CN112577643B - A Large Range Capacitive Flexible Sensor for Three-axis Force Measurement - Google Patents

Abstract

The invention provides a large-range capacitive flexible sensor that realizes three-axis force measurement. The bottom of the upper flexible substrate is provided with a plurality of substrate bosses with the same height, the upper electrode is a metal layer covering the bottom of the upper flexible substrate, and the lower The electrode includes a number of intermediate electrodes and peripheral electrodes surrounding the periphery of the intermediate electrodes, and the intermediate electrodes correspond to the peripheral electrodes one-to-one; the capacitive sensor formed between the intermediate electrode and the upper electrode is used to measure the positive force, and the peripheral electrode and the upper electrode are formed between The capacitive sensor is used to measure the tangential force. The invention utilizes the flexibility of the upper flexible substrate itself and the substrate boss at the bottom, so that after the dielectric layer is completely compressed, the upper flexible substrate can still be compressed for a certain stroke, thereby effectively improving the range of the sensor; the arrangement of the lower electrodes is used. , to measure the normal and tangential forces, respectively.

Description

A Large Range Capacitive Flexible Sensor for Three-axis Force Measurement

technical field

The invention belongs to the field of capacitive flexible sensors, in particular to a large-range capacitive flexible sensor that realizes three-axis force measurement.

Background technique

With the development of robotics and the popularization of human intelligent wearable devices, modern society has put forward higher and higher requirements for the performance of flexible sensors. Capacitive sensors are widely used due to their good temperature stability and simple structure.

However, the current capacitive flexible sensors still have certain problems. For example, a tactile sensor applied to a robot finger will be subjected to a triaxial force when holding an object, and the triaxial force can be decomposed into a positive force due to pressing and a tangential force due to friction. Including two mutually perpendicular tangential forces. Traditional capacitive sensors measure the normal force through the change in the distance between the plates and the tangential force through the change in the facing area between the plates. When the sensor is subjected to a normal force and two tangential forces at the same time, the distance and the facing area of the plates will change at the same time, so the sensor cannot measure the magnitude of the normal force and the two tangential forces at the same time. Therefore, it is very important to design a capacitive flexible sensor that can measure the normal force and two mutually perpendicular tangential forces simultaneously.

In addition, many researchers have proposed many design schemes for the structure of the dielectric layer to improve the sensitivity of the sensor. In the case of a certain initial capacitance, the larger the air ratio in the dielectric layer, the greater the sensitivity of the sensor, but the smaller the measurement range. Many dielectric layer designs sacrifice measurement range while increasing sensitivity.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a large-range capacitive flexible sensor that realizes three-axis force measurement, simultaneously measure the normal force and the tangential force, and increase the measurement range.

The technical solution adopted by the present invention to solve the above technical problems is: a large-range capacitive flexible sensor for realizing three-axis force measurement, the sensor includes an upper electrode plate, a dielectric layer and a lower electrode plate connected in sequence, and is characterized in that:

The upper electrode plate includes an upper flexible substrate and an upper electrode; the bottom of the upper flexible substrate is provided with several substrate bosses with the same height, and the bottom of the upper flexible substrate is provided with a thin wall in the circumferential direction; the upper electrode is covered with the upper flexible substrate. the metal layer at the bottom of the substrate, and the upper electrode is provided with an electrode boss having the same shape as the substrate boss;

The medium layer is an elastic medium layer with three-dimensional micropores, and the thin wall is fixedly connected with the medium layer; when the sensor is not subjected to external force, the electrode bosses are just in contact with the dielectric layer, and the adjacent electrode bosses are in contact with each other. There is a certain distance between them and the dielectric layer to form a cavity;

The lower electrode plate includes a lower flexible substrate and a lower electrode covering the top of the lower flexible substrate; the lower electrode includes a plurality of intermediate electrodes and peripheral electrodes surrounding the periphery of the intermediate electrodes, and the intermediate electrodes correspond to the peripheral electrodes one-to-one; The capacitive sensor formed between the upper electrodes is used to measure the normal force, and the capacitive sensor formed between the peripheral electrode and the upper electrode is used to measure the tangential force;

The vertical projection of the upper electrode on the lower electrode completely covers the middle electrode and partially covers the peripheral electrode.

According to the above scheme, the substrate boss is a trapezoid.

According to the above scheme, the substrate boss is provided with a bottom and a top, the bottom is a square of 600 μm×600 μm, and the top is a square of 300 μm×300 μm. Stretching to form the substrate bosses.

According to the above solution, the plurality of substrate bosses with the same height are arranged in an array.

According to the above solution, the upper flexible substrate has miniature elastic balls.

According to the above scheme, the middle electrodes are 4 and the shape is the same, the peripheral electrodes are 4 and the shape is the same; the capacitance sensors formed between the 4 middle electrodes and the upper electrode are used to measure the normal force; 4 Two pairs of differential capacitors are formed between the peripheral electrode and the upper electrode, which are used to measure two mutually perpendicular tangential forces.

According to the above scheme, each intermediate electrode is an isosceles right triangle electrode, four isosceles right triangle electrodes are arranged in a square structure, and the adjacent isosceles right triangle electrodes are separated by a certain distance; One-to-one corresponding rectangular electrodes, the four rectangular electrodes are arranged around the square structure formed by isosceles right-angled triangular electrodes, the vertical bisector of the long side of each rectangular electrode passes through the center of the lower flexible substrate, and the rectangular The long side of the electrode has a certain distance from the bottom side of the corresponding isosceles right triangle electrode.

According to the above scheme, each intermediate electrode is formed by splicing a trapezoid located on the inside and a rectangle located on the outside, the bottom edge of the trapezoid is connected to the length of the rectangle, and the outside of the rectangle is a comb-like structure; the peripheral electrodes are The inner side is a rectangle with a comb-like structure, and each peripheral electrode and the corresponding middle electrode intersect through the comb-like structure, and there is a certain distance at the intersection.

According to the above solution, the lower flexible substrate is made of PI material, and the top of the lower flexible substrate is covered with the lower electrode by photolithography or electroplating technology.

According to the above scheme, the upper flexible substrate is made of PI material, including a square sheet of 5500 μm×5500 μm×10 μm.

The beneficial effects of the present invention are:

1. Using the flexibility of the upper flexible substrate itself and the substrate boss at the bottom, after the dielectric layer is completely compressed, the upper flexible substrate can still be compressed for a certain stroke, thereby effectively improving the range of the sensor; using the arrangement of the lower electrodes , to measure the normal and tangential forces, respectively.

2. Since the number of intermediate electrodes is more than one, the distribution characteristics of the normal force can be obtained through multiple measurement results, which makes the measurement results more accurate; two pairs of differential capacitors can be formed through the four surrounding electrodes and the upper electrode, thereby Two mutually perpendicular tangential forces are measured; combined with the normal force measured by the intermediate capacitor, the triaxial force is finally measured. In addition, the specific directions of the two tangential forces can also be determined by the changes in the size of the four surrounding capacitors.

Description of drawings

FIG. 1 is a structural cross-sectional view of Embodiment 1 of the present invention.

FIG. 2 is a structural exploded diagram of Embodiment 1 of the present invention.

Figure 3 is an isometric view of the upper flexible substrate.

FIG. 4 is a cross-sectional view taken along line AA of FIG. 2 .

FIG. 5 is a schematic diagram of the structure of the upper electrode.

FIG. 6 is a schematic diagram of the deformation of the first embodiment of the present invention when subjected to a normal force.

FIG. 7 is a top view of the upper electrode and the lower electrode according to the first embodiment of the present invention.

FIG. 8 is a top view of the upper electrode and the lower electrode according to the second embodiment of the present invention.

In the figure: 1-upper flexible substrate, 1-1-substrate boss, 1-2-thin wall, 2-upper electrode, 2-1-electrode boss, 3-dielectric layer, 4-lower electrode, 4 -1- isosceles right triangle electrode, 4-2-rectangular electrode, 5-lower flexible substrate, 6-miniature elastic ball, 7-cavity, 8-upper plate, 9-lower plate.

Detailed ways

The present invention will be further described below with reference to specific examples and accompanying drawings.

Example 1:

Referring to FIGS. 1-7 , this embodiment is mainly composed of an upper flexible substrate 1 , an upper electrode 2 , a dielectric layer 3 , a lower electrode 4 , and a lower flexible substrate 5 . The upper flexible substrate 1 and the upper electrode 2 together form the upper electrode plate 8 , and the lower flexible substrate 5 and the lower electrode 4 together constitute the lower electrode plate 9 . These components are packaged together through various processes.

The upper flexible substrate is shown in FIG. 2 and FIG. 3 . The main body of the upper flexible substrate 1 is a square thin plate, and a number of substrate bosses 1-1 with the same height are arranged at the bottom of the upper flexible substrate. The vertical section of the bottom boss 1-1 is trapezoidal and arranged in an array. The periphery of the upper flexible substrate 1 is a circle of thin walls 1-2. In this embodiment, the height of the thin walls 1-2 is 15 μm.

The upper flexible substrate 1 described in this embodiment is made of PI material, and includes a square sheet of 5500 μm×5500 μm×10 μm, and the substrate boss 1-1 is arranged at the bottom of the square sheet. The substrate boss 1-1 is provided with a bottom and a top, the bottom is a square of 600 μm×600 μm, and the top is a square of 300 μm×300 μm. The substrate boss 1-1 is formed by stretching.

The upper electrode 2 is shown in FIG. 5 , which is a layer of metal thin film covering the bottom of the upper flexible substrate 1 , and has an electrode boss 2 - 1 having the same shape as the substrate boss 1 - 1 .

The medium layer 3 is an elastic medium layer with three-dimensional micropores, and the thin walls 1-2 are fixedly connected to the medium layer 3; when the sensor is not subjected to external force, the electrode bosses 2-1 and the medium layer 3 Just in the contact state, there is a certain distance between the adjacent electrode bosses 2 - 1 and the dielectric layer 3 so as to form a cavity 7 .

The lower electrode 4 includes a plurality of middle electrodes and peripheral electrodes surrounding the periphery of the middle electrodes, and the middle electrodes are in one-to-one correspondence with the peripheral electrodes. The lower flexible substrate 5 is a square thin plate structure, and the top of the lower flexible substrate 5 is covered with a layer of the above-mentioned lower electrode by processes such as photolithography and electroplating. And the side length of the lower flexible substrate is greater than the side length of the entire lower electrode. The capacitive sensor formed between the middle electrode and the upper electrode is used to measure the normal force, and the capacitive sensor formed between the peripheral electrode and the upper electrode is used to measure the tangential force. The vertical projection of the upper electrode 2 on the lower electrode 4 completely covers the middle electrode and partially covers the peripheral electrode.

In this embodiment, there are 4 intermediate electrodes with the same shape, and the peripheral electrodes are 4 with the same shape, all of which are connected to the outside through wires; the capacitance sensor formed between the 4 intermediate electrodes and the upper electrode is used for It is used to measure the normal force; two pairs of differential capacitances are formed between the four peripheral electrodes and the upper electrode, which are used to measure two mutually perpendicular tangential forces.

Further, each intermediate electrode is an isosceles right triangle electrode 4-1, the four isosceles right triangle electrodes 4-1 are arranged in a square structure, and the adjacent isosceles right triangle electrodes 4-1 are separated by a certain distance; The peripheral electrodes are rectangular electrodes 4-2 corresponding to the middle electrodes one-to-one. These four rectangular electrodes are arranged around the square structure formed by the isosceles right-angled triangular electrodes 4-1. Each rectangular electrode 4-2 The vertical bisectors of the long sides pass through the center of the lower flexible substrate, and the long sides of the rectangular electrodes 4-2 have a certain distance from the bottom sides of the corresponding isosceles right-angled triangle electrodes 4-1. The upper electrode 2 and the eight lower electrodes together form eight capacitors. As shown in Figure 7, the dashed line is the vertical projection of the frame of the upper electrode 2, and eight capacitive sensors are formed between the eight lower electrodes and the upper electrode, which are denoted as C11, C12, C13, C14 and C21, C22, C23 respectively. , C24. Among them, C11, C12, C13, and C14 represent the four capacitors in the middle, which are mainly used to measure the normal force. C21, C22, C23, and C24 represent four capacitors around, which are mainly used to measure the tangential force and determine the direction of the tangential force. C21 and C22 form a pair of differential capacitors, and C23 and C24 form a pair of differential capacitors.

In this embodiment, the base of the isosceles right-angled triangular electrode 4-1 is 3000 μm and the height is 1500 μm. The rectangular electrode 4-2 has a length of 2500 μm and a width of 1000 μm. The long side of the rectangular electrode 4-2 is 100 μm away from the bottom side of the isosceles right-angled triangular electrode 4-1.

On the one hand, the upper flexible substrate 1 is fixedly connected to the dielectric layer 3 through the thin wall 1-2; on the other hand, the thin wall 1-2 is made to facilitate the displacement of the upper flexible substrate 1 when it is subjected to tangential force . The main function of the upper flexible substrate 1 designed with the above structure is to improve the measurement range of the sensor. As shown in FIG. 6 , when the sensor is subjected to a normal force, its dielectric layer 3 will be compressed, so that the distance between the upper and lower pole plates 8 and 9 changes, and finally the capacitance changes. However, when the dielectric layer 3 is completely compressed, since the upper flexible substrate 1 has a substrate boss 1-1 filled with micro elastic balls 6, the upper flexible substrate 1 can still be further compressed, and the upper and lower plates 8 and 9 The distance between them can still vary. This allows the measuring range of the sensor to be increased.

Further, when the sensor is only subjected to a positive force, the four capacitances in the middle increase as the distance between the plates decreases. In practical applications of the sensor, since the magnitude of the normal force received by each position is not the same, the capacitance changes of the four capacitors in the middle are also different. From this, the normal force at four different positions within a certain range can be measured. Compared with the traditional capacitive sensor, which can only measure a positive force value in a plane range, the capacitive sensor designed in the present invention has more prominent advantages in normal force detection, and the device equipped with the sensor can not only identify The magnitude of the normal force can also determine the normal force and distribution characteristics, thereby improving the performance of the equipment.

已知电容的变化量，可以根据其他条件计算出上下电极正对面积的变化量，从而得到上极板的位移变化量，最终根据上极板位移变化量与切向力的关系确定切向力的大小。同理，可以得到当传感器受到-x、+y、-y这三个方向的切向力时所产生的的电容变化量，从而计算出切向力的大小。Further, when the sensor is subjected to a three-dimensional force, the three-dimensional force can be decomposed into a normal force and two mutually perpendicular tangential forces. Through the design of this upper and lower electrode structure, the magnitude of the normal force and the two tangential forces can be measured respectively. Since the tangential force has no effect on the change of the middle four capacitors, the magnitude and distribution characteristics of the normal force can still be measured through the middle four capacitors when the normal force and the tangential force are applied at the same time. The changes of the four capacitances around it mainly come from four aspects: the change in the distance between the plates caused by the normal force compressing the dielectric layer, the change in the distance between the plates caused by the positive force compressing the upper plate, the positive The change of the facing area between the pole plates caused by the compression of the upper pole plate by the force to make it expand to the outside and the change of the facing area between the pole plates caused by the displacement of the upper pole plate by the tangential force. Assuming that the sensor is subjected to a tangential force in the +x direction, the capacitance change of C24 is recorded as _Δ C ₂₄ , and the capacitance changes caused by the above four factors are respectively recorded as _Δ C ₁ , _Δ C ₂ , _Δ C ₃ , _Δ C ₄ ; the capacitance change of C23 is recorded as _Δ C ₂₃ , and the capacitance changes caused by the above four factors are respectively recorded as _Δ C ₁ , _Δ C ₂ , _Δ C ₃ , and _−Δ C ₄ . Finally, it can be concluded that the capacitance change due to the tangential force ΔC ₄ =(ΔC ₂₄ -ΔC ₂₃ )/2, and the values of _Δ C ₂₄ and _Δ C ₂₃ can be directly read and obtained. According to the formula

Knowing the change of capacitance, the change of the area facing the upper and lower electrodes can be calculated according to other conditions, so as to obtain the displacement change of the upper plate, and finally the tangential force is determined according to the relationship between the displacement change of the upper plate and the tangential force. the size of. Similarly, when the sensor is subjected to tangential forces in the three directions of -x, +y, and -y, the capacitance change can be obtained, so as to calculate the magnitude of the tangential force.

Further, as shown in the table, when the sensor is subjected to a tangential force in the x direction, C23 and C24 will change, while C21 and C22 will not change; when the sensor is subjected to a tangential force in the y direction, C21 and C22 will change. produce changes, while C23 and C24 do not produce changes. That is, the sensor does not interfere with each other in the measurement of the tangential force in the x-direction and the y-direction. This ensures that the sensor can simultaneously measure the magnitude of the normal force and the two mutually perpendicular tangential forces.

Further, as shown in the table, when the sensor is subjected to tangential forces in the four directions of +x, -x, +y, and -y, the four capacitances around it will have different changes. Therefore, the specific directions of the two mutually perpendicular tangential forces can finally be determined according to the changes of the four surrounding capacitors.

+x -x +y -y C21 constant constant increase reduce C22 constant constant reduce increase C23 reduce increase constant constant C24 increase reduce constant constant

Embodiment 2:

The structure and principle of this embodiment are the same as or similar to those of the first embodiment. The difference is that, as shown in FIG. 8 , each intermediate electrode is formed by splicing a trapezoid on the inside and a rectangle on the outside. The side is connected to the length of the rectangle, and the outside of the rectangle is a comb-like structure; the peripheral electrodes are rectangles with a comb-like structure on the inside, and each peripheral electrode and the corresponding middle electrode are intersected by the comb-like structure, and the intersection has a certain spacing.

All the lower electrodes are made into comb-like structures, which makes C23 and C24 as close as possible, so that the difference between the magnitudes of the normal forces received by the two capacitors is as small as possible, which further improves the measurement accuracy.

The present invention utilizes the substrate boss 1-1 of the upper flexible substrate 1 and the miniature elastic balls 6 inside, so that after the dielectric layer 3 is completely compressed, the upper flexible substrate 1 can still be compressed for a certain stroke, thereby effectively improving the capacitance range of the flexible sensor.

The four intermediate capacitors of the sensor are all used to measure the normal force, and the distribution characteristics of the normal force can be obtained through the four measurement results, which makes the measurement results more accurate.

Two pairs of differential capacitances can be formed through the four peripheral electrodes and the upper electrode, thereby measuring two mutually perpendicular tangential forces. Combined with the normal force measured by the intermediate capacitor, the triaxial force measurement is finally realized. In addition, the specific directions of the two tangential forces can also be determined by the changes in the size of the four surrounding capacitors.

The above embodiments are only used to illustrate the design ideas and features of the present invention, and the purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made according to the principles and design ideas disclosed in the present invention fall within the protection scope of the present invention.

Claims (7)

1. a large-scale capacitive flexible sensor that realizes three-axis force measurement, this sensor comprises an upper pole plate, a dielectric layer and a lower pole plate connected in sequence, it is characterized in that: The upper electrode plate includes an upper flexible substrate and an upper electrode; the bottom of the upper flexible substrate is provided with several substrate bosses with the same height, and the bottom of the upper flexible substrate is provided with a thin wall in the circumferential direction; the upper electrode is covered with the upper flexible substrate. the metal layer at the bottom of the substrate, and the upper electrode is provided with an electrode boss having the same shape as the substrate boss; The medium layer is an elastic medium layer with three-dimensional micropores, and the thin wall is fixedly connected with the medium layer; when the sensor is not subjected to external force, the electrode bosses are just in contact with the dielectric layer, and the adjacent electrode bosses are in contact with each other. There is a certain distance between them and the dielectric layer to form a cavity; The lower electrode plate includes a lower flexible substrate and a lower electrode covering the top of the lower flexible substrate; the lower electrode includes a plurality of intermediate electrodes and peripheral electrodes surrounding the periphery of the intermediate electrodes, and the intermediate electrodes correspond to the peripheral electrodes one-to-one; The capacitive sensor formed between the upper electrodes is used to measure the normal force, and the capacitive sensor formed between the peripheral electrode and the upper electrode is used to measure the tangential force; The vertical projection of the upper electrode on the lower electrode completely covers the middle electrode and partially covers the peripheral electrode; The plurality of substrate bosses with the same height are arranged in an array; The upper flexible substrate has miniature elastic balls; The middle electrodes are 4 and the shape is the same, the peripheral electrodes are 4 and the shape is the same; the capacitive sensor formed between the 4 middle electrodes and the upper electrode is used to measure the normal force; Two pairs of differential capacitors are formed between the electrodes for measuring two mutually perpendicular tangential forces. 2 . The sensor according to claim 1 , wherein the substrate boss is a trapezoid. 3 . 3 . The sensor according to claim 2 , wherein the substrate boss is provided with a bottom and a top, the bottom is a square of 600 μm×600 μm, and the top is a square of 300 μm×300 μm, and the centers of the two squares are 3. The two are overlapped in the vertical direction, and the two substrate bosses are formed by lofting and stretching. 4. The sensor according to claim 1, wherein each intermediate electrode is an isosceles right triangle electrode, 4 isosceles right triangle electrodes are arranged in a square structure, and the adjacent isosceles right triangle electrodes are spaced at a certain interval distance; the peripheral electrodes are rectangular electrodes corresponding to the middle electrodes one-to-one, the four rectangular electrodes are arranged around the square structure formed by the isosceles right triangle electrodes, and the vertical bisector of the long side of each rectangular electrode They all pass through the center of the lower flexible substrate, and the long sides of the rectangular electrodes have a certain distance from the bottom sides of the corresponding isosceles right triangle electrodes. 5. The sensor according to claim 1, wherein each intermediate electrode is formed by splicing a trapezoid located on the inside and a rectangle located on the outside, the bottom edge of the trapezoid is connected to the length of the rectangle, and the outside of the rectangle It is a comb-like structure; the peripheral electrodes are rectangles with a comb-like structure on the inside, and each peripheral electrode and the corresponding middle electrode intersect through the comb-like structure, and the intersections have a certain distance. 6 . The sensor according to claim 1 , wherein the lower flexible substrate is made of PI material, and the top of the lower flexible substrate covers the lower electrode by photolithography or electroplating technology. 7 . 7 . The sensor according to claim 1 , wherein the upper flexible substrate is made of PI material, including a square sheet of 5500 μm×5500 μm×10 μm. 8 .

Images