High-sensitivity proximity sense and three-dimensional pressure sense flexible capacitive sensor

Abstract

The invention discloses a high-sensitivity proximity sense and three-dimensional pressure sense flexible capacitive sensor. The capacitive sensor comprises a plurality of sensing units which are distributed in an array mode, and each sensing unit comprises a contact layer, a hierarchical porous composite sensitive conductive unit and an induction electrode unit which are sequentially arranged in a stacked mode. Dual-mode measurement of proximity sense and three-dimensional pressure sense is achieved through a single-sensing-body mechanism, when a measured object is not contacted, the sensing unit completely works in a dielectric state, proximity sense measurement can be achieved, after the measured object is contacted, the sensing unit works in a common electrode state, three-dimensional pressure sense measurement can be achieved, and the sensing unit can be used for measuring the proximity sense and the three-dimensional pressure sense. Compared with a traditional flexible dielectric material, the hierarchical porous composite material is used as the sensitive unit, so that the dielectric constant and the deformation capability of the sensitive unit are greatly improved, and high sensitivity of flexible proximity sense and three-dimensional pressure sense measurement is ensured.

Description

Technical Field

[0001] The invention relates to a flexible capacitive sensor in the field of sensor technology, and in particular to a highly sensitive proximity and three-dimensional pressure-tactile flexible capacitive sensor. Background Art

[0002] At present, in many fields such as automation industry and medical health, industrial robots have largely replaced human hands to complete complex operations that require a high degree of human-machine perception and interaction. However, for intelligent robot hands that integrate perception functions and work in unstructured environments, it is still necessary to further introduce artificial tactile perception systems similar to human skin through bionic interaction and functional integration to enhance the operational dexterity and reliability of robot hands. Capacitive tactile sensors have good repeatability, low temperature sensitivity, low power consumption, and high spatial resolution. They are particularly suitable for scenarios such as electronic skin that require large-area applications, and are gradually being used in the reconstruction of tactile force functions of intelligent robot hands. However, the following key points and problems continue to emerge during use:

[0003] 1) Robots are faced with various safety and predictability issues when used in human-computer interaction. Only by fully perceiving the real-time changes in the external environment, especially the distance, position, shape and other information of obstacles, and avoiding unnecessary collisions, can the safety of interaction between robots and humans be guaranteed.

[0004] 2) By constructing porous, surface patterned structures / doping high dielectric constant fillers to increase the deformation ability or dielectric constant of the dielectric layer, capacitive tactile sensors have achieved high sensitivity in the low pressure range, but even a slight increase in pressure will cause significant strain in microstructures such as porous and surface patterns, and quickly close the air gap, resulting in rapid attenuation of sensitivity. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a highly sensitive flexible capacitive sensor for proximity and three-dimensional pressure touch. The present invention adopts a single sensor mechanism to realize dual-modal measurement of proximity and three-dimensional pressure touch. When not in contact with the object to be measured, the sensitive unit works completely in a dielectric state, which can realize proximity measurement. After contacting the object to be measured, the sensitive unit works in a common electrode state, which can realize three-dimensional pressure touch measurement. Compared with traditional flexible dielectric materials, the present invention uses a graded porous composite material as a sensitive unit, which can greatly improve the dielectric constant and deformation capacity of the sensitive unit, ensuring the high sensitivity of flexible proximity and three-dimensional pressure touch measurements.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] 1. A Highly Sensitive Proximity and Three-Dimensional Pressure Tactile Flexible Capacitive Sensor

[0008] The sensor includes a sensing unit, which includes a contact layer, a graded porous composite sensitive conductive unit and a sensing electrode unit which are stacked in sequence; when there is a distance between the object to be measured and the contact layer, the graded porous composite sensitive conductive unit works completely as a dielectric state, and the sensing electrode unit is used to measure the approach distance of the object to be measured; when the object to be measured contacts and presses the contact layer, the graded porous composite sensitive conductive unit works as a common electrode state, and is used together with the sensing electrode unit to measure the force applied to the object to be measured.

[0009] A dome-shaped protrusion is arranged in the middle of the upper surface of the contact layer, and the object to be measured acts on the dome-shaped protrusion of the contact layer.

[0010] The capacitive sensor includes a plurality of sensing units, and the plurality of sensing units are spliced ​​in the form of an array.

[0011] The method for preparing the hierarchical porous composite sensitive conductive unit comprises the following steps:

[0012] First, a base gel and a curing agent are mixed to obtain a polydimethylsiloxane pre-solution, and then perfluorotributylamine is dispersed in the polydimethylsiloxane pre-solution and fully stirred to obtain a PDMS-FC43 emulsion; then, a multi-walled carbon nanotube conductive material is added to the PDMS-FC43 emulsion and fully stirred and mixed, followed by adding sugar particles, and the final mixed emulsion is poured into a mold and placed in a vacuum dryer for a degassing process until the residual bubbles in the gaps between the sugar particles are discharged; then, curing is performed, and the cured composite material is cleaned to dissolve the sugar particles in the material; finally, moisture is removed to obtain a graded porous composite sensitive conductive unit.

[0013] The sensing electrode unit comprises a sensing electrode layer, a first wire layer and a second wire layer which are stacked in sequence. The sensing electrode layer and the graded porous composite sensitive conductive unit are stacked. Four sensing electrodes arranged in a matrix array are laid in the sensing electrode layer. In a clockwise direction, they are respectively denoted as the first sensing electrode S 1 , the second sensing electrode S 2 , the third sensing electrode S 3 and the fourth sensing electrode S 4 Two parallel and spaced transverse copper wires are laid in the first conductor layer, respectively denoted as the second copper wire T 2 and the fourth copper conductor T 4 , the second copper wire T 2 Set on the first sensing electrode S 1 and the second sensing electrode S 2 Directly below, the fourth copper conductor T 4 Set at the third sensing electrode S 3 and the fourth sensing electrode S 4Two parallel and spaced longitudinal copper wires are laid in the second conductor layer, which are respectively denoted as the first copper wire T 1 and the third copper conductor T 3 , the first copper wire T 1 Set on the first sensing electrode S 1 and the fourth copper conductor T 4 Directly below, the third copper conductor T 3 Set at the second sensing electrode S 2 and the third sensing electrode S 3 Directly below the first sensing electrode S 1 With the first copper wire T 1 Electrical connection, second sensing electrode S 2 With the second copper wire T 2 Electrical connection, third sensing electrode S 3 With the third copper conductor T 3 Electrical connection, fourth sensing electrode S 4 With the fourth copper wire T 4 Electrical connection.

[0014] One copper wire in the first wire layer or the second wire layer is in an activated state, and the sensing electrode connected to the copper wire is recorded as a main sensing electrode; and two copper wires in another wire layer are both in an activated state, and the sensing electrodes connected to the two copper wires are recorded as secondary sensing electrodes, then the sensing electrode unit is in an independent measurement state, and is used to measure the shear force of the measured object;

[0015] The two copper wires in the first wire layer and the second wire layer are both in an activated state. Specifically, the first sensing electrode S 1 and the third sensing electrode S 3 Activate, the second sensing electrode S 2 and the fourth sensing electrode S 4 When activated, the sensing electrode unit is in full measurement state, and is used to measure the approach distance of the measured object and the normal force of the measured object, thereby realizing the perception of proximity and three-dimensional pressure touch.

[0016] 2. A Highly Sensitive Proximity and Three-Dimensional Pressure Tactile Perception Method

[0017] The sensing method adopts the proximity and three-dimensional pressure tactile flexible capacitive sensor, and includes the following steps:

[0018] When the object being measured is not in contact with the capacitive sensor, the sensing electrode layer in each sensing unit is in full measurement state, and the sensing capacitance C in each sensing electrode layer is detected. Ful , and compare it with the calibrated sensor capacitance-distance curve to calculate the distance between the object to be measured and the sensor unit;

[0019] When the object under test contacts the capacitive sensor, the sensing capacitance C of the sensing electrode layer in each sensing unit is detected when it is in the full measurement state. Ful and compare it with the calibrated sensor capacitance-normal force curve to calculate the normal force of the measured object; and detect the sensor capacitance C when the sensing electrode layer in each sensor unit is in an independent measurement state. Dual And compared with the calibrated sensor capacitance-shear force curve, the magnitude and direction of the shear force acting on the measured object are calculated, and the magnitude and direction of the final force are calculated based on the normal force and the shear force.

[0020] The sensing capacitance C of the sensing electrode layer in each sensing unit is detected when the sensing electrode layer is in an independent measurement state. Dual , and compared with the calibrated sensor capacitance-shear force curve, the shear force magnitude and direction of the measured object are calculated, including:

[0021] The first sensing electrode S 1 and the second sensing electrode S 2 The X-axis is established in the direction of the connection line, with the first sensing electrode S 1 and the fourth sensing electrode S 4 The Y axis is established in the direction of the connection, and the X axis is set perpendicular to the Y axis; the sensing electrode layer in each sensing unit is controlled to be in different independent measurement states, the change in the differential quantity between the main sensing electrode and the two auxiliary sensing electrodes in different independent measurement states is detected, and compared with the corresponding sensing capacitance-shear force component curve, the shear force magnitude on the X axis and the shear force magnitude on the Y axis are calculated, and then the shear force magnitude and direction of the force acting on the measured object are obtained.

[0022] The present invention has the following beneficial effects:

[0023] 1) An atypical capacitive tactile sensor array is designed by using conductive graded porous nanocomposites instead of traditional insulating dielectric materials, which greatly improves the dielectric constant and deformation capacity of the sensitive unit and achieves a stable sensitization effect under high pressure.

[0024] 2) According to the percolation effect of conductive composite materials under load, utilizing the differential responses of sensitive units in different load areas, a dynamic reconstruction strategy for distributed robot pressure tactile perception and a proximity recognition detection method are proposed based on the principle of single-cell tactile sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the sensor structure of the present invention.

[0026] Figure 2 It is a schematic diagram of the structure of the sensing unit of the sensor of the present invention.

[0027] Figure 3 It is a structural exploded diagram of the sensing unit of the sensor of the present invention.

[0028] Figure 4 This is a structural breakdown diagram of the sensing electrode layer of the sensor in this aspect.

[0029] Figure 5 It is a schematic diagram of the sensor capacitance measurement principle of the present invention.

[0030] Figure 6 It is a schematic diagram of the proximity measurement principle of the sensor of the present invention.

[0031] Figure 7 It is a schematic diagram of the equivalent dielectric constant measured by the proximity sensor of the present invention.

[0032] Figure 8 It is a schematic diagram of the tactile pressure measurement principle of the sensor of the present invention.

[0033] Fig. 9 This is a schematic diagram of the tactile shear force measurement principle of the sensor of the present invention.

[0034] In the figure: 1. sensing unit, 2. contact layer, 3. graded porous composite sensitive conductive unit, 4. sensing electrode unit, 5. sensing electrode, 6. transverse copper wire, 7. longitudinal copper wire, 8. measured object, 9. equivalent common electrode. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] The present invention proposes a highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor, the capacitive sensor comprises at least one sensing unit 1, and a plurality of sensing units 1 are spliced ​​in the form of an array. The capacitive sensor composed of 3×3 sensing units 1 is as follows: Figure 1 As shown. Figure 2 As shown, each sensing unit 1 includes a contact layer 2, a graded porous composite sensitive conductive unit 3 and a sensing electrode unit 4 which are stacked in sequence; when there is a distance between the object 8 to be measured and the contact layer 2, the sensing electrode unit 4 is used to measure the approach distance of the object 8 to be measured; when the object 8 to be measured contacts and presses the contact layer 2, the graded porous composite sensitive conductive unit 3 and the sensing electrode unit 4 are used to measure the force applied to the object 8 to be measured.

[0037] A dome-shaped protrusion is provided in the middle of the upper surface of the contact layer 2, and the object to be measured 8 acts on the dome-shaped protrusion of the contact layer 2. The dome-shaped protrusion decomposes the external pressure into xyz three-dimensional pressure tactile force.

[0038] When making the contact layer 2, a polydimethylsiloxane (PDMS) solution obtained by mixing the base gel and the curing agent (Sylgard 184, Dow Chemical Co., Milander, MI, USA) in a weight ratio of 10:1 is poured into the alloy mold and vacuum degassed in a vacuum drying oven for 25 minutes to fully remove some remaining bubbles and allow the PDMS solution to completely fill the grooves in the mold. Subsequently, an acrylic sheet is covered on the surface of the mold, and excess PDMS is squeezed out by applying pressure, and heated to 80°C for curing. Finally, the acrylic sheet is peeled off.

[0039] The preparation method of the hierarchical porous composite sensitive conductive unit 3 comprises the following steps:

[0040] First, a base gel and a curing agent were mixed at a ratio of 20:1 to obtain a polydimethylsiloxane (PDMS) pre-solution, and then perfluorotributylamine (FC43) was dispersed into the PDMS pre-solution at a concentration ratio of 40 vol%, and the mixture was stirred at 2000 rpm for 5 min to obtain a stable PDMS-FC43 emulsion. Then, conductive multi-walled carbon nanotubes (MWCNTs) were added to the PDMS-FC43 emulsion at a weight percentage of 1.5% and stirred thoroughly, and then sugar particles with a particle size of about 100 μm were added. The sugar particles and the added The volume ratio of the PDMS-FC43 emulsion after the conductive multi-walled carbon nanotubes are added is 4:1. The final mixed emulsion is poured into an aluminum alloy mold and placed in a vacuum dryer. The degassing process is carried out at 30°C for 30 minutes until the residual bubbles in the gaps between the sugar particles are discharged; then it is cured, specifically in a vacuum drying oven at 80°C for two hours; then the cured composite material is ultrasonically cleaned to dissolve the sugar particles in the material, and the cleaning agent is deionized water; finally, it is dried at 60°C for 1 hour to remove moisture, thereby obtaining a hierarchical porous composite sensitive conductive unit 3. The interior of the hierarchical porous composite sensitive conductive unit 3 is a hierarchical porous structure with uniformly distributed diameters of 100μm and 10μm. Among them, polydimethylsiloxane (PDMS) is a flexible substrate, and conductive multi-walled carbon nanotubes (MWCNTs) are fillers to prepare composite materials. In the preparation process, sugar particles are used as pore-forming agents and perfluorotributylamine (FC43) is a sacrificial solution.

[0041] like Figure 3 and Figure 4 As shown, the sensing electrode unit 4 is a multi-layered flexible printed circuit board, including a sensing electrode layer, a first wire layer and a second wire layer stacked in sequence, the sensing electrode layer and the graded porous composite sensitive conductive unit 3 are stacked, and four sensing electrodes 5 arranged in a matrix array are laid in the sensing electrode layer and arranged in a central symmetrical manner, which are respectively recorded as the first sensing electrode S in the clockwise direction. 1 , the second sensing electrode S2 , the third sensing electrode S 3 and the fourth sensing electrode S 4 , that is, the first sensing electrode S 1 and the third sensing electrode S 3 Diagonally arranged, the second sensing electrode S 2 and the fourth sensing electrode S 4 Diagonally arranged; two parallel and spaced transverse copper wires 6 are laid in the first conductor layer, respectively denoted as the second copper wires T 2 and the fourth copper conductor T 4 , the second copper wire T 2 Set on the first sensing electrode S 1 and the second sensing electrode S 2 Directly below, and the second copper wire T 2 The axial direction of the first sensing electrode S 1 and the second sensing electrode S 2 The fourth copper conductor T is parallel to the connection direction. 4 Set at the third sensing electrode S 3 and the fourth sensing electrode S 4 Directly below, and the fourth copper wire T 4 The axial direction of the third sensing electrode S 3 and the fourth sensing electrode S 4 The second conductor layer is provided with two parallel and spaced longitudinal copper conductors 7, respectively denoted as the first copper conductors T 1 and the third copper conductor T 3 , the first copper wire T 1 Set on the first sensing electrode S 1 and the fourth copper conductor T 4 Directly below, and the first copper wire T 1 The axial direction of the first sensing electrode S 1 and the fourth copper conductor T 4 The connection direction of the third copper conductor T 3 Set at the second sensing electrode S 2 and the third sensing electrode S 3 Directly below, and the third copper wire T 3 The axial direction of the second sensing electrode S 2 and the third sensing electrode S 3 The first sensing electrode S 1 With the first copper wire T 1 Electrical connection, second sensing electrode S 2 With the second copper wire T 2 Electrical connection, third sensing electrode S 3 With the third copper conductor T 3 Electrical connection, fourth sensing electrode S4 With the fourth copper wire T 4 Electrical connection.

[0042] When a copper wire in the first wire layer or the second wire layer is in an activated state, the sensing electrode connected to the copper wire is recorded as the main sensing electrode; and the two copper wires in the other wire layer are both in an activated state, and the sensing electrodes connected to the two copper wires are recorded as the secondary sensing electrodes, the activated sensing electrode pair will constitute the effective electrodes of the capacitor. At this time, the sensing electrode unit 4 is defined as being in an independent measurement state, which is used to measure the shear force of the measured object 8. In different independent measurement states, the sensing capacitance of the first sensing electrode and the sensing electrode pair composed of the second and fourth sensing electrodes is defined as the first sensing capacitance C Dual1 The sensing capacitance of the second sensing electrode and the sensing electrode pair consisting of the first and third sensing electrodes is defined as the second sensing capacitance C Dual2 The sensing capacitance of the third sensing electrode and the sensing electrode pair consisting of the second and fourth sensing electrodes is defined as the third sensing capacitance C Dual3 The sensing capacitance of the fourth sensing electrode and the sensing electrode pair consisting of the first and third sensing electrodes is defined as the fourth sensing capacitance C Dual4 .

[0043] When the two copper wires in the first wire layer and the second wire layer are both in an activated state, specifically the first sensing electrode S 1 and the third sensing electrode S 3 Activate, the second sensing electrode S 2 and the fourth sensing electrode S 4 Activated, the sensing electrode unit 4 is in full measurement state, such as Figure 5 As shown, the sensing electrode pair S 1 and S 3 With the sensing electrode pair S 2 and S 4 The sensing capacitance between Ful ; Used to measure the approach distance of the object 8 and the normal force of the object 8, so as to realize the perception of proximity and three-dimensional pressure touch.

[0044] The present invention also proposes a highly sensitive proximity and three-dimensional pressure tactile sensing method, which uses a proximity and three-dimensional pressure tactile flexible capacitive sensor and includes the following steps:

[0045] When the object 8 is not in contact with the capacitive sensor, the sensing electrode layer 4 in each sensing unit 1 is in a full measurement state, and the sensing capacitance C in each sensing electrode layer 4 is detected. Ful , and compared with the calibrated sensor capacitance-distance curve, the distance between the measured object 8 and the sensor unit 1 is calculated;

[0046] When the object 8 is in contact with the capacitive sensor, the sensing capacitance C of the sensing electrode layer 4 in each sensing unit 1 is detected when the sensing electrode layer 4 is in the full measurement state. Ful and compare it with the calibrated sensor capacitance-normal force curve to calculate the normal force magnitude of the measured object 8; and detect the sensor capacitance C of the sensing electrode layer 4 in each sensor unit 1 when it is in an independent measurement state. Dual , and compared with the calibrated sensor capacitance-shear force curve, the magnitude and direction of the shear force acting on the measured object 8 are calculated, the plane where the shear force is located is perpendicular to the plane where the normal force is located, and the magnitude and direction of the final force are calculated based on the normal force and the shear force of the acting force.

[0047] Detect the sensing capacitance C of the sensing electrode layer 4 in each sensing unit 1 when it is in an independent measurement state Dual , and compared with the calibrated sensor capacitance-shear force curve, the shear force magnitude and direction of the measured object 8 are calculated, including:

[0048] The first sensing electrode S 1 and the second sensing electrode S 2 The X-axis is established in the direction of the connection line, with the first sensing electrode S 1 and the fourth sensing electrode S 4 The Y axis is established in the direction of the connection line, and the X axis is set perpendicular to the Y axis; the sensing electrode layer 4 in each sensing unit 1 is controlled to be in different independent measurement states, the change in the differential component between the main sensing electrode and the two auxiliary sensing electrodes in different independent measurement states is detected, and compared with the corresponding sensing capacitance-shear force component curve, the shear force magnitude on the X axis and the shear force magnitude on the Y axis are calculated, and then the shear force magnitude and direction of the force acting on the measured object 8 are obtained.

[0049] The specific principles are as follows:

[0050] like Figure 6 and Figure 7 As shown, when the measured object 8 gradually approaches the sensor, the measured object 8, the contact layer 2, the graded porous composite sensitive conductive unit 3 and the air can be regarded as dielectrics with different dielectric constants. The size of the sensing capacitor is determined by the common equivalent dielectric constant of the measured object 8, the contact layer 2, the graded porous composite sensitive conductive unit 3 and the air. The height of the highest point of the measured object 8 from the sensing electrode 5 is defined as h 1 The height of the lowest point of the object 8 (the distance between the object 8 and the sensor) from the sensing electrode 5 is h 2 The height between the highest point of the contact layer 2 and the sensing electrode 5 is h 3 , the thickness of the sensitive unit 3 is h 4 , then as the distance of the measured object 8 approaches, h 1 and h2 The height will be adjusted accordingly, and the equivalent dielectric constant ε eff Changes occur, as shown in formula (1):

[0051]

[0052] Among them, ε obj is the dielectric constant of the object 8, ε air is the dielectric constant of air, ε PDMS is the dielectric constant of contact layer 2, ε com is the dielectric constant of the graded porous composite sensitive conductive unit 3, ε i is the i-th equivalent dielectric constant, and other related parameters have the following relationship:

[0053]

[0054] is the complete elliptic integral of the first kind, k = k i , k 0 ', k i ', k 0 , k i and k i ' is the first and second equivalent elliptic modulus, and the two initial modulus parameters k 0 , k 0 ' can be calculated based on the structural parameters of the electrodes on the same surface:

[0055]

[0056] Among them, h i (i=1, 2, 3, 4) are the thicknesses of the object to be measured 8, the contact layer 2, the graded porous composite sensitive conductive unit 3 and the air in the layered structure, and w and a represent the width of the sensing electrode 5 and half of the spacing between the sensing electrodes 5, respectively.

[0057] Therefore, under the premise of knowing the dielectric constant of the approaching object 8, the relationship between the relative change of the sensing capacitance and the distance can be obtained:

[0058]

[0059] Wherein, l represents the length of the sensing electrode 5 .

[0060] At this time, we only need to pay attention to the full measurement state sensor capacitance C Ful The change of the measured object 8 is clearly related to the distance h from the sensor. 2 The functional relationship of can realize proximity measurement.

[0061] The graded porous composite sensitive conductive unit 3 uses carbon nanotubes as conductive fillers, and combined with the graded porous structure, two basic micro-nano structures appear, including conductive paths and separated electrode plates, which can basically be equivalent to micro-resistance and micro-capacitance. Under the action of external load, the movement of conductive particles inside or on the surface of the sensitive unit 3 causes the conduction path to be rearranged, the micro-resistance effect gradually weakens, and percolation occurs at a specific threshold and manifests as a sharp decrease in conductivity. The potential drop inside the conductive composite material can be ignored. The sensitive unit 3 is equivalent to the common electrode 9, and the electric field only exists between the equivalent common electrode 9 and the bottom sensing electrode 5. The equivalent common electrode 9 and the four sensing electrodes 5 constitute four equivalent capacitors, which can be defined as C according to the serial number of the corresponding sensing electrode 5. S1 ,C S2 ,C S3 and C S4 At the same time, under the action of load, charges accumulate on the surface of carbon nanotubes, forming an interface polarization effect, the microcapacitor area is enlarged and the distance between electrodes is shortened, so that the dielectric constant will be improved.

[0062] Therefore, when the object to be measured 8 contacts the surface of the contact layer 2, according to the specific state of motion, it acts on the contact layer 2 in the form of positive pressure or shear force, and the contact surface generates a pressure tactile force, causing the graded porous composite sensitive conductive unit 3 to deform. At this time, the external load will cause the plate spacing between the equivalent common electrode 9 and the sensing electrode 5 to change, and the equivalent dielectric constant will also change. Under the combined effect of the two changes, the sensing capacitance value changes.

[0063] like Figure 8 As shown, when the tactile force acts on the contact layer 2 of the sensing unit 1 in the form of shear force, the shear force can be decomposed into F x and F y , where F x The equivalent capacitance C S2 and C S3 The distance between the plates decreases, the capacitance increases, C S1 and C S4 The distance between the plates increases, and the capacitance decreases; F y The equivalent capacitance C S1 and C S2 The distance between the plates decreases, the capacitance increases, C S3 and C S4 The distance between the plates increases and the capacitance decreases. The shear force does not cause the graded porous composite sensitive conductive unit 3 to produce compression deformation in the vertical direction, so the equivalent dielectric constant hardly changes. x The equivalent capacitance change caused by S1 and C S4 ) and (C S2 and CS3 ) is obtained by the difference, and the shear force F y The equivalent capacitance change caused by S1 and C S2 ) and (C S3 and C S4 ) is obtained by calculating the difference between the two. In the present invention, four equivalent capacitors (C S1 ,C S2 ,C S3 and C S4 ) cannot be measured directly, and its relationship with the actual measured sensor capacitance is shown in formula (4):

[0064]

[0065] Therefore, the above difference can be calculated by the sensor capacitance (C Dual1 , C Dual2 , C Dual3 , C Dual4 ) is obtained by the difference between them.

[0066]

[0067] in, Indicates shear force F x The equivalent capacitance change caused by Indicates shear force F y The equivalent capacitance change caused by

[0068] By quantizing the four sensing capacitors (C Dual1 , C Dual2 , C Dual3 , C Dual4 The proportional relationship between the differential change of ) and the shear force measured by the sensor can realize the measurement of the shear force in the xy direction.

[0069] like Fig. 9 As shown in FIG. 1 , when the tactile force acts on the contact layer 2 of the sensing unit 1 in the form of normal pressure, the graded porous composite sensitive conductive unit 3 produces compression deformation in the vertical direction, so the equivalent dielectric constant changes significantly. At the same time, it is noted that in the full measurement state, the electrode pair S 1 and S 3 The center point of the equivalent capacitance between the common electrode 9 and the sensing electrode matrix of the entire sensing unit 1 is the same, so the capacitance will not be affected by the shear pressure change, but only by the normal pressure. Therefore, the capacitance change caused by the normal pressure can be simply calculated by the sensor capacitance C under the full measurement state. Ful The amount of change is obtained.

[0070]

[0071] Among them, 1 / C Ful =1 / C S1+S3 +1 / C S2+S4 , Represents the sensing capacitance C Ful The initial value of Indicates the normal pressure F z The equivalent capacitance change caused by

[0072] At this time, by quantifying the sensor capacitance C in the full measurement state Ful The proportional relationship between the change in and the normal pressure can realize the measurement of the normal pressure tactile force.

[0073] According to the percolation effect of conductive composite materials under load, the present invention utilizes the differential responses of sensitive units in different load areas, and proposes a dynamic reconstruction strategy for distributed robot pressure tactile perception and a proximity recognition detection method based on the principle of single-body tactile sensing. When not in contact with the object to be measured, the sensitive unit works completely in a dielectric state, which can realize proximity measurement. After contacting the object to be measured, the sensitive unit works in a common electrode state, which can realize three-dimensional pressure tactile measurement. Compared with traditional flexible dielectric materials, using graded porous composite materials as sensitive units can greatly improve the dielectric constant and deformation capacity of the sensitive units, thereby ensuring the high sensitivity of flexible proximity and three-dimensional pressure tactile measurements.

[0074] Finally, it should be noted that the above embodiments and explanations are only used to illustrate the technical solution of the present invention rather than to limit it. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope disclosed in the technical solution of the present invention, which should be included in the scope of protection of the claims of the present invention.

Claims

1. A highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor, characterized in that: The sensor unit (1) comprises a contact layer (2), a graded porous composite sensitive conductive unit (3) and a sensing electrode unit (4) which are sequentially stacked; when there is a distance between the measured object (8) and the contact layer (2), the graded porous composite sensitive conductive unit (3) completely works in a dielectric state, and the sensing electrode unit (4) is used to measure the approach distance of the measured object (8); when the measured object (8) contacts and presses the contact layer (2), the graded porous composite sensitive conductive unit (3) works in a common electrode state, and is used together with the sensing electrode unit (4) to measure the force applied to the measured object (8).

2. A highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 1, characterized in that: A dome-shaped protrusion is provided in the middle of the upper surface of the contact layer (2), and the object to be measured (8) acts on the dome-shaped protrusion of the contact layer (2).

3. A highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 1, characterized in that: The capacitive sensor comprises a plurality of sensing units (1), and the plurality of sensing units (1) are spliced ​​in the form of an array.

4. A highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 1, characterized in that: The preparation method of the hierarchical porous composite sensitive conductive unit (3) comprises the following steps: First, a base gel and a curing agent are mixed to obtain a polydimethylsiloxane pre-solution, and perfluorotributylamine is dispersed in the polydimethylsiloxane pre-solution and stirred thoroughly to obtain a PDMS-FC43 emulsion; then, a multi-walled carbon nanotube conductive material is added to the PDMS-FC43 emulsion and stirred thoroughly, and then sugar particles are added, and the final mixed emulsion is poured into a mold and placed in a vacuum dryer for degassing until the residual bubbles in the gaps between the sugar particles are discharged; then, curing is performed, and the cured composite material is cleaned to dissolve the sugar particles in the material; finally, moisture is removed to obtain a hierarchical porous composite sensitive conductive unit (3).

5. The high-sensitivity proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 1, characterized in that: The sensing electrode unit (4) comprises a sensing electrode layer, a first wire layer and a second wire layer which are stacked in sequence. The sensing electrode layer and the graded porous composite sensitive conductive unit (3) are stacked. Four sensing electrodes (5) arranged in a matrix array are laid in the sensing electrode layer, which are respectively marked as a first sensing electrode S1, a second sensing electrode S2, a third sensing electrode S3 and a fourth sensing electrode S4 in a clockwise direction. Two parallel and spaced transverse copper wires (6) are laid in the first wire layer, which are respectively marked as a second copper wire T2 and a fourth copper wire T4. The second copper wire T2 is arranged directly below the first sensing electrode S1 and the second sensing electrode S2. The fourth copper wire T3 is arranged directly below the first sensing electrode S1 and the second sensing electrode S2. The wire T4 is arranged directly below the third sensing electrode S3 and the fourth sensing electrode S4; two parallel and spaced longitudinal copper wires (7) are laid in the second wire layer, which are respectively denoted as the first copper wire T1 and the third copper wire T3; the first copper wire T1 is arranged directly below the first sensing electrode S1 and the fourth copper wire T4, and the third copper wire T3 is arranged directly below the second sensing electrode S2 and the third sensing electrode S3; the first sensing electrode S1 is electrically connected to the first copper wire T1, the second sensing electrode S2 is electrically connected to the second copper wire T2, the third sensing electrode S3 is electrically connected to the third copper wire T3, and the fourth sensing electrode S4 is electrically connected to the fourth copper wire T4.

6. A highly sensitive proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 5, characterized in that: One copper wire in the first wire layer or the second wire layer is in an activated state, and the sensing electrode connected to the copper wire is recorded as a main sensing electrode; and two copper wires in another wire layer are both in an activated state, and the sensing electrodes connected to the two copper wires are recorded as secondary sensing electrodes, then the sensing electrode unit (4) is in an independent measurement state, and is used to measure the shear force of the measured object (8); The two copper wires in the first wire layer and the second wire layer are both in an activated state, specifically the first sensing electrode S1 and the third sensing electrode S3 are activated, and the second sensing electrode S2 and the fourth sensing electrode S4 are activated, then the sensing electrode unit (4) is in a full measurement state, and is used to measure the approach distance of the measured object (8) and the normal force magnitude of the measured object (8), thereby realizing the perception of proximity and three-dimensional pressure touch.

7. A highly sensitive proximity and three-dimensional pressure tactile perception method, characterized in that: The sensing method adopts the proximity and three-dimensional pressure tactile flexible capacitive sensor according to claim 6, comprising the following steps: When the measured object (8) is not in contact with the capacitive sensor, the sensing electrode layer (4) in each sensing unit (1) is in a full measurement state, and the sensing capacitance C in each sensing electrode layer (4) is detected. Ful and compares it with a calibrated sensor capacitance-distance curve to calculate the distance between the measured object (8) and the sensor unit (1); When the object to be measured (8) contacts the capacitive sensor, the sensing capacitance C of the sensing electrode layer (4) in each sensing unit (1) is detected when the sensing capacitance C is in a full measurement state. Ful and compares it with the calibrated sensor capacitance-normal force curve to calculate the normal force magnitude of the measured object (8); and detects the sensor capacitance C of the sensing electrode layer (4) in each sensor unit (1) when it is in an independent measurement state. Dual and compared with the calibrated sensor capacitance-shear force curve, the magnitude and direction of the shear force acting on the measured object (8) are calculated, and the magnitude and direction of the final force are calculated based on the normal force and the shear force.

8. A highly sensitive proximity and three-dimensional pressure tactile perception method according to claim 7, characterized in that: The sensing capacitance C of the sensing electrode layer (4) in each sensing unit (1) when being in an independent measurement state is detected. Dual , and compared with the calibrated sensor capacitance-shear force curve, the shear force magnitude and direction of the force acting on the measured object (8) are calculated, specifically including: An X-axis is established by the connection direction of the first sensing electrode S1 and the second sensing electrode S2, and a Y-axis is established by the connection direction of the first sensing electrode S1 and the fourth sensing electrode S4, wherein the X-axis and the Y-axis are arranged perpendicularly; the sensing electrode layer (4) in each sensing unit (1) is controlled to be in different independent measurement states, the change amount of the difference component between the main sensing electrode and the two auxiliary sensing electrodes in different independent measurement states is detected, and the difference amount is compared with the corresponding sensing capacitance-shear force component curve, and the shear force magnitude on the X-axis and the shear force magnitude on the Y-axis are calculated, thereby obtaining the shear force magnitude and direction of the force acting on the measured object (8).

Images