Piezoresistive capacitance composite sensor

Abstract

The utility model relates to a piezoresistance-capacitance composite sensor, which comprises a sensing array, a piezoresistance measuring circuit, a capacitance digital conversion circuit, a switch array and a processing module. Each measuring point in the sensing array is provided with a piezoresistive material which is separated to form an insulation interval, the piezoresistive material of each measuring point is correspondingly provided with a first electrode and a second electrode, the first electrode is reused as a capacitance sensing electrode, the second electrode is used as a near-ground end of the measuring point, and a gating switch is connected in series between the second electrode and the ground; the piezoresistance measuring circuit is respectively coupled with the first electrode and the second electrode of each point position through the switch array, and the capacitance digital conversion circuit is respectively coupled with the first electrode of each point position through the switch array; and the processing module is respectively coupled with the piezoresistance measuring circuit and the capacitance digital conversion circuit, and controls the on-off of each switch. The sensor provided by the utility model is simple and compact in structure, and has high spatial resolution and high sensitivity.

Description

TECHNICAL FIELD

[0001] The utility model relates to machine tactile perception, especially a piezoresistive and capacitive composite sensor. BACKGROUND

[0002] In the task of fine operation or dynamic interaction with the environment, surface tactile perception and proximity perception are two key capabilities, surface tactile perception detects the pressure distribution of the object surface, common scenarios are controlling the force when grabbing the object, stopping moving immediately after collision, non-contact detection realizes the perception of the distance, direction and motion trend of surrounding objects before contact, common scenarios are obstacle avoidance or pre-grab planning.

[0003] CN113970395B proposes a flexible sensing array with contact and non-contact, including interlaced arrangement from top to bottom of interdigital electrode packaging layer, interdigital electrode layer, interdigital electrode substrate layer, capacitive isolation layer, piezoresistive top electrode layer, porous piezoresistive material layer and piezoresistive bottom electrode layer, the essence is that the capacitive sensor and the piezoresistive sensor are stacked, although the dual-mode integration can be realized, the piezoresistive layer needs to be deformed to detect the pressure, after stacking, the pressure is absorbed by the packaging and substrate part of the capacitive electrode, there are problems of tactile response lag, low sensitivity and the like.

[0004] CN210036760U proposes a capacitive and piezoresistive dual-mode sensor, the transmitting electrode, piezoresistive sensitive layer and conducting electrode constitute a piezoresistive sensor, a receiving electrode is additionally arranged beside the transmitting electrode, the transmitting electrode is multiplexed with the receiving electrode to constitute a capacitive sensor, achieving dual-mode multiplexing, but the surface tactile needs to be realized by the densely distributed piezoresistive units for fine force distribution detection, it is difficult to meet the demand of high spatial resolution for the side receiving electrode, and the difficulty of lead wire is increased. UTILITY MODEL CONTENT

[0005] In order to improve the defects of the prior art, the utility model provides a piezoresistive and capacitive composite sensor.

[0006] The piezoresistive capacitor composite sensor structure provided by the first aspect of the utility model, including measurement branch, switch array, processing module, and at least two measurement points, each measurement point is arranged to form a sensing array, each measurement point in the sensing array is used for detecting the spatial position of the force action point of the sensor, each measurement point is provided with piezoresistive material, the piezoresistive material between each measurement point or the collection area formed by several measurement points is formed into an insulating interval, the piezoresistive material of each measurement point is correspondingly provided with a first electrode and a second electrode, the first electrode and the second electrode are arranged on the upper and lower surfaces of the piezoresistive material respectively, the first electrode is used as a capacitor sensing electrode at the top surface of the piezoresistive material, the second electrode is used as the near-ground end of the measurement point, and the second electrode is connected in series with the ground through a gate switch, the measurement branch includes a piezoresistive measurement circuit and a capacitor digital conversion circuit, the piezoresistive measurement circuit is coupled with the first electrode and the second electrode of each point through the switch array, is used for acquiring the piezoresistive signal between the first electrode and the second electrode on each point when the object contacts, the capacitor digital conversion circuit is coupled with the first electrode of each point through the switch array, is used for acquiring the self-capacitance of the first electrode and / or the mutual capacitance between two mutually insulated first electrodes when the object approaches, the processing module is coupled with the piezoresistive measurement circuit and the capacitor digital conversion circuit respectively, and the on-off of each switch is controlled.

[0007] Further, the first electrode and the second electrode are strip electrodes, each first electrode is arranged at a certain interval along the horizontal direction, and each second electrode is arranged at a certain interval along the vertical direction, so as to form a matrix staggered point array in the vertical projection direction, and the staggered positions are used as the measurement points.

[0008] Further, the first electrode and the second electrode of each measurement point are point electrodes, each first electrode is arranged into an array above the piezoresistive material, and each second electrode is arranged into an array below the piezoresistive material.

[0009] Further, the first electrode of each measurement point is a point electrode, and each first electrode is arranged into an array; the second electrode of each measurement point in the same collection area is integrally formed into a whole common electrode, and the point electrode is located above the common electrode.

[0010] Further, the first electrode and / or the second electrode is a flexible electrode.

[0011] Further, the measurement points have at least three, and the switch array is configured to selectively combine any at least two first electrodes to form a pair of electrode groups for detecting mutual capacitance and / or selectively connect any at least two first electrodes in parallel to form a large electrode with increased area.

[0012] The second aspect of this utility model provides a piezoresistive-capacitive composite sensor structure, including a measurement branch, a switch array, a processing module, and at least two measurement points. The measurement points are arranged to form a sensing array. Each measurement point in the sensing array is used to detect the spatial position of the force application point of the sensor. Each measurement point is provided with a piezoresistive material. The piezoresistive materials between the measurement points or between the aggregated areas formed by several measurement points are separately insulated. A first electrode and a second electrode are correspondingly provided on the piezoresistive material at each measurement point. The first electrode and the second electrode are coplanarly disposed on the piezoresistive material. The first electrode is reused as a capacitance sensing electrode, and the second electrode serves as a measurement electrode. Near the ground end of the point, a selector switch is connected in series between the second electrode and the ground; the measurement branch includes a piezoresistive measurement circuit and a capacitance-to-digital conversion circuit. The piezoresistive measurement circuit is coupled to the first and second electrodes of each point through a switch array to obtain the piezoresistive signal between the first and second electrodes at each point when the object is in contact. The capacitance-to-digital conversion circuit is coupled to the first electrode of each point through a switch array to obtain the self-capacitance of the first electrode and / or the mutual capacitance between two mutually insulated first electrodes when the object approaches. The processing module is coupled to the piezoresistive measurement circuit and the capacitance-to-digital conversion circuit respectively, and controls the on / off state of each switch.

[0013] Furthermore, the first and second electrodes at each measurement point are point electrodes, and all the first and second electrodes are arranged in an array above the piezoresistive material.

[0014] The sensor structure of this utility model has the following advantages:

[0015] (1) Compared with the stacked scheme of capacitive and piezoresistive sensors, it has higher mechanical measurement sensitivity;

[0016] (2) Compared with the newly added side electrode scheme, it has higher spatial resolution;

[0017] (3) The first electrode on the top surface of the piezoresistive material is reused as the sensing electrode of the capacitive sensor, resulting in a simple and compact sensor structure.

[0018] (4) The second electrode serves as the near-ground terminal and is connected in series with the ground to select the switch, ensuring good operation under piezoresistive and capacitive multiplexing. Attached Figure Description

[0019] Figure 1 A schematic diagram of the piezoresistive-capacitive composite sensor array with electrodes arranged vertically is given;

[0020] Figure 2 An optional exemplary circuit topology between the piezoresistive-capacitive composite sensing array and the chip is given;

[0021] Figure 3 A schematic diagram of a strip electrode is given;

[0022] Figure 4 A structure diagram of a piezoresistive-capacitive composite sensing array electrode arranged in a coplanar left-right manner is given. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model.

[0024] Embodiment 1

[0025] Reference Figures 1 to 4 The piezoresistive-capacitive composite sensor comprises a sensing array and a circuit board, and the sensing array is arranged in a one-dimensional or two-dimensional array with at least two measuring points. Each measuring point in the sensing array is used to detect the spatial position of the force action point of the sensor. Specifically, each measuring point is provided with a piezoresistive material 10, and the layer where the piezoresistive material 10 is located serves as a piezoresistive layer 11. The piezoresistive materials 10 between the measuring points are separated to form an insulating interval, such as a 3X3 dot array, and each point in the array is provided with a piezoresistive material 10. The piezoresistive materials 10 between the points are separated and insulated, such as Figure 1 ; alternatively, an insulating interval is formed between the collection regions formed by the measuring points, for example, a 4X4 dot array, and the dot array is divided into four regions. The piezoresistive materials 10 of four points in each region are connected in one piece. The piezoresistive material 10 of each measuring point is correspondingly provided with a first electrode 20 and a second electrode 30, and the first electrode 20 and the second electrode 30 are arranged on the upper and lower surfaces of the piezoresistive material 10, respectively. The first electrode 20 is located on the top surface of the piezoresistive material 10 and is used as a capacitive sensing electrode. Since the piezoresistive detection characteristic needs to be grounded, the second electrode 30 serves as the near-ground end of the measuring point and is connected in series with the ground through a gating switch. The gating switch is switched to ground when collecting the piezoresistive signal and is disconnected to avoid the capacitive sensing electrode being short-circuited to the ground through the piezoresistive material when collecting the capacitive signal.

[0026] The circuit board comprises a measurement branch, a switch array and a processing module. The measurement branch has a piezoresistive measurement circuit and a capacitance digital conversion circuit (CDC). The piezoresistive measurement circuit is coupled to the first electrode 20 and the second electrode 30 of each point through the switch array, and is used to acquire the piezoresistive signal between the first electrode 20 and the second electrode 30 at each point when an object contacts, to perceive the force point pressure through the piezoresistive signal, and to realize tactile perception. The capacitance digital conversion circuit is coupled to the first electrode 20 of each point through the switch array, and is used to acquire the self-capacitance of the first electrode 20 and / or the mutual capacitance between two mutually insulated first electrodes 20 when an object approaches. When self-capacitance collection is performed, the CDC outputs excitation to the first electrode 20 and receives signals from the first electrode 20; when mutual capacitance collection is performed, the CDC outputs excitation to the first electrode 20 of the measurement point A and receives signals from the first electrode 20 of the measurement point B. The CDC channel realizes gating switching with the electrodes through the switch array. The object approaching causes changes in the self-capacitance and the mutual capacitance, realizing proximity perception, and the material of the object can be further identified based on the mutual capacitance signal. The processing module is coupled to the piezoresistive measurement circuit and the capacitance digital conversion circuit, and controls the on-off of each switch as a central control.

[0027] Figure 2 An optional circuit topology is given, S1-S4 are analog switches, R1 and R2 are piezoresistive materials, and Ir is a piezoresistive material measurement constant current source. As a piezoresistive measurement force application, S4 is in an open state, S1, S2 and S3 are in a closed state, ADC-S1-R-S3-GND forms a loop, Ir inputs current to the first electrode, and the piezoresistive change is A / D converted into voltage by the ADC of the MCU. As a capacitance detection proximity and contact measurement, S1, S2 and S3 are open, and S4 is closed. Since the input impedance of the capacitance detection is high, the piezoresistive material is approximately short-circuited, the second electrode 30 is connected to the first electrode 20 through the piezoresistive material 10 and the first electrode 20 to form a capacitance electrode, and a single electrode can be used for self-capacitance detection or mutual capacitance detection with a nearby piezoresistive electrode. Since the piezoresistive material is approximately short-circuited, Figure 2 The CDC can be connected to the first electrode 20 and / or the second electrode 30 through a switch, and in the example, it is connected to the second electrode 30 for convenient wiring.

[0028] The sensor structure of the utility model, with the first electrode 20 of piezoresistive material 10 top multiplexing as the sensing electrode of capacitance sensor, through the self-capacitance of first electrode 20 and / or mutual capacitance between two mutually insulated first electrode 20, realize proximity sense, tactile, sensor structure is simple, compact, with high spatial resolution and high sensitivity;Second electrode 30 as near ground terminal, with ground series gating switch, avoid electrode multiplexing as piezoresistive electrode and capacitance sensing electrode under, sensing electrode through piezoresistive short connection ground, the defect that capacitance is difficult to detect, ensure piezoresistive and capacitance good operation.

[0029] In the embodiment, the arrangement of the upper and lower electrodes can include:

[0030] (1) see Figure 3 , the first electrode 20 and the second electrode 30 are both strip electrodes, each first electrode 20 is arranged at a certain interval along the transverse direction, and each second electrode 30 is arranged at a certain interval along the longitudinal direction to form a staggered dot matrix in the vertical projection direction, and the staggered positions are used as measurement points. The row-column matrix structure can reduce the number of leads and simplify the wiring.

[0031] (2) see Figure 1 , the first electrode 20 and the second electrode 30 of each measurement point are both point electrodes, each first electrode 20 is arranged in an array above the piezoresistive material 10, and each second electrode 30 is arranged in an array below the piezoresistive material 10. The upper and lower double layers are both point electrode structures, which can realize multi-point triggering, and at the same time meet the requirements of higher spatial resolution and lower crosstalk.

[0032] (3) the first electrode 20 of each measurement point is a point electrode, each first electrode 20 is arranged in an array, and the second electrode 30 of each measurement point in the same set area is integrally formed into a whole common electrode, and the point electrode is located above the common electrode to achieve balance.

[0033] Further, the first electrode 20 and / or the second electrode 30 is a flexible electrode.

[0034] Further, the measurement point has at least three, and the switch array is configured to selectively combine any at least two first electrodes 20 to form a pair of electrode groups for detecting mutual capacitance and / or selectively connect any at least two first electrodes 20 in parallel to form a large electrode with increased area. By merging to increase the electrode area, the capacitance detection sensitivity is further improved.

[0035] Embodiment 2

[0036] The embodiment is based on the embodiment 1, and the electrode arrangement mode of the piezoresistive material 10 is changed from up and down to left and right on the top layer, and the proximity sense and the tactile function are also considered. At this time, the sensor structure includes a measurement branch, a switch array, a processing module, and at least two measurement points. The measurement points are arranged to form a sensing array, and each measurement point in the sensing array is used to detect the spatial position of the force action point of the sensor. The piezoresistive material 10 is arranged at each measurement point, and the piezoresistive material 10 between the measurement points or the collection area formed by several measurement points is separately formed as an insulating interval. The piezoresistive material 10 of each measurement point is correspondingly provided with a first electrode 20 and a second electrode 30, and the first electrode 20 and the second electrode 30 are coplanarly arranged on the piezoresistive material 10. The first electrode 20 is used as a capacitive sensing electrode, and the second electrode 30 is used as the near-end of the measurement point. The second electrode 30 is connected in series with the gating switch between the second electrode 30 and the ground. The measurement branch includes a piezoresistive measurement circuit and a capacitive digital conversion circuit. The piezoresistive measurement circuit is coupled with the first electrode 20 and the second electrode 30 of each point through the switch array, and is used to obtain the piezoresistive signal between the first electrode 20 and the second electrode 30 at each point when the object contacts. The capacitive digital conversion circuit is coupled with the first electrode 20 of each point through the switch array, and is used to obtain the self-capacitance of the first electrode 20 and / or the mutual capacitance between two mutually insulated first electrodes 20 when the object approaches. The processing module is coupled with the piezoresistive measurement circuit and the capacitive digital conversion circuit, and controls the on-off of each switch.

[0037] In the sensor structure of the embodiment 2, the electrode arrangement is that the first electrode 20 and the second electrode 30 are both point electrodes, and the first electrode 20 and the second electrode 30 are arranged in an array above the piezoresistive material 10.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A piezoresistive-capacitive composite sensor, characterized in that: It includes a measurement branch, a switch array, a processing module, and at least two measurement points; Each measurement point is arranged to form a sensing array. Each measurement point in the sensing array is used to detect the spatial position of the force application point of the sensor. Each measurement point is provided with piezoresistive material. The piezoresistive materials between each measurement point or between the aggregate area formed by several measurement points are separately insulated. The piezoresistive material of each measurement point is provided with a first electrode and a second electrode. The first electrode and the second electrode are respectively provided on the upper and lower surfaces of the piezoresistive material. The first electrode is located on the top surface of the piezoresistive material and is reused as a capacitive sensing electrode. The second electrode is used as the near-ground end of the measurement point. A selection switch is connected in series between the second electrode and the ground. The measurement branch includes a piezoresistive measurement circuit and a capacitance-to-digital conversion circuit. The piezoresistive measurement circuit is coupled to the first electrode and the second electrode at each point through a switch array, and is used to obtain the piezoresistive signal between the first electrode and the second electrode at each point when the object is in contact. The capacitance-to-digital conversion circuit is coupled to the first electrode at each point through a switch array, and is used to obtain the self-capacitance of the first electrode and / or the mutual capacitance between two mutually insulated first electrodes when the object approaches. The processing module couples the piezoresistive measurement circuit and the capacitance-to-digital conversion circuit, and controls the on / off state of each switch.

2. The piezoresistive-capacitive composite sensor according to claim 1, characterized in that: Both the first electrode and the second electrode are strip electrodes. The first electrodes are arranged at a certain interval along the horizontal direction, and the second electrodes are arranged at a certain interval along the vertical direction, thus forming a row-and-column staggered dot matrix in the vertical projection direction. The staggered positions are used as the measurement points.

3. The piezoresistive-capacitive composite sensor according to claim 1, characterized in that: The first and second electrodes at each measurement point are point electrodes. The first electrodes are arranged in an array above the piezoresistive material, and the second electrodes are arranged in an array below the piezoresistive material.

4. The piezoresistive-capacitive composite sensor according to claim 1, characterized in that: The first electrode at each measurement point is a point electrode, and the first electrodes are arranged in an array. The second electrodes of each measurement point within the same set area are integrated to form a single common electrode, with the point electrodes located above the common electrode.

5. A piezoresistive-capacitive composite sensor, characterized in that: It includes a measurement branch, a switch array, a processing module, and at least two measurement points; Each measurement point is arranged to form a sensing array. Each measurement point in the sensing array is used to detect the spatial position of the force application point of the sensor. Each measurement point is provided with piezoresistive material. The piezoresistive materials between each measurement point or between the aggregate area formed by several measurement points are separately insulated. The piezoresistive material of each measurement point is provided with a first electrode and a second electrode. The first electrode and the second electrode are coplanarly disposed on the piezoresistive material. The first electrode is reused as a capacitive sensing electrode, and the second electrode is used as the near-ground end of the measurement point. A selection switch is connected in series between the second electrode and the ground. The measurement branch includes a piezoresistive measurement circuit and a capacitance-to-digital conversion circuit. The piezoresistive measurement circuit is coupled to the first electrode and the second electrode at each point through a switch array, and is used to obtain the piezoresistive signal between the first electrode and the second electrode at each point when the object is in contact. The capacitance-to-digital conversion circuit is coupled to the first electrode at each point through a switch array, and is used to obtain the self-capacitance of the first electrode and / or the mutual capacitance between two mutually insulated first electrodes when the object approaches. The processing module couples the piezoresistive measurement circuit and the capacitance-to-digital conversion circuit, and controls the on / off state of each switch.

6. The piezoresistive-capacitive composite sensor according to claim 5, characterized in that: The first and second electrodes at each measurement point are point electrodes, and all the first and second electrodes are arranged in an array above the piezoresistive material.

7. The piezoresistive-capacitive composite sensor according to claim 1 or 5, characterized in that: The first electrode and / or the second electrode are flexible electrodes.

8. The piezoresistive-capacitive composite sensor according to claim 1 or 5, characterized in that: The measurement points have at least three, and the switch array is configured to allow selective combination of any at least two first electrodes to form a pair of electrode groups for detecting mutual capacitance and / or selective parallel connection of any at least two first electrodes to form a large electrode with increased area.

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