A large-area split-type flexible magnetic tactile sensor with sensing function

Abstract

The application provides a large-area split-type flexible magnetic tactile sensor with a sensing function, which adopts a plurality of flexible square magnetic sheets magnetized in a thickness direction and arranged in a chessboard array mode with opposite polarities of adjacent flexible square magnetic sheets to simulate a flexible magnetic film magnetized in a folding mode, the magnetic flux density of a contact force collection area is enhanced, a U-net algorithm is used to fit the "field strength-force" relationship of the divided collection area, a contact force cloud map is generated, the Hall sensor and the flexible magnetic film can be kept at a larger distance for split-type large-area contact force sensing, and lossless split-type installation is realized; compared with a simple magnetic field mode such as one-way magnetization, the tactile sensor has higher sensitivity. According to the size of a required contact force measurement surface, more flexible magnetic tactile sensor arrays are arranged, a plurality of units jointly draw a contact force cloud map, and the application has application potential in the fields of bionic robots, flexible electronics, medical treatment and the like.

Description

Technical Field

[0001] This invention belongs to the field of flexible tactile sensors, specifically relating to a large-area split magnetic tactile sensor array with sensing function and its preparation method. Background Technology

[0002] Flexible pressure sensors have advantages such as good flexibility, small size, light weight, and ease of use, and can be widely used in fields such as electronic skin, wearable devices, smart homes, robots, and human-computer interaction devices.

[0003] Current flexible tactile sensors utilize various principles, including piezoelectric, piezoresistive, capacitive, and optical technologies. These sensors offer relatively high advantages in terms of high precision and fast response. However, as the pressure measurement area increases, the complexity of the internal circuitry of these sensors also increases, significantly increasing the difficulty of manufacturing. Furthermore, due to mechanical contact during use, the internal structure and circuitry are prone to damage; damage at a single location can often lead to compromised sensor accuracy or even render the entire sensor unusable.

[0004] Magnetic field-based flexible tactile sensors offer advantages such as simple structure, low cost, and the ability to fabricate large-area sensors, effectively overcoming the aforementioned problems. When a magnetic tactile sensor detects contact force, it converts the change in the magnetic field caused by the contact force into the magnitude and location of the force. In some existing solutions, because the magnetic field generated by soft magnetic energy is relatively small, hard permanent magnets are embedded to increase the magnetic field strength, but this reduces flexibility and makes them prone to damage under large external contact forces. Other solutions use flexible magnetic materials, but their magnetic field strength is weak, resulting in a small sensing range and failing to fully utilize the wireless propagation characteristics of magnetic fields. The magnetic tactile sensors and their magnetic field arrays in these solutions are mostly of fixed size, making it impossible to further expand the detection area after fabrication.

[0005] In addition, most existing flexible sensors are only single sensing units, which can only measure the force of point contact and cannot identify the contact force within a range. In many applications, multiple sensing units can only be combined and arranged to read the force of multiple points of contact, which has certain limitations on many applications in fields such as large-area sensing. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a large-area split flexible magnetic tactile sensor with sensing function and a preparation method thereof. The sensor can be flexibly arranged by split installation, and the sensor can be enlarged by simple splicing according to the current detection area. It makes full use of the magnetic field strength advantage of the folded magnetized magnetic film, and combined with the constructed "field strength-force" decoupling model, pressure cloud map can be calculated and drawn according to the magnetic field change generated by the pressure on the sole of the foot.

[0007] A split-type flexible magnetic tactile array sensor with contact force sensing function includes:

[0008] A flexible contact layer is installed on the outside of the base. The flexible contact layer includes a silicone rubber elastic layer and a flexible magnetic film sequentially disposed on the outside of the base. The silicone rubber elastic layer is composed of silicone rubber A layer with a cross-sectional size of 2mm and a Shore hardness of 00-30 and silicone rubber B layer with a cross-sectional size of 2mm and a Shore hardness of A30, which are aligned vertically and spliced ​​together. The flexible magnetic film is composed of flexible square magnetic sheets with a cross-sectional size of 2mm, and the flexible magnetic film and the silicone rubber elastic layer are aligned vertically and installed together. The flexible square magnetic sheets have a side length of 30mm and are arranged in a checkerboard pattern with alternating polarity according to the direction of the magnetic field, that is, the magnetic field polarity of each flexible magnetic sheet is opposite to that of the adjacent magnetic sheet.

[0009] The Hall sensor array is installed inside the base and consists of multiple three-dimensional Hall sensors arranged in a set position. One side of the Hall sensor array chip body is installed inside the base, and each Hall sensor chip is arranged at the midpoint of the edge line where the flexible square magnetic sheet is connected in pairs.

[0010] The flexible magnetic film and the Hall sensor array are arranged in parallel.

[0011] In the above structure, the magnetic film and the silicone rubber elastic layer are installed with their top and bottom aligned, meaning that each edge of both is aligned vertically. The base shown is the application surface of the split-type flexible magnetic tactile array sensor.

[0012] The split flexible magnetic tactile array sensor of the present invention adopts a split installation of a flexible contact layer and a Hall sensor array. The flexible contact layer is composed of a completely flexible silicone rubber elastic layer and a flexible magnetic film. There are no embedded electronic components or circuits, and there is no direct contact with the Hall sensor array, which increases the upper limit of the contact force, simplifies the manufacturing difficulty, and has high robustness.

[0013] The flexible contact layer of this invention adopts a design of splicing two layers of silicone rubber with different hardness. The low-hardness silicone rubber layer A is for subsequent identification of the deformation location, and the high-hardness silicone rubber layer B is for subsequent identification of the pressure at the deformation point. By referring to the material properties of silicone rubber such as Shore hardness, the appropriate cross-sectional dimension parameters of the elastic layer are analyzed and calculated, which meet the typical range of foot pressure acquisition and the size constraints of the pressure sensor placed on the device.

[0014] This invention employs a checkerboard-patterned alternating polarity array, utilizing the magnetic field distribution simulated by Maxwell, such as... Figure 6As shown, a flexible magnetic film is formed by arranging square flexible magnetic sheets, magnetizing them in the thickness direction, and then using a checkerboard pattern, where the magnetic field polarity of each square magnetic sheet is opposite to that of its adjacent sheets. This array arrangement, splicing, and bonding results in enhanced magnetic flux density at the boundaries of the square magnetic sheets. When the flexible magnetic film is subjected to contact force, it undergoes planar movement, causing the silicone rubber elastic layer to be compressed and / or stretched, resulting in spatial displacement relative to the Hall sensor. This causes a change in the spatial magnetic field at the location of the Hall sensor array. By analyzing and calculating the three-dimensional magnetic field strength data collected by each sensor chip in the Hall sensor array, the offset of each contact force position on the flexible magnetic film can be obtained. Combining this with the material properties such as the Shore hardness of the flexible contact layer, the flexible contact layer is divided into units, and the magnetic field data of all cells are filled into the corresponding cells. Appropriate interpolation methods are used for matrix expansion and color mapping. Using the U-Net algorithm for data fitting, a pressure cloud map can be obtained, enabling the sensing of a large range of contact forces.

[0015] The Hall sensor array of the present invention is based on the magnetic field distribution of the checkerboard alternating polarity array. Three-dimensional Hall sensors are arranged in the magnetic field intensity enhancement region, that is, the midpoint of the boundary of the flexible square magnetic sheet, so as to obtain a larger range of magnetic field intensity variation and thus a larger range of pressure variation.

[0016] The split-type flexible magnetic tactile array sensor of this invention can increase the number of flexible square magnetic sheets participating in the formation of the flexible magnetic film while maintaining the magnetic field arrangement regularity of the checkerboard alternating polarity array, thereby expanding the size of the sensor's flexible contact layer; and while maintaining the arrangement regularity of the three-dimensional Hall sensors, it can increase the number of three-dimensional Hall sensors participating in the formation of the Hall sensor array, thereby expanding the size of the Hall sensor array. By simultaneously expanding the flexible contact layer and the Hall sensor array, the overall size of the split-type flexible magnetic tactile array sensor can be increased, thus expanding the sensor's detection range. When the size of the fabricated split-type flexible magnetic tactile array sensor is insufficient to cover the entire test area, multiple fabricated split-type flexible magnetic tactile array sensors can be directly spliced ​​together to expand the sensor's detection range, simplifying the manufacturing process and eliminating the need to re-fabricate the sensor.

[0017] Preferably, the flexible square magnetic sheet can be prepared from the following materials by weight percentage:

[0018] Dragon Skin 30A component 25wt%

[0019] Dragon Skin 30B component 25wt%

[0020] 400-mesh neodymium iron boron permanent magnet particles, 50wt%

[0021] As a further preferred option, the fabrication process of the flexible square magnetic sheet magnetized in the thickness direction is as follows:

[0022] Dragon Skin 30A component, Dragon Skin 30B component, and 400-mesh rubidium iron boron permanent magnet particles were mixed by stirring and then pre-degassed to obtain a mixture.

[0023] The uniformly mixed mixture is placed in a pre-designed magnetic sheet mold and then degassed sequentially. A glass plate is then placed on top to squeeze out the excess mixture, making the height of the mixture consistent with the height of the mold. The glass plate and the mold are then placed together in a constant temperature oven to cure. Finally, the flexible square magnetic sheet of the required size is demolded.

[0024] All the flexible square magnetic sheets are placed in a strong magnetic coil to magnetize them in the thickness direction, thus obtaining the flexible square magnetic sheets.

[0025] Preferably, the adhesive for the flexible square magnetic sheet can be prepared from the following materials by weight percentage:

[0026] Dragon Skin 30A component 50wt%

[0027] Dragon Skin 30B component 50wt%

[0028] As a further preferred option, the preparation process of the flexible magnetic film is as follows:

[0029] The Dragon Skin 30A and Dragon Skin 30B components were mixed by stirring to obtain a mixture;

[0030] Flexible square magnetic sheets are arranged in a checkerboard pattern with alternating polarities, so that the magnetic field polarity of each flexible square magnetic sheet is opposite to that of its adjacent flexible square magnetic sheets. Adhesive is applied at the joints, and the sheets are spliced ​​together into a whole and then placed in a constant temperature chamber for curing to obtain the flexible magnetic film.

[0031] Preferably, the silicone rubber elastic layer can be prepared from the following materials by weight percentage:

[0032] Ecoflex 0030A component 25wt%

[0033] Ecoflex 0030B component 25wt%

[0034] Dragon Skin 30A component 25wt%

[0035] Dragon Skin 30B component 25wt%

[0036] As a further preferred option, the preparation process of the silicone rubber elastic layer is as follows:

[0037] The Ecoflex 0030A and Ecoflex 0030B components are mixed by stirring to obtain a mixture, which is then injected into a mold and degassed under vacuum. The mixture is then placed in a constant temperature oven for curing to obtain the silicone rubber A layer.

[0038] The Dragon Skin 30A and Dragon Skin 30B components are mixed by stirring to obtain a mixture, which is then injected into a mold and degassed under vacuum. The mixture is then placed in a constant temperature oven for curing to obtain the silicone rubber B layer.

[0039] Align the silicone rubber A layer and silicone rubber B layer vertically, apply adhesive to the joint, splice them into a whole, and then place them in a constant temperature oven to cure, thus obtaining the silicone rubber elastic layer.

[0040] Preferably, the Hall sensor array comprises multiple MLX90393 chips arranged in a specific pattern, including the MLX90393 chip body, PCB board, and ribbon cable interface. The arrangement scheme places each Hall sensor at the midpoint of the edges where two pairs of flexible square magnetic sheets intersect.

[0041] Preferably, the large-area split flexible magnetic tactile sensor also includes a microcontroller and a host computer control system connected to the Hall sensor array, which divides the magnetic field area into cells, maps the corresponding magnetic field data, performs interpolation processing on the magnetic field data, and uses the U-Net algorithm to perform data fitting and draw the contact force cloud map.

[0042] The design process for the cross-sectional dimensions of the silicone rubber elastic layer is as follows:

[0043] Treating the silicone rubber elastic layer as a spring, the expressions for the maximum compressive force and elastic coefficient of the silicone rubber elastic layer are as follows:

[0044] F = kx

[0045] In the formula, F is the maximum compressive force, and k is the elastic coefficient.

[0046] Based on the definition of strain and the stress-strain relationship:

[0047]

[0048] In the formula, ΔL represents the change in the cross-sectional dimensions of the material, L represents the original cross-sectional dimensions, σ represents the stress, and E represents Young's modulus.

[0049] The stress σ is defined as:

[0050]

[0051] In the formula, A is the area of ​​the force-bearing surface.

[0052] Based on the above formula, the expression for the elastic coefficient k can be derived:

[0053]

[0054] The relationship between Young's modulus and Shore hardness is as follows:

[0055]

[0056] In the formula, HA represents Shore hardness.

[0057] This method allows us to determine the maximum contact force that the silicone rubber elastic layer can withstand, and to design appropriate thicknesses for silicone rubber A layer and silicone rubber B layer according to the required conditions, and finally splice them together to form a complete silicone rubber elastic layer.

[0058] The process of constructing the contact force contour map model is as follows:

[0059] Suppose that in the xy plane, there exist multiple flexible square magnetic sheets of thickness d arranged in a checkerboard pattern with alternating polarities. Each flexible square magnetic sheet can be considered a magnetic dipole, and the magnetic field expression of the magnetic dipole is as follows:

[0060]

[0061] In the formula, B(r) is the magnetic field at position r, μ0 is the free permeability, m is the magnetic dipole moment, r is the vector from the magnetic dipole to the observation point, and ||r|| is the magnitude of r.

[0062] To solve for the magnetic dipole moment m, according to its definition:

[0063]

[0064] In the formula, H is the magnetic field strength and V is the volume of the object.

[0065] Assuming the flexible square magnetic sheet is uniformly magnetized and the internal magnetization (H) is negligible, the formula for the magnetic dipole moment m is obtained:

[0066]

[0067] Using a hypothetical magnetic dipole model, the magnetic field at various points in the surrounding area is calculated. The center point of the flexible magnetic membrane in the checkerboard array is set as the origin, and the coordinates of observation point P are (x, y, z). Then, for each magnet i (i ≤ 9), the magnetic field at P is:

[0068]

[0069] The total magnetic field at point P is B. total (P) Vector sum is:

[0070] B total (P)=∑B i (P)

[0071] The checkerboard array method can reduce magnetic field leakage at the edge of the magnet, make the magnetic flux form a closed loop between the magnets, and increase the local magnetic flux density.

[0072] Using the edge of the flexible magnetic film as a reference, a new square region is formed by equidistant inward spacing of 7.5mm, and this region is divided into 5×5 cell regions. For the cell containing the sensor chip, its magnetic field data is the z-axis magnetic field data collected by the corresponding sensor chip, and the magnetic field data of other cells is filled by interpolation to fill the data gaps.

[0073] As a further preferred embodiment, the steps of the interpolation method are as follows:

[0074] The 5×5 cell range is treated as a 5×5 matrix with data points f(i,j) (i,j = 1,2,3,4,5). The data at f(1,2), f(1,4), f(2,1), f(2,3), f(2,5), f(3,2), f(3,4), f(4,1), f(4,3), f(4,5), f(5,2), and f(5,4) are the z-axis data collected by the corresponding sensor chip. This matrix is ​​then expanded into a 1000×1000 grid, with new grid points represented as (x,y), and still divided into 5×5 intervals. Within each interval [x...]... i ,x i+1 ]×[y i ,y i+1 Use S(x,y) to represent the interpolation function:

[0075]

[0076] Among them, a kl These are the coefficients that need to be determined.

[0077] For each interval [x] i ,x i+1 ]×[y i ,y i+1 There are 16 conditions in total (4 function values, 8 first-order derivative values, and 4 mixed second-order derivative values), therefore, 16 coefficients 'a' need to be determined. kl : Calculate the function value f(i,j) and the first derivative f at each grid point. x(i,j)f y (i,j), mixed second derivative f xy After (i,j), for each interval [x i ,x i+1 ]×[y i ,y i+1 Establish 16 equations to form a matrix equation, and solve for the coefficient a. kl And construct the constructor S(x,y).

[0078] Using the edge of the flexible magnetic film as a reference, a new square region is formed by equidistant inward spacing of 7.5mm. This region is then divided into 5×5 cell areas, each measuring 15mm×15mm. For cells containing sensor chips, the magnetic field data is the z-axis magnetic field data acquired by the corresponding sensor chip. For cells not containing sensor chips, the magnetic field data is a composite result of the three-dimensional magnetic field data acquired by the sensor chips in adjacent cells. The calculation formula is as follows:

[0079]

[0080] In the formula, x i ,y i ,z i This represents the three-dimensional magnetic field data collected by adjacent sensor chips, with a maximum of four adjacent locations containing sensor chips.

[0081] This method assigns a corresponding data value to each cell, and the data values ​​from all cells form a 5×5 matrix. To further process this data, upper and lower limits are set for the matrix, and interpolation is used to expand its size. Finally, colors are mapped based on the data values ​​to visually represent the distribution of contact forces, thus creating a contour map.

[0082] Through the above steps, the present invention can effectively identify and display the distribution of contact force, providing users with intuitive and accurate contact force feedback.

[0083] The large-area split-type magnetic tactile sensor of this invention simulates folded magnetization by arranging a flexible magnetic film with a conjugate magnetic field, thereby enhancing the magnetic field strength of the flexible magnetic film at the location of each Hall sensor. A Hall sensor array and the flexible magnetic film perform split-type sensing, and the contact force cloud map is obtained after data fitting. Through the above configuration, the large-area split-type magnetic tactile sensor of this invention can calculate, sense, and draw large-area contact forces based on the three-dimensional magnetic field strength and the constructed cloud map, using multiple sensor units of the Hall sensor array. It has certain application potential in multiple fields such as flexible electronics and rehabilitation robots. Attached Figure Description

[0084] Figure 1 This is a schematic diagram of the main structure of an embodiment of the present invention;

[0085] Figure 2 This is a three-dimensional structural diagram of an embodiment of the present invention;

[0086] Figure 3 This is a three-dimensional structural diagram of the Hall sensor array in an embodiment of the present invention;

[0087] Figure 4 This is a schematic diagram of the magnetization method of the flexible square magnetic sheet in an embodiment of the present invention;

[0088] Figure 5 This is a schematic diagram showing the magnetic field arrangement direction of the flexible square magnetic sheet in the flexible magnetic film of the present invention.

[0089] Figure 6 A schematic diagram of the magnetic field distribution of a checkerboard array with alternating polarities, as simulated by Maxwell.

[0090] In the diagram: 1—flexible magnetic film, 2—silicone rubber elastic layer, 3—base, 4—PCB board, 5—ribbon cable interface, 6—MLX90393 chip, 7—flexible square magnetic sheet. Detailed Implementation

[0091] like Figure 1 and 2 As shown, the large-area split magnetic tactile sensor with sensing function proposed in this invention mainly comprises two parts: a flexible contact layer installed on the outside of the base and a Hall sensor array installed on the inside of the base.

[0092] The flexible contact layer consists of a flexible magnetic film 1 and a silicone rubber elastic layer 2. The flexible magnetic film 1 is composed of flexible square magnetic sheets 7 spliced ​​together. The silicone rubber elastic layer 2 and the flexible magnetic film 1 are sequentially installed on the outside of the base. The silicone rubber A layer in the silicone rubber elastic layer 2 is in contact with the flexible magnetic film 1. The thickness of the flexible magnetic film 1 is the same as the thickness of the silicone rubber A layer and the silicone rubber B layer in the silicone rubber elastic layer 2, and their edges are aligned vertically.

[0093] like Figure 3 As shown, the Hall sensor array includes a PCB board 4, a ribbon cable interface 5, and an MLX90393 sensor chip 6. The Hall sensor array has the MLX90393 sensor chip 6 mounted on one side of the main body and the inner side of the substrate. Each MLX90393 sensor chip 6 is arranged at the midpoint of the edge line where the flexible square magnetic sheet 7 is connected in pairs.

[0094] The material ratio for preparing the flexible square magnetic sheet 7 is: 25wt% Dragon Skin 30A component, 25wt% Dragon Skin 30B component, and 50wt% 400-mesh neodymium iron boron permanent magnet particles. The above components were mixed for 5 minutes at 1000 rpm using an electric stirrer. Then, the mixture was pressurized to 5 atmospheres using a vacuum pump and allowed to stand for 5 minutes. The homogeneous mixture was poured into a mold with a groove size of 30mm × 30mm × 2mm, and a glass plate was placed on top to press out excess mixture. The mold was then placed in a 30℃ constant temperature oven for curing for 6 hours. Finally, multiple 30mm × 30mm × 2mm flexible square magnetic sheets were demolded. The top and bottom edges of the multiple flexible square magnetic sheets were aligned, and they were placed in a magnetizer to complete the thickness magnetization.

[0095] The adhesive was prepared using the following material ratio: 50 wt% Dragon Skin 30A component and 50 wt% Dragon Skin 30B component. The components were mixed for 2 minutes using an electric mixer at 300 rpm.

[0096] The flexible magnetic film 1 is composed of multiple flexible square magnetic sheets 7 spliced ​​together, with the seams bonded together using adhesive. The flexible square magnetic sheets 7 are arranged according to the magnetization direction as follows: Figure 5 Arrange as shown.

[0097] The material ratio of silicone rubber elastic layer 2 is as follows: 25wt% Ecoflex 0030A component and 25wt% Ecoflex 0030B (silicone rubber A layer), 25wt% Dragon Skin 30A component and 25wt% Dragon Skin 30B component (silicone rubber B layer). Ecoflex 0030A and Ecoflex 0030B components are mixed for 5 minutes at 300 rpm using an electric stirrer. Dragon Skin 30A and Dragon Skin 30B components are also mixed for 5 minutes at 300 rpm using an electric stirrer. The two uniformly mixed mixtures are poured into two molds with groove dimensions of 90mm × 90mm × 2mm, respectively. Excess mixture is squeezed out by covering with a glass plate. The molds are then placed in a 30℃ constant temperature oven for curing for 6 hours. Finally, the 90mm × 90mm × 2mm silicone rubber A layer and silicone rubber B layer are demolded. Silicone rubber A layer and silicone rubber B layer are aligned and spliced ​​together using an adhesive to form silicone rubber elastic layer 2. After the silicone rubber elastic layer 2 is demolded, an adhesive is evenly applied to its upper surface. The flexible magnetic film 2, which is spliced ​​together by multiple flexible square magnetic sheets 7, is flatly attached to the upper surface of silicone rubber A layer in silicone rubber elastic layer 2. The edges of the two are aligned using a mold, and the film is cured in a constant temperature oven at 30°C for 6 hours to obtain the final flexible contact layer.

[0098] The Hall sensor array 3 consists of a PCB board 4, a ribbon cable interface 5, and an MLX90393 sensor chip 6. The PCB board 4 measures 90mm × 90mm × 1.6mm, and the MLX90393 sensor chip 6 measures 3mm × 3mm × 2mm. Each MLX90393 chip 6 is arranged at the midpoint of the edge line where the flexible square magnetic sheet 7 is connected in pairs.

[0099] Before using the Hall sensor array 3, each MLX90393 sensor chip 6 must be calibrated:

[0100] The initial values ​​acquired by each MLX90393 sensor chip 6 are known:

[0101]

[0102] By obtaining the offset of each MLX90393 sensor chip 6:

[0103]

[0104] Then, combining this with the mapping matrix of each MLX90393 sensor chip 6:

[0105]

[0106] The calibrated magnetic field data can then be obtained:

[0107]

[0108] In this embodiment, the base 3 used for demonstration is a 3D-printed resin block with dimensions of 90mm × 90mm × 3mm. Adhesive is uniformly applied to the lower surface of the silicone rubber B layer in the flexible contact layer's silicone rubber elastic layer 2, and the block is smoothly attached to the upper surface of the base 3. The edges are aligned using a mold, and the block is cured in a 30°C constant temperature oven for 6 hours. Then, a Hall sensor array is placed on the lower surface of the base 3, and the z-axis channel of each MLX90393 chip 6 in the Hall sensor array is activated. The Hall sensor array is moved close to the lower surface of the base 3, while the magnetic field strength of each MLX90393 chip 6 is measured and observed. When the absolute value of all values ​​reaches its maximum, it indicates that each MLX90393 chip 6 is positioned at the midpoint of the edges where each pair of flexible square magnetic sheets 7 intersects. After determining the position, adhesive is uniformly applied, and the Hall sensor array is attached to the lower surface of the base 3. The distance between the flexible magnetic film 1 and the MLX90393 chips 6 of the Hall sensor array is 8.6mm.

[0109] The process of constructing the contact force contour map model is as follows:

[0110] Using the edge of the flexible magnetic film as a reference, a new square region is formed by equidistant inward spacing of 7.5mm. This region is then divided into 5×5 cell areas, each measuring 15mm×15mm. For cells containing sensor chips, the magnetic field data is the z-axis magnetic field data acquired by the corresponding sensor chip. For cells not containing sensor chips, the magnetic field data is a composite result of the three-dimensional magnetic field data acquired by the sensor chips in adjacent cells. The calculation formula is as follows:

[0111]

[0112] In the formula, x i ,y i ,z i This represents the three-dimensional magnetic field data collected by adjacent sensor chips, with a maximum of four adjacent locations containing sensor chips.

[0113] This method assigns a corresponding data value to each cell, and the data values ​​from all cells form a 5x5 matrix. To further process this data, upper and lower limits are set for the matrix, and interpolation is used to expand its size. Finally, colors are mapped based on the data values ​​to visually represent the distribution of contact forces.

[0114] For other cell ranges, interpolation is performed:

[0115] The 5×5 cell range is treated as a 5×5 matrix with data points f(i,j) (i,j = 1,2,3,4,5). The data at f(1,2), f(1,4), f(2,1), f(2,3), f(2,5), f(3,2), f(3,4), f(4,1), f(4,3), f(4,5), f(5,2), and f(5,4) are the z-axis data collected by the corresponding sensor chip. This matrix is ​​then expanded into a 1000×1000 grid, with new grid points represented as (x,y), and still divided into 5×5 intervals. Within each interval [x...]... i ,x i+1 ]×[y i ,y i+1 Use S(x,y) to represent the interpolation function:

[0116]

[0117] Among them, a kl These are the coefficients that need to be determined.

[0118] For each interval [x] i ,x i+1 ]×[y i ,y i+1There are 16 conditions in total (4 function values, 8 first-order derivative values, and 4 mixed second-order derivative values), therefore, 16 coefficients 'a' need to be determined. kl : Calculate the function value f(i,j) and the first derivative f at each grid point. x (i,j)f y (i,j), mixed second derivative f xy After (i,j), for each interval [x i ,x i+1 ]×[y i ,y i+1 Establish 16 equations to form a matrix equation, and solve for the coefficient a. kl And construct the constructor S(x,y).

[0119] The matrix was then expanded to a 200×200 matrix to improve the resolution and detail of the data, and the data was color-mapped, with the maximum and minimum values ​​in the data serving as the boundaries of the color mapping.

Claims

1. A large-area, split-type flexible magnetic tactile sensor with sensing function, characterized in that, include: The large-area split-type flexible magnetic tactile sensor includes a flexible contact layer, a base, and a Hall sensor array: wherein... The base is made of rigid resin material; The flexible contact layer includes a silicone rubber elastic layer and a flexible magnetic film; The silicone rubber elastic layer is located on the outside of the base, with the side length of the silicone rubber elastic layer being the same as the side length of the base, and the edges being aligned vertically. The flexible magnetic film is disposed on the outside of the silicone rubber elastic layer and includes multiple flexible square magnetic sheets; the side length of the flexible square magnetic sheets is one-third of the side length of the silicone rubber elastic layer, and they are arranged in a 3×3 array. They are spliced ​​together by adhesive to form a flexible magnetic film, and the flexible magnetic film is installed with the edges of the silicone rubber elastic layer aligned vertically. The Hall sensor array is disposed on the inner side of the base, and the side length of the Hall sensor array is the same as the side length of the base, with the edges aligned vertically. The data acquisition component includes an IIC multiplexed chip PCB board, a lower-level computer, and a higher-level computer. The IIC multiplexed chip PCB board is connected to the Hall sensor array. The three-dimensional Hall sensor is assigned an address through the IIC multiplexed chip PCB board and inputs the data collected by the Hall sensor array to the lower-level computer control system. The magnetic field distribution of the flexible magnetic film is arranged by aligning the edges of multiple flexible square magnetic sheets vertically and magnetizing them in the thickness direction to ensure that the magnetic field polarity and magnetic flux density of all flexible square magnetic sheets are consistent. When splicing, the magnetic field polarity of each flexible square magnetic sheet is opposite to that of the adjacent flexible square magnetic sheet, i.e., a checkerboard polarity alternating array is used. Adhesive is applied to the joints of all flexible square magnetic sheets, and after curing, it becomes a flexible magnetic film.

2. The large-area split-type flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that... The silicone rubber elastic layer is 4mm thick, and the flexible magnetic film is 2mm thick.

3. The large-area split-type flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: The silicone rubber elastic layer is composed of silicone rubber A layer and silicone rubber B layer with different hardness. Silicone rubber A layer is softer than silicone rubber B layer. The low-hardness silicone rubber A layer is used to identify the deformation location, and the high-hardness silicone rubber B layer is used to identify the contact force at the deformation location. Silicone rubber A layer serves as a contact layer for the flexible magnetic film. The two silicone rubber layers are aligned vertically in the thickness direction and spliced ​​together. After being coated with adhesive and cured, they form the silicone rubber elastic layer.

4. The large-area split-type flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that: The sensor chips of the Hall sensor array are arranged in such a way that, according to the magnetic field distribution of the checkerboard alternating polarity array, three-dimensional Hall sensors are arranged in the area where the magnetic field strength is enhanced, that is, at the midpoint of the boundary of the flexible square magnetic sheet. The center point of each sensor chip is located at the midpoint of the edge line where the flexible square magnetic sheets are spliced ​​together, and a total of 12 sensor chips are arranged.

5. The large-area split-type flexible magnetic tactile sensor with sensing function according to claim 1, characterized in that, When a larger contact force sensing range is required, multiple sensors are spliced ​​together based on the current magnetic field distribution of the edge flexible square magnetic sheets. This ensures that the magnetic field distribution is regular, i.e., the magnetic field polarity of each flexible square magnetic sheet is opposite to that of the adjacent flexible square magnetic sheets, so as to obtain a contact force cloud map over a larger range.

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