CN106959175A - A kind of Grazing condition condenser type based on pyramid structure slides touch sensor - Google Patents

Abstract

The invention discloses a fully flexible capacitive sliding tactile sensor based on a pyramid structure. The upper and lower flexible printed circuit boards are respectively printed with an upper layer common electrode, a lower layer center electrode and four electrodes located on the periphery of each side of the lower layer center electrode. Rectangular sensing electrodes, where the upper common electrode layer and the lower central electrode are used to sense tactile information, the upper common electrode and 4 sensing electrodes are used to sense tangential information and slip information; a dielectric layer is arranged between the two flexible printed circuit boards , the upper surface of the dielectric layer is integrally formed with a pyramid structure; PDMS hemispherical contacts are fixed on the upper flexible printed circuit board. The fully flexible capacitive sliding tactile sensor of the present invention can not only distinguish small tactile forces, but also realize the measurement of shearing forces in various directions, greatly improve the mechanical sensitivity of the sensor, and realize the sliding of the sensor in the shearing direction. sensory detection function.

Description

A fully flexible capacitive sliding tactile sensor based on pyramid structure

technical field

The invention belongs to the field of sensor technology, and in particular relates to a fully flexible capacitive sliding touch sensor applied to artificial intelligence skin.

Background technique

As an effective way for intelligent robots to perceive the external environment, the sliding tactile sensor is used to realize the grasping detection of the target, the proximity contact during the approach process, and the discrimination of the sliding state, etc., and plays a pivotal role in the field of electronic skin research. With the development of the times, electronic skin has been applied in robotics, tactile detection, temperature monitoring, health care and other fields.

Among the various applications of electronic skin, inductive touch and slip detection occupy an extremely important position. Sliding tactile sensors imitate the human hand to have sensory functions such as touch, sliding, and heat, and are an essential medium for the direct interaction between robots and the environment. For example, the sliding tactile sensor can detect the three-dimensional force information between the manipulator and the contact interface, control the clamping force to prevent the relative sliding between the target object and the manipulator, and finally assist the robot to complete the grasping and manipulation tasks. Among them, the sliding signal is the feedback information to realize the gripping force control of the manipulator, and is the key to the robot's high-precision grasping and manipulation tasks.

Scholars at home and abroad have made important progress in three-dimensional force measurement and sliding detection of tactile sensors, but there are still some shortcomings. Bao Zhenan and others from Stanford University in the United States filled the dielectric layer with a hemispherical microstructure, which can detect external pressure very sensitively, but cannot perform slip detection. Choong et al., Seoul National University, South Korea, proposed a resistive tactile sensor using a pyramidal microstructure as a dielectric layer. The sensor has high sensitivity in the biaxial stretching direction, but the measuring range is small and the preparation process is comparatively difficult. complex. And usually when this type of sensor uses bionic skin, it mostly uses a rigid substrate, which lacks the proper flexibility and is not suitable for application in places with large curvature such as robot joints.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the above-mentioned existing sensors, and propose a fully flexible capacitive sliding tactile sensor based on a pyramid structure, so as to solve the problem that the existing sensors cannot simultaneously detect three-dimensional forces with high precision and a large range. slippery problem.

The present invention adopts following technical scheme for solving technical problems:

The present invention is a fully flexible capacitive sliding tactile sensor based on a pyramid structure, which is characterized in that:

Including upper flexible printed circuit board and lower flexible printed circuit board;

An upper common electrode is printed on the surface of the upper flexible printed circuit board;

Printed on the surface of the lower flexible printed circuit board is a square lower central electrode and four identical rectangular sensing electrodes located at the periphery of each side of the lower central electrode at equal intervals; each sensing electrode is symmetrical to the center of the lower central electrode point pairwise symmetry;

A dielectric layer is provided between the upper flexible printed circuit board and the lower flexible printed circuit board, and the upper surface of the dielectric layer is integrally formed with a pyramid structure; the upper common electrode is in contact with the top of the pyramid structure, The lower center electrode is in contact with the lower surface of the dielectric layer;

PDMS hemispherical contacts are fixed on the upper flexible printed circuit board through a flexible protective layer.

The length of the long side of each sensing electrode is equal to the side length of the lower central electrode, and the long side of each sensing electrode is parallel to the side of the adjacent lower central electrode.

The lower surface of the dielectric layer fully covers the lower central electrode and the four sensing electrodes; the upper common electrode is located directly above the lower central electrode, and the upper common electrode is on the lower flexible printed circuit board (6 The orthographic projection of the surface of ) completely covers the center electrode of the lower layer, and half covers each sensing electrode.

The dielectric layer is made of PDMS. The flexible substrates of the upper flexible printed circuit board and the lower flexible printed circuit board are made of polyimide. The flexible protective layer is made of silicon rubber.

On the flexible base of the upper flexible printed circuit board, there is an upper layer common electrode pad in the form of a via hole. The pads of the lower central electrode in the form of via holes and the pads of the sensing electrodes are arranged on the top, and the central electrode of the lower layer and the sensing electrodes are respectively led to their respective pads through enameled wires, and then led out through signal lines. This via method can make the wiring more flexible and easy to array.

The upper common electrode layer and the lower central electrode are used for sensing tactile information, and the upper common electrode and the lower four sensing electrodes are used for sensing tangential information and sliding information.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The fully flexible capacitive sliding tactile sensor based on the pyramid structure of the present invention, compared with ordinary tactile sensors and pressure sensors, can not only sense tactile force, but also realize the measurement of shear force in all directions, and improve the mechanical sensitivity of the sensor , and at the same time realize the detection of sliding tactile information and improve the applicability of the sensor;

2, the present invention is based on the fully flexible capacitive sliding tactile sensor of pyramid structure, adopts FPCB (its flexible substrate is polyimide) as electrode layer, adopts PDMS as medium layer, is flexible material, compares with traditional sensor, has Very good flexibility, so that the sensor can be placed in a wider range;

3. The fully flexible capacitive sliding tactile sensor based on the pyramid structure of the present invention greatly improves the normal sensitivity and tangential sensitivity of the sensor by adopting the medium layer of the pyramid structure compared with the general multi-layer upper and lower structure force sensitive sensor; and The invention can change the sensitivity and measuring range of the sensor by changing the ratio of the medium layer and adjusting the inclination angle of the pyramid structure, and further expands its application range;

4. The preparation process of the fully flexible sliding tactile sensor based on the pyramid structure of the present invention is simple and easy to popularize.

Description of drawings

Fig. 1 is the vertical sectional structural diagram of the fully flexible sliding tactile sensor based on pyramid structure of the present invention;

Fig. 2 is the split perspective view of the fully flexible sliding tactile sensor based on the pyramid structure of the present invention;

Fig. 3 is the three-dimensional coordinate system diagram of the fully flexible sliding tactile sensor based on the pyramid structure of the present invention;

Fig. 4 is the curve relationship diagram of the capacitance-normal force of the fully flexible sliding tactile sensor based on the pyramid structure and the plane dielectric layer structure sensor of the present invention;

Fig. 5 is the dynamic response curve that the present invention is based on the fully flexible sliding tactile sensor of pyramid structure in little pressure action;

Fig. 6 is the capacitance-tangential force curve relationship diagram of the fully flexible sliding tactile sensor based on the pyramid structure and the planar dielectric layer structure sensor of the present invention;

Fig. 7 is the collection slip signal of the fully flexible slip tactile sensor based on the pyramid structure in the present invention;

Numbers in the figure: 1 PDMS hemispherical contact; 2 flexible protective layer; 3 upper flexible printed circuit board; 4 upper common electrode; 5 dielectric layer; 6 lower flexible printed circuit board; 7 lower central electrode; 8 first sensing electrode; 9 The second sensing electrode; 10 the third sensing electrode; 11 the fourth sensing electrode; 4A upper common electrode pad; 7A lower center electrode pad; 8A first sensing electrode pad; 9A second sensing electrode pad; 10A third Induction electrode pad; 11A fourth induction electrode pad; 12 enameled wire.

detailed description

Example 1

As shown in Figure 1 and Figure 2, the fully flexible sliding tactile sensor based on the pyramid structure in this embodiment includes an upper flexible printed circuit board 3 and a lower flexible printed circuit board 6;

An upper common electrode 4 is printed on the surface of the upper flexible printed circuit board 3;

The surface of the lower flexible printed circuit board 6 is printed with a lower central electrode 7 which is a square and four identical rectangular sensing electrodes (the first sensing electrode 8; the second sensing electrode 9; The induction electrode 10; the fourth induction electrode 11); each induction electrode is symmetrical in pairs with the center of the lower layer central electrode 7 as a symmetrical point;

A dielectric layer 5 is arranged between the upper flexible printed circuit board 3 and the lower flexible printed circuit board 6, and the upper surface of the dielectric layer 5 is integrally formed with a pyramid structure; the upper common electrode 4 is in contact with the top of the pyramid structure, and the lower central electrode 7 is in contact with the lower surface of the dielectric layer 5; that is to say, the dielectric layer is composed of a plane layer and a pyramid structure located on the plane layer. Increasing the pyramid structure layer can improve the resolution of the sensor and detect tiny Tactile information, while the existence of the planar layer increases the normal vector range of the sensor.

PDMS hemispherical contacts are fixed on the upper flexible printed circuit board 3 through the flexible protective layer 2 .

Specifically, the length of the long side of each sensing electrode is equal to the side length of the lower central electrode, and the long side of each sensing electrode is parallel to the side of the adjacent lower central electrode. The lower surface of the dielectric layer fully covers the lower central electrode and the four sensing electrodes; the upper common electrode 4 is located directly above the lower central electrode 7, and the orthographic projection of the upper common electrode 4 on the surface of the lower flexible printed circuit board 6 covers the lower central electrode 7 For full coverage, half-cover each sensing electrode along the midline of the long side.

Specifically, the bottom plane of the dielectric layer 5 is 8 mm long, 8 mm wide, and 1 mm thick, and the bottom surface of the pyramid structure located on it has a side length of 2 mm, a layer height of 1 mm, and an inclination angle of 45°. The thickness of the upper common electrode 4, the lower central electrode 7 and each sensing electrode is 0.25mm, the thickness of the flexible protective layer and the flexible base of the two flexible printed circuit boards is 0.25mm, and the radius of the PDMS hemispherical contact is 4mm. The entire sensor The height is 7.25mm. The size of the lower central electrode 7 is 5mm×5mm, the size of each sensing electrode is 5mm×1.5mm, the distance between each sensing electrode and the adjacent side of the lower central electrode is 0.5mm, and the size of the upper common electrode 4 is 7.5mm×7.5mm.

Specifically, an upper layer common electrode pad 4A in the form of a via hole is arranged on the flexible base of the upper flexible printed circuit board. The flexible substrate of the printed circuit board is provided with the lower layer center electrode pad 7A of the via hole form and the pads of each induction electrode (the first induction electrode pad 8A; the second induction electrode pad 9A; the third induction electrode pad 10A ; The fourth sensing electrode pad 11A), the lower center electrode and each sensing electrode are respectively led to their respective pads through enameled wires, and then lead out through signal lines. This via method can make the wiring more flexible and easy to array. Moreover, based on FPCB technology, each electrode and each pad is fabricated on a flexible substrate, so that each electrode and pad can be bent and deformed arbitrarily, and has good flexibility.

Specifically, the flexible protective layer 2 is a thin layer of silicon rubber that is spin-coated on the upper flexible printed circuit board 3 for protecting the upper flexible printed circuit board and conducting contact forces. The flexible protective layer 2 is made of GD401 silicone rubber from Zhonghao Chenguang Chemical Research Institute Co., Ltd., which can be cured at room temperature and has good flexibility after curing.

Specifically, the PDMS hemispherical contact is to use 3D printing technology to print a hemispherical mold with a radius of 8mm, pour an appropriate amount of PDMS into the mold, wait for it to solidify and form, and take out the formed contact layer from the mold. .

Specifically, based on flexible printed circuit board (FPCB) technology, the flexible substrates of the upper flexible printed circuit board 3 and the lower flexible printed circuit board 6 are made of polyimide, and the corresponding electrode layers are plated on the surface of the flexible substrate polyimide layer of copper foil.

Specifically, the dielectric layer 5 uses PDMS (10:1) as the sensitive material. 3D printing technology is used to print an inverted pyramid-shaped mold. In order to ensure the sensitivity and stability of the sensor, the two components of PDMS are mixed and stirred evenly, degassed in a vacuum chamber, and then injected into the mold. Place the mold on the lower central electrode and sensing electrode of the lower flexible printed circuit board, align the mold with each electrode, wait for the mixed solution to be molded at room temperature, and after curing at 90°C for 60 minutes, remove the mold to obtain A medium layer 5 of a pyramid structure with an ideal shape.

The dielectric layer, the two flexible printed circuit boards, the flexible protective layer and the PDMS hemispherical contacts were bonded together after 90 seconds of plasma treatment. Ensure that the filler is evenly distributed to form a stable mechanical structure and ensure mechanical properties.

Example 2

As shown in Figure 3, the three-dimensional coordinate system diagram of the fully flexible sliding tactile sensor based on the pyramid structure is constructed, in which the center of the center electrode of the lower layer is the origin, the Z axis is along the height direction of the sensor, and the X axis is parallel to the first sensing electrode and In the direction of the long side of the third sensing electrode, the Y axis is along a direction parallel to the long sides of the second sensing electrode and the fourth sensing electrode.

The capacitance extraction in this embodiment uses the AD7147-1 with I ² C compatible serial interface and on-chip environment self-calibration function, up to 16-bit CDC accuracy, and 13 capacitive inputs. It can be easily realized with the single-pole double-throw switch ADG734 Acquisition of multi-channel capacitance signals.

The mechanism of the fully flexible capacitive sliding tactile sensor of this embodiment to detect the sense of touch is as follows: when the hemispherical contact is subjected to an external normal force (force along the Z-axis direction), the upper common electrode 4 and the lower central electrode at the upper and lower ends of the dielectric layer 5 The spacing between the 7 becomes smaller, and at the same time, the pyramid-shaped PDMS replaces part of the air, resulting in an increase in the effective dielectric constant, resulting in an increase in capacitance. When the sensor is squeezed by different magnitudes of external force, the spacing between the upper common electrode and the lower central electrode changes differently, and the dielectric layer is also affected to different degrees, so that the capacitance value changes also differently. The capacitive signal between the upper common electrode 4 and the lower central electrode 7 is collected by AD7147-1, and converted into a digital signal and sent to the microprocessor to calculate the normal force acting on the sensor.

For comparison, the dielectric layer in Example 1 was changed from the structure of “bottom plane + pyramid” to a planar structure of 8mm×8mm×2mm, and the rest of the structure was the same to form a sensor based on the planar dielectric layer structure.

The capacitance-normal force relationship curves of the sensor (pyramid) based on the pyramid structure and the sensor (plane) based on the planar dielectric layer structure are shown in Figure 4 (where C ₀ is the original capacitance between the upper common electrode and the lower central electrode value, ΔC is the change in capacitance after applying force). It can be seen that when the pressure is less than 3.6N, the sensitivity of the sensor based on the pyramid structure is 0.01kpa ^-1 , while the sensitivity of the sensor based on the planar dielectric layer structure is 0.0005kpa ^-1 , so the sensor based on the pyramid structure is in the small range ( 0～3.6N) has higher sensitivity and can better distinguish and detect tactile force. In a large range, the sensitivity of the two is equivalent. When the pressure exceeds 3.6N, the change of the capacitance value of the sensor based on the pyramid structure tends to be moderate, because the pyramid structure is completely squeezed, and the sensitivity drops to 0.0005kpa ^-1 at this time, but the measuring range of the sensor increases. In order to have both the functions of micro-tactile force detection and relatively large pressure detection, the sensor structure of the present invention combines the two advantages of high sensitivity and large range.

The normal force is applied and released at intervals to the fully flexible sliding tactile sensor of this embodiment, and its dynamic response and recovery characteristics are shown in Figure 5. It can be seen that the sensor can quickly sense the force information and has good repeatability.

Example 3

The mechanism of the fully flexible capacitive sliding tactile sensor in this embodiment to detect the sliding sensation is as follows: when the hemispherical contact is subjected to an external tangential force (three-dimensional force), first the upper common electrode and the lower central electrode will be separated due to the force along the Z axis. Generate the capacitance change as described in Embodiment 2; secondly, relative sliding will occur between the upper layer common electrode and the four sensing electrodes due to the force along the X-axis and Y-axis directions, and the relative area and relative permittivity will change. cause a change in capacitance. The tangential information of the sensor can be obtained by detecting the capacitance change between the upper common electrode and the four sensing electrodes.

Convert the normal force in Example 2 into a tangential force (at this time, the normal force along the Z-axis direction is constant), and the rest remain the same as in Example 2. When the static normal force is 2N, the upper common electrode and the The response state of the capacitance between the sensing electrodes in the lower layer under different tangential forces is shown in Figure 6 (Figure 6 shows the tangential force along the Y-axis direction, and the force in the X-axis direction is 0 at this time). In Figure 6, C ₁₀ , C ₂₀ , C ₃₀ , and C ₄₀ are the original capacitances between the upper common electrode and the first sensing electrode, the second sensing electrode, the third sensing electrode, and the fourth sensing electrode, respectively, ΔC ₁ , ΔC ₂ , ΔC ₃ , and ΔC ₄ are the changes in the corresponding capacitance after the force is applied, respectively.

In the state where the static normal force is 2N, a tangential force is applied, and the movement of the upper common electrode induces tangential deformation of the pyramid structure, resulting in a change in the sensing capacitance. When a tangential force along the positive direction of the X-axis is applied, within the range range (0-4N), the relative area between the upper common electrode and the fourth sensing electrode increases, the distance becomes smaller, and the relative permittivity increases, resulting in two The capacitance C ₄ between them increases; while the relative area between the upper common electrode and the second sensing electrode decreases, the distance becomes smaller, the relative permittivity increases, and C ₂ decreases; thereafter, the change is relatively slow. C ₁ and C ₃ are basically unchanged. Similarly, when a positive tangential force along the Y-axis is applied, within the range (0-4N), C ₁ increases and C ₃ decreases, and then changes slowly; C ₂ and C ₄ basically remain unchanged.

It can be seen from Figure 6 that when the static normal force is 2N, when the tangential force along the positive direction of the Y axis is applied, the changes of C ₂ and C ₄ are very small. C ₁ and C ₃ are in the range range (0-4N), C ₁ increases and C ₃ decreases, the sensitivity of the sensor based on the pyramid structure is 0.0625kpa ^-1 , after that the change is relatively slow, and the sensitivity decreases; while the sensor based on the planar dielectric layer The sensitivity of the structured sensor is 0.025kpa ^-1 . The comparison shows that under the same conditions, the sensor based on the pyramid structure is more sensitive than the sensor based on the planar dielectric layer structure.

Extract the change of capacitance _C4 when the tangential force along the positive direction of the X-axis gradually increases when the static normal force is 2N. It can be seen from Figure 7 that before sliding, when the tangential force gradually increases to 4N, The capacitance has been increasing steadily. When the shear force increases to 4N, the capacitance signal vibrates obviously, and the frequency increases, but then tends to be stable. When the tangential force is greater than 4N, the capacitance remains basically unchanged.

The above descriptions are only exemplary embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. a kind of Grazing condition condenser type based on pyramid structure slides touch sensor, it is characterised in that：Including upper flexible printing Circuit board (3) and lower flexible printed circuit board (6)；

The surface printing of flexible printed circuit board (3) has upper strata public electrode (4) on described；

There is square lower floor's central electrode (7) and equidistantly in the surface printing of the lower flexible printed circuit board (6) Four identical rectangle induction electrodes positioned at each side periphery of lower floor's central electrode；Each induction electrode is with lower floor's central electrode (7) center is that symmetric points are symmetrical two-by-two；

Dielectric layer (5) is provided between flexible printed circuit board (3) and lower flexible printed circuit board (6) on described, is given an account of The upper surface integrated molding of matter layer (5) has pyramid structure；The upper strata public electrode (4) and the tower of the pyramid structure Top contact, lower floor's central electrode (7) contacts with the lower surface of the dielectric layer (5)；

PDMS hemisphericals contact (1) is fixed with by flexible cover sheet (2) on flexible printed circuit board (3) on described.

2. Grazing condition condenser type according to claim 1 slides touch sensor, it is characterised in that：The long side of each induction electrode The length of side be equal to lower floor's central electrode the length of side, each induction electrode it is long while the lower floor central electrode adjacent with its while put down OK.

3. Grazing condition condenser type according to claim 1 or 2 slides touch sensor, it is characterised in that：The dielectric layer Lower surface is by lower floor's central electrode and four induction electrode all standings；The upper strata public electrode (4) is located at the lower floor center The surface of electrode (7), and orthographic projection of the upper strata public electrode (4) on lower flexible printed circuit board (6) surface will Lower floor's central electrode (7) all standing, by each induction electrode half mulching.

4. Grazing condition condenser type according to claim 1 slides touch sensor, it is characterised in that：The dielectric layer (5) with PDMS is material.

5. Grazing condition condenser type according to claim 1 slides touch sensor, it is characterised in that：The upper flexible printing electricity The flexible substrates of road plate (3) and the lower flexible printed circuit board (6) are using polyimides as material.

6. Grazing condition condenser type according to claim 1 slides touch sensor, it is characterised in that：The flexible cover sheet (2) silicon rubber material is used.