Flexible pressure sensor array for measuring airspeed of unmanned aerial vehicle and preparation method of flexible pressure sensor array

Abstract

The invention provides a flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle and a preparation method of the flexible pressure sensor array. The sensor array comprises a net-shaped structure and a plurality of flexible pressure sensors arranged at nodes of the net-shaped structure. The sensor is of a sandwich structure, a sensitive layer is arranged in the middle, a flexible substrate layer and an electrode layer are symmetrically arranged up and down, the sensitive layer is composite conductive foam with a conductive elastomer filling framework, and the composite conductive foam is obtained by dipping foam in a conductive material solution for multiple times. The sensitive layer framework is obtained by forming through holes in composite conductive foam in a laser array mode and filling conductive elastomers with the through holes. According to the sensor array, heterogeneous network porous foam with good conductivity and multi-layer pressure response characteristics is used as a sensitive layer, and the sensor array has a wide pressure response range; the conductive elastomer framework improves the problem that the foam structure is easy to collapse due to compression deformation, and the service life is prolonged; by utilizing the internet design, the Young modulus of the whole structure is reduced, and the device can be closely attached to the curved surface of the leading edge of the wing in a conformal manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensors, and in particular relates to a flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle and a method for preparing the flexible pressure sensor array. Background Art

[0002] The pitot tube is a mature instrument used for measurement in aerospace technology. It can directly and accurately measure air flow rate without complex conversion or multiple probes. However, the traditional pitot tube is affected by the surrounding environment and air quality, the geometric shape deviation of the pitot tube itself, etc., and the measurement is prone to errors. At the same time, it needs to be placed in a specific position where real-time pressure monitoring is required, which is not suitable for all aircraft structures. In addition, the pitot tube itself has a certain weight, and some aircraft require 2 to 4 sets of pitot tube speed measurement systems, which increases the overall weight and complexity. Since the lift of the fixed-wing UAV wing requires airspeed to generate a pressure difference, the flight control and status also need to be adjusted in time according to the airspeed, so higher requirements are placed on the high-precision and lightweight airspeed measurement system.

[0003] As a new type of electronic device, flexible pressure sensor can convert the external pressure into physical quantities (resistance, voltage, capacitance, etc.) that are easy to detect. It also has good flexibility and is widely used in many fields such as human-computer interaction and medical health. By attaching the flexible pressure sensor array to the surface of the UAV wing, the wind pressure on the wing during flight can be detected. The relationship between airspeed and wind pressure on the wing surface can be analyzed using a neural network model, and the airspeed measurement of the UAV can be realized by replacing the traditional pitot tube. This new airspeed measurement method can not only reduce the overall weight of the UAV, but also reduce the structural complexity of the UAV. Therefore, it is of great significance to develop a flexible pressure sensor array for UAV airspeed measurement to replace the pitot tube to complete the UAV airspeed measurement.

[0004] After searching the prior art, it was found that Yanan Ma, Nishuang Liu, et al. from Huazhong University of Science and Technology wrote an article titled "A highly flexible and sensitive piezoresistive sensor based on MXene with greatly changed interlayer distances" in Nature Communications, 2017, 8(1): 1207. The prepared sensor exhibited high sensitivity (strain factor ~180.1) and fast response (<30ms). However, this method directly drops the MXene solution in the middle of the interdigital electrodes and dries it to form a single-layer MXene piezoresistive layer. The lack of microstructure design makes the overall compressibility of the sensor low, and there is a problem of a small pressure detection range.

[0005] Dan Yang, Hengyu Guo et al. wrote an article titled "A flexible and wide pressure range triboelectric sensor array for real-time pressure detection and distribution mapping" in Journal of Materials Chemistry A, 2020, 8(45): 23827-23833, which prepared a flexible pressure sensor array for detecting the size and distribution of pressure. However, the arraying of sensors on a whole flexible polyimide film makes the Young's modulus of the overall structure too high, resulting in insufficient overall flexibility of the sensor array, which can only be used for pressure detection on flat or simple curved surfaces, and it is difficult to achieve conformal attachment to complex curved surfaces.

[0006] Li, X., Li, S. et al. wrote an article titled "Multifunctional polyether block amides / carbon nanostructures piezoresistive foams with largely linear range, enhanced and humidity-regulated microwave shielding" in Chemical Engineering Journal, 2023, 455: 140860. The conductive polymer foam of polyether block amide (PEBA) and carbon nanotubes was used as a pressure sensor. However, the Young's modulus of PEBA is low. When the pressure is high, the sensitive layer reaches the upper compressible limit and the impedance no longer changes, making it difficult to achieve wide-range pressure detection. At the same time, in the face of the demand for drone airspeed measurement that requires the sensor to be under pressure for a long time, the foam structure has the problem of structural collapse during compression deformation.

[0007] Therefore, in response to the needs of UAV airspeed measurement, especially fixed-wing UAV airspeed measurement, existing flexible pressure sensors have problems such as small pressure detection range, easy collapse of foam structure, and poor conformal adhesion due to insufficient array softness. Summary of the invention

[0008] In view of the defects and gaps in the prior art, the present invention provides a highly soft and wide-range flexible pressure sensor array for UAV airspeed measurement and a method for preparing the flexible pressure sensor array, which can effectively improve the pressure detection range, service life, softness and conformal attachment ability of the sensor array, and at the same time, meet the airspeed measurement needs of fixed-wing UAVs and provide a feasible solution for overall structural optimization and lightweight design.

[0009] To achieve the above purpose, the technical solution provided by the present invention is:

[0010] On the one hand, a flexible pressure sensor array for measuring the airspeed of a drone is provided, comprising a mesh structure and a plurality of flexible pressure sensors arranged at a plurality of nodes of the mesh structure in a one-to-one correspondence;

[0011] The mesh structure is used to be attached to the leading edge of the drone wing and is made of a material that can be processed into a soft waterproof insulating film. A hollow portion is provided at the node of the mesh structure, and the flexible pressure sensor is located in the hollow portion, with the film of the mesh structure serving as a packaging layer.

[0012] Each flexible pressure sensor adopts a sandwich structure, with a sensitive layer in the middle and symmetrical flexible substrate layers and electrode layers on the top and bottom. The electrode layer is bonded and electrically connected to the sensitive layer. The sensitive layer is a composite conductive foam with a conductive elastomer-filled skeleton. The composite conductive foam of the sensitive layer is obtained by repeatedly dipping the foam in a conductive material solution, and the skeleton of the sensitive layer is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with conductive elastomer.

[0013] Furthermore, the foam of the sensitive layer adopts one or more of polyurethane, melamine, polystyrene and polypropylene; the conductive material of the sensitive layer adopts one or more of MXene, AgNW, CNT, rGO and conductive polymer; the conductive elastomer of the sensitive layer adopts one or more of PDMS / CNT, TPU / AgNWs and SEBS / CNT.

[0014] Further, the encapsulation layer is made of one or more of PET, PDMS and PI.

[0015] Furthermore, the flexible substrate layer is a flexible PI film, and the electrode layer is made of metallic silver deposited by magnetron sputtering.

[0016] Furthermore, the mesh structure is an interconnected diamond mesh structure and includes nine nodes.

[0017] Furthermore, the hollow parts in the nodes of the mesh structure and the flexible pressure sensors therein are circular, and the parts connecting the nodes are long strips.

[0018] Furthermore, the thickness of the packaging layer is 100-200 μm, the thickness of the flexible substrate layer is 50-300 μm, the thickness of the electrode layer is 10-500 μm, the thickness of the sensitive layer is 0.1-2.0 mm, and a single pressure sensor is circular with a diameter of 1-5 cm.

[0019] On the other hand, a method for preparing the above-mentioned flexible pressure sensor array for measuring airspeed of an unmanned aerial vehicle is provided, comprising the following steps:

[0020] Step 1, cleaning and treating the film as the flexible base layer, and magnetron sputtering a layer of metal as an electrode layer on the surface of the film;

[0021] Step 2, preparing a plurality of composite conductive foams with conductive elastomer-filled skeletons as sensitive layers, comprising the following sub-steps:

[0022] Step 2.1, after the high-porosity open-cell foam is modified by low-pressure oxygen plasma, the high-porosity open-cell foam is subjected to a soaking-drying cycle in a conductive material solution and repeated multiple times to obtain a composite conductive foam;

[0023] Step 2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, injecting the solution into the etched through holes, and curing with ultraviolet light to complete the preparation of the sensitive layer;

[0024] Step 3, sandwiching each sensitive layer between two flexible substrate layers and electrode layers connected with wires, and electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged;

[0025] Step 4, preparing a packaging mold with a mesh structure, the mold as a whole is a mesh structure, including node casting grooves and connecting casting grooves that connect the node casting grooves to each other;

[0026] Step 5, prepare a solution for forming a packaging layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be packaged into different node casting grooves in the mold respectively, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped. After curing, a flexible pressure sensor array is obtained.

[0027] Furthermore, the composite conductive foam obtained in step 2.1 is a PU-MXene composite conductive foam; step 2.2 includes: using a CO2 laser to etch arrayed through holes on the PU-MXene composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a PDMS / CNT mixed solution, adding gas-phase silica to enhance thixotropy, and then adding a photoinitiator 2-hydroxy-2-methylpropiophenone to prepare a thixotropic-photocurable PDMS / CNT slurry, injecting the mixed slurry into the through holes using a syringe, and rapidly curing it using ultraviolet light to obtain a MXene-PDMS / CNT heterogeneous network porous foam as a sensitive layer.

[0028] Furthermore, in step 1, a PI film is used as a flexible substrate layer, and a layer of metallic silver is magnetron sputtered on the surface of the PI film to complete the preparation of the PI-Ag electrode; step 3 includes: using silver paste to connect the silver wire to the Ag side of the PI-Ag electrode, and then sandwiching the prepared MXene-PDMS / CNT heterogeneous network porous foam between two layers of PI-Ag electrode layers connected with the wires, and bonding them with silver paste.

[0029] The advantages of the present invention are:

[0030] 1. The flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle proposed by the present invention comprises a mesh structure and a plurality of flexible pressure sensors contained in a hollow part at a plurality of nodes of the mesh structure. The flexible pressure sensor is in a sandwich structure, with a symmetrical flexible substrate layer and an electrode layer on the top and the bottom, and a composite conductive foam with a conductive elastomer filling skeleton in the middle. Therefore, when the flexible pressure sensor array of the present invention is attached to the leading edge of the wing to record the pressure at multiple angles and directions in the three-dimensional space of the wing surface, when the pressure is low, the contact resistance change of the porous composite conductive foam dominates the response, the contact area increases, the conductive path increases, and the conductivity is improved. At the same time, the layer spacing of the multi-layer conductive material attached to the foam will decrease when it is compressed, further improving the conductivity of the composite material; when the pressure is high, the tunnel effect of the conductive elastomer skeleton filled in the foam dominates the response, the spacing of the conductive filler decreases, and the electrons tunnel through the insulating elastomer matrix barrier to form a tunneling current, thereby realizing the conversion of a large range of pressure changes that are difficult to measure into changes in physical quantity impedance that are easy to detect. Therefore, the conductive elastomer acts as the "skeleton" of the sensitive layer, and the porous composite conductive foam acts as the "nerves" of the sensitive layer, forming a synergistic conductive network, realizing multi-level pressure response, and expanding the pressure detection range; at the same time, the array-filled conductive elastomer skeleton improves the problem of easy collapse of the foam structure under compressive deformation, thereby extending the service life of the sensor array.

[0031] 2. The sensor array designed in the present invention has a mesh structure. Compared with the traditional sensor array prepared on a whole flexible substrate, the design of the Internet is used to greatly reduce the Young's modulus of the overall structure of the sensor array, and improve the conformal adhesion ability to the curved surface of the leading edge of the drone wing, effectively solving the problem of poor conformal adhesion ability of the existing array sensor due to insufficient softness of the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or other features and advantages of the present invention will become more easily understood through the following description with reference to the accompanying drawings, which are not drawn to scale and some features are exaggerated or reduced to show details of specific components. In the accompanying drawings:

[0033] Figure 1 It is an overall structural diagram of the flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle and a schematic diagram of the sensor microstructure of the present invention;

[0034] Figure 2 It is a schematic diagram of the preparation process of the flexible pressure sensor in the present invention;

[0035] Figure 3 It is a schematic diagram of the preparation process of the heterogeneous network porous foam of the flexible pressure sensor in the present invention;

[0036] Figure 4It is a schematic diagram of the structural change of the heterogeneous network porous foam of the flexible pressure sensor of the present invention when it is under pressure;

[0037] Figure 5 It is a schematic diagram of the change of the layer spacing when the multi-layer conductive material of the flexible pressure sensor of the present invention is under pressure;

[0038] Figure 6 It is a schematic diagram of the flexible pressure sensor array of the present invention attached to the leading edge of the wing of a fixed-wing UAV.

[0039] In the figure: 1-network structure; 2-flexible pressure sensor; 3-flexible substrate layer; 4-electrode layer; 5-sensitive layer, 51-polyurethane (PU) foam, 52-PU-MXene composite conductive foam, 53-MXene-PDMS / CNT heterogeneous network porous foam; 100-flexible pressure sensor array; 200-fixed-wing UAV, 201-wing leading edge. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings by means of exemplary embodiments of the present invention. It should be noted that the following detailed description of the present invention is only for the purpose of illustration, and is not intended to limit the present invention.

[0041] The present invention provides a flexible pressure sensor array for measuring the airspeed of an unmanned aerial vehicle and a method for preparing the flexible pressure sensor array. The flexible pressure sensor array is used to be attached to the leading edge surface of a wing of an unmanned aerial vehicle to record the pressure on the wing surface at multiple angles and directions in a three-dimensional space, and a neural network model is used to analyze and predict the relationship between the pressure value and the airspeed, thereby replacing a traditional pitot tube to complete the airspeed measurement during flight.

[0042] Reference Figure 1 The flexible pressure sensor array for measuring the airspeed of a drone provided by the present invention has a mesh structure, and includes a mesh structure and a plurality of flexible pressure sensors 2 arranged at a plurality of nodes of the mesh structure 1 in a one-to-one correspondence. The mesh structure 1 is used to be attached to the leading edge of the drone wing, and the flexible pressure sensor 2 is used to record the pressure on the wing surface.

[0043] In the embodiment shown in the present invention, the mesh structure 1 is an interconnected diamond mesh structure and includes five rows of nine nodes, specifically, one node is set at each of the four vertices and the middle of the diamond and the middle of the four sides, but this is not intended to limit the present invention, and different sensor array structures can be designed according to the complexity and shape of the different curved surfaces to which the sensor array is attached. The mesh structure 1 is made of a material that can be processed into a soft waterproof insulating film, which is one or more of PET, PDMS and polyimide (PI), preferably made of a PDMS film.

[0044] A hollow portion is provided at each node of the mesh structure 1, and the flexible pressure sensor 2 is located in the hollow portion. The thin film of the mesh structure 1 is used as an encapsulation layer, and the thickness of the encapsulation layer can be 100-200 μm. Preferably, the hollow portion in the node of the mesh structure 1 and the single flexible pressure sensor 2 therein are circular. Generally speaking, the diameter of the circle is greater than the thickness, and the diameter can be 1-5 cm; and the portion connecting the nodes is in the shape of a long strip, which is attached to the surface of the drone together with the encapsulation layer at the bottom of the flexible pressure sensor.

[0045] Each flexible pressure sensor 2 adopts a sandwich structure, with a sensitive layer 5 in the middle, and symmetrical flexible substrate layers 3 and electrode layers 4 above and below, and the electrode layer 4 is bonded and electrically connected to the sensitive layer 5, and the thickness of the flexible substrate layer 3 can be 50-300 μm, and the thickness of the electrode layer 4 is 10-500 μm. In some embodiments, the flexible substrate layer 3 is a flexible PI film, and the electrode layer 4 is made of metallic silver deposited by magnetron sputtering.

[0046] The sensitive layer 5 is a composite conductive foam with a conductive elastomer-filled skeleton, and the thickness is relatively thin, especially 0.1 to 2.0 mm. The composite conductive foam of the sensitive layer 5 is obtained by dipping the foam into a conductive material solution multiple times, and the skeleton of the sensitive layer 5 is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with a conductive elastomer. According to the present invention, the foam of the sensitive layer 5 uses one or more of polyurethane (PU), melamine, polystyrene and polypropylene; the conductive material of the sensitive layer 5 can use one or more of MXene, AgNW, CNT, rGO and conductive polymers; in addition, the conductive elastomer of the sensitive layer 5 uses one or more of PDMS / CNT, TPU / AgNWs and SEBS / CNT, among which the former is an insulating elastomer matrix and the latter is a conductive filler. According to the present invention, it is preferred to use polyurethane as the foam of the sensitive layer, MXene as the conductive material of the sensitive layer, and PDMS / CNT as the conductive elastomer of the sensitive layer. Alternatively, polyimide foam can be used as the porous network architecture of the sensitive layer and immersed in a silver nanowire solution to prepare a composite conductive foam sensitive layer. Polyimide foam can withstand high temperatures up to 400°C and is suitable for pressure detection in high-temperature environments such as the aerospace industry and high-temperature industrial equipment.

[0047] The sensor array of the present invention has a mesh structure. Compared with the traditional sensor array prepared on a whole flexible substrate, the design of the Internet is used to greatly reduce the Young's modulus of the overall structure of the sensor array, making it easier to conformally attach to the leading edge surface of the drone wing, thereby improving the conformal attachment capability to the leading edge surface of the wing.

[0048] The method for preparing the flexible pressure sensor array for measuring airspeed of a drone provided by the present invention may include the following steps:

[0049] Step S1, cleaning and treating the film as the flexible base layer, and magnetron sputtering a layer of metal as an electrode layer on the surface of the film;

[0050] Step S2, preparing a plurality of composite conductive foams with conductive elastomer-filled skeletons as sensitive layers;

[0051] Step S3, sandwiching each sensitive layer between two layers of flexible substrate layer-electrode layer connected with wires and electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged;

[0052] Step S4, preparing a packaging mold with a mesh structure, the mold as a whole is a mesh structure, including node casting grooves and connecting casting grooves that connect the node casting grooves to each other;

[0053] Step S5, prepare a solution for forming an encapsulation layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be packaged into different node casting grooves in the mold respectively, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped, and obtain a flexible pressure sensor array after curing.

[0054] Step S2 specifically includes the following sub-steps:

[0055] Step S2.1, after low-pressure oxygen plasma modification of the high-porosity open-cell foam, the high-porosity open-cell foam is subjected to a soaking-drying cycle in a conductive material solution and repeated multiple times to obtain a composite conductive foam;

[0056] Step S2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, and injecting the solution into the etched through holes, curing with ultraviolet light, and completing the preparation of the sensitive layer.

[0057] Reference Figure 2 In the embodiment shown in the present invention, the preparation method is specifically implemented by the following steps:

[0058] In the first step, a polyimide (PI) film with a diameter of 3 cm was prepared by laser cutting, and the surface was treated with oxygen plasma. Then, the PI film was fixed on the substrate holder in the vacuum chamber, and the vacuum pump was started to reduce the pressure to 1.3x10 -3 Pa, and then high-purity argon (Ar) is filled as the working gas, and magnetron sputtering is started to sputter a layer of metallic silver on the surface of the PI film to complete the preparation of the PI-Ag electrode;

[0059] Step 2: Refer to Figure 3As shown, first, a 0.1 mm thick high-porosity open-cell polyurethane (PU) foam 51 is exposed to 50 Pa of low-pressure oxygen and discharged in a plasma chamber to complete oxygen plasma surface treatment to obtain a modified polyurethane foam. By low-pressure oxygen plasma treatment, polar groups can be introduced on the PU surface to make the PU foam have good hydrophilicity and improve the adhesion between PU and MXene. Then, the modified PU foam is immersed in a multilayer MXene (Ti3C2T X ) solution, and then immersed again after drying, and five immersion-drying cycles were performed to make a layer of MXene (Ti3C2T X ) forming a PU-MXene composite conductive foam 52;

[0060] The third step is to use a CO2 laser to process the PU-MXene composite conductive foam 52 prepared in the previous step, laser-etch out arrayed through holes, and then use oxygen plasma to clean the hole wall to enhance the bonding force. According to the ratio of PDMS prepolymer to curing agent of 10:1, the amount of CNT added is 5% of the mass of PDMS to prepare a PDMS / CNT mixed solution, and 1% of the total mass of PDMS is added with gas-phase silica to improve the thixotropy and achieve shear thinning, solve the problem of poor fluidity of high-viscosity materials during injection, and ensure that the viscosity recovers quickly after shearing is stopped to prevent the material from penetrating the porous structure. Then, 1% of the total mass of PDMS is added as a photoinitiator 2-hydroxy-2-methylpropiophenone, and the mixed thixotropic-photocurable PDMS / CNT slurry is injected into the through hole using a syringe, and it is quickly cured using ultraviolet light to complete the preparation of MXene-PDMS / CNT heterogeneous network porous foam 53.

[0061] In the fourth step, the silver wire is bonded to the silver-plated side of the PI-Ag electrode using silver paste, and then the MXene-PDMS / CNT heterogeneous network porous foam 53 is sandwiched between two PI-Ag electrodes and bonded using silver paste to complete the preparation of a single sensor;

[0062] Step 5: Prepare a packaging mold with a diamond-shaped mesh structure, wherein the mold as a whole is a mesh structure, including a plurality of circular casting grooves and rectangular casting grooves connecting the circular grooves to each other;

[0063] The sixth step is to prepare a PDMS solution in a ratio of 10:1 between the base polymer and the cross-linking agent, introduce the PDMS solution into a mold of an interconnected diamond network structure, and after semi-curing, place the prepared multiple sensors one by one into the circular grooves of the mold, and after drying, complete the preparation of an interconnected diamond network structure flexible pressure sensor array.

[0064] Reference Figure 4When the flexible pressure sensor array of the present invention is used to measure the airspeed of a drone, when the pressure is low, the contact resistance change of the porous composite conductive foam is the dominant response, the contact area increases, the conductive path increases, and the conductivity is improved. At the same time, the layer spacing of the multi-layer conductive material attached to the foam will decrease when it is compressed, further improving the conductivity of the composite material; when the pressure is high, the tunnel effect of the conductive elastomer skeleton filled in the foam is the dominant response, the spacing of the conductive filler decreases, and the electrons tunnel through the insulating elastomer matrix barrier to form a tunneling current, thereby realizing the conversion of a large range of pressure changes that are difficult to measure into changes in physical impedance that are easy to detect. As a result, the conductive elastomer serves as the "skeleton" of the sensitive layer, and the porous composite conductive foam serves as the "nerve" of the sensitive layer, forming a coordinated conductive network, realizing multi-level pressure response, and expanding the pressure detection range; at the same time, the arrayed filled conductive elastomer skeleton improves the problem of easy collapse of the foam structure under pressure deformation structure, and prolongs the service life of the sensor array.

[0065] Reference Figure 5 After a conductive material such as MXene is attached to a foam such as PU, when the sensitive layer of the pressure sensor is compressed, the external force will cause the MXene hierarchical structure to change, reducing the interlayer spacing and thereby increasing the MXene conductivity and reducing the impedance. Therefore, after PU and MXene are compounded, the high compressibility of the PU foam itself and the characteristics of the pressure-bearing hierarchical changes of MXene can be combined to improve the sensitivity of pressure detection.

[0066] Reference Figure 6 The flexible pressure sensor array 100 can be conformally and tightly attached to the curved surface of the leading edge 201 of the wing of the fixed-wing UAV 200. A plurality of pressure sensors form a dense pressure sensing array distributed from top to bottom on the leading edge of the wing, which can effectively detect the pressure on the surface of the UAV wing in different directions during flight, and obtain the wind pressure distribution during flight in a three-dimensional range. The convolutional neural network model is trained and verified using the detected pressure distribution data to obtain a convolutional neural network model that can accurately predict the airspeed during flight, thereby replacing the traditional pitot tube to complete the airspeed measurement.

[0067] The mesh structure of the flexible pressure sensor array of the present invention can be changed in various ways. For example, when monitoring leg exercise pressure for sports health, because the leg muscle activity range is large, the sensor array can be designed as an interconnected serpentine mesh structure. The curved serpentine connection design improves the stretchability of the structure. When facing a variety of complex and large-amplitude leg movements, it can still maintain good adhesion performance to achieve long-term and reliable pressure monitoring.

[0068] Finally, it should be noted that the features mentioned and / or shown in the above description of the exemplary embodiments of the present invention may be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or substituted for the corresponding features in other implementations. The technical solutions obtained by these combinations or substitutions shall also be deemed to be included in the protection scope of the present invention.

Claims

1. A flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles, characterized in that: It comprises a mesh structure and a plurality of flexible pressure sensors arranged at a plurality of nodes of the mesh structure in a one-to-one correspondence; The mesh structure is used to be attached to the leading edge of the drone wing, and is made of a material that can be processed into a soft waterproof insulating film. A hollow portion is provided at the node of the mesh structure, and the flexible pressure sensor is located in the hollow portion, with the film of the mesh structure serving as a packaging layer; Each flexible pressure sensor adopts a sandwich structure, with a sensitive layer in the middle and symmetrical flexible substrate layers and electrode layers on the top and bottom. The electrode layer is bonded and electrically connected to the sensitive layer. The sensitive layer is a composite conductive foam with a conductive elastomer-filled skeleton. The composite conductive foam of the sensitive layer is obtained by repeatedly dipping the foam in a conductive material solution, and the skeleton of the sensitive layer is obtained by laser arraying through holes in the composite conductive foam and filling the through holes with a conductive elastomer.

2. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1, characterized in that: The foam of the sensitive layer is one or more of polyurethane, melamine, polystyrene and polypropylene; The conductive material of the sensitive layer is one or more of MXene, AgNW, CNT, rGO and conductive polymer; The conductive elastomer of the sensitive layer is one or more of PDMS / CNT, TPU / AgNWs and SEBS / CNT.

3. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1 or 2, characterized in that: The encapsulation layer is made of one or more of PET, PDMS and PI.

4. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1 or 2, characterized in that: The flexible substrate layer is a flexible PI film, and the electrode layer is made of metallic silver deposited by magnetron sputtering.

5. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1 or 2, characterized in that: The mesh structure is an interconnected diamond mesh structure and includes nine nodes.

6. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1 or 2, characterized in that: The hollow parts in the nodes of the mesh structure and the flexible pressure sensors therein are circular, and the parts connecting the nodes are long strips.

7. The flexible pressure sensor array for measuring airspeed of unmanned aerial vehicles according to claim 1 or 2, characterized in that: The thickness of the packaging layer is 100-200 μm, the thickness of the flexible substrate layer is 50-300 μm, the thickness of the electrode layer is 10-500 μm, the thickness of the sensitive layer is 0.1-2.0 mm, and a single pressure sensor is circular with a diameter of 1-5 cm.

8. A method for preparing a flexible pressure sensor array for measuring airspeed of an unmanned aerial vehicle according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, cleaning and treating the film as the flexible base layer, and magnetron sputtering a layer of metal as an electrode layer on the surface of the film; Step 2, preparing a plurality of composite conductive foams with conductive elastomer-filled skeletons as sensitive layers, comprising the following sub-steps: Step 2.1, after the high-porosity open-cell foam is modified by low-pressure oxygen plasma, the high-porosity open-cell foam is subjected to a soaking-drying cycle in a conductive material solution and repeated multiple times to obtain a composite conductive foam; Step 2.2, etching arrayed through holes on the composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a conductive elastomer solution, injecting the solution into the etched through holes, and curing with ultraviolet light to complete the preparation of the sensitive layer; Step 3, sandwiching each sensitive layer between two flexible substrate layers and electrode layers connected with wires, and electrically connecting and bonding them, thereby obtaining a plurality of flexible pressure sensors to be packaged; Step 4, preparing a packaging mold with a mesh structure, the mold as a whole is a mesh structure, including node casting grooves and connecting casting grooves that connect the node casting grooves to each other; Step 5, prepare a solution for forming a packaging layer, inject part of the solution into the mold, and after semi-solidification, place the multiple pressure sensors to be packaged into different node casting grooves in the mold respectively, place the wires into the mold, and then inject the remaining solution so that each sensor is completely wrapped. After curing, a flexible pressure sensor array is obtained.

9. The preparation method according to claim 8, characterized in that: The composite conductive foam obtained in step 2.1 is a PU-MXene composite conductive foam; step 2.2 includes: using a CO2 laser to etch arrayed through holes on the PU-MXene composite conductive foam, cleaning the hole walls with oxygen plasma, preparing a PDMS / CNT mixed solution, adding gas-phase silica to enhance thixotropy, and then adding a photoinitiator 2-hydroxy-2-methylpropiophenone to prepare a thixotropic-photocurable PDMS / CNT slurry, injecting the mixed slurry into the through holes with a syringe, and rapidly curing it with ultraviolet light to obtain a MXene-PDMS / CNT heterogeneous network porous foam as a sensitive layer.

10. The preparation method according to claim 9, characterized in that: In step 1, PI film is used as the flexible substrate layer, and a layer of metallic silver is magnetron sputtered on the surface of the PI film to complete the preparation of the PI-Ag electrode; step 3 includes: using silver paste to connect the silver wire to the Ag side of the PI-Ag electrode, and then sandwiching the prepared MXene-PDMS / CNT heterogeneous network porous foam between two layers of PI-Ag electrode layers connected with the wires, and bonding them with silver paste.

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