Capacitive mechanical sensor based on elastic electrode, electronic skin and robot

Abstract

The invention relates to a capacitive mechanical sensor based on an elastic electrode, electronic skin and a robot. The sensor comprises a base body, a capacitance digital conversion circuit and a processing module, an action electrode is arranged on the surface of the base body and is an elastic bending electrode, one or more static electrodes are arranged above or below the action electrode, the projection of each action electrode relative to the corresponding static electrode at least covers part of the area of the corresponding static electrode, and at least one end of the bending electrode is fixed to the base body for positioning. The other end is bent to form a suspended end far away from the static electrode; the action electrode is isolated from the static electrode through an insulating layer, and the action electrode deforms under the action of external force to change the indirect contact area of the bent part on the static electrode; the capacitance digital conversion circuit is coupled with the corresponding electrode to obtain capacitance between the action electrode and the static electrode; the processing module is coupled with the capacitance digital conversion circuit and used for outputting an electric signal representing the acting force according to the capacitance.

Description

Technical Field

[0001] The invention relates to tactile perception of a robot, and in particular to a capacitive mechanical sensor, electronic skin and a robot based on elastic electrodes. Background Art

[0002] The intelligent robot relies on the tactile sensors of the electronic skin on its outer surface to achieve tactile perception and forms an intelligent response by collecting and processing tactile information.

[0003] In terms of tactile sensors, capacitive tactile sensors are currently widely favored by the market due to their many advantages such as high detection accuracy, easy layout, and low cost. At the same time, the existing mature technology capacitance-to-digital conversion circuit (CDC), such as DAI7142 and ADI7147, uses a Δ-∑ modulation method to charge and discharge the measured capacitance multiple times and compare it with the reference capacitance (see: US Patent Number: 5,134,401) to directly convert the measured capacitance value into a digital value, which can increase the measurement sensitivity of the capacitance to 1ff level, and it is also easy to meet the measurement system's requirements for capacitance measurement sensitivity. At the same time, it also has the characteristics of immunity to stray capacitance. In particular, the design of these chips has multiple channels, making the circuit design simple and convenient.

[0004] CN108446042B proposes a capacitive touch sensor and an intelligent robot. The interior of the multifunctional layer is provided with two layers of electrodes, the upper layer is a cross-shaped common electrode, and the lower layer is four independent electrodes corresponding to the upper cross-shaped common electrode. The upper static electrode constitutes four parallel plate capacitors for measuring the size and direction of three-dimensional force. The scheme mainly relies on pressing to generate a change in the distance between the upper static electrodes to change the capacitance. The capacitance change is relatively small, resulting in the pressure resolution of the sensor not being particularly excellent.

[0005] In order to improve the pressure resolution of the detection, CN111896165A proposes a capacitive three-dimensional force vector sensor structure. Through the upper electrode of the multifunctional layer, the four-petal lower electrode arranged below, and the insulating layer in the middle, the capacitance is changed mainly by the change of the contact area to realize the detection of the size and direction of the three-dimensional force, and the force resolution of 0.01 grams is achieved, which exceeds the force resolution of 0.019 grams of human fingers. Although the three-dimensional force vector sensing structure of CN111896165A has good mechanical resolution, it also has weaknesses: the upper electrode is inverted to form a lower convex hemisphere inside the multifunctional layer to contact the insulating layer on the lower electrode. The upper electrode must meet both flexible deformation and rebound. The material must be made of conductive rubber. After pressing, the center of the lower convex spherical surface of the conductive rubber is difficult to accurately return to the center of the four-petal lower electrode. The center reference is prone to position deviation. At the same time, long-term use of the lower conductive rubber contact surface wear and material aging are likely to aggravate this problem. Summary of the invention

[0006] The present invention realizes tactile sensing detection based on capacitive technology, achieves layout and cost advantages, and realizes high pressure resolution capability, while solving the problem of center position deviation of pressing rebound.

[0007] To this end, a capacitive mechanical sensor based on elastic electrodes is provided, comprising a substrate, a capacitance-to-digital conversion circuit, and a processing module; an action electrode is arranged on the surface of the substrate, the action electrode is an elastic bending electrode, one or more static electrodes are arranged above or below the action electrode, the projection of each action electrode relative to the static electrode at least covers a partial area of ​​the corresponding static electrode, at least one end of the bending electrode is fixed to the substrate for positioning, and the other end is bent to form a suspended end far away from the static electrode; the action electrode is isolated from the static electrode by an insulating layer, and the action electrode is deformed under the action of an external force to change the indirect contact area of ​​the bending part on the static electrode; the capacitance-to-digital conversion circuit is coupled to the corresponding electrode to obtain the capacitance between the action electrode and the static electrode; the processing module is coupled to the capacitance-to-digital conversion circuit, and is used to output an electrical signal representing the force based on the capacitance.

[0008] As an implementation scheme, the action electrode is provided with a first electrode, and the static electrode is provided with a second electrode, and the projection of the first electrode relative to the static electrode at least covers a partial area of ​​the second electrode.

[0009] As another implementation scheme, a first electrode is set as a dynamic electrode, and a second electrode and a third electrode are set as a static electrode. The projection of the first electrode relative to the static electrode at least synchronously covers a portion of the area of ​​the second electrode and the third electrode, and the shape of the first electrode is configured so that it can form a difference in the projection area and / or distance relative to the second electrode and the third electrode when subjected to circumferential twisting by an external force.

[0010] As another implementation scheme, a first electrode is provided as a static electrode, and at least three electrodes are provided as action electrodes. The action electrodes are circumferentially distributed around the geometric center of the first electrode, and the projection of the first electrode relative to the action electrode at least synchronously covers a partial area of ​​each action electrode.

[0011] As another implementation scheme, at least three electrodes are arranged in a circumferential distribution for the action electrode, and each action electrode is arranged corresponding to at least one static electrode, and the projection of each action electrode relative to the static electrode at least covers a partial area of ​​the corresponding static electrode. Further, at least two static electrodes are arranged corresponding to each action electrode, and the projection of the action electrode relative to the static electrode at least synchronously covers a partial area of ​​the corresponding static electrodes, and the shape of the action electrode is configured to form a difference in the projection area and / or distance of the corresponding static electrodes when subjected to circumferential twisting by an external force. Further, each action electrode and / or static electrode is formed into an axisymmetric distribution. Further, it includes a rigid pressure-bearing component for bearing force, and the suspended ends of each action electrode are commonly connected to the rigid pressure-bearing component. Further, the action electrode is bent outward or inward relative to the center of its circumferential distribution.

[0012] As another improvement, a shielding electrode is provided on the substrate, the shielding electrode is arranged around the static electrode, and forms a shield by grounding or forms an equipotential shield by coupling a capacitor digital conversion circuit. Further, the action electrode is coupled with the shielding electrode; and / or one end of the action electrode is physically connected to the shielding electrode to form a positioning. Further, the substrate is a circuit board, the static electrode and / or the shielding electrode are printed on the surface of the circuit board; and the action electrode is a metal spring.

[0013] As another improvement, the curved electrode is made of pure elastic material.

[0014] As another improvement, the thickness of the insulating layer is configured to be between 10 nanometers and 1 millimeter.

[0015] Also provided is an electronic skin comprising the capacitive mechanical sensor.

[0016] A robot is also provided, comprising the electronic skin.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] (1) The moving electrode is isolated from the static electrode by an insulating layer, so that the change in contact area of ​​the curved part produces a huge change in capacitance, achieving a high mechanical resolution;

[0020] (2) The action electrode is a curved electrode, and the fixed end plays a positioning role. It uses its own elasticity to press back to the center and maintain the uniformity of the reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The schematic diagram of the mechanical sensor structure using elastic electrodes to measure XYZ three-dimensional forces is given;

[0022] Figure 2The structure for further measuring torque on the three-dimensional force sensor is given;

[0023] Figure 3 A schematic diagram of the structure in which the action electrode bends outward relative to the center is given;

[0024] Figure 4 A schematic diagram of another mechanical sensor structure using elastic electrodes to measure three-dimensional forces is given;

[0025] Figure 5a A schematic diagram of a mechanical sensor structure using elastic electrodes to measure only normal force is given; and Figure 5b A schematic diagram of the structure of a mechanical sensor using elastic electrodes to measure normal force and torque is given. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0027] The capacitive mechanical sensor based on elastic electrodes of the embodiment of the present invention includes a substrate, a capacitance-to-digital conversion circuit, a processing module and an electrode unit. The substrate can be implemented using a circuit board as a carrier. The electrode unit includes an action electrode arranged on the surface of the circuit board, and the action electrode is an elastic bending electrode, which can be implemented using a bent metal spring. There are one or more static electrodes above or below the action electrode, and the static electrode is fixed to the circuit board. A metal electrode is formed as a static electrode by printing on the surface of the circuit board. The projection of each action electrode relative to the static electrode at least covers a partial area of ​​the corresponding static electrode, forming an upper and lower distribution and an intersection of the projections. At least one end of the action electrode is fixed to the substrate for positioning, and it rebounds by its own elasticity when pressed, and the other end of the action electrode is bent to form a suspended end away from the static electrode.

[0028] The action electrode and the static electrode are isolated by an insulating layer. The insulating layer is formed into a coating using insulating ink, for example, to achieve the purpose of a thin layer, thereby reducing the distance between the action electrode and the static electrode. The action electrode is deformed under the action of an external force to change the indirect contact area of ​​the bending part on the static electrode, that is, the area where the action electrode is pressed on the static electrode. The capacitance-to-digital conversion circuit is coupled to the corresponding electrode to obtain the capacitance between the action electrode and the static electrode. The processing module is coupled to the capacitance-to-digital conversion circuit to output an electrical signal representing the force based on the capacitance.

[0029] When the suspended end is subjected to pressure, the actuating electrode bends downward or pulls sideways in the direction of the force, and the indirect contact area between the bent part and the static electrode changes significantly, and the capacitance value changes. Since there is only a thin insulating layer between the two electrodes, the electrode spacing in the contact area is very small. Such a close distance plus the dielectric constant of the insulating layer is several times greater than that of air, the capacitance change generated based on the significant change in the indirect contact area is very large, achieving a higher mechanical resolution. After pressing and releasing, the fixed end of the actuating electrode is positioned, and the rest of the elasticity returns to the original position, restoring the center alignment and maintaining a unified reference.

[0030] As an exemplary implementation, as an improvement, the curved electrode is made of pure elastic material, such as in the form of elastic metal sheets, which is a further improvement over the rubber doped with conductive graphite carbon black or metal particles, which changes the rubber properties, deteriorates the elasticity, and has insufficient rebound speed. As another improvement, the thickness of the insulating layer is configured to be between 10 nanometers and 1 mm. The insulating layer is coated with insulating ink. If the thickness of the insulating ink is 10 microns, the dielectric constant of the insulating ink is 3. According to the capacitance formula C = εr*ε0*A / d, ε0 = 8.854187817x 10-12F / m, ε0 is the vacuum dielectric constant, εr is the relative dielectric constant, and 1mm 2 The contact area capacitance is 886*3=2.66pF. The actual capacitance is the series connection of air capacitance and insulating ink. When it is 10 microns away, the capacitance becomes the series connection of 0.886pF and 2.66pF, which will drop to 0.66pF, which is equivalent to 2pF. According to the high-precision capacitance measurement of the above sensor structure, the change can reach 4 million. If MEMS technology is used, the insulating coating can be 1um, 0.1mm 2 Just change.

[0031] To help understand the various possibilities of implementing the above-mentioned solutions, multiple implementation schemes are given below. It should be understood that these schemes are merely illustrations of exemplary structural implementation methods.

[0032] Figure 1The schematic diagram of the structure of a mechanical sensor using elastic electrodes to measure XYZ three-dimensional forces is given. The sensor includes a circuit board 101, a static electrode 102, an action electrode 103, and an upper laminate 104. A capacitance detection chip is arranged on the circuit board 101, and the chip integrates a capacitance digital conversion circuit and a processing module. Four fan-shaped static electrodes 102 are printed on the top surface of the board 101. The action electrode 103 is provided with four strip metal electrodes distributed circumferentially, and each action electrode 103 corresponds to a fan-shaped static electrode 102, and the projection of each action electrode relative to the static electrode at least covers a partial area of ​​the corresponding static electrode. One end of the action electrode 103 is connected and fixed to the circuit board 101, and one end is connected to the press plate 104. The four action electrodes 103 jointly support and lift the press plate 104, and the bent part of the action electrode 103 is pressed on the static electrode 102 to form an indirect contact. When the pressure plate 104 is subjected to vertical pressure, the action electrode 103 bends downward with the pressure plate, the contact area with the fan-shaped electrode increases, and the capacitance value increases; when the pressure plate 104 receives horizontal pressure, the action electrode 103 is pulled sideways with the pressure plate, and the contact area between the four action electrodes and the fan-shaped electrode changes differently, thereby judging the direction and magnitude of the horizontal pressure. In the above, the pressure plate 104 serves as a rigid pressure-bearing component for bearing force, and the suspended ends of each action electrode 103 are connected to the rigid pressure-bearing component together, so that the sensor returns to normal position and is corrected together under the interaction of multiple action electrodes 103. Each action electrode 103 and / or static electrode 102 is axially symmetrically distributed, forming a uniform distribution to improve the accuracy of the sensor.

[0033] Furthermore, the pressing can be set to achieve the change from line contact to surface contact, forming a large multiple of the area change of the front and rear indirect contact areas during the pressing process, further expanding the range of capacitance value change.

[0034] Figure 2 The structure for further measuring torque on the three-dimensional force sensor is shown. Among them, each action electrode 103 is correspondingly provided with at least two static electrodes 1021, 1022, and the projection of the action electrode relative to the static electrode at least synchronously covers the partial area of ​​the corresponding static electrodes, and the shape of the action electrode is configured to be able to form a difference in the projection area and / or distance of the corresponding static electrodes when subjected to circumferential twisting by an external force. Specifically, each action electrode 103 is arranged to span two fan-shaped electrodes in the width direction, and when the pressing plate 104 is subjected to vertical pressure, the action electrode 103 bends downward with the pressing plate, and the indirect contact area with the electrodes 1021, 1022 becomes larger, and the capacitance value becomes larger; when the pressing plate 104 is subjected to circumferential force, the action electrode 103 is circumferentially twisted with the pressing plate, and the capacitance C1 formed by the action electrode 103 and the static electrode 1021, and the capacitance C2 formed by the action electrode 103 and the static electrode 1022, the two capacitance values ​​are different, and the torque can be obtained based on the difference.

[0035] Further, see Figure 1 , Figure 2 , a printed shielding electrode 105 is provided on the substrate 101, and the shielding electrode 105 is arranged around the static electrode 102, and forms a shield by grounding or forms an equipotential shield by coupling a capacitor digital conversion circuit, so as to improve the anti-interference ability of mechanical measurement. Preferably, the action electrode 103 is coupled with the shielding electrode 105 to jointly form a shield for the static electrode 102, and the action electrode 103 is used as a part of the shielding electrode to improve the stability of the sensor; and / or, one end of the action electrode 103 is directly physically connected to the shielding electrode to form a positioning, so as to achieve a simplified and stable structure.

[0036] As an example, the action electrode 103 can be set as follows Figure 1 or Figure 2 As shown, the center of the circumferential distribution of each action electrode is bent inward, and it can also be set as follows Figure 3 The center of the circumferential distribution is shown to bend outwards, at which time the shielding electrode 105 is located on the pressure plate 104 to couple the various action electrodes. The outward bending solution expands when pressed, forming a larger bending deformation than the inward bending solution, so the outward bending solution has the advantage of a wider range.

[0037] Figure 4 Another mechanical sensor structure schematic diagram using elastic electrodes to measure three-dimensional force is given. Relatively simplified, specifically, the static electrode 102 is printed on the top surface of the substrate 201, and the static electrode 102 is set as a ring as the first electrode. The action electrode 203 is set with four electrodes, and each action electrode 203 forms a circumferential distribution around the geometric center of the first electrode, and the projection of the first electrode relative to the action electrode at least synchronously covers a part of the area of ​​each action electrode. The suspended ends of each action electrode 203 jointly support the pressure plate 204, and the bent part of the action electrode 203 presses on the static electrode to form an indirect contact. When the pressure plate 204 is subjected to vertical pressure, the action electrode 203 bends downward with the pressure plate, and the contact area of ​​each action electrode 203 with the static electrode becomes larger, and the capacitance value becomes larger; when the pressure plate 204 receives horizontal pressure, the action electrode 203 is pulled sideways with the pressure plate, and the indirect contact area of ​​the four action electrodes with the static electrode changes differently, and the four capacitance outputs formed by the four action electrodes and the static electrode are different, which is used to judge the direction and magnitude of the horizontal pressure.

[0038] In some cases where only the normal force needs to be measured, the sensor can be further simplified. Figure 5a A schematic diagram of a mechanical sensor structure that uses elastic electrodes to measure only normal force is given. The action electrode is provided with a first electrode 301, and the static electrode is provided with a second electrode 302. The projection of the first electrode relative to the static electrode covers at least part of the area of ​​the second electrode. When the pressure plate is subjected to vertical pressure, the first electrode 301 bends downward with the pressure plate, and the indirect contact area with the second electrode 302 increases, and the capacitance value increases.

[0039] Figure 5b The schematic diagram of the structure of a mechanical sensor using elastic electrodes to measure normal force and torque is given. The action electrode is provided with a first electrode 301, and the static electrode is provided with a second electrode 3021 and a third electrode 3022. The projection of the first electrode 301 relative to the static electrode at least synchronously covers part of the area of ​​the second electrode 3021 and the third electrode 3022, and the shape of the first electrode 301 is configured to form a difference in the projection area and / or distance relative to the second electrode 3021 and the third electrode 3022 when subjected to circumferential torsion by an external force. When the pressing plate is subjected to vertical pressure, the first electrode 301 bends downward with the pressing plate, and the indirect contact area with the electrodes 3021 and 3022 increases, and the capacitance value increases; when the pressing plate is subjected to circumferential force, the first electrode 301 is subjected to circumferential torsion with the pressing plate, and 301 forms two capacitance values ​​with 3021 and 3022 respectively to produce a difference, and the torque is further measured based on this.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, 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 essence and scope of the technical solution of the present invention.

Claims

1. A capacitive mechanical sensor based on elastic electrodes, characterized in that: It includes a substrate, a capacitance-to-digital conversion circuit, and a processing module; An action electrode is arranged on the surface of the substrate, the action electrode is an elastic bending electrode, one or more static electrodes are arranged above or below the action electrode, the projection of each action electrode relative to the static electrode at least covers a part of the area of ​​the corresponding static electrode, at least one end of the bending electrode is fixed to the substrate for positioning, and the other end is bent to form a suspended end far away from the static electrode; The action electrode and the static electrode are isolated by an insulating layer, and the action electrode is deformed under the action of external force to change the indirect contact area of ​​the bending part on the static electrode; The capacitance-to-digital conversion circuit is coupled to the corresponding electrodes to obtain the capacitance between the action electrode and the static electrode; The processing module is coupled to a capacitance-to-digital conversion circuit and is used to output an electrical signal representing the force according to the capacitance.

2. The capacitive mechanical sensor according to claim 1, characterized in that: The action electrode is provided with a first electrode, and the static electrode is provided with a second electrode, and the projection of the first electrode relative to the static electrode at least covers a partial area of ​​the second electrode.

3. The capacitive mechanical sensor according to claim 1, characterized in that: The action electrode is provided with a first electrode, and the static electrode is provided with a second electrode and a third electrode. The projection of the first electrode relative to the static electrode at least synchronously covers a portion of the area of ​​the second electrode and the third electrode, and the shape of the first electrode is configured so that it can form a difference in the projection area and / or distance relative to the second electrode and the third electrode when subjected to circumferential twisting by an external force.

4. The capacitive mechanical sensor according to claim 1, characterized in that: The static electrode is provided with a first electrode, and the action electrode is provided with at least three electrodes. The action electrodes are circumferentially distributed around the geometric center of the first electrode, and the projection of the first electrode relative to the action electrode at least synchronously covers a partial area of ​​each action electrode.

5. The capacitive mechanical sensor according to claim 1, characterized in that: The action electrode is provided with at least three electrodes distributed circumferentially, each action electrode is provided with at least one static electrode correspondingly, and the projection of each action electrode relative to the static electrode at least covers a partial area of ​​the corresponding static electrode.

6. The capacitive mechanical sensor according to claim 5, characterized in that: At least two static electrodes are arranged corresponding to each action electrode, and the projection of the action electrode relative to the static electrode at least synchronously covers a portion of the area of ​​each corresponding static electrode. The shape of the action electrode is configured so that it can form a difference in the projection area and / or distance of each corresponding static electrode when subjected to circumferential twisting by an external force.

7. The capacitive mechanical sensor according to claim 4, 5 or 6, characterized in that: The various action electrodes and / or static electrodes are distributed in an axisymmetric manner.

8. The capacitive mechanical sensor according to claim 5 or 6, characterized in that: It comprises a rigid pressure-bearing component for bearing force, and the suspended ends of each action electrode are commonly connected to the rigid pressure-bearing component.

9. The capacitive mechanical sensor according to claim 5 or 6, characterized in that: The actuating electrodes are bent outward or inward relative to the center of their circumferential distribution.

10. The capacitive mechanical sensor according to any one of claims 1 to 6, characterized in that: A shielding electrode is arranged on the substrate, which is arranged around the static electrode and forms a shield through grounding or forms an equipotential shield through a coupling capacitor digital conversion circuit.

11. The capacitive mechanical sensor according to claim 10, characterized in that: The action electrode is coupled to the shielding electrode; And / or, one end of the action electrode is physically connected to the shielding electrode to form the positioning.

12. The capacitive mechanical sensor according to claim 11, characterized in that: The substrate is a circuit board, and the static electrode and / or the shielding electrode are printed on the surface of the circuit board; The action electrode is a metal spring.

13. The capacitive mechanical sensor according to claim 1, characterized in that: The curved electrodes are made of pure elastic material.

14. The capacitive mechanical sensor according to claim 1, characterized in that: The thickness of the insulating layer is configured to be between 10 nanometers and 1 millimeter.

15. An electronic skin, characterized in that: Comprising a capacitive mechanical sensor as claimed in any one of claims 1 to 14.

16. A robot, characterized in that: Comprising the electronic skin as described in claim 15.

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