Three-dimensional force-temperature dual-mode tactile sensor based on magnetic thin film

Abstract

The invention relates to a three-dimensional force-temperature dual-mode tactile sensor based on a magnetic thin film. The sensor comprises a graphene-silica gel elastomer, a thermocouple, a magnetic film, an elastomer strut, a wrapping body, a Z-axis TMR element and a flexible printed circuit board, wherein the three Z-axis TMR elements are distributed on the flexible printed circuit board in a right-angle shape; the wrapping body covers the flexible printed circuit board and wraps the Z-axis TMR element array therein; the five elastomer supporting columns are distributed on the wrapping body in a five-point plum blossom shape; the graphene-silica gel elastomer is fixed on the five elastomer supporting columns; a magnetic film and a thermocouple are wrapped in the graphene-silica gel elastomer, and the thermocouple is located on the magnetic film. The touch sensor has the advantages of being low in hysteresis, high in resolution, high in sensitivity, easy to decouple and multifunctional, and double information sensing of external three-dimensional force and temperature can be achieved at the same time.

Description

Technical Field

[0001] Based on the edge effect of magnetic film and the Seebeck effect of thermocouple, the present invention manufactures a dual-mode tactile sensor with three-dimensional force and temperature information measurement functions. The sensor can simultaneously realize the decoupling of three-dimensional force and the detection of external temperature information, helping the robot hand to realize various types of grasping operations. Background Art

[0002] With the continuous development of robotics and artificial intelligence technology, flexible tactile sensors with more environmental information perception capabilities have attracted widespread attention. Tactile sensors are an important component of robotic systems and are the basis for helping intelligent robots accurately and timely perceive various external physical stimuli. It is of great significance to develop miniaturized, multifunctional, integrated, and low-hysteresis tactile sensors.

[0003] At present, a variety of tactile sensors that can measure single-direction force have been born one after another. At present, the research direction of force tactile sensors has gradually shifted towards obtaining three-dimensional force information, but there are relatively few studies on dual-modal tactile sensors that combine three-dimensional force and temperature. Compared with three-dimensional force tactile sensors with other sensing mechanisms such as capacitive, piezoelectric, and resistive, magnetic sensors have the advantages of low hysteresis, high sensitivity, and high physical robustness.

[0004] The patent (application number 202210973441.4) uses pillars and magnetic films as the basic structure. The magnetic film is suspended above the giant magnetoresistive element by four elastomeric pillars. The tilt deformation of the pillars under tangential force is used to move the magnetic film. The giant magnetoresistive element below is used to detect changes in the magnetic field signal, which mainly realizes the measurement of tangential force; however, the invention is limited to the measurement of tangential force, and cannot realize the detection of three-dimensional force. In addition, the response to external signals is single, and it does not have other environmental stimulus response functions. It cannot realize the three-dimensional force detection function, has narrow applicability, and is difficult to be used in the actual operation of the robot arm. Summary of the invention

[0005] In view of the lack of current research on three-dimensional force-temperature dual-mode tactile sensors, the present invention provides a dual-mode tactile sensor based on a double-layer film, a right-angle TMR array and a pillar structure, and proposes an effective means of utilizing the edge effect of the magnetic field of the magnetic film. The sensor uses a magnetic film and a right-angle TMR array to form a three-dimensional force perception; the right-angle TMR array, the TMR element in the center is used to detect the normal force, and the edge TMR element is used to detect the special magnetic field generated by the edge effect to complete the detection of shear force and the decoupling of the three-dimensional force, overcoming the neglect or suppression of the effect of the magnetic field distortion caused by the edge effect on the sensor; the thermocouple, as the temperature sensing part, is wrapped and protected by an organic elastomer doped with graphene, and generates a voltage signal under the influence of the external temperature, and is not affected by stress. The tactile sensor of the present invention has the characteristics of low hysteresis, high resolution, high sensitivity, easy decoupling, and multi-function, and can simultaneously realize the dual information perception of external three-dimensional force and temperature.

[0006] The technical solution of the present invention is:

[0007] A three-dimensional force-temperature dual-mode tactile sensor based on a magnetic film, the sensor comprising a graphene-silicone elastomer, a thermocouple, a magnetic film, an elastomer support, an attached body, a Z-axis TMR element and a flexible printed circuit board;

[0008] Among them, three Z-axis TMR elements are distributed on the flexible printed circuit board in a right angle shape; the attachment body covers the flexible printed circuit board and wraps the Z-axis TMR element array therein; five elastic body pillars are distributed on the attachment body in a five-point plum blossom shape (that is, four are distributed in a square shape on the periphery, and the fifth is in the center); the graphene-silicone elastomer is fixed on the five elastic body pillars; a magnetic film and a thermocouple are wrapped in the graphene-silicone elastomer, and the thermocouple is located on the magnetic film;

[0009] The rectangular array distribution is that on the square projection of the square magnetic film, there is a Z-axis TMR element in the center, and there is a Z-axis TMR element in the middle of each of the two adjacent sides of the square;

[0010] The projections of the center of the magnetic film, the center of the square formed by the five elastic pillars, and the magnetic field measurement point of the Z-axis TMR element at the right angle point overlap;

[0011] The magnetic film is made of a mixture of NdFeB particles and PDMS silica gel, with a mass ratio of 3:1, and the magnetization direction is along the height direction of the film;

[0012] The wrapping body is epoxy resin with a thickness of 1.2 to 1.4 mm;

[0013] The TMR element model is TMR2505;

[0014] The particle size of the NdFeB particles is 30-50 μm;

[0015] The particle size of the graphene nanoparticles is 20 to 40 nm;

[0016] The graphene-silicone elastomer is made by mixing Smooth-On's Ecoflex00-30 series A agent, B agent and graphene nanoparticles in a mass ratio of 5:5:1. The upper surface of the elastomer is square with a side length of 9 to 11 mm and a thickness of 1 to 2 mm.

[0017] The magnetic film layer has a side length of 7 to 9 mm and a thickness of 400 to 600 μm;

[0018] The thermocouple is a thin-sheet thermocouple, and the temperature measuring part is 5 to 6 mm long and 0.08 to 0.16 mm wide;

[0019] The elastic pillar has a radius of 0.8 to 1.2 mm and a height of 1.8 to 2.3 mm;

[0020] The center of the magnetic film is aligned with the TMR element at the center of the sensing layer in the vertical direction, and the midpoints of two adjacent sides of the magnetic film are aligned with the other two TMR elements in the vertical direction respectively;

[0021] The distance between the lower surface of the magnetic film and the TMR element is 2 to 2.5 mm.

[0022] The essential features of the present invention are:

[0023] In current technology, magnetic film tactile sensors mainly realize sensing functions based on the internal uniform magnetic field after ignoring the edge effect, and there are few studies on the dual-modal tactile perception of three-dimensional force and temperature;

[0024] The present invention mainly utilizes the special magnetic field distribution in the edge area of ​​the magnetic film, based on the magnetic field change caused by the regular spatial displacement of the magnetic film suspended by the elastic body pillar under the external force, and realizes the decoupling of three-dimensional force through the special position relationship between the Z-axis TMR2505 array arranged at a right angle directly below the magnetic film and the magnetic film; the temperature sensing layer utilizes the graphene-silicone elastomer to increase the thermal conductivity and temperature uniformity of the upper layer of the sensor, and realizes temperature detection based on the Seebeck effect of the thermocouple; the thin film thermocouple used is small in size and less affected by stress, and the graphene-silicone elastomer used protects the temperature sensing part (thermocouple) while enabling the sensor to obtain better response speed and temperature sensing ability, that is, the buffering effect of the graphene-silicone elastomer is utilized to further reduce the stress applied to the thin film thermocouple and avoid coupling caused by stress. At the same time, the insulating graphene-silicone elastomer can improve the disadvantage that the thermocouple cannot measure the temperature of objects with poor insulation;

[0025] The present invention can detect two external environmental factors at the same time without interfering with each other. The decoupling principle of three-dimensional force is simple, the sensitivity of tangential force is greatly improved, the temperature perception effect is optimized while ensuring flexibility, and the joint detection of three-dimensional force and temperature information is realized, with multi-information perception function.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention utilizes a NdFeB-Si elastomer magnetic film with high magnetic properties and strong flexibility as a three-dimensional force sensing part, and utilizes the difference in magnetic field distribution between the center and edge of the magnetic film and the relative position relationship between the right-angle TMR array and the magnetic film to achieve decoupling of the three-dimensional force; since the magnetic film is magnetized in the vertical direction, the magnetic field direction in the central area is uniform and only along the Z-axis direction (the Z-axis refers to the axis parallel to the height of the sensor), while the Z-axis magnetic field components in the areas below the four sides are not uniform and contain magnetic field components in other directions, which results in that when the magnetic film is horizontally displaced, the Z-axis magnetic field component below the central area will not change, while the Z-axis magnetic field component below the edge part will change; when the upper magnetic film is subjected to normal pressure, the elastic support is compressed, and the magnetic film produces a vertical spatial displacement, which causes the surrounding space magnetic field to change; the Z-axis TMR element located directly below the center of the magnetic film detects the Z-axis magnetic field component of the central part of the magnetic film, and generates a regular voltage output when the sensor is subjected to normal pressure; when the upper magnetic film is subjected to horizontal tangential force, the elastic support is compressed, and the magnetic film produces a vertical spatial displacement, which causes the surrounding space magnetic field to change; the Z-axis TMR element located directly below the center of the magnetic film detects the Z-axis magnetic field component of the central part of the magnetic film, and generates a regular voltage output when the sensor is subjected to normal pressure; When the pillar tilts, the magnetic film produces a horizontal spatial displacement, which causes the magnetic field in the surrounding space to change. The two Z-axis TMR elements located directly below the edge of the magnetic film detect the unevenly distributed Z-axis magnetic field component below the edge of the magnetic film, and produce another regular voltage output when the sensor is subjected to a horizontal tangential force. When the upper magnetic film is subjected to a three-dimensional force in any direction, the magnetic film simultaneously produces a horizontal and vertical spatial displacement. The magnetic field change located directly below the center of the magnetic film only comes from the vertical displacement of the magnetic film. Therefore, the output of the central Z-axis TMR element only represents the magnitude of the normal force, and the outputs of the two TMR elements located directly below the two mutually perpendicular sides of the magnetic film represent the coupling of the X-axis tangential force and the normal force and the coupling of the Y-axis tangential force and the normal force (the X and Y axes refer to the two directions parallel to the two mutually perpendicular sides of the square magnetic film). This coupling is regular and can be expressed by a formula. Therefore, based on the different outputs of these three TMR elements, the components of the three-dimensional force in the X, Y, and Z directions can be easily decomposed to achieve the measurement of three-dimensional force.

[0028] 2. Compared with the prior art, the present invention provides an effective means of utilizing the edge effect of magnetic films, and proposes a three-dimensional force decoupling method;

[0029] 3. The present invention can obtain sensing devices with different force measurement ranges and sensitivities by adjusting the Young's modulus of the elastic support (when an elastic body with a higher Young's modulus is used, the force measurement range will be increased and the sensitivity will be reduced; when an elastic body with a lower Young's modulus is used, the force measurement range will be reduced and the sensitivity will be increased.), which is more flexible in selection and application range;

[0030] 4. The temperature sensing layer of the present invention adopts graphene-silicone elastomer. Graphene has high thermal conductivity and can effectively improve thermal conductivity after mixing with silica gel ( Fig. 9 As shown), a temperature-sensing layer with high thermal conductivity and high flexibility is obtained, and the surface temperature of the sensor can be made more uniform;

[0031] 5. The present invention uses the Seebeck effect of thermocouple to measure temperature, avoiding the coupling of pressure and temperature and simplifying data analysis;

[0032] 6. The present invention adopts a unique geometric spatial distribution and uses appropriate geometric parameters to ensure a highly regular output within the measurement range, and obtains a highly sensitive micro-force detection function. For the embodiment cited, a shear force measurement sensitivity of 908.57mV / N has been obtained, which is three times the sensitivity of the patent "202420976957.9 A cross-shaped three-dimensional force tactile sensor".

[0033] 7. Compared with the existing three-dimensional force measurement technology, the overall size of the present invention is smaller, the length and width of the sensing part are only 10-12 mm, and the height is 4-4.5 mm. It can be arranged into an array as a unit for application as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a structural breakdown diagram of a three-dimensional force-temperature dual-modal tactile sensor;

[0035] Figure 2 is an assembly perspective view of a three-dimensional force-temperature dual-modal tactile sensor;

[0036] Figure 3 This is the overall appearance of the three-dimensional force-temperature dual-modal tactile sensor;

[0037] Figure 4 is a top perspective view of a three-dimensional force-temperature dual-modal tactile sensor;

[0038] Figure 5 is a diagram of a rectangular array of TMR elements of a three-dimensional force-temperature dual-modal tactile sensor;

[0039] Figure 6 It is the normal force characteristic test output diagram of the three-dimensional force-temperature dual-mode tactile sensor;

[0040] Figure 7It is the output diagram of the tangential force characteristic test of the three-dimensional force-temperature dual-mode tactile sensor;

[0041] Figure 8 This is a test diagram of the force response time of the three-dimensional force-temperature dual-mode tactile sensor;

[0042] Fig. 9 is the temperature response curve of the three-dimensional force-temperature dual-modal tactile sensor;

[0043] Among them, 1-graphene-silicone elastomer, 2-thermocouple, 3-magnetic film, 4-elastomeric pillar, 5-wrapped body, 6-Z-axis TMR element, 7-flexible printed circuit board, 8-x-edge TMR element, 9-center TMR element, 10-y-edge TMR element. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings. 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.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] The sensor comprises a sensing layer, a supporting layer and a receiving layer;

[0047] The sensing layer includes a magnetic film, a thermocouple, and a graphene-silicone elastomer;

[0048] The support layer is composed of five elastic support pillars; among them, four elastic support pillars are located below the four corners of the square magnetic film layer, and one elastic support pillar is located below the center of the magnetic film layer;

[0049] The receiving layer includes a wrapper, a TMR array and a flexible printed circuit board;

[0050] The dual-mode tactile sensor of this embodiment is as follows Figure 2As shown. The graphene-silicone elastomer 1 is 10mm long, 10mm wide, and 1.5mm high. The internal K-type thermocouple 2 is 6mm long, 1mm wide, and 0.16mm high. The magnetic film 3 is 8mm long, 8mm wide, and 0.5mm high. The radius of the elastomer support 4 is 1mm and the height is 2mm. The magnetic sensitive direction of TMR2505 is the Z-axis direction. The package form is SOT23-5, 3mm long, 3mm wide, and 1mm high. The TMR element array 6, the magnetic film layer 3, and the graphene-transfer elastomer 1 are all placed in parallel, and the three TMR2505s are distributed at right angles. The top view is as shown. Figure 4 , Figure 5 As shown, the midpoints of the graphene-silicone elastomer 1 and the magnetic film 3 are aligned with the central TMR element 9, the magnetic field measurement point of the x-edge TMR element 8 is 4 mm to the left of the magnetic field measurement point of the central TMR element 9, and is aligned with the center of one edge of the magnetic film, the magnetic field measurement point of the y-edge TMR element is 4 mm below the magnetic field measurement point of the central TMR element 9, and is aligned with the center of the other edge of the magnetic film, and the TMR element is wrapped by the wrapping layer 5. When measuring normal static pressure, the force measurement range remains linear within 0-1N, the sensitivity is 123.25mV / N, and the maximum force measurement range can reach 0-20N. When measuring static tangential force, the force measurement range remains linear within 0-0.1N, and the sensitivity is 908.57mV / N.

[0051] The software and protocols involved in the present invention are all known technologies.

[0052] The present invention is further described in detail below in conjunction with the accompanying drawings. This embodiment is only a specific description of the invention and is not to be regarded as limiting the scope of protection.

[0053] Example 1

[0054] The present invention designs a three-dimensional force-temperature dual-mode tactile sensor based on the edge effect of square NdFeB magnetic film, the Seebeck effect of thermocouple and the tunnel magnetoresistance effect of TMR element. The structural decomposition diagram is shown in FIG. Figure 1 As shown, it is composed of a graphene-silicone elastomer 1, a thermocouple 2, a magnetic film 3, an elastomer support 4, an attached body 5, a Z-axis TMR element 6 and a flexible printed circuit board 7;

[0055] Among them, three Z-axis TMR elements 6 are distributed in a right angle shape (i.e. one is in the center of the circuit board, and the other two are respectively located at the edge centers of two adjacent sides of the circuit board) on the flexible printed circuit board 7; the attachment 5 covers the flexible printed circuit board 7 and attaches the Z-axis TMR element array 6 therein; five elastic body pillars 4 are distributed in a five-point plum blossom shape (i.e. four are distributed in a square shape at the periphery, and the fifth is in the center) on the attachment 5; the graphene-silicone elastomer 1 is fixed on the five elastic body pillars 4; the graphene-silicone elastomer 1 is attached with a magnetic film 3 and a thermocouple 2, and the thermocouple 2 is located on the magnetic film 3. Since there are five pillars supporting it from below and it is integrally manufactured and formed in the viscosity stage of the silicone, it has structural stability.

[0056] The rectangular array distribution is that on the square projection of the square magnetic film, there is a Z-axis TMR element in the center, and there is a Z-axis TMR element in the middle of each of the two adjacent sides of the square;

[0057] The center of the magnetic film 3, the center of the square formed by the five elastic pillars 4 and the projection of the magnetic field measurement point of the Z-axis TMR element 6 at the right angle point overlap;

[0058] The magnetic field measurement point refers to the effective area where the TMR element measures the magnetic field;

[0059] The sensor is composed of a thermocouple 2 and a magnetic film 3 wrapped by a graphene-silicone elastomer 1 to sense external environmental stimuli. The TMR right-angle array 6 receives three-dimensional force signals and serves as the core of three-dimensional force decoupling with the square magnetic film 3. The sensor can accurately obtain three-dimensional force information and temperature information at the same time.

[0060] For ease of description, the following Figure 5 An XY coordinate system on a horizontal plane is established based on the coordinate axes shown, and the angle φ is used to assist in explaining the direction of the shear force applied in the experiment. The TMR element located at the center is called the center TMR element 9, the TMR element located on the left is called the x-edge TMR element 8, and the TMR element located at the bottom is called the y-edge TMR element 10;

[0061] When an external force is applied to the sensor surface, the magnetic film layer 3 based on the elastic support 5 undergoes regular spatial displacement, causing the magnetic field below to change. The signal of the magnetic field change is received by the three Z-axis TMR2505 elements and converted into a voltage signal through the internal tunnel magnetoresistance effect. The voltage signal data is collected by the data acquisition card and visualized by the computer. Figure 4As shown, three TMR2505 elements are distributed in a right-angle array on the flexible printed circuit board 7 and are integrally cast inside the attached body 5. The central magnetic field of the magnetic film magnetized along the Z-axis direction is uniform and only along the Z-axis direction. The vertical component of the edge magnetic field in the Z-axis direction remains uniform in a specific direction and changes in another specific direction. The central TMR element 9 is used to sense the normal component of the external force and will not produce output under the action of a single tangential force. The x-edge TMR element 8 and the y-edge TMR element 10 located below the edge of the magnetic film are used to sense and decouple the X component and Y component of the external force on the horizontal plane, respectively. When the surface temperature of the sensor changes, the temperature of the graphene-silicone elastomer 1 changes rapidly, and the internal thermocouple 2 generates an electric potential based on the Seebeck effect, and the data is visualized through the post-processing circuit and the computer;

[0062] The magnetic film 3 is composed of PDMS prepolymer, curing agent (hydrogen-containing silicone oil), NdFeB particles (Nd2Fe 14 B1) mixed in a mass ratio of 10:1:33, put into a stirrer and stirred for 120 minutes to obtain a NdFeB-silicone prepolymer; put the NdFeB-silicone prepolymer into a degassing machine to degas for 30 minutes, pour the degassing prepolymer into a 3D printed metal mold, heat at 80°C for 1h to solidify, and obtain a NdFeB-silicone elastic film; lay the NdFeB-silicone elastic film flat in a magnetizer for magnetization, and the magnetization direction is perpendicular to the surface of the magnetic film to obtain a magnetic film 3;

[0063] The particle size of the NdFeB particles is 40 μm;

[0064] The inner shape of the metal mold is a cuboid of 8mm×8mm×0.5mm;

[0065] The graphene-silicone elastomer 1 is prepared by mixing the Ecoflex00-30 series A agent and B agent of Smooth-On Company with graphene nanoparticles in a mass ratio of 5:5:1, and putting it into a blender for stirring for 60 minutes to obtain a graphene-silicone prepolymer; putting the graphene-silicone prepolymer into a degassing machine for degassing for 30 minutes; placing the thermocouple 2 and the magnetic film 3 at the center of the 3D printed rectangular parallelepiped mold, slowly pouring the degassing graphene-silicone prepolymer into the mold, and then curing it at room temperature for 4 hours to obtain a connector for the sensing layer;

[0066] The particle size of the graphene nanoparticles is 30 nm;

[0067] The inner shape of the rectangular parallelepiped mold is a rectangular parallelepiped of 10mm×10mm×1.2mm;

[0068] The thermocouple 2 is a K-type thin-film thermocouple with a length of 6 mm, a width of 1 mm, and a thickness of 0.16 mm.

[0069] The elastomer pillar 4 is prepared by mixing the Ecoflex00-30 series A agent and B agent of Smooth-On Company in a ratio of 1:1, and then put it into a stirrer for 10 minutes and then put it into a defoamer for 30 minutes to obtain a prepolymer, and then pour the prepolymer into a 3D printed cylindrical resin mold, and lay the prepared sensing layer on the top, and let it stand at room temperature for 4 hours to obtain a connector between the pillar layer and the sensing layer;

[0070] The exact center of the square graphene-silicone elastomer, the temperature measuring point of the thermocouple, and the exact center of the square magnetic film are aligned; the temperature measuring point of the thermocouple is located above the square magnetic film;

[0071] The cylindrical resin mold has five cylindrical holes with a hole radius of 1 mm and a height of 2 mm; four of the cylindrical holes are located at the four corners of a square, 8 mm apart, and the fifth hole is located in the center of the square;

[0072] The wrapping body 5 is prepared by mixing epoxy resin agent A and agent B at a mass ratio of 2.5:1, and after stirring for 5 minutes, is cast on the flexible printed circuit board 7 welded with the TMR element 6 with the aid of a mold;

[0073] The wrapping body is 12 mm long, 12 mm wide and 1.2 mm high;

[0074] The TMR element is TMR2505, packaged as SOT23-5; the TMR array is arranged as follows Figure 5 As shown, three TMR2505s are distributed at right angles, with a center distance of 4 mm;

[0075] The overall appearance of the three-dimensional force-temperature dual-mode tactile sensor is shown in FIG. Figure 3 As shown, it is 12mm long, 12mm wide and 4.5mm high; when a normal force is applied to the upper surface, the elastic pillar 4 is compressed, and it quickly returns to its original state after the pressure is removed; when a tangential force is applied to the side, the elastic pillar 4 is transversely deformed, and it quickly returns to its original state after the pressure is removed. It is known from experiments that the elastic body will not undergo plastic deformation within the experimental force measurement range; after the upper surface is used to contact objects of different temperatures within the temperature measurement range, temperature data can be quickly obtained, and the magnetic field distribution of the lower magnetic film and the output of the TMR element 6 will not be affected;

[0076] The thickness of the flexible printed circuit board is 0.1 mm, and the output is connected to a data acquisition card to collect voltage output signals;

[0077] The thermocouple is connected to a post-processing circuit and a temperature signal is output by a computer;

[0078] Embodiment 2-6

[0079] On the basis of the same embodiment 1, the side length of the magnetic film layer 2 is changed to 8mm, 10mm, 12mm, 14mm, and 16mm respectively, and the bottom TMR array is kept still directly below the center and edge of the magnetic film layer 3; a tangential force of 0.1N is applied to the sensor along the positive direction of the X-axis using a digital push-pull gauge;

[0080] The experiment found that with the increase of the side length of the magnetic film layer 3, the output change of the central TMR element 9 when the sensor is subjected to the same magnitude of tangential force first increases and then decreases. When a magnetic film with a side length of 8 mm is selected, the output of the central TMR element 9 is almost unchanged under the influence of the tangential force. When the side length is 12 mm, the output voltage change of TMR element 9 No. 1 is the largest, and when the side length is 16 mm, the output of the central TMR element 9 has only a slight change. This shows that the magnetic field in the central area of ​​the magnetic film with a side length of 8 mm and the magnetic film with a side length of more than 16 mm is more uniform. Considering the miniaturization of the sensor, the magnetic film layer with a side length of 8 mm should be the best choice.

[0081] Embodiment 7-9

[0082] On the basis of the same embodiment 1, the distance between the lower surface of the magnetic film and the TMR element was changed to 1mm, 2mm, and 3mm respectively, and a tangential force of 0.05N was applied to the sensor along the positive direction of the X-axis using a digital push-pull gauge;

[0083] The experiment found that as the distance between the lower surface of the magnetic film and the TMR element increases, the output peak of the central TMR element 9 first decreases and then increases when the sensor is subjected to the same magnitude of tangential force. That is, a distance that is too close or too far will lead to an uneven magnetic field at TMR element No. 1 9. When the height is 2mm, the output of TMR element No. 1 remains almost unchanged under the influence of the tangential force. Therefore, it is most ideal to keep the distance between the lower surface of the magnetic film and the TMR element at around 2mm. Considering the downward displacement of the magnetic film during the use of the sensor, 2 to 2.5mm is selected as the appropriate range.

[0084] Example 10

[0085] The static normal force characteristic test is performed on the dual-mode tactile sensor. The main purpose of this embodiment is to determine the static force measurement range, input-output relationship and static force sensitivity of the sensor.

[0086] The test platform consists of a digital push-pull force gauge (Eidelberg HP-30), a DC regulated power supply (HY3005B), a dynamic data acquisition card (DH8301) and a computer. Figure 2 As shown, the sensor is assembled and fixed on the base of the digital push-pull force gauge. A DC regulated power supply is used to power the TMR element, and the output of the TMR element is connected to the data acquisition card.

[0087] Experimental process and results: Set the step size to 0.2N, use a digital push-pull meter to apply a normal force in the vertical downward direction, the maximum is 0-2N, and keep the external force for a few seconds each time, and then remove the external force. The output voltage of the TMR element 9 in the center of the sensor is as follows Figure 6 The output voltage of the central TMR element 9 shows a good linear relationship with the pressure in the range of 0-1N. The output voltage can remain stable under constant pressure and quickly returns to 0 after the external force is removed. The sensor has good static characteristics. When the pressure is 1N, the sensitivity is 123.25mV / N.

[0088] Embodiment 11

[0089] Test the output of the dual-mode tactile sensor when a static tangential force is applied. The main purpose of this embodiment is to test the sensor's recognition of the tangential force direction and the tangential force sensitivity, and to determine the relationship between the output voltage and the force.

[0090] Test platform construction: Figure 2 As shown in the figure, the three-dimensional force sensor is assembled and fixed on the angle table, placed on the base of the push-pull force gauge, the transmission rod of the digital push-pull force gauge is aligned with the sensor sensing layer, a DC regulated power supply is used to power the TMR element, and the element output is connected to the data acquisition card.

[0091] Experimental process and results: The sensor position was changed so that the tangential force angles φ applied by the push-pull force gauge were 0°, 90°, 180°, and 270° respectively. The force step was set to 0.02N, and a tangential force of 0-0.1N was applied using a digital push-pull gauge. For the tangential force along the x-axis, the output voltage of the x-edge TMR element 8 is as follows: Figure 7 As shown. The x-edge TMR element 8 has a good linear relationship between the tangential force and the output voltage in the force measurement range of 0-0.1N in the positive and negative directions. The output voltage can remain stable under a constant tangential force and quickly returns to 0 after the external force is removed. The sensor has good static characteristics. The uniaxial tangential force measurement range is 0-0.1N. When the X-axis component of the tangential force is 0.1N, the sensitivity is 908.57mV / N.

[0092] Examples 12-13

[0093] Testing the dynamic force performance of the dual-modal tactile sensor. The main purpose of this embodiment is to verify the dynamic performance of the sensor and preliminarily test the sensor response time and recovery time.

[0094] Test platform construction: The test platform includes a signal generator (AFG2021-SC), a power amplifier (MB500VI), and an exciter (MODAL50). The signal output by the signal generator is transmitted to the exciter through the power amplifier, and the driving rod acts on the receiving layer of the sensor. The DC regulated power supply supplies power to the TMR element, and the element output is connected to the data acquisition card. The output voltage sampling frequency of the TMR element is 1kHz, the sampling time is 1s, and the output waveform is sent to the computer.

[0095] Experimental process and results: Use a signal generator to output a 4Hz square wave force signal, apply a square wave normal force with a frequency of 4Hz and an amplitude of 0.5N to the sensor contact through a signal amplifier, process the output voltage of the central TMR element 9, and obtain the average output voltage waveform. The waveform of one cycle is intercepted as shown in the figure. Figure 8 As shown, the response time of the sensor normal force is 38ms and the recovery time is 40ms. The sensor position is changed, and a square wave tangential force with a frequency of 4Hz and an amplitude of 0.05N is applied to the sensor contact through the signal amplifier. The output voltage of the x-edge TMR element 8 is processed to obtain the average output voltage waveform. The waveform of one cycle is intercepted as shown in Fig. 9 As shown, it can be seen that the response time of the sensor to the tangential force is 36ms, and the recovery time is 44ms. Both the response time and the recovery time are less than 50ms, which meets the response time requirements of human skin.

[0096] Examples 14-15

[0097] The temperature characteristic test of the dual-mode tactile sensor is mainly aimed at determining the temperature sensing performance of the sensor, verifying that the graphene-silicone elastomer used can obtain better response speed and temperature sensing ability while protecting the temperature sensing part (thermocouple) compared with the use of silicone for protection, and at the same time demonstrate the temperature sensing ability of the sensor. The protection refers to: avoiding the coupling of stress and temperature information, and making up for the disadvantage that the thermocouple cannot measure the temperature of objects with poor insulation.

[0098] Test platform construction: Sensors were made using a sensing layer wrapped with silicone and a sensing layer wrapped with graphene, and were placed inversely on a constant temperature heating table. A DC regulated power supply was used to power the TMR element and the thermocouple acquisition module, and the output was connected to a data acquisition card.

[0099] Experimental process and results: Change the temperature of the heating platform, keep it for 10 minutes each time to stabilize the temperature of the heating platform, then move the sensor so that its surface contacts the surface of the heating platform, keep it for 10 minutes, and then move the sensor away from the heating platform; during the experiment, the output voltage of the TMR element is almost unchanged, which shows that the change of temperature within the test range has almost no effect on the output of the magnetic film and the TMR element 6; the temperature output is as follows Fig. 9 As shown, the sensor wrapped by graphene-silicone elastomer has much better response time and temperature sensing performance than the sensor wrapped by silicone.

[0100] Through the above embodiments, in the sensor of the present invention, when the sensor is subjected to external forces, the upper magnetic film produces spatial displacement, causing changes in the surrounding magnetic field strength, and the decoupling of the three-dimensional force can be completed according to the different voltage signal outputs of the three TMR elements located at different positions below the magnetic film. The three TMR elements are respectively placed directly below the center of the square magnetic film and directly below the midpoints of two vertical sides of the square magnetic film to form a right-angle TMR array. The TMR element in the center is used to detect the normal force, and the edge TMR element is used to detect the special magnetic field generated by the edge effect to complete the detection of the shear force and the decoupling of the three-dimensional force. As the temperature sensing part, the thermocouple is wrapped and protected by an organic elastomer doped with graphene, and generates a voltage signal under the influence of the external temperature, and is not affected by stress.

[0101] Matters not covered by the present invention are known technologies.

Claims

1. A three-dimensional force-temperature dual-mode tactile sensor based on a magnetic film, characterized in that: The sensor includes a graphene-silicone elastomer, a thermocouple, a magnetic film, an elastomer support, an attached body, a Z-axis TMR element and a flexible printed circuit board; Among them, three Z-axis TMR elements are distributed in a right angle shape on the flexible printed circuit board; the attachment covers the flexible printed circuit board and wraps the Z-axis TMR element array therein; five elastomer pillars are distributed in a five-point plum blossom shape on the attachment; the graphene-silicone elastomer is fixed on the five elastomer pillars; a magnetic film and a thermocouple are wrapped in the graphene-silicone elastomer, and the thermocouple is located on the magnetic film.

2. The three-dimensional force-temperature dual-mode tactile sensor based on magnetic film as claimed in claim 1, characterized in that: The rectangular array distribution is that on the square projection of the square magnetic film, there is a Z-axis TMR element in the center, and there is a Z-axis TMR element in the middle of each of the two adjacent sides of the square.

3. The three-dimensional force-temperature dual-mode tactile sensor based on magnetic film as claimed in claim 1, characterized in that: The magnetic film is made of a mixture of NdFeB particles and PDMS silica gel, with a mass ratio of 3:1, and the magnetization direction is along the height direction of the film; The graphene-silicone elastomer is made by mixing Smooth-On's Ecoflex00-30 series A agent, B agent and graphene nanoparticles in a mass ratio of 5:5:

1. The upper surface of the elastomer is square with a side length of 9 to 11 mm and a thickness of 1 to 2 mm. The wrapping body is epoxy resin with a thickness of 1.2-1.4 mm; the TMR element model is TMR2505.

4. The three-dimensional force-temperature dual-mode tactile sensor based on magnetic film as claimed in claim 1, characterized in that: The particle size of the NdFeB particles is 30-50 μm; The particle size of the graphene nanoparticles is 20-40 nm.

5. The three-dimensional force-temperature dual-mode tactile sensor based on magnetic film as claimed in claim 1, characterized in that: The magnetic film layer has a side length of 7 to 9 mm and a thickness of 400 to 600 μm; The thermocouple is a thin-sheet thermocouple, and the temperature measuring part is 5 to 6 mm long and 0.08 to 0.16 mm wide; The elastic body pillar has a radius of 0.8 to 1.2 mm and a height of 1.8 to 2.3 mm.

6. The three-dimensional force-temperature dual-mode tactile sensor based on magnetic film as claimed in claim 1, characterized in that: The center of the magnetic film is aligned with the TMR element at the center of the sensing layer in the vertical direction, and the midpoints of two adjacent sides of the magnetic film are aligned with the other two TMR elements in the vertical direction respectively; The distance between the lower surface of the magnetic film and the TMR element is 2 to 2.5 mm; The center of the magnetic film, the center of the square formed by the five elastic pillars, and the projection of the magnetic field measurement point of the Z-axis TMR element at the right angle point overlap.

Images