Capacitive three-dimensional force dot matrix sensor, electronic skin and robot

Abstract

The utility model relates to a capacitive three-dimensional force dot matrix sensor, an electronic skin and a robot. The capacitive three-dimensional force dot matrix sensor comprises a sensing unit, a switch array, a CDC and a digital processing circuit, the sensing unit is provided with a flexible conductive layer, the conductive layer faces downwards to form a plurality of elastic curved surfaces arranged in a dot matrix, a first detection electrode, a second detection electrode, a third detection electrode and a fourth detection electrode are sequentially arranged below each elastic curved surface, and the first detection electrodes in the same row in the dot matrix are mutually coupled to form a row line. The third detection electrodes are mutually coupled to form another row line, the second detection electrodes in the same column in the dot matrix are mutually coupled to form a column line, and the fourth detection electrodes are mutually coupled to form another column line; the CDC is respectively coupled with each row and column line in the network through the switch array; each elastic curved surface is insulated from the corresponding detection electrode, and the flexible conductive layer is deformed by external force to change the material density and spatial distribution of the elastic curved surfaces in a mutual capacitance electric field; digital processing circuitry is coupled with the CDC.

Description

Technical Field

[0001] This utility model relates to machine tactile sensing, and more particularly to a capacitive three-dimensional force array sensor, electronic skin, and robot. Background Technology

[0002] With the rapid development of robotics technology, tactile sensing capabilities have become key to improving the intelligence level of robot environmental interaction.

[0003] Traditional robot tactile sensors generally achieve force detection based on piezoresistive, piezoelectric, photoelectric, and parallel plate mutual capacitance methods. Our company previously applied for patent CN119827015A, proposing a tactile sensor that uses planar mutual capacitance for force detection. The planar mutual capacitance field constructed by the double helix electrode structure achieves high sensitivity and high accuracy of force detection. Combined with the row and column scanning circuit topology network, a small number of CDC channels are used to form high-density multi-point measurement, which meets the tactile spatial resolution requirements of robot electronic skin. However, the solution mainly focuses on single-dimensional force detection and cannot capture the three-dimensional force (normal force and shear force) distribution of the contact surface, making it difficult to meet the needs of precision operation (such as flexible grasping) and complex environment perception. Utility Model Content

[0004] To address the shortcomings of existing technologies, a sensor for three-dimensional force lattice measurement using planar mutual capacitance is proposed.

[0005] This utility model discloses a capacitive three-dimensional force dot matrix sensor, comprising a sensing unit, a switch array, a capacitance-to-digital conversion circuit, and a digital processing circuit. The sensing unit has at least one flexible conductive layer, which protrudes downwards to form multiple elastic surfaces. These elastic surfaces are arranged to form a dot matrix that meets spatial resolution requirements. Below each elastic surface are a first detection electrode, a second detection electrode, a third detection electrode, and a fourth detection electrode arranged sequentially along its circumference. The first detection electrodes in the same row of the dot matrix are coupled to each other to form one row line in a staggered row-column circuit topology network, and the third detection electrodes are coupled to each other to form another row line. The second detection electrodes are coupled to form one column line in the network, and the fourth detection electrodes are coupled to form another column line. The capacitance-to-digital conversion circuit couples each row and column line in the network through a switch array to obtain the planar mutual capacitance formed by the two detection electrodes at each point. Each elastic surface is insulated from the corresponding detection electrode, and the downward projection of the elastic surface covers at least part of the area of ​​each corresponding detection electrode. The changes in the material density and spatial distribution of the elastic surface involved in the deformation of the flexible conductive layer by external force in the mutual capacitance electric field between each pair of corresponding detection electrodes are also considered. A digital processing circuit is coupled to the capacitance-to-digital conversion circuit.

[0006] The capacitive three-dimensional force array sensor of this utility model also includes the following auxiliary solutions:

[0007] The flexible conductive layer has a flexible insulating protective layer on its top surface, and the bottom surface of the protective layer has downward protrusions corresponding to the positions of each elastic curved surface. The flexible conductive layer is formed on the bottom surface of the protective layer by coating with conductive material, and the elastic curved surface is formed by the shape of the protrusions.

[0008] The gaps between each elastic surface and the detection electrode are filled with flexible insulating material.

[0009] The flexible conductive layer serves as the electric field disturbance electrode.

[0010] In this circuit, the capacitor-to-digital converter is coupled to a flexible conductive layer via a switch array. The flexible conductive layer serves as a multiplexed electrode for both proximity detection and electric field disturbance. The switch array acts as a time-division multiplexing channel for the flexible conductive layer to be coupled to the capacitor-to-digital converter or ground.

[0011] The flexible conductive layer comprises at least two layers that are insulated from each other; the flexible conductive layer serves as a self-capacitance electrode for detecting proximity and / or forms mutual capacitance electrodes in pairs.

[0012] The flexible conductive layer is coupled to ground via a gating switch.

[0013] The flexible conductive layer contains a corresponding region, and each detection electrode is located inside one or more flexible conductive layers.

[0014] Each detection electrode is arranged on the top surface of the circuit board; traces are arranged around the dot matrix on the top surface of the circuit board, and the outer edge of the flexible conductive layer is pressed onto the traces to form electrical coupling.

[0015] Among them, the elastic surface is a spherical surface or an ellipsoidal surface.

[0016] An electronic skin is also provided, including the aforementioned three-dimensional force sensor.

[0017] A robot is also provided, which includes the aforementioned electronic skin.

[0018] The three-dimensional force lattice sensing structure of this invention has advantages such as high force detection sensitivity and accuracy, easy three-dimensional force decoupling, significantly improved sensitivity of force detection in the shear direction, and saving CDC channels under the three-dimensional force dense lattice. Attached Figure Description

[0019] Figure 1 A stereoscopic view of the three-dimensional force array sensor is presented.

[0020] Figure 2 An exploded view of the three-dimensional force array sensor is given.

[0021] Figure 3The structure formed by coating a flexible conductive layer with a protective layer is presented.

[0022] Figure 4 The layout structure of the flexible circuit board is given.

[0023] Figure 5 Enlarged views of the detection electrodes and row / column traces on the flexible circuit board are provided. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0025] The three-dimensional force array sensor includes a sensing unit and a control chip. The control chip, as a microcomputer system, integrates a switch array, a capacitor-to-digital converter circuit, and a digital processing circuit.

[0026] See Figures 1 to 3 The sensing unit is the core of the sensor detection, including at least one flexible conductive layer 200. The flexible conductive layer 200 protrudes downward to form multiple elastic curved surfaces 210. The elastic curved surfaces 210 are arranged to form an 8x8 dense dot matrix, 1cm 2 The system uses 64 points arranged in a central array, and employs an interpolation algorithm to achieve a spatial resolution of ≥0.1mm.

[0027] See Figure 4 , Figure 5 Each elastic surface 210 has four electrodes below it. These four electrodes are formed by cutting a circular electrode into four equally sized segments, arranged sequentially along the circumference of the elastic surface 210 as a first detection electrode R1, a second detection electrode C1, a third detection electrode R2, and a fourth detection electrode C2. In the dot matrix, the first detection electrodes R1 in the same row are coupled to form a row line A1, and the third detection electrodes R2 are coupled to form another row line A2. In the dot matrix, the second detection electrodes C1 in the same column are coupled to form a column line B1, and the fourth detection electrodes C2 are coupled to form another column line B2. The row and column lines of adjacent electrodes are staggered, forming a two-row, two-column staggered circuit topology. Each elastic surface 210 is insulated from its corresponding detection electrode, and the downward projection of the elastic surface 210 at least covers a portion of the area of ​​each corresponding detection electrode.

[0028] The capacitance-to-digital converter (CDC) uses Δ-Σ modulation to directly convert the measured capacitance value into a ≥24-bit digital value by repeatedly charging and discharging the capacitor and comparing it with a reference capacitance. This improves the measurement sensitivity to the 1ff level. The digital value is then transmitted to a digital processing circuit for processing. The CDC uses a switch array to couple each row and column line in the network to obtain the planar mutual capacitance formed by the pairs of detection electrodes at each point. See [link to relevant documentation] Figure 5Below each sensing unit, through row and / or column scanning, the planar mutual capacitance combinations are listed as: (R1,C2), (C2,R2), (R2,C1), (R1,C2), (R1,R2), (C1,C2), (C1+R1,C2+R2), (C1+R2,C2+R1).

[0029] When the flexible conductive layer 200 is pressed by an external force, it deforms, which changes the material density and spatial distribution of the elastic surface 210 involved in the mutual capacitance electric field between each pair of corresponding detection electrodes. The spatial distribution of the dielectric constant of the material changes accordingly, causing the mutual capacitance of the underlying plane to change. The change corresponds to the external force, thereby reflecting the pressure change.

[0030] The three-dimensional force lattice sensing structure in this embodiment, by utilizing the flexible deformation of the elastic surface 210 and planar mutual capacitance measurement, achieves high force detection sensitivity and accuracy, with a static pressure accuracy of up to 1%FS. The four electrodes at each point form multiple sets of planar mutual capacitance for three-dimensional force decoupling, reducing the difficulty of decoupling normal and shear forces and significantly improving the sensitivity of shear force detection, reaching a measurement range of 0-15 N / cm. 2 The four electrodes are arranged in two rows and two columns, with the rows and columns interleaved, which saves CDC channels under a three-dimensional force-dense dot matrix, solves the wiring problem, and ensures the reliability of the sensor.

[0031] In this embodiment, the elastic surface 210 adopts a spherical surface or an ellipsoidal surface to further improve the force detection sensitivity.

[0032] See Figure 2 As an improvement, the top surface of the flexible conductive layer 200 has a flexible insulating protective layer 100 made of wear-resistant material. The bottom surface of the protective layer 100 has downward protrusions corresponding to each elastic curved surface 210. The flexible conductive layer 200 is formed on the bottom surface of the protective layer 100 by coating with conductive material. The positions affected by the shape of the protrusions form elastic curved surfaces 210. Based on current technology, a sensor thickness of 1mm (0.4mm protective layer wall thickness + 0.4mm protrusion height + 0.15mm FPC) and a bending radius ≤ 0.5cm can be achieved. Furthermore, the gaps between each elastic curved surface 210 and the detection electrode are filled with flexible insulating material 300 to replace the spatial gaps, which can increase the measuring range.

[0033] See Figure 2 , Figure 4The circuit board 400 uses an FPC (Flexible Printed Circuit), and each detection electrode is arranged on the top surface of the circuit board 400. A flexible conductive layer 200 contains a corresponding area, and each detection electrode is located inside one or more flexible conductive layers 200 to reduce external electric field interference. Traces 410 are arranged around the dot matrix on the top surface of the circuit board 400. The outer edge of the flexible conductive layer 200 is pressed onto the traces 410 to form electrical coupling, creating an enclosure and achieving electrical connection, facilitating wiring.

[0034] As an improved design, the flexible conductive layer 200 acts as an electric field disturbance electrode, causing a change in planar mutual capacitance when pressure is applied. Furthermore, the capacitance-to-digital conversion circuit is coupled to the flexible conductive layer 200 via a switch array. The flexible conductive layer 200 serves as a multiplexed electrode for both the proximity detection electrode and the electric field disturbance electrode, and the switch array acts as a time-division multiplexing channel for coupling the flexible conductive layer 200 to the capacitance-to-digital conversion circuit or ground. Before pressure is detected, the flexible conductive layer 200, coupled to the capacitance-to-digital conversion circuit, acts as a proximity detection electrode to sense the approach of an object; after the object is detected, it is switched to ground via the switch array, forming a shield and gradually absorbing the planar mutual capacitance electric field as pressure is applied. Furthermore, at least two flexible conductive layers 200 can be provided and are mutually insulated, such as... Figure 3 The inner surface conductive coating is divided into four regions, each region serving as a self-capacitance electrode for proximity detection, and / or forming a pair of mutual capacitance electrodes. It should be understood that the flexible conductive layer 200 may not be configured with proximity detection functionality, but only serves as a shield and absorbs the electric field during force measurement. In this case, the flexible conductive layer 200 is coupled to ground through a gating switch.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit the scope of protection of this utility model. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the essence and scope of the technical solutions of this utility model.

Claims

1. A capacitive three-dimensional force array sensor, characterized in that: Includes sensing unit, switch array, capacitor-to-digital converter circuit, and digital processing circuit; The sensing unit has at least one flexible conductive layer, which protrudes downward to form multiple elastic curved surfaces. The elastic curved surfaces are arranged to form a dot matrix that meets the spatial resolution requirements. Below each elastic surface are arranged a first detection electrode, a second detection electrode, a third detection electrode, and a fourth detection electrode in sequence along its circumference. The first detection electrodes in the same row of the dot matrix are coupled to each other to form one row line in the row-column misaligned circuit topology network, the third detection electrodes are coupled to each other to form another row line, the second detection electrodes in the same column of the dot matrix are coupled to each other to form one column line in the network, and the fourth detection electrodes are coupled to each other to form another column line. The capacitance-to-digital conversion circuit uses a switch array to couple each row and column line in the network to obtain the planar mutual capacitance formed by the two detection electrodes at each point. Each elastic surface is insulated from its corresponding detection electrode. The downward projection of the elastic surface covers at least a portion of the area of ​​each corresponding detection electrode. The changes in the material density and spatial distribution of the elastic surface involved in the deformation of the flexible conductive layer by external force in the mutual capacitance electric field between each pair of corresponding detection electrodes. The digital processing circuit is coupled to the capacitor-to-digital converter circuit.

2. The capacitive three-dimensional force array sensor according to claim 1, characterized in that: The top surface of the flexible conductive layer has a flexible insulating protective layer, and the bottom surface of the protective layer has a downward protrusion corresponding to each elastic curved surface. The flexible conductive layer is formed on the bottom surface of the protective layer by coating with conductive material, and the elastic curved surface is formed by the influence of the raised shape.

3. The capacitive three-dimensional force array sensor according to claim 1 or 2, characterized in that: The gaps between each elastic curved surface and the detection electrode are filled with flexible insulating material.

4. The capacitive three-dimensional force array sensor according to claim 1, characterized in that: The flexible conductive layer serves as an electrode for electric field disturbance.

5. The capacitive three-dimensional force array sensor according to claim 4, characterized in that: The capacitor-to-digital converter circuit is coupled to a flexible conductive layer through a switch array. The flexible conductive layer serves as a multiplexed electrode for proximity detection and electric field disturbance. The switch array serves as a time-division multiplexing channel for the flexible conductive layer to be coupled to the capacitor-to-digital converter circuit or ground.

6. The capacitive three-dimensional force array sensor according to claim 5, characterized in that: The flexible conductive layer has at least two layers that are insulated from each other; The flexible conductive layer serves as a self-capacitance electrode for detecting proximity and / or as a mutual capacitance electrode in pairs.

7. The capacitive three-dimensional force array sensor according to claim 4, characterized in that: The flexible conductive layer is coupled to ground via a gating switch.

8. The capacitive three-dimensional force array sensor according to claim 1, characterized in that: The flexible conductive layer contains a corresponding region, and each detection electrode is located inside one or more flexible conductive layers.

9. The capacitive three-dimensional force array sensor according to claim 8, characterized in that: Each detection electrode is arranged on the top surface of the circuit board; The top surface of the circuit board has traces arranged around the dot matrix, and the outer edge of the flexible conductive layer is pressed onto the traces to form electrical coupling.

10. The capacitive three-dimensional force array sensor according to claim 1, characterized in that: The elastic surface is either a spherical surface or an ellipsoidal surface.

11. An electronic skin, characterized in that, Including the capacitive three-dimensional force array sensor as described in any one of claims 1-10.

12. A robot, characterized in that, Including the electronic skin as described in claim 11.

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