Flexible multi-dimensional force sensor based on centripetal gradient magnetic field design and preparation method thereof

Abstract

The invention discloses a flexible multi-dimensional force sensor based on centripetal gradient magnetic field design and a preparation method thereof, and belongs to the field of electronic devices. A flexible multi-dimensional force sensor sequentially comprises, from top to bottom, a protection layer comprising a flexible substrate material having a force sensitive characteristic; a cross-shaped groove is formed in the bottom face of the magnetic film layer, the edge of the groove is in an arc shape, and a magnetic field with gradient magnetic flux can be formed; a buffer layer including a strained material having a stepped shape; and the transmission layer comprises an electromagnetic effect chip with a triaxial magnetic field sensing capability and a reading circuit of the electromagnetic effect chip. Compared with the prior art, the sensor provided by the invention realizes natural decoupling from the magnetic field design, and has decoupling capability on three axes. The gradient design enables the sensor to have different response slopes at different stress stages when the sensor is stressed, the force measurement range of the device is greatly improved, and the sensing sensitivity and the sensing range on three axes are the same.

Description

Technical Field

[0001] The invention relates to the field of electronic devices, and in particular to a flexible multi-dimensional force sensor designed based on a centripetal gradient magnetic field and a preparation method thereof. Background Art

[0002] With the rapid rise of artificial intelligence and robots, a variety of electronic sensor devices such as vision and auditory devices are driving the development of bionic humanoid robots and natural interaction robots. However, tactile devices, which are particularly important in natural interaction, especially sensors for multi-dimensional force of robots, still face challenges such as the difficulty of rigid sensors to adapt to bionic flexible skin, the difficulty of decoupling multi-dimensional force signals under a single sensor, the poor force sensing performance of flexible tactile sensors, and the difficulty of large-scale manufacturing. In actual use, robots cannot achieve rich human-like tactile interaction.

[0003] The difficulty in developing multi-dimensional force sensors lies in the decoupling of multi-dimensional force signals. The traditional piezoresistive and piezocalytic sensing mechanisms are the sensing and analysis of one-dimensional signals at the physical level. It is difficult to analyze multi-dimensional force signals, and complex device structures need to be added during design. The magnetic field is a natural physical field with three-dimensional vector properties. After good design and calculation, a two-way mapping between the magnetic field and the multi-dimensional force field can be established as a force sensing mechanism, effectively solving the problem of multi-dimensional force sensing and analysis. Compared with traditional mechanisms, there are fewer practical options in this direction, and there are still challenges such as insufficient decoupling dimensions, poor decoupling effects, and cumbersome processes.

[0004] Some existing technologies cannot achieve natural decoupling, resulting in a complex settlement process and limited accuracy. Some existing technologies can achieve self-decoupling, but are limited to normal force and tangential force stimulation. For the same xy-axis plane, it is impossible to decouple the forces on the x and y axes.

[0005] Therefore, to address the above challenges, a new type of flexible magnetic multi-dimensional force device with the potential for large-scale production is needed. Through simple design, it can achieve multi-dimensional force decoupling in all directions in space while having high mechanical properties, and the manufacturing process is simple and the cost is low. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a flexible multi-dimensional force sensor based on a centripetal gradient magnetic field design and a preparation method thereof, constructs a three-dimensional magnetic field with a centripetal gradient magnetic flux density, and the preparation process can match large-scale manufacturing, is suitable for multi-dimensional force sensing and analysis, and is particularly suitable for wide application in application scenarios such as robot touch; and proposes a flexible buffer layer, which can utilize the gradient stress structure and gradient material modulus design to control the sensor to have the same stress sensitivity in the tangential and normal directions, and is suitable for a flexible multi-dimensional force sensor.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] The first aspect of the present invention relates to a flexible multi-dimensional force sensor, which comprises, from top to bottom:

[0009] a protective layer including a flexible base material having force-sensitive properties;

[0010] The magnetic film layer has a cross-shaped groove on the bottom surface, and the edge of the groove is arc-shaped, which can form a centripetal magnetic field with a gradient magnetic flux;

[0011] a buffer layer including a strain material in a stepped shape;

[0012] And, the transmission layer includes an electromagnetic effect chip with three-axis magnetic field sensing capability and a readout circuit thereof.

[0013] Optionally, the cross-section of the protective layer is trapezoidal, spherical or conical.

[0014] Optionally, the hardness of the stepped strain material increases from top to bottom.

[0015] Optionally, the electromagnetic effect chip is a three-axis Hall sensor chip or a three-axis magnetoresistive sensor chip.

[0016] Optionally, in the stepped strain material, the hardness between different layers of the strain material is controlled by the amount of curing agent added.

[0017] Optionally, the material of the magnetic film layer is: NdFeB / polydimethylsiloxane composite material or other polymer material composited with rare earth magnetic material and flexible polymer material.

[0018] Optionally, the center of the cross-shaped groove of the magnetic film layer is in a straight line with the center of the north magnetic pole of the electromagnetic effect chip.

[0019] A second aspect of the present invention relates to a method for preparing a flexible multi-dimensional force sensor, comprising the following steps:

[0020] A structure having a cross-shaped groove at the bottom is obtained by mold forming or etching, and the edge of the groove is arc-shaped; a magnetic field density modulus with a decreasing gradient toward the center is induced, a centripetal gradient magnetic field is formed in the central area of ​​the cross-shaped groove, and the magnetic flux density gradient decreases, thereby obtaining a magnetic film layer;

[0021] A buffer layer having a stepped shape is prepared by mold forming or etching forming;

[0022] An electromagnetic effect chip with three-axis magnetic field sensing capability and a readout circuit thereof are provided as an output layer;

[0023] The transmission layer, the buffer layer, the magnetic film layer and the protective layer formed by the mold are bonded and assembled from bottom to top to obtain the flexible multi-dimensional force sensor.

[0024] A third aspect of the present invention relates to the above-mentioned flexible multi-dimensional force sensor decoupling method, comprising the following steps:

[0025] Representing the three-dimensional magnetic field of the magnetic film layer as a superposition of three sine waves in orthogonality;

[0026] The magnetic flux density and ratio under the magnetic film layer are calculated by using the magnetostatic scalar potential, magnetic field and magnetization intensity;

[0027] Calculate the deformation in the x, y, and z directions in the three-dimensional coordinate system according to the magnetic flux density and the ratio;

[0028] According to Hooke's law, the three-dimensional force is calculated by the contact area, shear modulus / elastic modulus, the deformation amount and thickness.

[0029] The fourth aspect of the present invention relates to the application of the above-mentioned magnetic film layer in inducing the construction of a centripetal gradient magnetic field, wherein the magnetic film layer can induce a magnetic field density modulus that gradually decreases toward the center through a cross-groove structure, forming a centripetal gradient magnetic field in the central area of ​​the cross-groove; and the magnetic flux density gradient decreases.

[0030] The specific principle is that the magnetic film with a cross-arc groove structure, compared with a planar magnetic film without a structure, will induce magnetic flux lines to flow along the surface of the cross-groove structure, forming a centripetal tangential vector component magnetic field that is different from the unidirectional normal magnetic field of the planar magnetic film, so that a centripetal magnetic field exists in a specific area below the original planar magnetic film.

[0031] Optionally, the magnetic film material can be a flexible material or a metal material, and the magnetic film can be a rigid material or a flexible material. At the same time, different preparation processes are used according to different materials, such as photolithography or reverse molding.

[0032] Optionally, the size of the cross groove can be adjusted according to the size of the central force decoupling area required by the sensor, and the central area of ​​the cross groove is the size of the force decoupling area. For example, in Example 1, the central area is 3mm*3mm. At the same time, different preparation processes are selected according to the size of the groove, such as photolithography or reverse molding.

[0033] A fifth aspect of the present invention relates to a manipulator comprising the above-mentioned flexible multi-dimensional force sensor.

[0034] Beneficial effects of the present invention:

[0035] The sensor device of the present application realizes natural decoupling from the perspective of magnetic field design and has decoupling capabilities on three axes.

[0036] The buffer layer of the present application adopts a gradient design, so that when the sensor is subjected to stress, it has different response slopes at different stress stages, which greatly improves the force measurement range of the device, and the sensing sensitivity and range on the three axes are the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be further described below in conjunction with the accompanying drawings.

[0038] Figure 1 This is a schematic diagram of the structure of the flexible multi-dimensional force sensor of the present application;

[0039] Figure 2 This is a schematic diagram of the structure of the central magnetic film layer of the sensor of this application;

[0040] Figure 3 A schematic diagram of the magnetic field gradient on the lower surface of the sensor of the present application;

[0041] Figure 4 A schematic diagram of the magnetic field gradient of each sensing surface below the sensor of the present application;

[0042] Figure 5 A cross-sectional view of a magnetic flow field simulation of a magnetic film layer of the present application;

[0043] Figure 6 A top view of a magnetic flow field simulation of a magnetic film layer of the present application;

[0044] Figure 7 A top view of a magnetic flow field simulation in the central area of ​​a magnetic film layer of the present application;

[0045] Figure 8 This is the magnetic field response diagram to the triaxial force of this application;

[0046] Fig. 9 The magnetic field of the present application identifies the direction of force in the xoy plane;

[0047] Fig.10 The magnetic film layer etching effect diagram of the present application;

[0048] Fig.11 Example diagram of the application of the sensor in the robot arm;

[0049] Fig.12 This is a diagram of the robot touch data for this application.

[0050] The components corresponding to the numbers in the figure are as follows:

[0051] 1. Protective layer; 2. Magnetic film layer, the middle gray is a cross groove 12; 3. Top layer of the first internal buffer layer; 4. Second internal buffer layer; 5. Third internal buffer layer; 6. Transmission layer three-axis electromagnetic effect chip; 7. Buffer filler; 8. First external buffer layer; 9. Second external buffer layer; 10. Third external buffer layer; 11. Transmission layer circuit board; 12. Cross groove. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] In some embodiments of the present application, a flexible multi-dimensional force sensor is disclosed, and its structure diagram is as follows: Figure 1 shown.

[0054] (1) The top layer is composed of a protective layer 1 with a raised structure. This layer can be made of various inert flexible substrate materials, such as soft silicone, PDMS, etc. The design idea is to protect the sensor from external corrosion, oxidation and other interference. At the same time, the raised structure has force-sensitive characteristics, especially sensitive to tangential force input. The thickness of this layer can be changed according to different usage scenarios, and it can also be changed to trapezoidal, spherical, conical and other shapes.

[0055] (2) Please refer to Figure 2 to Figure 7 , the second layer is a flexible magnetic film layer 2, which is the core layer of the sensor. The sensor uses a composite material made of rare earth magnetic materials and flexible base materials, such as NdFeB magnetic powder mixed with Ecoflex soft silicone, FeSmN magnetic powder mixed with Ecoflex soft silicone, etc., which can realize the sensing function. There is a cross groove 12 at the bottom of this layer. The groove surface is arc-shaped, and the center square area is formed by rounding the corners. The size of the center square area is related to the size of the magnetoelectric conversion chip of the fourth layer, and the former needs to be larger than the latter. The specific size and the corresponding preparation method can be seen in Example 1,

[0056] 2. After the preparation of this layer, it needs to be magnetized on a magnetizer to turn it into a permanent magnet. The magnetization direction of the magnetizer is the normal direction of the planar layer. The N pole can pass through the plane downward or the S pole can pass through the plane downward. The difference in direction only affects the positive and negative of the normal sensing signal. After force-magnetic field calibration, it does not affect the device performance.

[0057] (3) The third layer is the buffer layer. The buffer layer has an ingenious gradient stress structure, which can well balance the normal and tangential force deformation of the device. The layer first contains sub-layers with increasing gradients from top to bottom. Each gradient in the layer uses flexible strain materials with different ratios of materials (there is no restriction on specific base materials, only the hardness of the material is required to be adjustable through the preparation ratio). For example, the top layer of the gradient uses PDMS with 10% curing agent added, the middle layer uses PDMS with 30% curing agent added, and the bottom layer uses PDMS with 50% curing agent added. Such a gradient design allows the sensor to have different response slopes at different stress stages when subjected to stress, greatly improving the force measurement range of the device. In some specific examples, the buffer layer structure is such as Figure 1 As shown, the first internal buffer layer top layer 3, the second internal buffer layer 4, and the third internal buffer layer 5 are arranged from top to bottom in sequence above the outgoing layer three-axis electromagnetic effect chip 6, and the surrounding buffer filler 7. The first external buffer layer 8, the second external buffer layer, and the third external buffer layer 10 are arranged outside the buffer filler 7. The internal buffer layer and the external buffer layer can be arranged in a gradient. Those skilled in the art should also know that Figure 1 The structure in the figure is only an example, and the arrangement and number of buffer layers can be adjusted according to actual needs.

[0058] (4) The fourth layer is the output layer. This layer contains a magnetoelectric effect chip and the corresponding readout circuit of the chip. The magnetoelectric effect chip is required to be a chip with three-dimensional magnetic field sensing capability, and the optional devices are three-axis Hall sensors or three-axis magnetoresistive sensors, etc. Since the sensing mechanism of the sensor of the present application is a three-dimensional design on the magnetic field, the selection of different sensor chips has little effect on the decoupling and multi-directional sensing capabilities. It only affects the response time and range of the data. If the three-dimensional data is calibrated, it can show a stable three-dimensional decoupling and multi-dimensional force sensing effect. The circuit layer of this layer can be more suitable for the application scenario of the sensor. The attachment needs to adopt hard PCB or flexible PCB materials. For example, in curved surface integration, flexible PI material needs to be used as the circuit substrate. In some specific instances, the structure of the output layer is such as Figure 1 As shown, the outgoing layer three-axis electromagnetic effect chip 6 is arranged in the middle of the outgoing layer circuit board 11 , and its upper end surface is attached to the bottom surface of the third internal buffer layer 5 .

[0059] In some embodiments of the present application, the materials that can be used for each layer of the sensor are as follows:

[0060] (1) Protective layer 1: Inert flexible polymer materials such as Ecoflex silicone materials

[0061] (2) Magnetic film layer 2: NdFeB / polydimethylsiloxane (PDMS) and other magnetic flexible composite materials;

[0062] (3) Buffer layer: flexible materials such as PDMS or SEBS with different ratios

[0063] (4) Transmission layer: The substrate used for the circuit can be a silicon board or a PI flexible board.

[0064] In some embodiments of the present application, a centrally symmetrical arc edge microstructure is constructed in the second layer, i.e., the magnetic film layer 2, and a magnetic field with a gradient magnetic flux is formed on the lower surface and directly below the magnetic film layer 2, such as Figure 3 and Figure 4 As shown; the gradient magnetic field can form centripetal rotating magnetic flux lines in three-dimensional space, such as Figure 5 , Figure 6 , Figure 7 The decoupling principle of the three-dimensional magnetic field can be proved by the following mathematical derivation:

[0065] Through simulation, we know that the three-dimensional magnetic field can be expressed as the superposition of three orthogonal sine waves:

[0066] M x =M0sin(kx),M y =M0sin(kx),M z =M0cos(kx) (S1)

[0067] where k is the wave number and M0 is the maximum amplitude of each component. The static magneto-scalar potential under the magnetic film layer 2 is calculated by the second-order differential equation: Can be derived as:

[0068]

[0069] In MKS-SI units, the magnetic flux density B is proportional to the sum of the magnetic field H and the magnetization M, that is:

[0070] B=μ0(H+M)(S3)

[0071] where μ0 is the free space permeability, which is 4π×10 -7 H·m-1. The magnetic field H is a scalar potential The negative gradient of the magnetic material, the magnetization intensity M outside the magnetic material is zero:

[0072]

[0073] M=0(S5)

[0074] Combining equations (S2)-(S5), the magnetic flux density Bx (along the x-axis) and Bz (along the z-axis) below the magnetic film layer 2 can be obtained as:

[0075]

[0076]

[0077]

[0078] According to (S8), (S9) and (S10), we can calculate B at any point (x, z) or (y, z) on the xz plane or yz plane below the magnetic film layer 2. x , B y and B z The total (combined) magnetic flux density B and ratio R B as follows:

[0079]

[0080]

[0081]

[0082]

[0083] Then we can calculate the change in magnetic intensity (ΔB%) under displacement load along the z-axis (ΔZ) as follows:

[0084]

[0085] To summarize the above formula, the magnetic film layer 2 receives the normal pressure to form a longitudinal displacement ΔZ, that is, the magnetic field change caused by the displacement of the central part of the magnetic film layer 2 caused by the pressure is ΔB (%) = e kΔZ -1

[0086] When receiving the resultant force with tangential component, R B The displacement of the magnet in the x and y directions Δx, Δy and the displacement in the z direction Δz are calculated from the changes in A(x) and B(z).

[0087] From (S8) and (S9), we can get:

[0088]

[0089]

[0090]

[0091] Therefore, the shear component F of the external force F is x and the normal component F z They can be calculated using the displacements Δx and Δz of the magnet, respectively, since the applied force is linearly related to the corresponding displacement of the elastic material according to Hooke's law:

[0092]

[0093]

[0094]

[0095] Where S is the contact area, γ, ε, G, E, and h are the shear strain, normal strain, shear modulus, elastic modulus, and thickness of the elastic layer, respectively. For isotropic elastic materials, G = E / (2(1+V)), where V is the Poisson's ratio of the material. The center of the cross groove 12 of the magnetic film layer 2 is aligned with the center of the north magnetic pole of the three-axis Hall sensor, and the static state is used as the initial point, which can be regarded as setting the B(x, y, z) state to zero. Substituting Δx, Δy, and Δz in (S14-S16) and introducing four compensation coefficients, the decoupling calculation formula for arbitrary directional forces on the three axes can be obtained:

[0096]

[0097]

[0098]

[0099] Where c1 and c2 are the compensation coefficients for the elastic modulus and shear modulus, respectively, because the overall elastic / shear modulus of the sensor is the result of the modulus of the top or middle layer (and some invisible defects in the manufacturing process). b1-b3 are systematic deviations to represent the calibration of the fourth layer magnetoelectric chip signal in different applications.

[0100] Embodiment 1:

[0101] This embodiment discloses the preparation of the above-mentioned sensor, specifically using the following materials:

[0102] (1) Protective layer 1: Ecoflex-0030 material; thickness 1 mm, trapezoidal; bottom length and width are 10 mm*10 mm, top length and width are 6 mm*6 mm.

[0103] (2) Magnetic film layer 2: NdFeB / Ecoflex-0030; length and width are 10 mm*10 mm, thickness is 1 mm; bottom groove depth is 0.5 mm, and the size of the center area of ​​the groove is 3 mm*3 mm.

[0104] (3) Buffer layer: The gradient layer uses PDMS with a thickness of 0.5 mm, the top layer is 5 mm*5 mm in length and width, and the gradient is +1 mm / layer; the filling layer uses Ecoflex-0030 with a thickness of 2 mm and a length and width of 10 mm*10 mm.

[0105] (4) Transmission layer: A three-axis Hall sensor chip is used, the length and width of the chip are 3mm*3mm, and the PCB substrate uses a silicon substrate with an overall thickness of 1.2mm.

[0106] Preparation process:

[0107] 1. Design a mold according to the thickness and shape of each layer and perform 3D modeling, and use a 3D printer to prepare the mold; pay attention to the mold design for the cross groove 12 structure of the second layer, that is, the magnetic film layer 2;

[0108] 2. Position the PCB of the outgoing layer (the fourth layer) and mark the center of the Hall sensor chip, and the preparation of the fourth layer is completed;

[0109] 3. Mix the PDMS solution and its curing agent in a ratio of 10:1, stir mechanically for 2-3 minutes, pressurize to defoam for 0.5 minutes, pour into the gradient structure mold, cure at 80 degrees Celsius for one hour, take out, align the four-layer Hall sensor chip, place the gradient structure in the designed position, pour in the solution Ecoflex-0030 for filling, and heat cure to prepare the third layer;

[0110] 4. Prepare Ecoflex-0030 mixed solution, then add 5 micron diameter mixed NdFeB rare earth material, and stir it with Ecoflex-0030 mixed solution at a ratio of 1:1 using a planetary gravity mixer at ultra-high speed for 2 minutes, and pressurize and rotate to defoam for 0.5 minutes, then pour it into the mold of magnetic film layer 2 structure, take it out after thermal curing to form a film, put it into a unidirectional magnetizing magnetizer, magnetize the lower surface with the north pole, and the magnetizing intensity is 2T, that is, the magnetic film layer 2 is prepared, and adhere it on the top of the buffer layer with silicone rubber adhesive, and pay attention to the center alignment;

[0111] 5. At the same time, pour the solution of Ecoflex-0030 into the mold corresponding to the top layer, take it out after thermal curing to form a film, prepare the protective layer 1, and use silicone rubber adhesive to adhere it on the top of the magnetic film layer 2. Pay attention to the center alignment, and the device preparation is completed.

[0112] like Figure 8 and Fig. 9 As shown, the sensor prepared by the above method can be connected to the Arduino host computer to communicate with the computer and transmit three-dimensional sensing signals. After the force test of the press on three axes, it can be seen that the sensor applies pressure to the three axes, and the magnetic field responses on the three axes do not interfere with each other. When pressure is applied to multiple arbitrary directions in the horizontal direction, the magnetic fields of the x-axis and y-axis can distinguish different directions with high precision, proving that it has good decoupling.

[0113] Embodiment 2:

[0114] This embodiment discloses the preparation of the above-mentioned sensor, specifically using the following materials:

[0115] (1) Protective layer 1: Ecoflex-0030 material; thickness 1 mm, semicircular; bottom length and width 3 mm*3 mm.

[0116] (2) Magnetic film layer 2: NdFeB / Ecoflex-0030; thickness 0.5 mm, bottom groove depth 0.25 mm; length and width 3 mm*3 mm.

[0117] (3) Buffer layer: The gradient layer uses Ecoflex-0030 with a thickness of 0.5 mm, the top layer is 1 mm*1 mm in length and width, and the gradient is +1 mm / layer; the filling layer uses Ecoflex-0010 with a thickness of 1 mm and a length and width of 3 mm*3 mm.

[0118] (4) Transmission layer: A three-axis Hall sensor chip is used, the length and width of the chip are 3mm*3mm, and the PCB substrate uses a flexible PI substrate with an overall thickness of 1mm.

[0119] Preparation process:

[0120] 1. According to the thickness of each layer, the material preparation and thermal curing process of each layer in Example 1 are followed to prepare a four-layer film with a smooth surface;

[0121] 2. Perform low-power laser engraving on the structures of the protective layer 1, magnetic film layer 2, and buffer layer to etch out the designed structure and shape, such as Fig.10 As shown;

[0122] 3. Glue the four-layer structure together with soft silicone adhesive, and pay attention to the alignment of the center of the magnetoelectric chip with the four layers above.

[0123] According to the above-mentioned embodiments, the sensor device of the present application can be applied in the field of machine touch perception, for example, it can be applied in the touch component of a robot. Fig.11 and Fig.12 As shown, when the robot touches the human skin, it finds a lump. The sensor receives an increase in the oblique force, and the magnetic fields of the x and z axes change. After that, it is pressed several times to determine that it is a lump.

[0124] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0125] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A flexible multi-dimensional force sensor, characterized in that: From top to bottom, they include: a protective layer including a flexible base material having force-sensitive properties; The magnetic film layer has a cross-shaped groove on the bottom surface, and the edge of the groove is arc-shaped, which can form a centripetal magnetic field with a gradient magnetic flux; a buffer layer including a strain material in a stepped shape; And, the transmission layer includes an electromagnetic effect chip with three-axis magnetic field sensing capability and a readout circuit thereof.

2. The flexible multi-dimensional force sensor according to claim 1, characterized in that: The cross section of the protective layer is trapezoidal, spherical or conical.

3. The flexible multi-dimensional force sensor according to claim 1, characterized in that: The hardness of the stepped strain material increases from top to bottom.

4. The flexible multi-dimensional force sensor according to claim 1, characterized in that: The electromagnetic effect chip is a three-axis Hall sensor chip or a three-axis magnetoresistive sensor chip.

5. The flexible multi-dimensional force sensor according to claim 1, characterized in that: The material of the magnetic film layer is a polymer material formed by a composite of a rare earth magnetic material and a flexible polymer material.

6. The flexible multi-dimensional force sensor according to claim 1, characterized in that: The center of the cross-shaped groove of the magnetic film layer is in a straight line with the center of the north magnetic pole of the electromagnetic effect chip.

7. A method for preparing a flexible multi-dimensional force sensor, characterized in that: The following steps are involved: A structure having a cross-shaped groove at the bottom is obtained by mold forming or etching, and the edge of the groove is arc-shaped; a magnetic field density modulus with a decreasing gradient toward the center is induced, a centripetal gradient magnetic field is formed in the central area of ​​the cross-shaped groove, and the magnetic flux density gradient decreases, thereby obtaining a magnetic film layer; A buffer layer having a stepped shape is prepared by mold forming or etching forming; An electromagnetic effect chip with three-axis magnetic field sensing capability and a readout circuit thereof are provided as an output layer; The transmission layer, the buffer layer, the magnetic film layer and the protective layer formed by the mold are bonded and assembled from bottom to top to obtain the flexible multi-dimensional force sensor.

8. The flexible multi-dimensional force sensor decoupling method according to any one of claims 1 to 6, characterized in that: The following steps are involved: The centripetal magnetic field of the magnetic film layer is represented as a superposition of three sine waves in orthogonality; The magnetic flux density and ratio under the magnetic film layer are calculated by using the magnetostatic scalar potential, magnetic field and magnetization intensity; Calculate the deformation in the x, y, and z directions in the three-dimensional coordinate system according to the magnetic flux density and the ratio; According to Hooke's law, the three-dimensional force is calculated by the contact area, shear modulus / elastic modulus, the deformation amount and thickness.

9. Use of the magnetic film layer according to any one of claims 1 to 6 in inducing a centripetal gradient magnetic field, characterized in that: The magnetic film layer can induce a magnetic field density modulus that gradually decreases toward the center through the cross groove structure, forming a centripetal gradient magnetic field in the cross center area; and the magnetic flux density gradient decreases.

10. A robot, characterized in that: The flexible multi-dimensional force sensor comprises any one of claims 1 to 6.

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