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

Abstract

The invention relates to a tactile sensor, a manipulator and a sole wearable device for detection by using planar mutual capacitance. 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] The present invention relates to machine touch, and in particular to a tactile sensor, a manipulator, and a sole wearable device that utilize planar mutual capacitance for detection. Background Art

[0002] The manipulator uses the gripper to perform tasks such as grasping, carrying or handling objects according to a fixed program. With the development of robots, the gripper of the manipulator needs to be able to sense the grasping pressure of the object to achieve machine touch. Electronic skin is mainly used to achieve machine touch perception. The electronic skin is attached to the mechanical surface that needs to sense touch and detects pressure through the built-in tactile sensor. Capacitive tactile sensors are favored in the application of machine touch due to the characteristics of easy electrode arrangement and convenient formation of dense arrays.

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

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

[0005] The mutual capacitance method basically adopts the principle of parallel plate capacitance. Through the upper and lower electrodes, CDC inputs excitation to one and the other as receiving. The force measurement is mainly achieved by changing the distance between the upper and lower electrodes. The mutual capacitance increases with pressing. CN111896165A discloses a touch sensor structure. The upper electrode protrudes downward to form a hemispherical elastic electrode. The lower electrode measures single-dimensional force when one is used and three-dimensional force when four are used. The upper layer is used for excitation and the lower layer is used for receiving. The indirect contact area (with an insulating layer in the middle) of the hemispherical protrusion on the lower electrode is mainly pressed to form an order of magnitude change from point to surface to achieve high-sensitivity mechanical perception, but the essence is that the mutual capacitance increases with pressing. Summary of the invention

[0006] The present invention improves or supplements the deficiencies of the prior art and provides a tactile sensor, a manipulator, and a wearable device for the sole of the foot that utilize planar mutual capacitance for detection.

[0007] To this end, a tactile sensor using planar mutual capacitance for detection is provided, including a sensing unit, a capacitance-to-digital conversion 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 a side of the flexible electrode facing a first direction, and the outer surface of the protrusion is an elastic curved surface, and each protrusion is correspondingly provided with a first detection electrode and a second detection electrode, and 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, and the projection of the protrusion toward the first direction at least covers a partial area of ​​each corresponding detection electrode, and the deformation change of the flexible electrode due to an external force involves The indirect contact area of ​​the protrusion on each corresponding detection electrode, and the gap shape between the first detection electrode and the second detection electrode are configured so that the protrusion gradually changes the area of ​​indirect contact with the first detection electrode and the second detection electrode and / or the length of the mutual capacitance gap path between the two within the projection area of ​​the protrusion as the protrusion is deformed by the force; each flexible electrode is configured to be coupled to the ground when sampling the capacitance of the detection electrode; the capacitance-to-digital conversion circuit is coupled to each detection electrode respectively, so as to obtain at least the planar mutual capacitance between the first detection electrode and the second detection electrode; the digital processing circuit is used for logic processing and / or logic sequence control, and is coupled to the capacitance-to-digital conversion circuit.

[0008] In the tactile sensor structure of the present invention, the protrusion of the flexible electrode is easily deformed when subjected to force, thereby retaining high-sensitivity mechanical perception; the flexible electrode is coupled to the ground during force measurement and acts as a shielding electrode to ensure high accuracy of internal mechanical perception; a first and a second detection electrode are correspondingly arranged under the protrusion, and the two form a planar mutual capacitance, that is, the CDC inputs excitation to one of them and the other receives it, and the planar mutual capacitance is used to overcome detection interference when there is a large area of ​​metal on the surface of the manipulator or it is too close to the ground. At the same time, since the flexible electrode is coupled to the ground, the first and second detection electrodes construct a planar mutual capacitance. As the protrusion is pressed, it gradually approaches the electric field and absorbs the planar mutual capacitance electric field lines through the ground, and the mutual capacitance decreases as the pressure is pressed, thereby meeting the application requirements of special occasions.

[0009] The tactile sensor provided by the present invention also includes the following subsidiary solutions:

[0010] Wherein, within the projection area of ​​the protrusion relative to the detection electrode, the first detection electrode and the second detection electrode form a partially 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 gradually rotate outward around the center of the corresponding protrusion on the plane to form a spiral involute.

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

[0013] Among them, the protrusions have multiple dot arrays, the first detection electrodes in the same row of the dot array are coupled to each other, and the second detection electrodes in the same column of the dot array are coupled to each other; the digital processing circuit controls the capacitance 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] Among them, there are at least two flexible electrodes that are insulated from each other; the tactile sensor is provided with a switch array, the capacitance-to-digital conversion circuit is coupled to each flexible electrode through the switch array, and the switch array serves as a time-sharing selection channel for coupling the flexible electrode to the capacitance-to-digital conversion circuit or the ground.

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

[0016] There are at least three flexible electrodes, and the flexible electrodes form mutual capacitance in pairs; in each round of detection, the change in mutual capacitance between each flexible electrode and the other flexible electrodes is obtained in turn.

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

[0018] A robot arm is also provided, comprising the above-mentioned tactile sensor.

[0019] A foot wearable device is also provided, comprising the above-mentioned tactile sensor. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0022] Figure 3 A convex lattice-style distribution structure is given;

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

[0024] Figure 5a The principle of mutual capacitance detection of objects approaching each other by two flexible electrodes is given. Figure 5b The schematic diagram of grounding and shielding of the flexible electrode when measuring force with the detection electrode underneath is given;

[0025] Figure 6 The principle of flexible electrodes forming ECT-like mutual capacitance is given;

[0026] Figure 7a A schematic diagram of the structure of the clamping jaw for installing the tactile sensor of the present invention is given. Figure 7b A schematic diagram of the structure of a manipulator equipped with the tactile sensor of the present invention is given. DETAILED DESCRIPTION

[0027] 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.

[0028] Figure 1 The exemplary structure of the tactile sensor is given. The tactile sensor of this structure constructs a planar mutual capacitance for single-dimensional force (normal) pressure detection, including a sensing unit, a capacitance digital conversion circuit (CDC)

[0029] ), digital processing circuit. The capacitance digital conversion circuit and the digital processing circuit are arranged on the circuit board, and the two are coupled to each other. The digital processing circuit can use a processor for logic processing to realize software control, or use a state controller for logic sequence control to realize hardware logic control.

[0030] The sensing unit is provided with at least one flexible electrode 100, and at least one protrusion 200 is formed on one side of the flexible electrode 100 facing the first direction. The first direction can be arbitrary, and the downward direction is used as an example in the figure. The outer surface of the protrusion 200 is an elastic curved surface, and each protrusion 200 is correspondingly provided with 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 a 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 of a comb cross formed between the first detection electrode 301 and the second detection electrode 302 is given. Figure 2b A schematic diagram of the structure of star-shaped radiation lines between the first detection electrode 301 and the second detection electrode 302 is given. Figure 2cA schematic diagram of a structure in which a spiral gradient line is formed between the first detection electrode 301 and the second detection electrode 302 and gradually spreads outward is given. An insulating layer is provided between each protrusion 200 and the corresponding detection electrode to achieve electrical isolation. The projection of the protrusion 200 toward the first direction at least covers a part of the area of ​​each corresponding detection electrode, that is, at least the upper and lower parts or all of the projection areas are aligned. The indirect contact area of ​​the protrusion 200 on each corresponding detection electrode involved in the deformation change of the flexible electrode 100 under external force, and the shape of the gap between the first detection electrode 301 and the second detection electrode 302 is configured so that the protrusion 200 gradually changes the area of ​​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 the two within the projection area of ​​the protrusion 200 as the deformation under force causes the planar mutual capacitance to change. Each flexible electrode 100 is configured to be coupled to the ground when sampling the detection electrode capacitance; the capacitance-to-digital conversion circuit is coupled to each detection electrode respectively, for obtaining at least the planar mutual capacitance between the first detection electrode 301 and the second detection electrode 302; the digital processing circuit is used for logic processing and / or logic sequence control, and is coupled to the capacitance-to-digital conversion circuit.

[0031] Through the above-mentioned design scheme, since the protrusion 200 of the flexible electrode 100 is easily deformed under force, high-sensitivity mechanical perception is retained; the flexible electrode 100 is coupled with the ground during force measurement and acts as a shielding electrode to ensure high accuracy of internal mechanical perception; the first and second detection electrodes 301 and 302 are correspondingly arranged 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 manipulator or it is too close to the ground. At the same time, since the flexible electrode 100 is coupled with the ground and the electrodes 301 and 302 construct a planar mutual capacitance, the protrusion 200 gradually approaches the electric field as it is pressed, and the planar mutual capacitance electric field lines are absorbed through the ground, and the mutual capacitance decreases as it is pressed, meeting the application requirements of special occasions.

[0032] As an improved solution, the first detection electrode 301 and the second detection electrode 302 are arranged in a partially or completely symmetrical distribution pattern around the corresponding protrusion 200 within the projection area of ​​the protrusion 200 relative to the detection electrode. Figure 2c As shown, the outer surface of the protrusion 200 forms a spherical surface, and the first detection electrode 301 and the second detection electrode 302 gradually rotate outward on the plane around the center of the corresponding protrusion 200 to form a spiral involute, and the spiral involute is circular and gradually opens outward. The surface of the protrusion 200 corresponds to a spherical surface. When the protrusion is pressed, the indirect contact area on the detection electrode gradually opens, which is consistent with the gradual opening change of the gap between the first detection electrode 301 and the second detection electrode 302. The consistency relationship between the changes of the two is good, and the force and capacitance changes are regular, which can effectively improve the resolution of the change of force. 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 convex lattice style distribution structure is given, Figure 4 A schematic diagram of the row-column connection of the first detection electrode 301 and the second detection electrode 302 is given. As another improvement scheme, the protrusion 200 has a plurality of dot arrays, the first detection electrodes 301 in the same row in the dot array are coupled to each other, and the second detection electrodes 302 in the same column in the dot array are coupled to each other; the digital processing circuit controls the capacitance digital conversion 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-column scanning method. By scanning the mutual capacitance in rows and columns, a small number of CDC channels can be used to form high-density multi-point force measurement, meeting the spatial resolution requirements of the tactile sense of the electronic skin. In addition, one electrode end of the double helix structure is on the right, and the other electrode end is on the right, and the two are separated, which is easy to route on the PCB.

[0034] Figure 5a The principle of mutual capacitance detection of objects approaching each other by two flexible electrodes is given. Figure 5b The schematic diagram of the ground shielding of the flexible electrode when the detection electrode below is measuring force is given. As another improvement scheme, the flexible electrode 100 has at least two and is insulated from each other; the tactile sensor is provided with a switch array, and the capacitance-to-digital conversion circuit is coupled to each flexible electrode 100 through the switch array, and the switch array serves as a time-sharing gating channel for coupling the flexible electrode 100 to the capacitance-to-digital conversion circuit or the ground. During the sampling of the detection electrode capacitance, the digital processing circuit configures each flexible electrode 100 to be commonly coupled to the ground through the switch array as a ground shield; and / or during the period of stopping sampling the detection electrode, the digital processing circuit couples the flexible electrodes 100 to the capacitance-to-digital conversion circuit through the switch array to form mutual capacitance for sensing the approach of an object.

[0035] For further information, see Figure 6 , more flexible electrodes 100 are provided, such as at least three, and the flexible electrodes 100 form mutual capacitances in pairs; in each round of detection, the change in mutual capacitance between each flexible electrode 100 and the remaining flexible electrodes 100 is obtained in turn. By gradually traversing all 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 an excitation, the other flexible electrodes are controlled to receive, and the mutual capacitance between the first flexible electrode and each of the remaining flexible electrodes is obtained, and then the next flexible electrode is operated in the same way, until the last flexible electrode is used as an excitation to complete this round of acquisition, forming a plane-like ECT effect, and further subdividing and identifying the surface concave-convex conditions and / or material conditions of the approaching object.

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

[0037] See also Figure 7a , 7b The electronic skin formed by the tactile sensor of the present invention can be laid on the surface of the gripper of a robot to form grip detection, or it can be installed on a shoe or other wearable device for the robot to wear under the foot to detect the pressure distribution on the sole of the foot to form posture adjustment when walking.

[0038] 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 tactile sensor using planar mutual capacitance for detection, characterized in that: It includes a sensing unit, a capacitance-to-digital conversion 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 one side of the flexible electrode facing the first direction, and the outer surface of the protrusion is an elastic curved surface, and each protrusion is correspondingly provided with a first detection electrode and a second detection electrode, and 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 at least covers a partial area of ​​each corresponding detection electrode, the indirect contact area of ​​the protrusion on each corresponding detection electrode involved in the deformation change of the flexible electrode under external force, and the shape of the gap between the first detection electrode and the second detection electrode is configured so that within the projection area of ​​the protrusion, the protrusion gradually changes with the deformation under force, and the area of ​​the indirect contact with the first detection electrode and the second detection electrode and / or the length of the mutual capacitance gap path between the two; Each flexible electrode is configured to be coupled to ground when sampling the detection electrode capacitance; The capacitance-to-digital conversion circuit is coupled to each detection electrode respectively, and is used to obtain at least the planar mutual capacitance between the first detection electrode and the second detection electrode; The digital processing circuit is used for logic processing and / or logic sequence control and is coupled to the capacitance digital conversion circuit.

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

3. The tactile sensor according to claim 2, characterized in that: The outer surface of the convexity forms a spherical curved surface; The first detection electrode and the second detection electrode gradually rotate outward around the center of the corresponding protrusion on the plane 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 protrusions have a plurality of dot arrays, the first detection electrodes in the same row in the dot array are coupled to each other, and the second detection electrodes in the same column in the dot array are coupled to each other; The digital processing circuit controls the capacitance-to-digital conversion circuit to obtain the variation of the mutual capacitance between the first detection electrode and the second detection electrode at each point according to the row-column scanning method.

6. The tactile sensor according to claim 1, characterized in that: The flexible electrodes have at least two electrodes and are insulated from each other; The tactile sensor is provided with a switch array, and the capacitance-to-digital conversion circuit is coupled to each flexible electrode through the switch array. The switch array serves as a time-sharing gating channel for coupling the flexible electrode to the capacitance-to-digital conversion circuit or the ground.

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

8. The tactile sensor according to claim 7, characterized in that: There are at least three flexible electrodes, and the flexible electrodes form mutual capacitance in pairs; In each round of detection, the change in mutual capacitance between each flexible electrode and the remaining flexible electrodes is obtained 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 robot, characterized in that: The method comprises the tactile sensor as claimed in any one of claims 1 to 9.

11. A foot wearable device, characterized in that: The method comprises the tactile sensor as claimed in any one of claims 1 to 9.

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