Tactile sensor for detection by using planar mutual capacitance, manipulator and sole wearable device

Abstract

The utility model relates to a tactile sensor, a manipulator and a sole wearable device using planar mutual capacitance for detection. The tactile sensor comprises a sensing unit, a CDC and a digital processing circuit. The sensing unit is provided with a flexible electrode, the flexible electrode forms an elastic curved surface bulge, each bulge corresponds to the first detection electrode and the second detection electrode, and the bulges and the first detection electrode form planar mutual capacitance; an insulating layer is arranged between each bulge and the corresponding detection electrode, and the shape of a gap between the first detection electrode and the second detection electrode is configured as follows: the bulge gradually changes the area of indirect contact between the first detection electrode and the second detection electrode and / or the length of a mutual capacitance gap path between the first detection electrode and the second detection electrode along with stress deformation in the projection area of the bulge; each flexible electrode is configured to be coupled with the ground during detection electrode capacitance sampling; the CDC is respectively coupled with each detection electrode; and the digital processing circuit is used for logic processing and / or logic sequence control and is coupled with the CDC.

Description

Technical Field

[0001] This utility model relates to machine tactile sensing, and more particularly to a tactile sensor, robotic arm, and foot-wearing device that utilizes planar mutual capacitance for detection. Background Technology

[0002] Robotic arms use grippers to perform tasks such as grasping, handling, or manipulating objects according to a fixed program. With the development of robotics, the grippers of robotic arms need to be able to sense the pressure applied to objects, achieving machine tactile sensing. Electronic skin is mainly used to achieve machine tactile sensing. Electronic skin is attached to the mechanical surface where tactile sensation is needed, and pressure is detected through built-in tactile sensors. Capacitive tactile sensors are favored in machine tactile applications due to their ease of electrode placement and the ability to form dense arrays.

[0003] Capacitive pressure sensing is mainly divided into self-capacitance and mutual capacitance methods.

[0004] In the self-capacitance method, the capacitance-to-digital converter (CDC) excites the input electrode and obtains the capacitance from the electrode itself. The problem is that the self-capacitance is a capacitance to ground. When a large area of ​​metal is used on the surface of some robotic arms, the detection of the self-capacitance is greatly affected. Especially when pressure distribution detection is performed on the sole of the robot's foot (for walking posture control of the robotic foot), the sole of the foot is too close to the ground, and the influence of the ground on the self-capacitance almost makes it impossible to measure effective information.

[0005] The mutual capacitance method basically adopts the principle of parallel plate capacitors. Through the upper and lower electrodes, the CDC inputs excitation to one and receives from the other. Force measurement is mainly achieved by changing the distance between the upper and lower electrodes, and the mutual capacitance increases with pressure. CN111896165A discloses a touch sensor structure where the upper electrode protrudes downward to form a hemispherical elastic electrode. One lower electrode measures single-dimensional force, and four electrodes measure three-dimensional force. The upper layer acts as the excitation, and the lower layer as the receiver. High-sensitivity mechanical sensing is achieved by creating an order-of-magnitude change in the indirect contact area (with an insulating layer in between) between the hemispherical protrusion and the lower electrode through pressure, resulting in a point-to-surface indirect contact area. However, the essence is still that the mutual capacitance increases with pressure. Utility Model Content

[0006] This invention aims to improve or supplement the deficiencies of the prior art by providing a tactile sensor, robotic arm, and foot-wearing device that utilizes planar mutual capacitance for detection.

[0007] To address this, a tactile sensor utilizing planar mutual capacitance for detection is provided, comprising a sensing unit, a capacitance-to-digital conversion circuit, and a digital processing circuit. The sensing unit has at least one flexible electrode, and at least one protrusion is formed on the side of the flexible electrode facing a first direction. The outer surface of the protrusion is an elastic curved surface. Each protrusion corresponds to a first detection electrode and a second detection electrode, which form a planar mutual capacitance for pressure detection. An insulating layer is provided between each protrusion and its corresponding detection electrode. The projection of the protrusion towards the first direction at least covers a portion of the area of ​​each corresponding detection electrode. The deformation of the flexible electrode under external force involves… The protrusion has an indirect contact area on each corresponding detection electrode. The gap shape between the first and second detection electrodes is configured such that the area of ​​indirect contact between the first and second detection electrodes and / or the length of the mutual capacitance gap path between them gradually changes with the deformation of the protrusion under force within the projected area of ​​the protrusion. Each flexible electrode is configured to be coupled to ground when performing detection electrode capacitance sampling. A capacitance-to-digital conversion circuit is coupled to each detection electrode to obtain at least the planar mutual capacitance between the first and second detection electrodes. A digital processing circuit, used for logic processing and / or logic sequence control, is coupled to the capacitance-to-digital conversion circuit.

[0008] The tactile sensor structure of this invention features a flexible electrode that is easily deformed under force, while retaining high sensitivity for mechanical sensing. The flexible electrode couples with the ground during force measurement, acting as a shielding electrode to ensure high accuracy of internal mechanical sensing. A first and second detection electrode are positioned beneath the protrusion, forming a planar mutual capacitance. This means that the CDC inputs excitation to one electrode while the other receives it. The planar mutual capacitance overcomes detection interference caused by large areas of metal on the robotic arm surface or excessive proximity to the ground. Furthermore, because the flexible electrode is coupled to the ground and the first and second detection electrodes form a planar mutual capacitance, the protrusion gradually approaches the electric field as pressure is applied, drawing the electric field lines of the planar mutual capacitance away through the ground. The mutual capacitance decreases with pressure, meeting the needs of special applications.

[0009] The tactile sensor provided by this utility model also includes the following auxiliary solutions:

[0010] Within the projected area of ​​the protrusion relative to the detection electrode, the first detection electrode and the second detection electrode form a locally or completely symmetrical distribution pattern around the corresponding protrusion.

[0011] The outer surface of the protrusion forms a spherical curved surface; the first detection electrode and the second detection electrode rotate outward in a plane around the corresponding protrusion center to form a spiral involute.

[0012] The first detection electrode and the second detection electrode form an equidistant spiral.

[0013] The protrusion has multiple forming dots, and the first detection electrodes in the same row of the dot matrix are coupled to each other, and the second detection electrodes in the same column of the dot matrix are coupled to each other; the digital processing circuit controls the capacitor digital conversion circuit to obtain the change in mutual capacitance between the first detection electrode and the second detection electrode at each point according to the row and column scanning method.

[0014] The flexible electrode has at least two parts and is insulated from each other; the tactile sensor is equipped with a switch array, and the capacitor-to-digital converter circuit is coupled to each flexible electrode through the switch array. The switch array serves as a time-division multiplexing channel for the flexible electrode to be coupled to the capacitor-to-digital converter circuit or ground.

[0015] During the sampling and detection of electrode capacitance, the digital processing circuit configures each flexible electrode to be coupled to ground via a switch array; and / or during the period when sampling of the detection electrode is stopped, the digital processing circuit couples the flexible electrodes to the capacitance-to-digital conversion circuit via the switch array to form mutual capacitance for sensing the approach of an object.

[0016] The system includes at least three flexible electrodes, with each pair of flexible electrodes forming a mutual capacitance. In each round of detection, the change in mutual capacitance between each flexible electrode and the other flexible electrodes is acquired sequentially.

[0017] The thickness of the insulating layer is configured to be between 10 nanometers and 1 millimeter.

[0018] A robotic hand is also provided, including the aforementioned tactile sensor.

[0019] A foot-worn device is also provided, including the aforementioned tactile sensor. Attached Figure Description

[0020] Figure 1 An exemplary structural diagram of a tactile sensor is given;

[0021] Figure 2a A schematic diagram of the comb-like cross structure formed between the first and second detection electrodes is given. Figure 2b A schematic diagram of the star-shaped radial structure between the first and second detection electrodes is given. Figure 2c A schematic diagram of the structure in which a spiral gradient line gradually diffuses outward between the first detection electrode and the second detection electrode is given;

[0022] Figure 3 The distribution structure of the raised dot pattern is given;

[0023] Figure 4 A schematic diagram showing the row and column connection of the first and second detection electrodes is given;

[0024] Figure 5a A schematic diagram illustrating the principle of measuring the proximity of objects by forming mutual capacitance between pairs of flexible electrodes is given. Figure 5b A schematic diagram of grounding and shielding is given when the flexible electrode is used for force measurement by the underlying detection electrode;

[0025] Figure 6 A schematic diagram of the principle of flexible electrodes forming ECT-like mutual capacitance is given;

[0026] Figure 7a A schematic diagram of the gripper structure for mounting the tactile sensor of this invention is provided. Figure 7b A schematic diagram of the structure of a robotic arm equipped with the tactile sensor of this utility model is given. Detailed Implementation

[0027] 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.

[0028] Figure 1 An exemplary structural diagram of a tactile sensor is provided. This tactile sensor structure utilizes planar mutual capacitance for single-dimensional force (normal) pressure detection, and includes a sensing unit and a capacitance-to-digital converter (CDC) circuit.

[0029] The digital processing circuit consists of a capacitor-to-digital converter and a digital processing circuit mounted on a circuit board. The two circuits are coupled together. The digital processing circuit can be controlled by a processor for logic processing through software control, or by a state controller for logic sequence control through hardware logic control.

[0030] The sensing unit includes at least one flexible electrode 100. Each flexible electrode 100 has at least one protrusion 200 on its side facing a first direction. The first direction can be arbitrary; the downward direction is used as an example in the figure. The outer surface of the protrusion 200 is an elastic curved surface. Each protrusion 200 corresponds to a first detection electrode 301 and a second detection electrode 302. The first detection electrode 301 and the second detection electrode 302 form a planar mutual capacitance for pressure detection. The CDC inputs an excitation signal to the first detection electrode 301 and receives the mutual capacitance value from the second detection electrode 302. The planar arrangement structure between the first detection electrode 301 and the second detection electrode 302 can be diverse, such as… Figure 2a A schematic diagram of the structure in which the first detection electrode 301 and the second detection electrode 302 form a comb-like intersection is given. Figure 2b A schematic diagram of the star-shaped radial structure between the first detection electrode 301 and the second detection electrode 302 is given. Figure 2cA schematic diagram of a structure is provided showing a spiral gradient line gradually spreading outward between the first detection electrode 301 and the second detection electrode 302. Each protrusion 200 is electrically isolated from its corresponding detection electrode by an insulating layer. The projection of the protrusion 200 toward the first direction covers at least a portion of the area of ​​each corresponding detection electrode, meaning that at least the upper and lower portions or all of the projected area are aligned. The indirect contact area of ​​the protrusion 200 on each corresponding detection electrode is affected by the deformation of the flexible electrode 100 under external force. The gap shape between the first detection electrode 301 and the second detection electrode 302 is configured such that the area of ​​the protrusion 200 in indirect contact with the first detection electrode 301 and the second detection electrode 302 and / or the length of the mutual capacitance gap path between them gradually change within the projected area of ​​the protrusion 200 as it deforms under force, thereby causing a change in planar mutual capacitance. Each flexible electrode 100 is configured to be coupled to ground when performing detection electrode capacitance sampling; a capacitance-to-digital conversion circuit is coupled to each detection electrode to obtain at least the planar mutual capacitance between the first detection electrode 301 and the second detection electrode 302; a digital processing circuit, used for logic processing and / or logic sequence control, is coupled to the capacitance-to-digital conversion circuit.

[0031] Through the above design, the protrusion 200 of the flexible electrode 100 is easily deformed under force, thus retaining high-sensitivity mechanical sensing. The flexible electrode 100 is coupled to the ground when measuring force, and acts as a shielding electrode to ensure high accuracy of internal mechanical sensing. The first and second detection electrodes 301 and 302 are respectively set under the protrusion 200, and the two form a planar mutual capacitance. The planar mutual capacitance overcomes the detection interference when there is a large area of ​​metal on the surface of the robot or when it is too close to the ground. At the same time, since the flexible electrode 100 is coupled to the ground and the electrodes 301 and 302 form a planar mutual capacitance, the protrusion 200 gradually approaches the electric field as it is pressed, and the electric field lines of the planar mutual capacitance are absorbed by the ground. The mutual capacitance decreases with the pressure, which meets the application requirements of special occasions.

[0032] As an improvement, within the projected area of ​​the protrusion 200 relative to the detection electrode, the first detection electrode 301 and the second detection electrode 302 form a locally or completely symmetrical distribution pattern around the corresponding protrusion 200. Preferably, as shown below... Figure 2c As shown, the outer surface of the protrusion 200 forms a spherical curved surface. The first detection electrode 301 and the second detection electrode 302 gradually rotate outward in a plane around the center of the corresponding protrusion 200 to form a spiral involute. The spiral involute gradually expands outward in a circular shape, and the surface of the protrusion 200 is a corresponding spherical curved surface. When pressed, the indirect contact area between the protrusion and the detection electrode gradually expands, which matches the gradual expansion of the gap between the first detection electrode 301 and the second detection electrode 302. The consistency of the changes between the two is good, and the regularity of force and capacitance changes is strong, which can effectively improve the resolution of force changes. Most preferably, the first detection electrode 301 and the second detection electrode 302 form an equidistant spiral to enhance the linearity of the change.

[0033] Figure 3 The distribution structure of the raised dot pattern is given. Figure 4 A schematic diagram of the row and column connection of the first detection electrode 301 and the second detection electrode 302 is shown. As an improved design, the protrusion 200 has multiple forming dots. The first detection electrodes 301 in the same row of the dot matrix are coupled to each other, and the second detection electrodes 302 in the same column are coupled to each other. The digital processing circuit controls the capacitor-to-digital converter circuit to obtain the change in mutual capacitance between the first detection electrode 301 and the second detection electrode 302 at each point according to the row and column scanning method. By scanning the mutual capacitance in rows and columns, a high-density multi-point force measurement can be formed using a small number of CDC channels, meeting the spatial resolution requirements of tactile sensing in electronic skin. Furthermore, the double-helix structure has one electrode end on the right and the other electrode end on the left, separating them and facilitating PCB routing.

[0034] Figure 5a A schematic diagram illustrating the principle of measuring the proximity of objects by forming mutual capacitance between pairs of flexible electrodes is given. Figure 5b A schematic diagram of the flexible electrode grounding shielding during force measurement by the underlying detection electrode is provided. As an improved scheme, the flexible electrode 100 has at least two components that are mutually insulated; the tactile sensor is equipped with a switch array, and the capacitance-to-digital conversion circuit couples each flexible electrode 100 separately through the switch array. The switch array serves as a time-division multiplexing channel for coupling the flexible electrode 100 to the capacitance-to-digital conversion circuit or ground. During sampling of the detection electrode capacitance, the digital processing circuit configures each flexible electrode 100 to be jointly coupled to ground through the switch array, serving as a grounding shield; and / or during periods when sampling of the detection electrode is stopped, the digital processing circuit couples each flexible electrode 100 to the capacitance-to-digital conversion circuit through the switch array to form mutual capacitances for sensing object proximity.

[0035] Further, see Figure 6 Multiple flexible electrodes 100 are provided, such as at least three, and each pair of flexible electrodes 100 forms a mutual capacitance. In each round of detection, the change in mutual capacitance between each flexible electrode 100 and the other flexible electrodes 100 is acquired sequentially. By gradually traversing all the mutual capacitances between each flexible electrode 100 and other flexible electrodes in the detection cycle, that is, when the first flexible electrode is used as the excitation, the other flexible electrodes are controlled to be in the receiving state, and the mutual capacitance between the first flexible electrode and each of the other flexible electrodes is acquired. Then the next flexible electrode is operated in the same way until the last flexible electrode is used as the excitation to complete this round of acquisition, forming a planar ECT-like effect, which can further subdivide and identify the surface unevenness and / or material of the approaching object.

[0036] As another improvement, the thickness of the insulating layer is configured to be between 10 nanometers and 1 millimeter, further enhancing the high sensitivity of the sensor for pressure detection.

[0037] See Figure 7a , 7b The electronic skin formed by the tactile sensor of this invention can be laid on the gripper surface of a robotic arm to detect gripping force, or it can be installed on foot-wearing devices such as shoes, so that the robotic foot can be worn on the foot and detect the pressure distribution of the foot during walking to adjust posture.

[0038] 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 tactile sensor that utilizes planar mutual capacitance for detection, characterized in that: Includes a sensing unit, a capacitance-to-digital converter circuit, and a digital processing circuit; The sensing unit is provided with at least one flexible electrode, and at least one protrusion is formed on the side of the flexible electrode facing the first direction. The outer surface of the protrusion is an elastic curved surface. Each protrusion is provided with a first detection electrode and a second detection electrode. The first detection electrode and the second detection electrode form a planar mutual capacitance for pressure detection. An insulating layer is provided between each protrusion and the corresponding detection electrode. The projection of the protrusion toward the first direction covers at least a portion of the area of ​​each corresponding detection electrode. The indirect contact area of ​​the protrusion on each corresponding detection electrode is affected by the deformation of the flexible electrode under external force. The gap shape between the first detection electrode and the second detection electrode is configured such that the area of ​​the protrusion indirectly contacting the first detection electrode and the second detection electrode and / or the length of the mutual capacitance gap path between them gradually changes with the deformation of the protrusion under force within the projected area of ​​the protrusion. Each flexible electrode is configured to be coupled to ground when performing detection electrode capacitance sampling; The capacitance-to-digital conversion circuit is coupled to each detection electrode to obtain at least the planar mutual capacitance between the first detection electrode and the second detection electrode. Digital processing circuitry, used for logic processing and / or logic sequence control, coupled with a capacitor-to-digital converter circuit.

2. The tactile sensor according to claim 1, characterized in that: Within the projected area of ​​the protrusion relative to the detection electrode, the first detection electrode and the second detection electrode form a locally or completely symmetrical distribution pattern around the corresponding protrusion.

3. The tactile sensor according to claim 2, characterized in that: The raised outer surface forms a spherical curved surface; The first and second detection electrodes rotate outwards on the plane around the corresponding protrusion center to form a spiral involute.

4. The tactile sensor according to claim 3, characterized in that: The first detection electrode and the second detection electrode form an equidistant spiral.

5. The tactile sensor according to claim 1 or 3, characterized in that: The protrusion has a plurality of forming lattice, wherein the first detection electrodes in the same row of the lattice are coupled to each other, and the second detection electrodes in the same column of the lattice are coupled to each other. The digital processing circuit controls the capacitor digital conversion circuit to obtain the change in mutual capacitance between the first detection electrode and the second detection electrode at each point according to the row and column scanning method.

6. The tactile sensor according to claim 1, characterized in that: The flexible electrodes are at least two insulated from each other; The tactile sensor is equipped with a switch array. The capacitance-to-digital converter circuit is coupled to each flexible electrode through the switch array. The switch array serves as a time-division multiplexing channel for the flexible electrodes to be coupled to the capacitance-to-digital converter circuit or ground.

7. The tactile sensor according to claim 6, characterized in that: During the sampling and detection of electrode capacitance, the digital processing circuit configures each flexible electrode to be coupled to ground via a switch array; and / or During the period when sampling of the detection electrodes is stopped, the digital processing circuit couples the flexible electrodes to the capacitance-to-digital conversion circuit via a switch array to form mutual capacitances for sensing the approach of an object.

8. The tactile sensor according to claim 7, characterized in that: The flexible electrode has at least three electrodes, and each pair of flexible electrodes forms a mutual capacitance. In each round of testing, the change in mutual capacitance between each flexible electrode and the other flexible electrodes is acquired in turn.

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

10. A robotic arm, characterized in that, Including the tactile sensor as described in any one of claims 1-9.

11. A foot-worn device, characterized in that, Including the tactile sensor as described in any one of claims 1-9.

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