A removable intermediate fixture for a sensor and method

Abstract

The application discloses a detachable intermediate fixing tool and method for a sensor, and belongs to the technical field of aerospace structure dynamics testing. The tool comprises a base and an elastic clamping mechanism. The base is accurately attached to the surface of a measured structure such as a composite wing or blade through a three-dimensional curved surface. The elastic clamping mechanism provides an installation resonance frequency of the sensor-tool system of no less than 2000 Hz to meet the high-frequency testing requirement. The application also provides a quantitative method for realizing controllable fracture through the cooperative design of an additive manufacturing process parameter and a preset fracture zone geometric parameter, including the engineering calculation of a printing direction, layer thickness, filling density and fracture toughness. The application solves the problems of traditional glue fixing, such as pollution damage to the sensor, damage to the sensor during removal, difficulty in curved surface directional installation, high-frequency distortion of testing data and the inability to monitor the hidden failure of the installation state, and is especially suitable for the modal testing of lightweight composite structures such as the propeller, wing and blade of an unmanned aerial vehicle and a helicopter.

Description

Technical Field

[0001] This invention belongs to the field of aerospace structural dynamics testing technology, specifically relating to a detachable intermediate fixing fixture and method for sensors. Background Technology

[0002] In modal testing of lightweight and composite material structures such as drone propellers, helicopter blades, and drone wings, sensor installation faces significant challenges. These structures have low natural frequencies, complex curved surfaces, and may contain mold release agents. Traditional methods present inherent contradictions: directly using high-strength adhesives (such as epoxy resin) to fix the sensor, while ensuring reliable connections, can lead to sensor contamination, damage, and difficulty in disassembly (miniature sensors, with their tiny size and precise construction, are commonly rendered unusable due to adhesive or degreasing agents seeping into the joints, or joint breakage during disassembly, etc.). Figure 10 As shown, the cost is high (a single miniature accelerometer used for propeller modal testing can cost tens of thousands of yuan), and it may also damage the structure under test (delamination failure in composite material structures). Disassembly presents a dilemma of "preserving the sensor or the sample." Using temporary adhesives (such as beeswax or double-sided tape) makes it difficult to maintain consistent bonding at the reinstallation interface, and these adhesives are prone to failure and detachment under low-frequency, high-amplitude vibrations. When detached, the failure typically manifests as "partial connection," where the connection quality no longer meets experimental requirements but is difficult to detect or identify visually, leading to invalid test data. Magnetic bases are completely ineffective on non-ferromagnetic composite materials, and their large mass affects the test results of lightweight structures. The sensor's planar surface cannot be tightly fitted to curved surfaces, making it impossible to guarantee the sensor's precise orientation and reinstallation position. This field urgently needs a solution that can achieve both reliable connection and non-destructive quick-release on complex surfaces.

[0003] While existing technologies in industries such as machinery, construction, vehicles, and home appliances offer various sensor fixtures, such as positioning fixtures for aligning signal teeth on engine pulleys, multi-axis adjustment fixtures for calibration, or fixing fixtures that use three-point support clamping, they are all designed to solve the problems of "rigid clamping" or "precision positioning." Their structures are complex and bulky, and the mounting base is limited to planes or regular curved surfaces. They cannot be adapted to fixing sensors on the curved surfaces of composite materials such as wings and blades, and cannot achieve accurate orientation of sensors on curved surfaces. They also do not consider the non-destructive recycling of sensors after testing, making it difficult to meet the high reliability measurement requirements of lightweight and complex curved surface samples such as UAV blades and wings.

[0004] Furthermore, the non-destructive assembly and disassembly of sensors is a critical issue that requires additional attention. High-precision accelerometers, especially the miniature high-precision accelerometers used in UAVs and composite materials, are expensive and dependent on imports, with a single unit costing tens of thousands of yuan. Different batches of tests require repeated assembly and disassembly of the sensors for reuse, but the sensors themselves are extremely fragile and sensitive (some models have connectors made of thin-walled threaded tubes less than 2 mm in diameter and less than 0.2 mm thick), making them highly susceptible to damage during assembly and disassembly (see appendix). Figure 1 If external damage or adhesive contamination occurs, it will incur high economic costs and time-consuming costs, such as having to return the device to the original manufacturer overseas for repair, or even cause the expensive sensor to be scrapped.

[0005] Therefore, there is an urgent need for a sensor mounting solution that can simultaneously achieve high rigidity and reliable fixation (ensuring test bandwidth), directional installation (acquiring motion signals of curved surface specimens in specific directions, such as the bending direction of an airfoil), rapid and non-destructive assembly and disassembly (improving test efficiency and protecting the sensor), strong versatility (adapting to different curved surfaces or micro-sized test pieces), and low cost. Summary of the Invention

[0006] The technical problem to be solved: To overcome the shortcomings of existing technologies, this invention provides a detachable intermediate fixing fixture and method for sensors, targeting the problem scenario of UAV-related structural dynamics tests. The sensor type is an accelerometer, and the acceleration signal acquisition and modal test results are highly dependent on the sensor's installation quality and orientation. This solution introduces a customized fixture between the sensor and the structure under test, combining the functions of "permanent / high-strength reliable connection with the structure under test" and "temporary / detachable connection with the sensor," enabling directional installation of the sensor on composite materials and complex curved surfaces.

[0007] The technical solution of the present invention is: a detachable intermediate fixing fixture for a sensor, comprising a fixture body, wherein the fixture body has: The base has a mounting surface at its bottom, the surface morphology of which matches the local three-dimensional morphology of the surface of the structure being measured, and is used to mount the tooling body onto the surface of the structure being measured. The elastic clamping mechanism is located on the base and is detachably connected to the sensor through an interference fit. The elastic clamping mechanism also has an installation position indication structure. A further technical solution of the present invention is: the elastic clamping mechanism includes a sensor receiving cavity formed on the tooling body, at least one elastic constraint arm and at least one fixed constraint arm; the static dimension of the sensor receiving cavity is slightly smaller than the external dimension of the corresponding part of the sensor to be fixed, so that after the sensor is pressed into place, a continuous radial preload is formed between the wall of the receiving cavity and the sensor housing, thus forming an interference fit.

[0008] A further technical solution of the present invention is that the height of the fixed constraint arm satisfies the following condition: when the sensor is installed in the sensor housing, a specific surface or mark on the sensor housing is flush with the top of the fixed constraint arm to provide a visual and / or tactile indication of installation in place.

[0009] A further technical solution of the present invention is: the elastic constraint arm is connected to a release arm. When the release arm is operated, it drives the elastic constraint arm to undergo elastic deformation to release the interference fit and realize the non-destructive disassembly of the sensor; after the operating force is removed, the elastic constraint arm returns to its original state, allowing the sensor to be reinstalled and locked.

[0010] A further technical solution of the present invention is: the elastic constraint arm is connected to a release arm, and when the release arm is operated, the elastic constraint arm breaks from a preset fracture zone at its root, thereby permanently releasing the lock on the sensor; the preset fracture zone is selected from at least one of a V-groove, a root thinning zone, and a pre-formed crack. A further technical solution of the present invention is that the tooling body is integrally formed using additive manufacturing process, and satisfies at least one of the following process parameter combinations: (a) The printing lamination direction at the root of the elastic constraint arm is perpendicular to its fracture force direction, so that the lamination interface coincides with the expected fracture surface; (b) The local fill density at the root of the elastic constraint arm is less than the fill density of its main body, and the difference between the two is not less than 30%; (c) The root of the elastic constraint arm is provided with a V-shaped stress concentration groove, the depth of which is 30% to 60% of the thickness of the elastic arm, and the angle is 45° to 90°; (d) The thickness of the printed layer is 0.1mm to 0.3mm.

[0011] A further technical solution of the present invention is: the root of the elastic constraint arm, from the base end to the top end, comprises in sequence: In the transition chamfer area, the chamfer radius R is 20% to 50% of the thickness of the elastic arm or 12% to 45% of the thickness of the sensor housing; The main body region has a uniform cross-section and a height of 1 to 3 times the thickness T of the elastic arm. The pre-defined fracture zone has a height of 0.5 to 1 times T. The upper main arm area is configured to guide the sensor into the installation position during sensor installation and to transfer the operating force to the preset fracture zone during disassembly. The safe distance between the preset fracture zone and the transition chamfer zone shall not be less than 0.5 times T; Furthermore, the dimensions of the transition chamfer area, the equal cross-section main body area, and the preset fracture area are coordinated so that the exposed thickness of the sensor after the elastic constraint arm breaks is not less than 45% of the total thickness of the sensor.

[0012] A further technical solution of the present invention is: the mounting base is a curved surface customized according to the three-dimensional topographic data of the surface of the structure being measured, or an inclined base designed to maintain the sensor orientation on an inclined or curved surface; the tooling body is made of a material with a Young's modulus greater than 2 GPa. A sensor testing system includes a structure under test, a sensor, and a sensor intermediate fixing fixture.

[0013] A modal testing method, using the aforementioned sensor-intermediate fixing fixture, includes the following steps: Step 1: Based on the test requirements and the material and geometric characteristics of the structure under test, obtain the surface morphology at the test point through 3D scanning or 3D model, and select or customize the sensor intermediate fixing fixture that matches it. Step 2: Fix the mounting base of the sensor intermediate fixing fixture to the preset measuring point of the structure under test; Step 3: Press the sensor into the elastic clamping mechanism of the sensor intermediate fixing fixture until the installation indicator structure confirms that the sensor has been installed in place; Step 4: Perform modal excitation and signal acquisition; Step 5: After the test is completed, operate the release arm of the fixture to disassemble the sensor.

[0014] Beneficial effects The beneficial effects of this invention are as follows: This invention solves the problems of traditional adhesive fixing causing sensor contamination and damage, sensor damage during removal, difficulties in curved surface orientation installation, high-frequency distortion of test data, and inability to monitor latent failures during installation. It is particularly suitable for modal testing of lightweight composite material structures such as UAV propellers, wings, and helicopter blades. Specific effects are analyzed below: Reliable Sensor Fixation: The fixture is firmly bonded to the structure under test using adhesives or other methods, and the integrated lightweight structure reduces the impact of added mass. The sensor and fixture are connected via an interference fit, generating a continuous radial preload between the cavity wall and the sensor housing, achieving gapless surface contact. The connection stiffness is significantly higher than conventional elastic snap-fit ​​structures that rely on hook points for locking. Compared to directly using high-strength structural adhesive, this invention maintains a near-perfect test bandwidth (installation resonant frequency not lower than 2000Hz, fully meeting the modal testing requirements of aerospace structures such as UAVs) while completely avoiding the risk of adhesive contamination of the sensor. Compared to temporary bonding methods such as double-sided tape and beeswax, this invention provides higher connection stiffness and reliability. The flush indication design of the fixed constraint arm allows even minor sensor loosening to be detected visually or by touch, eliminating the hidden failure risk of "sensor present, signal lost." The designed installation positioning mechanism facilitates the maintenance and inspection of sensor installation quality, reducing differences in sensor installation quality at different measurement points and contributing to obtaining more accurate frequency response function data over a wider frequency band. The hammer test verified that the frequency response function of the tooling of the present invention is highly consistent with the frequency response function of the high-strength structural adhesive directly bonded in the range of 0~5000Hz, and the effectiveness of the connection stiffness is confirmed.

[0015] Non-destructive, convenient, and quick disassembly: Through mechanical means and tooling, it can be quickly disassembled and assembled, realizing "press-to-install and one-click release". There is no adhesive residue on the sensor and no need for cleaning. It avoids the risk of adhesive seeping into the sensor cable connector and damaging the sensor. It completely avoids adhesive contamination and damage, greatly improves testing efficiency, and protects the expensive miniature sensor.

[0016] Achieving sensor matching and installation on curved surfaces: The mounting base can be customized into any complex curved surface or a flexible and bendable base, solving the problems of reliable installation and directional installation on irregular curved surfaces such as UAV propellers, and reducing measurement errors caused by sensor installation position and orientation.

[0017] High integration: It can integrate functions such as wiring management, direction marking, and test point marking to improve the standardization of on-site testing operations.

[0018] Improved testing efficiency: The sensor can be repeatedly, quickly, and accurately installed and removed at the same location, greatly improving the efficiency of multi-point, repeatable testing. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a sensor intermediate fixing fixture in Embodiment 1 of the present invention (sensor installed state).

[0020] Figure 2 This is a schematic diagram of a sensor intermediate fixing fixture in Embodiment 1 of the present invention (sensor not installed).

[0021] Figure 3 This is a cross-sectional view of a sensor intermediate fixing fixture according to Embodiment 1 of the present invention, showing the sensor in the installed position.

[0022] Figure 4 This is an isometric view of Embodiment 2 of the present invention (with a flexible bottom surface).

[0023] Figure 5 This is a cross-sectional view of Embodiment 3 of the present invention (three-dimensional curved base / tilted angle installation).

[0024] Figure 6 This is a schematic diagram of the disassembly of Embodiment 4 of the present invention (reusable elastic constraint arm).

[0025] Figure 7 This is a schematic diagram of the fracture disassembly of Embodiment 5 (one-time fracture elastic constraint arm) of the present invention.

[0026] Figure 8 This is a schematic diagram showing the division of the four functional sections of the elastic constraint arm in an embodiment of the present invention.

[0027] Figure 9 This refers to the frequency response function of the tooling installation and traditional high-strength adhesive fixing test in the embodiments of the present invention.

[0028] Figure 10 This is a photograph of a sensor whose connector broke during disassembly using a traditional fixing method.

[0029] Explanation of reference numerals in the attached drawings: 1. Sensor; 2. Tooling body; 3. Base; 4. Sensor housing cavity; 5. Elastic constraint arm; 6. Fixed constraint arm; 7. Guide slope; 8. Flexible base; 9. Mounting surface; 10. Curved mounting surface; 11. Oriented mounting base; 12. Preset fracture zone. Detailed Implementation

[0030] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] Many existing technologies employ flexible arms to hold sensors or other devices (such as CN220625352U and CN111829091A). However, these general-purpose clamping structures are designed solely to "constrain the device to a fixed position," neglecting the specific functional requirement of accurately sensing external vibration signals. For the application of accelerometers in structural modal testing, the sensor's fixation must simultaneously meet the following stringent conditions: (1) Connection stiffness requirements - The sensor mounting resonant frequency must be significantly higher than the upper limit frequency of the test band (engineering experience requires 3 to 5 times or more), otherwise the fixture itself will become a "low-pass filter", causing signal attenuation and distortion within the test band. For modal testing of composite material structures such as UAV wings and blades, the modal frequencies of interest are usually below 200Hz. Therefore, a mounting resonant frequency of not less than 1000Hz is sufficient to meet basic engineering requirements. This invention can reach more than 5000Hz, providing sufficient stiffness reserve; (2) Directional accuracy requirement - The directional deviation of the sensor's sensitive axis must be less than ±1°, otherwise the modal reconstruction will produce serious errors; (3) Repeatability requirement: The same sensor must be installed and disassembled at different locations with consistent mechanical boundary conditions; otherwise, the frequency response functions of different measurement points will not be comparable. (4) Latent failure detection requirements—A tiny loosening of the sensor must be reliably identified before data acquisition; otherwise, false valid data will be generated, indicating that the signal exists but is distorted. The design goals, stiffness parameters, and failure detection mechanisms of existing general-purpose elastic clamping structures are fundamentally different from such strict constraints and cannot be directly transplanted and used.

[0033] To address the aforementioned problems, this invention proposes a sensor intermediate fixing fixture, comprising a fixture body, wherein the fixture body has: The base has a mounting surface at its bottom, the surface morphology of which matches the local three-dimensional morphology of the surface of the structure being measured, and is used to mount the tooling body onto the surface of the structure being measured. The elastic clamping mechanism is located on the base and is detachably connected to the sensor through an interference fit. The elastic clamping mechanism also has an installation position indication structure.

[0034] The present invention also proposes a sensor testing system, including the structure under test, the sensor, and the sensor intermediate fixing fixture.

[0035] This invention also proposes a modal testing method, which utilizes the aforementioned sensor-intermediate fixing fixture, and includes the following steps: Step 1: Based on the test requirements and the material and geometric characteristics of the structure under test, obtain the surface morphology at the test point through 3D scanning or 3D model, and select or customize the sensor intermediate fixing fixture that matches it. Step 2: Fix the mounting base of the sensor intermediate fixing fixture to the preset measuring point of the structure under test; Step 3: Press the sensor into the elastic clamping mechanism of the sensor intermediate fixing fixture until the installation indicator structure confirms that the sensor has been installed in place; Step 4: Perform modal excitation and signal acquisition; Step 5: After the test is completed, operate the release arm of the fixture to disassemble the sensor.

[0036] The above technical solution will be further analyzed below with reference to the accompanying drawings and examples: In one embodiment, refer to Figures 1-7 As shown, the core of a sensor intermediate fixing fixture is that it includes a fixture body 2, the fixture body 2 has a base 3 for fitting and fixing to the surface of the structure being measured, and an elastic clamping mechanism for detachably clamping and fixing the sensor; the base 3 and the clamping mechanism are rigidly integrated.

[0037] The bottom of the base 3 is a mounting base surface, and the surface morphology of the mounting base surface matches the local three-dimensional morphology of the surface of the structure being measured, so as to install the tooling body 2 on the surface of the structure being measured. The elastic clamping mechanism is located on the base 3 and includes a sensor receiving cavity 4 formed on the tooling body, at least one elastic constraint arm 5, and at least one fixed constraint arm 6. The shape of the sensor receiving cavity 4 matches the shape of the micro-sensor to be fixed, allowing the sensor to be smoothly and accurately placed into the receiving cavity. Its static dimension is slightly smaller than the external dimension of the corresponding part of the sensor to be fixed, so that after the sensor is pressed into place, a continuous radial preload is formed between the wall of the receiving cavity and the sensor housing, forming an interference fit. This interference fit mechanism differs from the conventional elastic snap-fit ​​structure that relies on hook locking: the interference fit provides continuous surface contact rather than point contact, eliminating the microscopic gap between the sensor and the tooling, thereby obtaining higher connection stiffness and signal transmission fidelity; at the same time, the preload is maintained by the elastic deformation of the elastic constraint arm, not relying on the geometric locking of the hook and groove, so even under external force impact, there will be no sudden failure of "snap disengagement".

[0038] The upper ends of the sensor housing cavity 4, elastic constraint arm 5, and fixed constraint arm 6 are perpendicular to the bottom surface of the housing cavity or have rounded or chamfered surfaces, which guide, direct, and assist the sensor to be smoothly pressed into the housing cavity; and the normal direction of the bottom surface of the housing cavity forms a preset angle with the normal direction of the fixed surface of the mounting base.

[0039] The elastic constraint arms 5 are arranged in pairs symmetrically with respect to the sensor, and the elastic deformation restoring force is directed to the side of the fixed constraint arm to ensure effective clamping and fixing of the sensor. One end of the elastic constraint arm 5 is connected to the base, and the other end is located inside the cavity, with its wall surface perpendicular to the bottom surface of the cavity. The elastic clamping arm 5 is an asymmetric elastic structure with directional compliance characteristics. It provides a stable clamping force in the radial direction and allows small elastic displacement in the tangential direction, thereby ensuring the reliability of sensor fixation while reducing the high-frequency coupling of the vibration of the measured structure to the sensor.

[0040] The height of the fixed constraint arm 6 ensures that the height of the cavity inside the accommodating chamber matches the height of the sensor, or the height difference between the sensor's markings, specific surfaces, and its bottom surface. This ensures that when the sensor is pressed into place, the aforementioned markings and surfaces are flush with the top of the fixed constraint arm, indicating that the sensor has been pressed into place. In structural modal testing, if the sensor experiences even slight loosening, its output signal may still exist but will be severely distorted. With traditional fixing methods, this failure is difficult to detect visually or during pre-test inspection, constituting a "latent failure" and a major reason for invalidating test data. The targeted design of the fixed constraint arm and elastic constraint arm establishes a clear and reliable "installation state benchmark," clearly indicating and monitoring whether the sensor installation is loose, offset, or detached during subsequent testing and use.

[0041] The geometric dimensions of the accommodating cavity and the stiffness of the elastic arm are designed so that when the sensor is pressed into the accommodating cavity and installed in place, the sensor surface is flush with the cavity wall, indicating that the sensor is installed and fixed in place. The elastic constraint arm resets after elastic deformation, clamping the sensor to achieve self-locking fixation.

[0042] The elastic constraint arm 6 is connected to a release arm, which is used to move the elastic arm away from the accommodating cavity to release the locking of the sensor. In order to realize the detachable fixation of the sensor, the release arm adopts at least one of the following two release modes: Mode 1 (elastic recovery type) is suitable for routine tests that require multiple assembly and disassembly, and Mode 2 (one-time break type) is suitable for single batch tests or test scenarios with extremely high requirements for sensor connection quality.

[0043] Mode 1 (Elastic Recovery): Operating the release arm causes the elastic constraint arm to elastically deform, thereby releasing the sensor; after the operating force is removed, the elastic constraint arm returns to its original state, allowing the sensor to be re-locked.

[0044] Mode 2 (One-time fracture): Operating the release arm can cause the elastic constraint arm to break from its preset position, thereby permanently releasing the lock on the sensor; the root of the elastic constraint arm is provided with a preset fracture zone (selected from at least one of V-groove, root thinning zone, and pre-made crack) to guide the fracture to occur at the predetermined position.

[0045] The above design allows the sensor to be released from its clamping and removed.

[0046] In one embodiment, the release arm is located at the top of the elastic arm and protrudes from the fixed arm and the sensor surface via a prying boss, making it easy to bend and deform the elastic arm with fingers to release the sensor.

[0047] In one embodiment, the base has a thin plate-like bottom surface or a grid-like structure at its bottom to enhance the fit with low-curvature surfaces and increase the bonding contact area.

[0048] In one embodiment, the mounting base is a curved surface customized based on the three-dimensional topographic data of the surface of the structure under test to maximize the contact area and connection strength. In addition to the reference horizontal base, there is also an inclined base with an inclination angle to ensure that the sensor orientation is in the direction required by the test design when installing on curved or inclined surfaces.

[0049] The mounting base surface is customized through the following steps: (1) Obtain the curvature parameters or contour features of the local surface of the object under test through digital modeling or measurement; (2) Based on the curvature parameters and the test sensitive direction vector of interest in the experiment, automatically generate the mounting base surface that matches the surface under test; (3) A transition connection area is provided between the mounting base and the elastic clamping arm to achieve smooth load transfer.

[0050] By using the above-mentioned base surface generation method, the clamping device can be stably and effectively fixed on the surface of different objects being tested, and the sensor measurement direction required for testing can be achieved.

[0051] In one embodiment, the tooling body is made using 3D printing additive manufacturing process to achieve low-cost and customized matching of the sensor mounting surface. By designing a chamfer at the root of the support arm (the chamfer radius is 12% to 45% of the sensor thickness), stress concentration at the root is eliminated while enhancing local bending stiffness, ensuring that sufficient clamping load can be provided when the sensor is installed in place, and avoiding unexpected breakage. For Mode 2 (one-time fracture), the present invention further utilizes the adjustable process characteristics of 3D printed components to achieve quantitative prediction and control of fracture load by controlling the combination of the following parameters: Printing direction: Set the printing lamination direction at the root of the elastic constraint arm to be perpendicular to its fracture force direction, so that the lamination interface coincides with the expected fracture surface; Layer thickness: Select the layer thickness parameter according to the target fracture force (preferably 0.1 to 0.3 mm); Filling density: A localized low filling density (30%–50%) is used in the predetermined fracture zone at the root to differentiate it from the main area (>80%); Preset fracture zone geometry parameters: Set V-groove (depth of 30% to 60% of the elastic arm thickness, angle of 45° to 60°), root thinning zone or pre-made crack. Considering the process characteristics of 3D printing, the pre-made fracture location does not need a macroscopically visible V-groove. It is only necessary to set 1-3 layers of cross-sectional contour inward at the expected fracture location to configure a local low-strength layer, so as to achieve the effect of stress concentration and pre-made fracture location.

[0052] Through the coordinated design and process described above, the tooling can be made to have the functions of stable and effective fixation of the accelerometer and easy disassembly without damage as needed. The fracture load of the one-time fracture mode can be controlled within the range of 5 to 20 N, and the coefficient of variation between batches is ≤15%.

[0053] In one embodiment, the accommodating cavity fixing arm and elastic arm are provided with through slots, dividing them into multiple sections, so that their structure can be slightly deformed. This allows the sensor to be placed and clamped in place, while also serving as a channel to assist in ejecting and removing the sensor.

[0054] In one embodiment, the tooling is provided with markings prepared by printing, embossing, pressing, or other methods on the upper surface of the base, the outer wall of the accommodating cavity, etc., to mark and indicate the position of the center measuring point of the sensor when the sensor is installed in the accommodating cavity, so as to facilitate the high-precision positioning and installation of the sensor and the positioning of the sensor installation measuring point.

[0055] In one embodiment, the tooling is marked with labels on the outer wall of the accommodating cavity or other locations to distinguish the sensor and measuring point numbers, or the surface is roughened to allow it to absorb ink, watercolor, or ink stains, so that users can mark the measuring point numbers and sensor numbers with a marker pen during the test.

[0056] In one embodiment, the tooling body is made of rigid engineering plastic or resin to ensure installation rigidity, improve the weather resistance of sensor installation and fixation, expand the available test environment conditions, and improve test frequency response.

[0057] Implementation Case: Example 1 (Basic Reusable Tooling) like Figures 1 to 3As shown, this embodiment provides a sensor intermediate fixing fixture 2 with a basic structure. This fixture is preferably integrally formed using a 3D printing process. The fixture body includes a base 3, with a sensor accommodating cavity 4 at its center for accommodating a miniature accelerometer 1.

[0058] Two cantilever beam-type elastic constraint arms 5 extend symmetrically from the sidewalls of the accommodating cavity 4. Each elastic constraint arm 5 is positioned on the outer side of the base 3. Furthermore, the accommodating cavity 4 also includes at least one fixed constraint arm 6, positioned alternately with or opposite to the elastic constraint arms 5. Its height is designed so that when the sensor 1 is installed in place, a specific profile or mark on the sensor housing is flush with the top of the fixed constraint arm, providing the user with a visual indication of proper installation.

[0059] During installation, sensor 1 is vertically pressed into the receiving cavity 4 via the guide ramp 8. The housing of sensor 1 contacts and presses against the guide ramp, forcing the two elastic constraint arms 5 to elastically deform outward and open. When sensor 1 is fully in place, the elastic constraint arms 5 return to their original position under their own elastic restoring force, achieving reliable locking (e.g., Figure 3 (As shown). During disassembly, the user only needs to pinch the tops of the two elastic constraint arms simultaneously with their thumb and forefinger to force the elastic constraint arms 5 to open outward again, releasing the locking effect of the interference fit, thereby allowing the sensor 1 to be removed without damage. During this process, the elastic constraint arms 5 remain within their elastic deformation range and can completely return to their original shape after the pressure is removed, making both the fixture and the sensor reusable. This method is suitable for routine testing situations that require multiple assembly and disassembly.

[0060] Example 2 (Surface Adaptive Variant) like Figure 4 As shown, based on Embodiment 1, this embodiment optimizes the base 3 to expand the tooling's adaptability to complex curved surfaces. A flexible base 9 with elasticity is printed on this base. When the tooling is bonded to a slightly curved surface, this flexible base can undergo micro-elastic deformation to better conform to the surface, while simultaneously increasing the adhesive's contact area and mechanical interlocking effect, significantly enhancing connection reliability and preventing the tooling from detaching or loosening during testing.

[0061] Example 3 (Customized Curved Surface and Oriented Mounting Fixture) like Figure 5As shown, this embodiment demonstrates the application of the present invention in solving the problem of oriented installation on complex curved surfaces. The mounting base 3 of the intermediate fixing fixture 2 is a precisely customized curved surface based on the three-dimensional topographic data of specific measuring points on the surface of the UAV composite blade 11 to ensure maximum contact. During installation, a thin layer of epoxy adhesive or cyanoacrylate adhesive is used to fix the mounting base 3 to the blade 11. An inclined boss is provided on the bottom normal of the sensor housing cavity and the bottom surface of the fixture. This design ensures that even on curved or inclined surfaces, the sensor can be precisely fixed in a preset spatial orientation.

[0062] Example 4 (Disposable Fracture Release Fixture) This embodiment is designed for extreme testing scenarios where absolute disassembly reliability or single-use is required. Its tooling structure is similar to that of Embodiment 1, but its release mechanism is designed as a "one-time breakage" mode.

[0063] In this embodiment, the elastic constraint arm 5 performs two functions simultaneously: first, it provides sufficient clamping force to secure the sensor when it is installed (achieved by the chamfered area at the root); second, it can break cleanly at a predetermined position under external force when disassembly is required (achieved by the preset fracture zone). These two functions place opposite demands on the mechanical properties of the elastic constraint arm: the clamping function requires sufficient strength and toughness at the root to prevent accidental breakage during normal use; the release function requires easy breakage under controlled conditions. To resolve this contradiction, the present invention employs a specific dimensional coordination design for the chamfered area and the preset fracture zone.

[0064] (1) Design of the chamfered area (to ensure tight clamping) A transition chamfer (the chamfer radius R is 12%–45% of the sensor housing thickness, or 20%–50% of the elastic arm thickness) is provided at the root of the connection between the elastic constraint arm 5 and the base 3. The purpose of this chamfer is to eliminate stress concentration caused by geometric abrupt changes when the sensor 1 is pressed into the receiving cavity 4, ensuring a uniform distribution of bending stress along the root and preventing unexpected breakage under normal clamping conditions. Simultaneously, the size of the chamfer area must match the external dimensions of the sensor 1—the thicker and heavier the sensor, the larger the chamfer radius should be to reduce the peak stress at the root.

[0065] (2) Design of the pre-set fracture zone (to ensure a clean fracture) A pre-set fracture zone 14 is set at a predetermined fracture location away from the opening end of the chamfered area (i.e., outside the chamfered influence zone), selected from a typical V-groove (depth...). The angle is 30% to 60% of the thickness T of the elastic arm. (45°~90°), localized thinning zone (thinning thickness) The fracture zone can be 30%–60% of the thickness of the T, with localized layered necking (reducing the cross-sectional area of ​​1–3 3D printed layers to 65%–85% of the cross-sectional area of ​​the elastic arm body) or pre-initiated cracks. The location of this pre-initiated fracture zone must maintain a safe distance from the chamfered area (usually more than 0.5 times the thickness of the elastic arm body) to ensure that the stress improvement effect of the chamfered area does not interfere with the determination of the fracture location.

[0066] (3) Specific implementation of coordinated design The preset fracture location and chamfer size must be coordinated to ensure that after the elastic constraint arm breaks, the exposed thickness of the sensor is not less than 45% of its total thickness, so as to ensure that the clamping force of the tooling on the sensor is significantly reduced after the constraint arm breaks, making it easy to remove the sensor without damage.

[0067] The root of the elastic restraint arm is divided into four functional sections starting from base 3. Figure 8 ): The first section (transition chamfer area): height L1 ≈ (1~2)R, its function is to smooth the transition, eliminate stress concentration, and ensure that it will not break under normal clamping conditions; The second section (the main section with constant cross-section): height L2 ≈ (1~3)T, its function is to provide a stable elastic deformation zone; The third section (preset fracture zone): height L3 ≈ (0.5~1)T, with a V-groove or thinning structure, is the predetermined fracture location. The fourth section (upper main arm section): Its function is to wrap the sensor to indicate the installation position, guide the sensor to be installed in place during installation, and transmit force to cause the preset fracture zone to break during disassembly.

[0068] Through the above four-section design, when the elastic constraint arm 5 is normally clamping the sensor, the maximum bending stress occurs at the end of the chamfered area (but is below the material fatigue limit); when the user applies disassembly force, the local stress at the preset fracture zone 14 quickly exceeds the fracture threshold, achieving a clean and crisp fracture with a flat fracture surface and no debris.

[0069] (4) Collaborative design of additive manufacturing processes When using fused deposition modeling (FDM) technology, the fracture force can be quantitatively controlled further through the following parameters: Printing direction: Set the printing lamination direction at the root of the elastic constraint arm to be perpendicular to the fracture force direction, so that the lamination interface coincides with the expected fracture surface; Layer thickness: 0.1–0.3 mm is recommended, and should be selected according to the target fracture force and coordinated with the wall thickness; Fill density: Use a low fill density of 30% to 50% in the preset fracture area, and a high fill density of >80% in the main body and chamfer area.

[0070] Through the above coordinated design, this embodiment achieves the dual objectives of "fastening and clamping during normal use and breaking cleanly during disassembly", with the fracture load controllable within the range of 5 to 20 N and the batch-to-batch variation coefficient ≤ 15%.

[0071] Explanation of preferred manufacturing methods: The intermediate fixing fixture described in this invention can be manufactured using various processes such as machining, injection molding, or additive manufacturing. Through in-depth research, the inventors have confirmed that using additive manufacturing (3D printing) for one-piece molding can achieve the following significant advantages:

[0072] 1. Achieve extreme low cost and agile customization: For the complex curved surface in Example 3, additive manufacturing can directly form it based on the digital model without the need for expensive molds, perfectly meeting the small-batch, multi-variety customization needs in R&D and testing.

[0073] 2. Empowering innovative functional design: As shown in Example 5, the unique process characteristics of additive manufacturing (such as anisotropy) can be actively utilized to achieve new functions that are difficult to achieve in traditional homogeneous material processing processes, such as "controllable low-force fracture".

[0074] 3. Optimized Lightweight Design and Functional Integration: To achieve lightweight design, the tooling can be internally designed with a lattice structure; simultaneously, functional details such as cable trays and identifiers can be integrated and printed in a single step. Additive manufacturing has irreplaceable advantages in achieving integrated molding of such complex structures.

[0075] Experimental verification: To verify the connection stiffness of the tooling of this invention, the installation resonant frequency of the sensor-tooling system was tested using a force hammer excitation method. The test configuration is as follows:

[0076] Test object: The intermediate fixing fixture was fixed on a 10kg anvil, and the sensor (0.8g, sensitivity 100mV / g) was pressed into place. As a comparison, the same sensor was directly glued to the same position on the anvil using cyanoacrylate adhesive.

[0077] Excitation and Data Acquisition: Using a force hammer equipped with a steel hammerhead (force sensor sensitivity 4pC / N, external impedance transformer 1mV / pC, data acquisition terminal sensitivity set to 4mV / N), gently tap the top of the sensor housing and the anvil near the sensor along the sensor's sensitive axis. Simultaneously acquire force and acceleration response signals at a sampling rate of 128kHz, and perform 6 linear averages.

[0078] Data processing: Calculate the frequency response function (FRF) for each excitation and extract the coherence function. Figure 9 The FRF amplitude curves (0~5000Hz) are shown for two installation methods.

[0079] Results analysis: Figure 9 The frequency response function amplitude curves (0~5000Hz) for two installation methods are shown. It is evident that the FRF curves of the tooling installation and direct adhesive installation of this invention highly overlap across the entire frequency band, with the main peak frequencies being consistent (deviation <1%). Comparative analysis of additional test results under conditions such as changing the anvil boundary conditions and the sensor's added mass reveals that the peak frequency of 3.5kHz is the modal peak of the anvil body, not the resonance peak at the sensor-tooling connection interface. Throughout the entire test frequency band, no additional resonance peaks attributable to the sensor-tooling connection interface were observed under the tooling installation state. The measured connection resonance frequency of the tooling of this invention is higher than 5kHz, fully meeting the requirements of UAV-related fields (not lower than 2000Hz).

[0080] In summary, the tooling of this invention can provide connection stiffness comparable to high-strength adhesives, thereby ensuring the fidelity of the frequency response function in modal testing; at the same time, it enables non-destructive and rapid assembly and disassembly of sensors, avoiding adhesive contamination and disassembly damage.

[0081] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A detachable intermediate fixing fixture for a sensor, characterized in that, Includes a tooling body, the tooling body having: The base has a mounting surface at its bottom, the surface morphology of which matches the local three-dimensional morphology of the surface of the structure being measured, and is used to mount the tooling body onto the surface of the structure being measured. The elastic clamping mechanism is located on the base and is detachably connected to the sensor through an interference fit. The elastic clamping mechanism also has an installation positioning indication structure.

2. The detachable intermediate fixing fixture for a sensor according to claim 1, characterized in that: The elastic clamping mechanism includes a sensor receiving cavity formed on the tooling body, at least one elastic constraint arm, and at least one fixed constraint arm; the static dimension of the sensor receiving cavity is slightly smaller than the external dimension of the corresponding part of the sensor to be fixed, so that after the sensor is pressed into place, a continuous radial preload is formed between the wall of the receiving cavity and the sensor housing, forming an interference fit.

3. The detachable intermediate fixing fixture for a sensor according to claim 2, characterized in that: The height of the fixed constraint arm satisfies the following condition: when the sensor is installed in the sensor housing, a specific profile or mark on the sensor housing is flush with the top of the fixed constraint arm to provide a visual and / or tactile indication of installation in place.

4. The detachable intermediate fixing fixture for a sensor according to claim 2, characterized in that: The elastic constraint arm is connected to a release arm. When the release arm is operated, it drives the elastic constraint arm to undergo elastic deformation to release the interference fit and achieve non-destructive disassembly of the sensor. After the operating force is removed, the elastic constraint arm returns to its original state, allowing the sensor to be reinstalled and locked.

5. The detachable intermediate fixing fixture for a sensor according to claim 2, characterized in that: The elastic constraint arm is connected to a release arm. When the release arm is operated, the elastic constraint arm breaks from a preset fracture zone at its root, thereby permanently releasing the lock on the sensor. The preset fracture zone is selected from at least one of a V-groove, a root thinning zone, and a pre-formed crack.

6. The detachable intermediate fixing fixture for a sensor according to claim 2, characterized in that: The tooling body is integrally formed using additive manufacturing technology and meets at least one of the following process parameter combinations: (a) The printing lamination direction at the root of the elastic constraint arm is perpendicular to its fracture force direction, so that the lamination interface coincides with the expected fracture surface; (b) The local fill density at the root of the elastic constraint arm is less than the fill density of its main body, and the difference between the two is not less than 30%; (c) The root of the elastic constraint arm is provided with a V-shaped stress concentration groove, the depth of which is 30% to 60% of the thickness of the elastic arm, and the angle is 45° to 90°; (d) The thickness of the printed layer is 0.1mm to 0.3mm.

7. The detachable intermediate fixing fixture for a sensor according to claim 2, characterized in that: The root of the elastic constraint arm, from the base end to the top end, includes the following components in sequence: In the transition chamfer area, the chamfer radius R is 20% to 50% of the thickness of the elastic arm or 12% to 45% of the thickness of the sensor housing; The main body region has a uniform cross-section and a height of 1 to 3 times the thickness T of the elastic arm. The pre-defined fracture zone has a height of 0.5 to 1 times T. The upper main arm area is configured to guide the sensor into the installation position during sensor installation and to transfer the operating force to the preset fracture zone during disassembly. The safe distance between the preset fracture zone and the transition chamfer zone shall not be less than 0.5 times T; Furthermore, the dimensions of the transition chamfer area, the equal cross-section main body area, and the preset fracture area are coordinated so that the exposed thickness of the sensor after the elastic constraint arm breaks is not less than 45% of the total thickness of the sensor.

8. The detachable intermediate fixing fixture for a sensor according to claim 1, characterized in that: The mounting base is a curved surface customized based on the three-dimensional topographic data of the surface of the structure being measured, or an inclined base designed to maintain the sensor orientation on a slope or curved surface; the tooling body is made of a material with a Young's modulus greater than 2 GPa.

9. A sensor testing system, characterized in that, Includes the structure under test, the sensor, and the sensor intermediate fixing fixture as described in any one of claims 1-8.

10. A modal testing method, characterized in that, The sensor intermediate fixing fixture according to any one of claims 1-8 includes the following steps: Step 1: Based on the test requirements and the material and geometric characteristics of the structure under test, obtain the surface morphology at the test point through 3D scanning or 3D model, and select or customize the sensor intermediate fixing fixture that matches it. Step 2: Fix the mounting base of the sensor intermediate fixing fixture to the preset measuring point of the structure under test; Step 3: Press the sensor into the elastic clamping mechanism of the sensor intermediate fixing fixture until the installation indicator structure confirms that the sensor has been installed in place; Step 4: Perform modal excitation and signal acquisition; Step 5: After the test is completed, operate the release arm of the fixture to disassemble the sensor.

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