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

Abstract

The application discloses a three-dimensional force-temperature dual-mode tactile sensor based on a magnetic film. The sensor comprises a graphene-silica gel elastomer, a thermocouple, a magnetic film, an elastomer support, a wrapping body, a Z-axis TMR element and a flexible printed circuit board. Three Z-axis TMR elements are distributed in a right angle shape on the flexible printed circuit board. The wrapping body covers the flexible printed circuit board and wraps the Z-axis TMR element array. Five elastomer supports are distributed in a five-point plum blossom shape on the wrapping body. The graphene-silica gel elastomer is fixed on the five elastomer supports. The graphene-silica gel elastomer wraps the magnetic film and the thermocouple, and the thermocouple is located above the magnetic film. The tactile sensor has the characteristics of low hysteresis, high resolution, high sensitivity, easy decoupling and multi-function, and can realize the dual information perception of the external three-dimensional force and temperature.

Description

TECHNICAL FIELD

[0001] The application is based on the edge effect of the magnetic film and the Seebeck effect of the thermocouple to manufacture a dual-mode tactile sensor with three-dimensional force and temperature information measurement function. The sensor can realize three-dimensional force decoupling and external temperature information detection at the same time, helping the robot hand to realize various types of grabbing operations. BACKGROUND

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

[0003] At present, various tactile sensors capable of measuring single-direction force have emerged. The research direction of force tactile sensors has gradually shifted to obtaining three-dimensional force information. However, there are relatively few dual-mode tactile sensors that combine three-dimensional force and temperature. Compared with other three-dimensional force tactile sensors such as capacitive, piezoelectric, and resistive sensors, magnetic sensors have the advantages of low hysteresis, high sensitivity, and high physical robustness.

[0004] Patent (application number 202210973441.4) uses a pillar and a magnetic film as the basic structure. The magnetic film is suspended above the giant magnetoresistance element by four elastic pillars. The tilting deformation of the pillars under the tangential force causes the magnetic film to move. The giant magnetoresistance element below is used to detect changes in the magnetic field signal, mainly realizing the measurement of tangential force. However, this invention is limited to tangential force measurement and cannot achieve three-dimensional force detection. The response to external signals is single, and it does not have other environmental stimulus response functions. It cannot achieve three-dimensional force detection function, has narrow applicability, and is difficult to be used in actual operations of robot hands. SUMMARY

[0005] The present application aims at the lack of research on three-dimensional force-temperature dual-mode tactile sensor at present, provides a dual-mode tactile sensor based on double-layer film, right-angle TMR array and support structure, and proposes an effective utilization method for magnetic film magnetic field edge effect. The sensor adopts magnetic film and right-angle TMR array to form three-dimensional force sensing; the right-angle TMR array, the TMR element at the center is used for detecting normal force, and the edge TMR element is used for detecting the special magnetic field generated by the edge effect to complete the detection of shear force and the decoupling of three-dimensional force, so that the neglect or inhibition of the effect of the magnetic field distortion caused by the edge effect on the sensor is overcome; the thermocouple is used as the temperature sensing part, and the organic elastomer doped with graphene is wrapped and protected, so that a voltage signal is generated under the influence of external temperature, and the voltage signal is not affected by stress. The tactile sensor has the characteristics of low hysteresis, high resolution, high sensitivity, easy decoupling and multi-function, and can realize dual information sensing of external three-dimensional force and temperature.

[0006] The technical scheme of the present application is:

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

[0008] Three Z-axis TMR elements are distributed in a right-angle shape on the flexible printed circuit board; the wrapping body is covered on the flexible printed circuit board and wraps the Z-axis TMR element array therein; five elastomer supports 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 wrapping body; the graphene-silica elastomer is fixed on the five elastomer supports; the graphene-silica elastomer wraps the magnetic film and the thermocouple, and the thermocouple is located above the magnetic film;

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

[0010] The projection of the magnetic field measurement point of the Z-axis TMR element at the right-angle point position overlaps the center of the square composed of the center of the magnetic film and the five elastomer supports;

[0011] The magnetic film is made of neodymium iron boron 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 1.2-1.4 mm;

[0013] The TMR element model is TMR2505;

[0014] The particle size of the Nd-Fe-B particles is 30-50 mu m;

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

[0016] The graphene-silica gel elastomer is made by mixing Ecoflex 00-30 series A agent, B agent and graphene nanoparticles in a mass ratio of 5:5:1, the upper surface of the elastomer is a square with a side length of 9-11 mm and a thickness of 1-2 mm;

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

[0018] The thermocouple is a sheet thermocouple, the temperature measuring part has a length of 5-6 mm and a width of 0.08-0.16 mm;

[0019] The radius of the elastomer support is 0.8-1.2 mm, and the height is 1.8-2.3 mm;

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

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

[0022] The substantial features of the present application are:

[0023] In the current technology, the magnetic film tactile sensor mainly realizes sensing function based on the internal uniform magnetic field ignoring the edge effect, and the research on three-dimensional force and temperature dual-mode tactile sensing is less;

[0024] The present application mainly utilizes the special magnetic field distribution of the edge area of the magnetic film, based on the regular spatial displacement of the magnetic film suspended by the elastomer support under external force, realizes the decoupling of three-dimensional force through the special position relationship between the Z-axis TMR2505 array arranged directly below the right angle position of the magnetic film and the magnetic film; the temperature sensing layer utilizes the graphene-silica gel 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 has a small volume and is less affected by stress, the graphene-silica gel elastomer used protects the temperature sensing part (thermocouple) while enabling the sensor to have better response speed and temperature sensing capability, i.e. the stress applied to the thin film thermocouple is further reduced by the buffering effect of the graphene-silica gel elastomer, avoiding the coupling caused by stress, and at the same time, the insulating graphene-silica gel elastomer can improve the disadvantage that the thermocouple cannot measure the temperature of objects with poor insulation;

[0025] The application can simultaneously detect two external environmental factors without interference, the decoupling principle of three-dimensional force is simple, the tangential force sensitivity is greatly improved, the temperature sensing effect is optimized under the premise of ensuring flexibility, the common detection of three-dimensional force and temperature information is realized, and the multi-information sensing function is achieved.

[0026] The application has the following beneficial effects:

[0027] 1. The application uses a neodymium-iron-boron-silicon elastomer magnetic film with high magnetic performance and strong flexibility as a three-dimensional force sensing part, and uses the difference in magnetic field distribution of the center and the edge of the magnetic film and the relative position relationship between the right-angle TMR array and the magnetic film to realize the decoupling of three-dimensional force; the magnetic film is magnetized in the vertical direction, the magnetic field direction of the center area is uniform and only along the Z axis direction (the Z axis refers to the axis parallel to the sensor), and the Z axis magnetic field component of the area below the four edges is not uniform and contains magnetic field components in other directions, which leads to that when the magnetic film is horizontally displaced, the Z axis magnetic field component below the center area does not change, and the Z axis magnetic field component below the edge part changes; when the upper magnetic film is subjected to normal pressure, the elastomer support is compressed, and the magnetic film produces a vertical spatial displacement, which leads to a change in the surrounding space magnetic field; the Z axis TMR element located directly below the center of the magnetic film detects the Z axis magnetic field component of the center part of the magnetic film, and produces a regular voltage output when the sensor is subjected to normal pressure; when the upper magnetic film is subjected to horizontal tangential force, the elastomer support is tilted, and the magnetic film produces a horizontal spatial displacement, which leads to a change in the surrounding space magnetic field; the two Z axis TMR elements located directly below the edges of the magnetic film detect the unevenly distributed Z axis magnetic field component below the edges of the magnetic film, and produce another regular voltage output when the sensor is subjected to horizontal tangential force; when the upper magnetic film is subjected to three-dimensional force in any direction, the magnetic film simultaneously produces horizontal and vertical spatial displacements, the change in the magnetic field located directly below the center of the magnetic film only comes from the vertical displacement of the magnetic film, so the output of the center Z axis TMR element only represents the size of the normal force, and the outputs of the two TMR elements located directly below the two edges of the magnetic film perpendicular to each other 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 (X, Y axes refer to two directions parallel to the two edges of the square magnetic film perpendicular to each other), the coupling is regular and can be expressed by a formula, so the three-dimensional force components in the X, Y and Z directions can be easily separated based on the different outputs of the three TMR elements, and the measurement of three-dimensional force is realized;

[0028] 2. Compared with the prior art, the application provides an effective utilization means for the edge effect of the magnetic film, and proposes a three-dimensional force decoupling method;

[0029] 3. The present application can obtain different force measurement ranges and sensitivity of the sensor device by adjusting the Young's modulus of the elastomer support (using an elastomer with a higher Young's modulus will increase the force measurement range and reduce the sensitivity; using an elastomer with a lower Young's modulus will reduce the force measurement range and increase the sensitivity), which is more flexible in selection and application range;

[0030] 4. The temperature sensing layer of the present application uses graphene-silica gel elastomer, graphene has high thermal conductivity, which can effectively improve the thermal conductivity after mixing with silica gel (as shown in the figure), to obtain a temperature sensing layer with high thermal conductivity and high flexibility, and can make the surface temperature of the sensor more uniform; Figure 9

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

[0032] 6. The present application uses a unique geometric spatial distribution to ensure highly regular output within the measurement range and obtain high sensitivity micro-force detection function. For the example given, a shear force measurement sensitivity of 908.57 mV / 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 existing three-dimensional force measurement technology, the present application has a smaller overall size, with a sensing part length and width of only 10-12 mm and a height of 4-4.5 mm, which can be arranged into an array as needed for application. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structure split view of a three-dimensional force-temperature dual-mode tactile sensor;

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

[0036] Figure 3 is an overall appearance view of a three-dimensional force-temperature dual-mode tactile sensor;

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

[0038] Figure 5 is a TMR element right-angle array view of a three-dimensional force-temperature dual-mode tactile sensor;

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

[0040] Figure 7 ​is the tangential force characteristic test output graph of the three-dimensional force-temperature bimodal tactile sensor;

[0041] Figure 8 is the force response time test graph of the three-dimensional force-temperature bimodal tactile sensor;

[0042] Figure 9 is the temperature response curve of the three-dimensional force-temperature bimodal tactile sensor;

[0043] Wherein, 1-graphene-silica elastomer, 2-thermocouple, 3-magnetic film, 4-elastomer support, 5-wrapping body, 6-Z-axis TMR element, 7-flexible printed circuit board, 8-x-edge TMR element, 9-central TMR element, 10-y-edge TMR element. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings, and the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

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

[0046] The sensor comprises a sensing layer, a support layer and a receiving layer.

[0047] The sensing layer comprises a magnetic film, a thermocouple and a graphene-silica elastomer.

[0048] The support layer is composed of five elastomer supports, wherein four elastomer supports are located below the four corners of the square magnetic film layer, and one elastomer support is located below the center of the magnetic film layer.

[0049] The receiving layer comprises a wrapping body, a TMR array and a flexible printed circuit board.

[0050] The bimodal tactile sensor of the present embodiment is as shown in Figure 2As shown in the figure. The graphene-silica gel elastomer 1 is 10 mm long, 10 mm wide and 1.5 mm high, the internal K-type thermocouple 2 is 6 mm long, 1 mm wide and 0.16 mm high, the magnetic film 3 is 8 mm long, 8 mm wide and 0.5 mm high, the elastomer support 4 has a radius of 1 mm and a height of 2 mm, the magnetic sensitive direction of the TMR2505 is the Z-axis direction, the packaging form is SOT23-5, the length is 3 mm, the width is 3 mm and the height is 1 mm. The TMR element array 6, the magnetic film layer 3 and the graphene-silica gel elastomer 1 are placed in parallel, the three TMR2505 are distributed at right angles, and the top view is as shown in the figure Figure 4 、 Figure 5 As shown in the figure, the midpoints of the graphene-silica gel elastomer 1 and the magnetic film 3 are aligned with the center TMR element 9, the magnetic field measurement point of the x-edge TMR element 8 is aligned with the center of one edge of the magnetic film at a position 4 mm to the left of the magnetic field measurement point of the center TMR element 9, the magnetic field measurement point of the y-edge TMR element is aligned with the center of the other edge of the magnetic film at a position 4 mm below the magnetic field measurement point of the center TMR element 9, and the TMR element is wrapped by the wrapping layer 5. When performing normal static pressure measurement, 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 performing static tangential force measurement, the force measurement range remains linear within 0-0.1N, and the sensitivity is 908.57mV / N.

[0051] The software or protocol involved in the application is a known technology.

[0052] The application will be further described in detail below with reference to the accompanying drawings. The embodiments are only specific descriptions of the application and should not be considered as limiting the scope of protection.

[0053] Embodiment 1

[0054] The application is based on the edge effect of the square neodymium-iron-boron magnetic film, the Seebeck effect of the thermocouple and the tunneling magnetoresistance effect of the TMR element to design a three-dimensional force-temperature dual-mode tactile sensor, and a structure disassembly view is as shown in the figure Figure 1 The graphene-silica gel elastomer 1, the thermocouple 2, the magnetic film 3, the elastomer support 4, the wrapping body 5, the Z-axis TMR element 6 and the flexible printed circuit board 7 are shown in the figure;

[0055] The three Z-axis TMR elements 6 are arranged in a right angle (i.e. one in the center of the circuit board and the other two in the center of the edges of the adjacent two sides of the circuit board) on the flexible printed circuit board 7; the wrapping body 5 covers the flexible printed circuit board 7 and wraps the Z-axis TMR element array 6; the five elastic body supports 4 are arranged in a five-point plum blossom shape (i.e. four arranged in a square shape at the periphery and the fifth in the center) on the wrapping body 5; the graphene-silica gel elastic body 1 is fixed on the five elastic body supports 4; the magnetic film 3 and the thermocouple 2 are wrapped in the graphene-silica gel elastic body 1, and the thermocouple 2 is located above the magnetic film 3. Due to the support of the five supports below and the integral molding in the adhesive stage of silica gel, the structure is stable.

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

[0057] The projection of the magnetic field measurement point of the Z-axis TMR element 6 at the right angle point position overlaps the center of the square composed of the center of the magnetic film 3 and the five elastic body supports 4;

[0058] The magnetic field measurement point refers to the effective area of the magnetic field measured by the TMR element;

[0059] The sensor senses the external environmental stimulus by the thermocouple 2 and the magnetic film 3 wrapped by the graphene-silica gel elastic body 1, the TMR right angle array 6 receives the three-dimensional force signal and serves as the core of three-dimensional force decoupling with the square magnetic film 3, and the sensor can accurately obtain three-dimensional force information and temperature information at the same time;

[0060] For convenience of description, the X-Y coordinate system on the horizontal plane is established based on the coordinate axes shown in Figure 5 The TMR element located in 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 on the bottom is called the y-edge TMR element 10;

[0061] When an external force is applied to the surface of the sensor, the magnetic film layer 3 based on the elastic body support 5 occurs regular spatial displacement, resulting in changes in the magnetic field below, and the signal of the magnetic field changes is received by the three Z-axis TMR 2505 elements, which is converted into a voltage signal through the internal tunneling magnetoresistance effect, and the voltage signal data is collected through a data acquisition card, and the data visualization is realized through a computer. As shown in Figure 4As shown, three TMR 2505 elements are distributed in a right-angle array on the flexible printed circuit board 7, and are integrally cast inside the wrapping body 5. The central magnetic field of the magnet 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 certain direction and changes in another certain direction, the central TMR element 9 is used to sense the normal component of the external force, and will not generate 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 in the horizontal plane respectively. When the temperature of the sensor surface changes, the temperature of the graphene-silica elastomer 1 changes rapidly, and the internal thermocouple 2 generates an electric potential based on the Seebeck effect, and the data is visualized through post-processing circuit and computer;

[0062] The magnetic film 3 is prepared by mixing PDMS prepolymer, curing agent (containing hydrogen silicone oil), neodymium-iron-boron particles (Nd2Fe 14 B1) in a mass ratio of 10:1:33, stirring for 120 minutes to obtain neodymium-iron-boron-silica prepolymer; the neodymium-iron-boron-silica prepolymer is placed in a bubble remover for 30 minutes, and the defoamed prepolymer is poured into a 3D printed metal mold, heated at 80°C for 1h to cure, to obtain a neodymium-iron-boron-silica elastic film; the neodymium-iron-boron-silica elastic film is laid in a magnetizer and magnetized, and the magnetization direction is perpendicular to the surface of the magnetic film, to obtain the magnetic film 3;

[0063] The particle size of the neodymium-iron-boron particles is 40μm;

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

[0065] The graphene-silica elastomer 1 is prepared by mixing Ecoflex 00-30 series A agent, B agent and graphene nanoparticles in a mass ratio of 5:5:1, stirring for 60 minutes in a blender to obtain graphene-silica prepolymer; the graphene-silica prepolymer is placed in a bubble remover for 30 minutes; the thermocouple 2 and the magnetic film 3 are placed at the center of the 3D printed cuboid mold, the defoamed graphene-silica prepolymer is slowly poured into the mold, and then cured at room temperature for 4h to obtain the connecting piece of the sensing layer;

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

[0067] The internal shape of the cuboid mold is a cuboid with a size of 10mm×10mm×1.2mm;

[0068] The thermocouple 2 adopts K-type sheet thermocouple with a length of 6mm, a width of 1mm and a thickness of 0.16mm;

[0069] The elastomer pillar 4 is prepared by mixing Ecoflex 00-30 series A and B at a ratio of 1:1, stirring for 10 minutes, and then degassing for 30 minutes to obtain a prepolymer, which is then poured into a 3D-printed cylindrical resin mold, and a prepared sensing layer is laid on the top, and the connection between the pillar layer and the sensing layer is obtained after standing at room temperature for 4 hours;

[0070] The center of the square graphene-silica elastomer, the temperature measuring point of the thermocouple, and the 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 radius of 1 mm and a height of 2 mm; four of the cylindrical holes are located at the four corners of a square, with a distance of 8 mm, and the fifth hole is located at the center of the square;

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

[0073] The wrapping body has a length of 12 mm, a width of 12 mm, and a height of 1.2 mm;

[0074] The TMR element is TMR2505, packaged as SOT23-5; the TMR array arrangement is as shown in Figure 5 The 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 as shown in Figure 3 The length is 12 mm, the width is 12 mm, and the height is 4.5 mm; when a normal force is applied to the upper surface, the elastomer pillar 4 is compressed, and quickly returns to its original shape after the pressure is removed; when a tangential force is applied to the side, the elastomer pillar 4 is laterally deformed, and quickly returns to its original shape after the pressure is removed; experiments show that the elastomer does not undergo plastic deformation within the experimental force range; after contacting objects at different temperatures within the contact 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 are not affected;

[0076] The flexible printed circuit board has a thickness of 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 to output temperature signals from a computer;

[0078] Examples 2-6

[0079] Based on the same method as in Example 1, the side lengths of the magnetic film layer 2 were changed to 8 mm, 10 mm, 12 mm, 14 mm, and 16 mm, respectively, while maintaining the bottom TMR array directly below the center and edge of the magnetic film layer 3. A tangential force of 0.1 N was applied to the sensor along the positive direction of the X-axis using a digital push-pull gauge.

[0080] Experiments have found that as the side length of the magnetic film layer 3 increases, the output change of the central TMR element 9 first increases and then decreases when the sensor is subjected to the same magnitude of tangential force. When a magnetic film with a side length of 8 mm is selected, the output of the central TMR element 9 remains 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] Examples 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 1 mm, 2 mm, and 3 mm respectively, and a tangential force of 0.05 N was applied to the sensor along the positive direction of the X axis using a digital push-pull gauge;

[0083] Experiments have 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 around 2mm. Taking into account 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 of the dual-modal tactile sensor is performed. 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] The experiment process and results: the step is set to 0.2N, the normal force is applied vertically downward by using the digital push-pull gauge, the force is 0-2N, the external force is kept for several seconds, and then the external force is removed. The output voltage of the sensor center TMR element 9 is as shown in the figure. Figure 6 The output voltage of the center TMR element 9 in the range of 0-1N shows a good linear relationship with the pressure, the output voltage can be kept stable under constant pressure, and quickly returns to 0 after the external force is removed, the sensor has good static characteristics, and the sensitivity is 123.25mV / N when the pressure is 1N.

[0088] Example 11

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

[0090] Test platform building: assemble the three-dimensional force sensor according to the figure Figure 2 and fix it on the angle table, place it on the base of the push-pull gauge, align the transmission rod of the digital push-pull gauge with the sensor sensing layer, use a DC stabilized power supply to power the TMR element, and connect the element output to the data acquisition card.

[0091] Experiment process and results: change the sensor position, so that the tangential force angle φ applied by the push-pull gauge is 0°, 90°, 180° and 270°, set the force step to 0.02N, and use the digital push-pull gauge to apply a tangential force of 0-0.1N. For the tangential force along the x-axis direction, the output voltage of the x-edge TMR element 8 is as shown in the figure. Figure 7 The x-edge TMR element 8 shows a good linear relationship between the tangential force and the output voltage in the range of 0-0.1N in the positive and negative directions, the output voltage can be kept stable under constant tangential force, and quickly returns to 0 after the external force is removed, the sensor has good static characteristics, the tangential force measuring range of the single-axis is 0-0.1N, and the sensitivity is 908.57mV / N when the X-axis component of the tangential force is 0.1N.

[0092] Examples 12-13

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

[0094] Test platform building: The test platform includes signal generator (AFG2021-SC), power amplifier (MB500VI), 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 TMR element is powered by a DC stabilized power supply, 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 connected to the computer.

[0095] Experimental process and results: A 4Hz square wave force signal is output by the signal generator, and a 4Hz square wave normal force with an amplitude of 0.5N is applied to the sensor contact through the signal amplifier. The output voltage of the center TMR element 9 is processed to obtain the average output voltage waveform, and the waveform of one period is as shown in Figure 8 It can be seen that the response time of the sensor normal force is 38ms, and the recovery time is 40ms. Change the sensor position, and apply a 4Hz square wave tangential force with an amplitude of 0.05N 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, and the waveform of one period is as shown in Figure 9 It can be seen that the response time of the sensor tangential force is 36ms, and the recovery time is 44ms. The response time and recovery time are both less than 50ms, which meets the human skin response time requirement.

[0096] Examples 14-15

[0097] Temperature characteristics test of dual-mode tactile sensor, the main purpose of this embodiment is to determine the temperature sensing performance of the sensor, to verify that compared with using silica gel for protection, the graphene-silica gel elastomer used can obtain better response speed and temperature sensing ability while protecting the temperature sensing part (thermocouple), and at the same time, the temperature sensing ability of the sensor is demonstrated. The protection refers to: avoiding the coupling of stress and temperature information, and at the same time, making up for the shortcomings that the thermocouple cannot measure the temperature of objects with poor insulation.

[0098] Test platform building: The sensor with silica gel wrapped receiving layer and the sensor with graphene receiving layer are made respectively and placed reversely above the constant temperature heating table, and the TMR element and thermocouple acquisition module are powered by a DC stabilized power supply, and the output is connected to the data acquisition card.

[0099] Experimental process and result: change the temperature of the heating platform, keep 10 minutes after each change to make the temperature stable, then move the sensor to make its surface contact with the surface of the heating platform, keep 10 minutes, then move the sensor away from the heating platform; during the experiment, the output voltage of the TMR element is almost unchanged, which indicates that the change of temperature almost has no effect on the output of the magnetic film and the TMR element 6 in the test range; the temperature output is shown in Figure 9 The sensor wrapped by the graphene-silica gel elastomer has better response time and temperature sensing performance than the sensor wrapped by silica gel.

[0100] Through the above examples, in the sensor of the application, when the sensor is subjected to external force, the upper magnetic film produces spatial displacement, causing the change of the surrounding magnetic field strength, and the decoupling of 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 the midpoint of two perpendicular edges of the square magnetic film, forming a right-angle TMR array, the TMR element at 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 three-dimensional force. The thermocouple as the temperature sensing part is wrapped and protected by the organic elastomer doped with graphene, and generates a voltage signal under the influence of external temperature, and is not affected by stress.

[0101] The remaining matters of the application are known technologies.

Claims

1. A three-dimensional force-temperature dual-modal tactile sensor based on a magnetic film, characterized by: The sensor includes a graphene-silicone elastomer, a thermocouple, a magnetic film, an elastomer support, an attachment, 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 wrapping body covers the flexible printed circuit board and wraps the Z-axis TMR element array in it; five elastomer pillars are distributed in a five-point plum blossom shape on the wrapping body; 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-modal tactile sensor based on a magnetic film as claimed in claim 1, characterized in that: The rectangular 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-modal tactile sensor based on a 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 9-11 mm and a thickness of 1-2 mm. The wrapping body is made of epoxy resin with a thickness of 1.2-1.4 mm; the TMR element model is TMR2505.

4. The three-dimensional force-temperature dual-modal tactile sensor based on a magnetic film as claimed in claim 3, 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-modal tactile sensor based on a 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-film thermocouple with a temperature measuring portion of 5 to 6 mm in length and 0.08 to 0.16 mm in width; The elastic pillar has a radius of 0.8-1.2 mm and a height of 1.8-2.3 mm.

6. The three-dimensional force-temperature dual-modal tactile sensor based on a 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 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.

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