes in the same plane; each set of interdigitated electrodes includes an interdigitated electrode support plate (13) and its extended finger electrodes (14) arranged in parallel at a defined interval; the finger electrodes (14) of the two sets of interdigitated electrodes are arranged in a cross-connection to form a parallel capacitor, and each of the two sets of interdigitated electrodes is connected to the ground lead (3) and the signal lead (4) through the capacitor electrode contacts (9) fabricated on the interdigitated electrode support plate (13). A transverse reinforcing beam (12) perpendicular to the direction of the finger electrode (14) is provided on the inner and outer surfaces of the flexible substrate (1) corresponding to the cross area of ​​the two sets of interdigitated electrodes.

[0012] Furthermore, the flexible substrate (1) includes an inner cover layer (5), a sensing medium layer (6), and an outer cover layer (7) from the inside out.

[0013] The interdigitated capacitor structure (8) of the strain sensing unit (2) is located in the sensing medium layer (6). The ground lead (3) is located between the inner cover layer (5) and the sensing medium layer (6) and is connected to the capacitor electrode contact (9) of the strain sensing unit (2) via the ground lead contact (10). The signal lead (4) is located between the outer cover layer (7) and the sensing medium layer (6) and is connected to the capacitor electrode contact (9) of the strain sensing unit (2) via the signal lead contact (11). A transverse reinforcing beam (12) orthogonal to the strain measurement direction of the interdigitated capacitor structure (8) is provided on the inner surface of the inner cover layer (5) and the outer surface of the outer cover layer (7).

[0014] Furthermore, the inner cover layer (5), the sensing medium layer (6), and the outer cover layer (7) are made of the same flexible polymer material, and their thicknesses are all in the range of 0.1 mm to 1 mm; the ground lead (3) and the signal lead (4) are made of a highly conductive, low Young's modulus metal material, and their thicknesses are in the range of 0.5 μm to 50 μm.

[0015] Furthermore, the strain sensing unit (2) in the flexible sensing module is a flexible substrate capacitive in-plane strain measuring element, specifically measuring the strain along the direction of the finger electrode: when the flexible substrate (1) generates strain along the direction of the finger electrode, the sensing medium layer (6) between the two sets of interdigitated electrodes deforms along the direction of the finger electrode, causing the area between the finger electrodes that cross to form a capacitor to change, thereby generating a change in the capacitance of the total interdigitated capacitor structure.

[0016] Furthermore, the interdigital electrode support plate (13) and the finger electrode (14) are integrally made of conductive material, which is required to have low resistance and high Young's modulus, and a thickness in the range of 20μm~200μm; the interdigital electrode support plate (13) improves the lateral stiffness by increasing the width or thickness, that is, its tensile stiffness perpendicular to the direction of the finger electrode; the lateral reinforcing beam (12) is a high tensile stiffness beam made of insulating material, which is used to improve the lateral stiffness of the interdigital capacitor area; thus, the combination of the interdigital electrode support plate (13) and the lateral reinforcing beam (12) reduces the lateral response of the strain sensing unit (2) while ensuring the longitudinal strain measurement sensitivity.

[0017] Furthermore, the capacitor electrode contacts (9) are made of conductive material with adhesive function and have a certain thickness. The material used is UV-curable conductive adhesive or conductive tape. The ground lead (3) and signal lead (4) are designed as serpentine lead structures to avoid deformation and damage to the connecting lines under large strain of the flexible substrate (1).

[0018] The present invention also provides a method for manufacturing the flexible sensing module for measuring the spatial curvature of the continuum mechanism, comprising:

[0019] Step 1, Fabrication of the interdigitated capacitor structure (8):

[0020] Using a high-precision thin plate structure processing technology, a conductor thin plate is processed according to the drawing of the interdigital capacitor structure (8) to obtain the interdigital capacitor structure (8); further, in order to ensure that the two sets of interdigital electrodes remain aligned during the assembly process, a connecting positioning beam is retained between the two sets of interdigital electrodes.

[0021] Step 2, inner and outer coating layers are coated and cured:

[0022] In a mold with a smooth and flat bottom and sufficient inner wall height, the inner transverse reinforcing beams are arranged and positioned according to the strain sensing unit array. Uncured liquid flexible substrate material of the designed thickness is poured and coated. After vacuum treatment and static setting to remove air bubbles, the inner cover layer (5) is obtained. The outer cover layer (7) is obtained by the same operation, except that the outer transverse reinforcing beams are positioned and positioned according to a symmetrical array.

[0023] Step 3: Fabricate leads on the inner and outer cover surfaces:

[0024] The micro-machining process of sputtering metal thin film directly on the surface of inner and outer cover layers under the cover of lead pattern cut template, or the high-precision processing process of laser processing and cutting metal sheet to obtain lead pattern and then transferring and mounting it to inner and outer cover layers, respectively aligning and fabricating ground lead (3) and signal lead (4) on the surface of inner and outer cover layers.

[0025] Step 4: Align and mount the interdigitated capacitor structure array onto the inner cover layer (5):

[0026] According to the array arrangement design, each interdigitated capacitor structure (8) is aligned with the ground lead surface of the inner cover layer (5). The interdigitated capacitor structure (8) is connected to the ground lead. The interdigitated electrode support plate (13) is used to make the capacitor electrode contact (9) at the corresponding ground lead contact (10) position of the interdigitated electrode support plate (13) connected to the ground lead in the interdigitated capacitor structure (8) and the ground lead contact (10) is glued to fix the interdigitated capacitor structure (8) and realize the electrical connection between the ground interdigitated electrode and the ground lead (3).

[0027] Step 5, Coating the sensing medium layer:

[0028] In the interdigital capacitor structure (8), the interdigital electrode support plate (13) connecting the signal lead (4) is made with conductive silver paste or conductive tape to create a capacitor electrode contact (9) with a certain height. Then, the uncured liquid flexible substrate material is slowly and steadily poured and coated so that its height overflows the surface of the interdigital capacitor structure (8) and the capacitor electrode contact (9) is exposed. The flexible substrate material of the sensing medium layer is semi-cured, and then the positioning beam between the two sets of interdigital electrodes is cut off.

[0029] Step 6, Align the outer cover layer (7):

[0030] Keep the semi-cured state of the poured sensing medium layer flexible substrate material, continue to pour and coat a thin layer of uncured liquid flexible substrate material to make up for the volume shrinkage during curing, and ensure that the capacitor electrode contacts (9) are exposed; align the outer cover layer (7) downward with the signal lead (4) to the interdigital capacitor structure array, and use the same material as the capacitor electrode contacts (9) to bond each capacitor electrode contact (9) and its corresponding signal lead contact (11); flatten the flexible substrate layer as a whole, and ensure that the surface of the outer cover layer is in full contact with the uncured liquid flexible substrate material supplemented by the sensing medium layer, and then cure it after vacuum treatment and standing to remove air bubbles.

[0031] The flexible sensing module and manufacturing method for measuring the spatial curvature of a continuum mechanism provided by this invention have the following advantages:

[0032] (1) For the application of continuum mechanism, a single-direction large strain sensing unit is arranged on the flexible substrate according to the axial coordinate and tangential angle of the corresponding measurement point. After the flexible substrate is wrapped on the surface of the continuum mechanism, the strain distribution information of the orthogonal feature points on the surface of the continuum mechanism can be directly measured simultaneously in an axial section when the continuum mechanism is bent and deformed, so as to further calculate and fit the deformation space curvature of the continuum mechanism.

[0033] (2) Based on a flexible substrate, a capacitive in-plane strain sensing element is combined with its transverse stiffness enhancement structure design to achieve unidirectional large tensile strain measurement with low cross-interference at the sensing point, thereby increasing the accuracy and range of curvature measurement of the continuum mechanism.

[0034] (3) The overall flexible sensing module is assembled by vertical alignment of a thin plate structure with a thickness of sub-millimeter level made by high-precision processing technology. Combining the advantages of flexible substrate and small thickness size, it is especially suitable for the integration of compact continuum mechanisms with limited radial dimensions and direct measurement of deformation at its operating end. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of the flattened structure of the flexible sensing module for the spatial curvature of the continuum mechanism provided by the present invention;

[0037] Figure 2 A schematic diagram of the encapsulation assembly structure of the flexible sensing module for the spatial curvature of the continuum mechanism provided by the present invention;

[0038] Figure 3 A schematic diagram of the strain sensing unit arrangement in the spatial curvature flexible sensing module of the continuum mechanism provided by the present invention.

[0039] Figure 4 A schematic cross-sectional view of the main structure of the flexible sensing module for spatial curvature of a continuum mechanism provided by the present invention;

[0040] Figure 5 A schematic diagram of a unidirectional strain sensing unit in the spatial curvature flexible sensing module of the continuum mechanism provided by the present invention.

[0041] Figure 6 A schematic diagram of the serpentine lead structure in the spatial curvature flexible sensing module of the continuum mechanism provided by the present invention;

[0042] Figure 7 A schematic diagram illustrating the manufacturing process of the flexible sensing module for the spatial curvature of the continuum mechanism provided by this invention.

[0043] Wherein: 1—flexible substrate; 2—strain sensing unit; 3—ground lead; 4—signal lead; 5—inner cover layer; 6—sensing medium layer; 7—outer cover layer; 8—interdigital capacitor structure; 9—capacitor electrode contact; 10—ground lead contact; 11—signal lead contact; 12—lateral reinforcing beam; 13—interdigital electrode support plate; 14—finger electrode; 15—serpentine lead structure. Detailed Implementation

[0044] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0045] This invention provides a flexible sensing module for measuring the spatial curvature of a continuum mechanism, comprising a flexible substrate 1 and a sensing array module arranged in a defined direction inside the flexible substrate 1; each sensing module in the sensing array module includes a strain sensing unit 2 and a ground lead 3 and a signal lead 4 connected to the strain sensing unit 2; the strain sensing unit 2 is a unidirectional strain sensing unit.

[0046] After the flexible sensing module is wrapped around the surface of the continuum mechanism, the axial tensile strain or axial 45° angle shear strain at different positions on the surface of the continuum mechanism is measured by each strain sensing unit 2. Then, the bending deformation and torsional deformation of the measurement range covered by the flexible sensing module are calculated by decoupling the deformation continuity of the continuum mechanism, and the spatial curvature distribution of the continuum mechanism is fitted and reconstructed.

[0047] The sensor array modules of the flexible sensing module are arranged periodically along the axial direction of the continuum mechanism; each period of the sensor array module includes 8 strain sensing units 2, which are respectively denoted as: strain sensing unit A1t, strain sensing unit A2sc, strain sensing unit B3sa, strain sensing unit B4t, strain sensing unit C1sa, strain sensing unit C2t, strain sensing unit D3t and strain sensing unit D4sc.

[0048] Along the axial direction from top to bottom, strain sensing units A1t and A2sc of equal height are set, strain sensing units B3sa and B4t of equal height are set at a fixed distance, strain sensing units C1sa and C2t of equal height are set at a fixed distance, and strain sensing units D3t and D4sc of equal height are set at a fixed distance.

[0049] In the horizontal projection direction, strain sensing unit A1t is arranged at the 0° position to measure strain along the axial direction; strain sensing unit C1sa is arranged at the 0° position to measure strain along the axial direction at an angle of -45°; strain sensing unit A2sc is arranged at the 90° position to measure strain along the axial direction at an angle of 45°; strain sensing unit C2t is arranged at the 90° position to measure strain along the axial direction; strain sensing unit B3sa is arranged at the 180° position to measure strain along the axial direction at an angle of -45°; strain sensing unit D3t is arranged at the 180° position to measure strain along the axial direction; strain sensing unit B4t is arranged at the 270° position to measure strain along the axial direction; strain sensing unit D4sc is arranged at the 270° position to measure strain along the axial direction at an angle of 45°.

[0050] Furthermore, each strain sensing unit 2 includes an interdigitated capacitor structure 8 composed of two sets of interdigitated electrodes in the same plane; each set of interdigitated electrodes includes an interdigitated electrode support plate 13 and its extended finger electrodes 14 arranged in parallel at a defined interval; the finger electrodes 14 of the two sets of interdigitated electrodes are arranged in a cross-connection to form a parallel capacitor, and each of the two sets of interdigitated electrodes is connected to the ground lead 3 and the signal lead 4 through the capacitor electrode contacts 9 fabricated on the interdigitated electrode support plate 13. A transverse reinforcing beam 12 perpendicular to the direction of the finger electrode 14 is provided on the inner and outer surfaces of the flexible substrate 1 corresponding to the intersection area of ​​the two sets of interdigitated electrodes.

[0051] Furthermore, the flexible substrate 1 includes, from the inside out, an inner covering layer 5, a sensing medium layer 6, and an outer covering layer 7;

[0052] The interdigitated capacitor structure 8 of the strain sensing unit 2 is located in the sensing medium layer 6. The ground lead 3 is located between the inner cover layer 5 and the sensing medium layer 6, and is connected to the capacitor electrode contact 9 of the strain sensing unit 2 via the ground lead contact 10. The signal lead 4 is located between the outer cover layer 7 and the sensing medium layer 6, and is connected to the capacitor electrode contact 9 of the strain sensing unit 2 via the signal lead contact 11. A transverse reinforcing beam 12 orthogonal to the strain measurement direction of the interdigitated capacitor structure 8 is provided on the inner surface of the inner cover layer 5 and the outer surface of the outer cover layer 7.

[0053] In practical applications, the inner cover layer 5, the sensing medium layer 6, and the outer cover layer 7 are made of the same flexible polymer material, and their thicknesses are all in the range of 0.1mm to 1mm; the ground lead 3 and the signal lead 4 are made of a highly conductive, low Young's modulus metal material, and their thicknesses are in the range of 0.5μm to 50μm.

[0054] The strain sensing unit 2 in the flexible sensing module is a flexible substrate capacitive in-plane strain measuring element, specifically measuring strain along the direction of the finger electrodes: when the flexible substrate 1 generates strain along the direction of the finger electrodes, the sensing medium layer 6 between the two sets of interdigitated electrodes deforms along the direction of the finger electrodes, causing the area between the finger electrodes that cross to form a capacitor to change, thereby generating a change in the capacitance of the total interdigitated capacitor structure.

[0055] The interdigital electrode support plate 13 and the finger electrode 14 are integrally fabricated from a conductive material, which is required to have low resistance and high Young's modulus, with a thickness in the range of 20μm to 200μm. The interdigital electrode support plate 13 improves its lateral stiffness, i.e., its tensile stiffness perpendicular to the direction of the finger electrode, by increasing its width or thickness. The lateral reinforcing beam 12 is a high tensile stiffness beam made of insulating material, used to improve the lateral stiffness of the interdigital capacitor region. Thus, the combination of the interdigital electrode support plate 13 and the lateral reinforcing beam 12 reduces the lateral response of the strain sensing unit 2 while ensuring the longitudinal strain measurement sensitivity.

[0056] The capacitor electrode contact 9 is made of a conductive material with adhesive function and has a certain thickness. The material used is UV-curable conductive adhesive or conductive tape. The ground lead 3 and the signal lead 4 are designed as a serpentine lead structure to avoid deformation and damage to the connecting lines under large strain of the flexible substrate 1.

[0057] An embodiment is described below with reference to the accompanying drawings:

[0058] The flexible sensing module structure of this invention is as follows: Figure 1 As shown, this is a sensor array module obtained by arranging unidirectional strain sensing units on a flexible substrate 1 in a defined direction. The overall structure consists of a flexible substrate 1, strain sensing units 2, and ground leads 3 and signal leads 4 that connect and lead out the signals of strain sensing units 2. Further for the application of measuring the spatial curvature of a continuum mechanism, the flexible substrate 1 is bent to cover the surface of the continuum mechanism. Each strain sensing unit 2 in the sensor array module is located on a pair of orthogonal measurement surfaces and measures the deformation along the axial direction of the mechanism and the strain at a 45° angle along the axial direction.

[0059] Preferably, after the flexible sensing module is covered on the surface of the continuum mechanism, the arrangement of the strain sensing units is as follows: Figure 3As shown: at the 0° position, strain sensing unit A1t measures strain along the axial direction, and C1sa measures strain along the axial direction at a -45° angle; at the 90° position, strain sensing unit A2sc measures strain along the axial direction at a 45° angle, and C2t measures strain along the axial direction; at the 180° position, strain sensing unit B3sa measures strain along the axial direction at a -45° angle, and D3t measures strain along the axial direction; at the 270° position, strain sensing unit B4t measures strain along the axial direction, and D4sc measures strain along the axial direction at a 45° angle. The strain sensing units numbered A, B, C, and D are sequentially positioned at fixed intervals along the axial direction.

[0060] Further as Figure 4 As shown, the flexible substrate 1 of the flexible sensing module of the present invention is composed of an inner cover layer 5, a sensing medium layer 6, and an outer cover layer 7 from the inside out. The main interdigital capacitor structure 8 of the strain sensing unit is located in the sensing medium layer 6. The ground lead 3 is located between the inner cover layer 5 and the sensing medium layer 6 and is connected to the capacitor electrode contact 9 of the strain sensing unit 2 via the ground lead contact 10. The signal lead 4 is located between the outer cover layer 7 and the sensing medium layer 6 and is connected to the capacitor electrode contact 9 of the strain sensing unit 2 via the signal lead contact 11. In addition, transverse reinforcing beams 12 orthogonal to the strain measurement direction of the interdigital capacitor structure 8 are provided on the inner surface of the inner cover layer 5 and the outer surface of the outer cover layer 7.

[0061] In the flexible sensing module of this invention, the inner cover layer 5, the sensing medium layer 6, and the outer cover layer 7 are made of the same flexible polymer material, such as polydimethylsiloxane (PDMS), and the thickness of each is in the range of 0.1 mm to 1 mm; the ground lead 3 and the signal lead 4 are made of highly conductive, low Young's modulus metal materials, such as gold, silver, aluminum, etc., and the thickness is in the range of 0.5 μm to 50 μm.

[0062] The unidirectional strain sensing unit structure in the flexible sensing module of this invention is as follows: Figure 5 As shown, two sets of interdigitated electrodes in the same plane constitute an interdigitated capacitor structure 8. Each set of interdigitated electrodes consists of an interdigitated electrode support plate 13 and its extended interdigitated electrodes 14 arranged in parallel at a defined interval. The interdigitated electrodes 14 of the two sets of interdigitated electrodes are arranged in a cross-connection to form a parallel capacitor. Each of the two sets of interdigitated electrodes is connected to the ground lead 3 and the signal lead 4 through the capacitor electrode contacts 9 fabricated on the interdigitated electrode support plate 13. Furthermore, transverse reinforcing beams 12 perpendicular to the direction of the interdigitated electrodes are provided on the inner and outer surfaces of the flexible substrate 1 in the area corresponding to the intersection of the two sets of interdigitated electrodes.

[0063] The unidirectional strain sensing unit in the flexible sensing module of this invention is a flexible substrate capacitive in-plane strain measurement element, specifically measuring strain along the direction of the finger electrodes: when the flexible substrate 1 generates strain along the direction of the finger electrodes, the sensing medium layer 6 between the two sets of interdigitated electrodes deforms along the direction of the finger electrodes, causing the area between the finger electrodes that cross to form a capacitor to change, thereby generating a change in the capacitance of the total interdigitated capacitor structure.

[0064] In the unidirectional strain sensing unit of the flexible sensing module of this invention, the interdigital electrode support plate 13 and the finger electrode 14 are integrally fabricated from conductive material. This conductive material is required to have low resistance and high Young's modulus, such as copper, with a thickness in the range of 20μm to 200μm. The interdigital electrode support plate structure in the unidirectional strain sensing unit improves the lateral stiffness, i.e., its tensile stiffness perpendicular to the direction of the finger electrode, by increasing the width or thickness. The lateral reinforcing beam 12 in the unidirectional strain sensing unit is a high tensile stiffness beam made of insulating material, used to improve the lateral stiffness of the interdigital capacitor region. Thus, the combination of the interdigital electrode support plate 13 and the lateral reinforcing beam structure significantly reduces the lateral response of the strain sensing unit 2, while ensuring the longitudinal strain measurement sensitivity.

[0065] The lateral dimension of the unidirectional strain sensing unit in the flexible sensing module of the present invention does not exceed 1 / 3 of the lateral spacing of the array, wherein the lateral dimension is the tangential direction corresponding to the flexible sensing module after covering the continuum mechanism.

[0066] The flexible sensing module of this invention uses an array of unidirectional strain sensing units to simultaneously measure the axial tensile strain or axial 45° angle shear strain of each axial coordinate and tangential position on the outer surface of a continuous mechanism within a certain length along the axial direction when it bends. Combined with the decoupling calculation of the deformation continuity of the continuous mechanism, the flexible sensing module covers the bending deformation and torsional deformation of the measurement range, and fits and reconstructs the spatial curvature distribution of the continuous mechanism.

[0067] Figure 1 The flexible sensing module shown is a measurement array for one cycle of the axial direction of a continuum mechanism. The flexible sensing module of the present invention can repeat the array in the longitudinal direction to extend the axial range of the measurement of the spatial curvature of the continuum mechanism. The longitudinal direction is the axial direction corresponding to the continuum mechanism after the flexible sensing module covers it.

[0068] In the flexible sensing module of this invention, the capacitor electrode contact 9 is made of a conductive material with adhesive function and has a certain thickness. The material can be UV-curable conductive adhesive or conductive tape.

[0069] In the flexible sensing module of this invention, the ground lead 3 and signal lead 4 are designed with a serpentine lead structure, such as... Figure 6 As shown, this is to avoid deformation damage to the connecting wires under large strain on the flexible substrate.

[0070] The fabrication process of the flexible sensing module of this invention is as follows: Figure 7 As shown:

[0071] Step 1, Fabrication of the interdigital capacitor structure unit:

[0072] Using high-precision thin-plate structure processing technology such as laser processing, conductor thin plates are processed according to the interdigital capacitor structure drawings to obtain interdigital capacitor structure 8; furthermore, to ensure that the two sets of interdigital electrodes remain aligned during the assembly process, a connecting positioning beam is retained between the two sets of interdigital electrodes.

[0073] Step 2, inner and outer coating layers are coated and cured:

[0074] In a mold with a smooth and flat bottom and sufficient inner wall height, the inner transverse reinforcing beams are arranged and positioned according to the strain sensing unit array. An uncured liquid flexible substrate material of the designed thickness is poured and coated. After vacuum treatment and static setting to remove air bubbles, the material is cured to obtain the inner cover layer 5. The outer cover layer 7 is obtained by the same operation, except that the outer transverse reinforcing beams are placed in a symmetrical array.

[0075] Step 3: Fabricate leads on the inner and outer cover surfaces:

[0076] The micro-machining process of sputtering a thin metal film directly onto the inner and outer cover layers under the cover of the lead pattern cut template, or the high-precision processing process of laser cutting of metal sheet to obtain the lead pattern and then transferring and mounting it onto the inner and outer cover layers, are used to align and fabricate ground lead 3 and signal lead 4 on the inner and outer cover layers respectively.

[0077] Step 4: Align and mount the interdigitated capacitor array onto the inner cover layer:

[0078] According to the array arrangement design, each interdigitated capacitor structure 8 is aligned with the surface of the ground lead of the inner cover layer. In the interdigitated capacitor structure 8, the interdigitated electrode support plate 13 that connects to the ground lead is used to make capacitor electrode contacts 9 at the corresponding ground lead contact 10 position with conductive silver paste or conductive tape, and the ground lead contact 10 is glued to fix the interdigitated capacitor structure 8 and realize the electrical connection between the grounding interdigitated electrode and the ground lead. This step is carried out using a mold in step 2.

[0079] Step 5, Coating the sensing medium layer:

[0080] In the interdigital capacitor structure 8, the interdigital electrode support plate connecting the signal leads is used to create capacitor electrode contacts 9 of a certain height at the corresponding signal lead contact positions using conductive silver paste or conductive tape. Then, uncured liquid flexible substrate material is slowly and steadily poured and coated, ensuring that its height covers the surface of the interdigital capacitor structure while exposing the capacitor electrode contacts 9. The flexible substrate material of the sensing medium layer is then semi-cured, and the positioning beam between the two sets of interdigital electrodes is cut off. This step is performed using the mold as described in step 4.

[0081] Step 6, Align the outer cover layer:

[0082] While maintaining the semi-cured state of the poured sensing medium layer flexible substrate material, continue to smoothly pour and coat a thin layer of uncured liquid flexible substrate material to compensate for the volume shrinkage during curing, ensuring that the capacitor electrode contacts 9 are exposed. Align the outer cover layer 7 downwards with the signal leads 4 onto the interdigital capacitor structure array, and use the same material as the capacitor electrode contacts 9 to bond each capacitor electrode contact 9 and its corresponding signal lead contact 11. Flatten the entire flexible substrate layer, ensuring full contact between the surface of the outer cover layer and the uncured liquid flexible substrate material added to the sensing medium layer. After removing air bubbles through vacuum treatment and allowing it to stand, perform a curing process. This step is performed using the mold as described in step 4.

[0083] The beneficial effects of the flexible sensing module for spatial curvature of the continuum mechanism of the present invention are:

[0084] (1) For the application of continuum mechanism, a single-direction large strain sensing unit is arranged on the flexible substrate according to the axial coordinate and tangential angle of the corresponding measurement point. After the flexible substrate is wrapped on the surface of the continuum mechanism, the strain distribution information of the orthogonal feature points on the surface of the continuum mechanism can be directly measured simultaneously in an axial section when the continuum mechanism is bent and deformed, so as to further calculate and fit the deformation space curvature of the continuum mechanism.

[0085] (2) Based on a flexible substrate, a capacitive in-plane strain sensing element is combined with its transverse stiffness enhancement structure design to achieve unidirectional large tensile strain measurement with low cross-interference at the sensing point, thereby increasing the accuracy and range of curvature measurement of the continuum mechanism.

[0086] (3) The overall flexible sensing module is assembled by vertical alignment of a thin plate structure with a thickness of sub-millimeter level made by high-precision processing technology. Combining the advantages of flexible substrate and small thickness size, it is especially suitable for the integration of compact continuum mechanisms with limited radial dimensions and direct measurement of deformation at its operating end.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a flexible sensing module for measuring the spatial curvature of a continuum mechanism, characterized in that, include: Step 1, Fabrication of the interdigitated capacitor structure (8): Using a high-precision thin plate structure processing technology, a conductor thin plate is processed according to the drawing of the interdigital capacitor structure (8) to obtain the interdigital capacitor structure (8); further, in order to ensure that the two sets of interdigital electrodes remain aligned during the assembly process, a connecting positioning beam is retained between the two sets of interdigital electrodes. Step 2, inner and outer coating layers are coated and cured: In a mold with a smooth and flat bottom and sufficient inner wall height, the inner transverse reinforcing beams are arranged and positioned according to the strain sensing unit array. Uncured liquid flexible substrate material of the designed thickness is poured and coated. After vacuum treatment and static setting to remove air bubbles, the inner cover layer (5) is obtained. The outer cover layer (7) is obtained by the same operation, except that the outer transverse reinforcing beams are positioned and positioned according to a symmetrical array. Step 3: Fabricate leads on the inner and outer cover surfaces: The micro-machining process of sputtering metal thin film directly on the surface of inner and outer cover layers under the cover of lead pattern cut template, or the high-precision processing process of laser processing and cutting metal sheet to obtain lead pattern and then transferring and mounting it to inner and outer cover layers, respectively aligning and fabricating ground lead (3) and signal lead (4) on the surface of inner and outer cover layers. Step 4: Align and mount the interdigitated capacitor structure array onto the inner cover layer (5): According to the array arrangement design, each interdigitated capacitor structure (8) is aligned with the ground lead surface of the inner cover layer (5). The interdigitated capacitor structure (8) is connected to the ground lead. The interdigitated electrode support plate (13) is used to make the capacitor electrode contact (9) at the corresponding ground lead contact (10) position of the interdigitated electrode support plate (13) connected to the ground lead in the interdigitated capacitor structure (8) and the ground lead contact (10) is glued to fix the interdigitated capacitor structure (8) and realize the electrical connection between the ground interdigitated electrode and the ground lead (3). Step 5, Coating the sensing medium layer: In the interdigital capacitor structure (8), the interdigital electrode support plate (13) connecting the signal lead (4) is made with conductive silver paste or conductive tape to create a capacitor electrode contact (9) with a certain height. Then, the uncured liquid flexible substrate material is slowly and steadily poured and coated so that its height overflows the surface of the interdigital capacitor structure (8) and the capacitor electrode contact (9) is exposed. The flexible substrate material of the sensing medium layer is semi-cured, and then the positioning beam between the two sets of interdigital electrodes is cut off. Step 6, Align the outer cover layer (7): Keep the semi-cured state of the poured sensing medium layer flexible substrate material, continue to pour and coat a thin layer of uncured liquid flexible substrate material to make up for the volume shrinkage of the curing, and also ensure that the capacitor electrode contacts (9) are exposed; align the outer cover layer (7) downward with the signal lead (4) to the interdigitated capacitor structure array, and use the same material as the capacitor electrode contacts (9) to bond each capacitor electrode contact (9) and its corresponding signal lead contact (11); flatten the flexible substrate layer as a whole, and ensure that the surface of the outer cover layer is in full contact with the uncured liquid flexible substrate material supplemented by the sensing medium layer, and then cure it after vacuum treatment and standing to remove air bubbles; The fabricated continuous mechanism spatial curvature measurement flexible sensing module includes a flexible substrate (1) and a sensing array module arranged in a defined direction inside the flexible substrate (1); each sensing module in the sensing array module includes a strain sensing unit (2) and a ground lead (3) and a signal lead (4) connected to the strain sensing unit (2); the strain sensing unit (2) is a unidirectional strain sensing unit.

2. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 1, characterized in that, After the flexible sensing module is covered on the surface of the continuum mechanism, the axial tensile strain or axial 45° angle shear strain at different positions on the surface of the continuum mechanism is measured by each strain sensing unit (2). Then, the bending deformation and torsional deformation of the measurement range covered by the flexible sensing module are decoupled by the deformation continuity of the continuum mechanism, and the spatial curvature distribution of the continuum mechanism is fitted and reconstructed.

3. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 2, characterized in that, The sensor array modules of the flexible sensing module are arranged periodically along the axial direction of the continuum mechanism; each period of the sensor array module includes 8 strain sensing units (2), which are respectively denoted as: strain sensing unit A1t, strain sensing unit A2sc, strain sensing unit B3sa, strain sensing unit B4t, strain sensing unit C1sa, strain sensing unit C2t, strain sensing unit D3t and strain sensing unit D4sc; Along the axial direction from top to bottom, strain sensing units A1t and A2sc of equal height are set, strain sensing units B3sa and B4t of equal height are set at a fixed distance, strain sensing units C1sa and C2t of equal height are set at a fixed distance, and strain sensing units D3t and D4sc of equal height are set at a fixed distance. In the horizontal projection direction, strain sensing unit A1t is arranged at the 0° position to measure strain along the axial direction; strain sensing unit C1sa is arranged at the 0° position to measure strain along the axial direction at an angle of -45°; strain sensing unit A2sc is arranged at the 90° position to measure strain along the axial direction at an angle of 45°; strain sensing unit C2t is arranged at the 90° position to measure strain along the axial direction; strain sensing unit B3sa is arranged at the 180° position to measure strain along the axial direction at an angle of -45°; strain sensing unit D3t is arranged at the 180° position to measure strain along the axial direction; strain sensing unit B4t is arranged at the 270° position to measure strain along the axial direction; strain sensing unit D4sc is arranged at the 270° position to measure strain along the axial direction at an angle of 45°.

4. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 2, characterized in that, Each strain sensing unit (2) includes an interdigitated capacitor structure (8) consisting of two sets of interdigitated electrodes in the same plane; each set of interdigitated electrodes includes an interdigitated electrode support plate (13) and its extended finger electrodes (14) arranged in parallel at a defined interval; the finger electrodes (14) of the two sets of interdigitated electrodes are arranged in a cross-connection to form a parallel capacitor, and each set of interdigitated electrodes is connected to the ground lead (3) and the signal lead (4) through the capacitor electrode contacts (9) fabricated on the interdigitated electrode support plate (13). A transverse reinforcing beam (12) perpendicular to the direction of the finger electrode (14) is provided on the inner and outer surfaces of the flexible substrate (1) corresponding to the cross area of ​​the two sets of interdigitated electrodes.

5. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 4, characterized in that, The flexible substrate (1) includes an inner cover layer (5), a sensing medium layer (6), and an outer cover layer (7) from the inside out. The interdigitated capacitor structure (8) of the strain sensing unit (2) is located in the sensing medium layer (6). The ground lead (3) is located between the inner cover layer (5) and the sensing medium layer (6) and is connected to the capacitor electrode contact (9) of the strain sensing unit (2) via the ground lead contact (10). The signal lead (4) is located between the outer cover layer (7) and the sensing medium layer (6) and is connected to the capacitor electrode contact (9) of the strain sensing unit (2) via the signal lead contact (11). A transverse reinforcing beam (12) orthogonal to the strain measurement direction of the interdigitated capacitor structure (8) is provided on the inner surface of the inner cover layer (5) and the outer surface of the outer cover layer (7).

6. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 5, characterized in that, The inner cover layer (5), the sensing medium layer (6), and the outer cover layer (7) are made of the same flexible polymer material, and their thicknesses are all in the range of 0.1 mm to 1 mm; the ground lead (3) and the signal lead (4) are made of a highly conductive, low Young's modulus metal material, and their thicknesses are in the range of 0.5 μm to 50 μm.

7. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 4, characterized in that, The strain sensing unit (2) in the flexible sensing module is a flexible substrate capacitive in-plane strain measuring element, specifically measuring the strain along the direction of the finger electrode: when the flexible substrate (1) generates strain along the direction of the finger electrode, the sensing medium layer (6) between the two sets of interdigitated electrodes deforms along the direction of the finger electrode, causing the area between the finger electrodes that cross to form a capacitor to change, thereby generating a change in the capacitance of the total interdigitated capacitor structure.

8. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 4, characterized in that, The interdigitated electrode support plate (13) and the finger electrode (14) are integrally made of conductive material with a thickness in the range of 20μm to 200μm. The interdigitated electrode support plate (13) increases its lateral stiffness, i.e., its tensile stiffness perpendicular to the direction of the finger electrode, by increasing its width or thickness. The lateral reinforcing beam (12) is a high tensile stiffness beam made of insulating material, used to increase the lateral stiffness of the interdigitated capacitor region. Thus, the combination of the interdigitated electrode support plate (13) and the lateral reinforcing beam (12) reduces the lateral response of the strain sensing unit (2) while ensuring the longitudinal strain measurement sensitivity.

9. The method for manufacturing the flexible sensing module for measuring the spatial curvature of a continuum mechanism according to claim 4, characterized in that, The capacitor electrode contacts (9) are made of conductive material with adhesive function and have a certain thickness. The material used is UV-curable conductive adhesive or conductive tape. The ground lead (3) and signal lead (4) are designed as serpentine lead structures to avoid deformation and damage to the connecting lines under large strain of the flexible substrate (1).

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