Capacitive tension sensor based on mechanical superstructure

Abstract

The application relates to the field of capacitive tension sensors, in particular to a capacitive tension sensor based on a mechanical superstructure, which comprises a first electrode sheet and a second electrode sheet parallel to the first electrode sheet; the first electrode sheet and the second electrode sheet are both flexible or elastic, a three-dimensional tensile structure is arranged between the first electrode sheet and the second electrode sheet, the edge of the first electrode sheet is connected with the edge of the second electrode sheet through the three-dimensional tensible structure, and the three-dimensional tensible structure is not conductive. In the application, when the first electrode sheet and / or the second electrode sheet are subjected to a tension parallel to itself, the area of the first electrode sheet and the second electrode sheet is synchronously and equally increased through the three-dimensional tensible structure, the increase of the electrode area leads to the increase of the capacitance value, and the size of the tension is calculated by measuring the change of the capacitance value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of capacitive tension sensors, in particular to a capacitive tension sensor based on a mechanical superstructure. BACKGROUND

[0002] The existing tension sensors are mainly resistance type tension sensors, which measure the size of the tension through the change of the resistance value when being pulled. Among them, the metal type tension sensor is relatively mature in design and has good reliability, so it is most widely used, but such sensor is relatively bulky and difficult to detect large deformation, and also has the disadvantage of high energy consumption when continuously detecting; another semiconductor tension sensor has very high sensitivity, but is easy to be damaged and also difficult to detect large deformation. In addition to the resistance type tension sensor, there are also some capacitive tension sensors, which have high sensitivity and lower energy consumption when continuously measuring. However, most of the existing capacitive tension sensors are based on flat capacitors, and since the stretching direction is perpendicular to the electrode, it is impossible to measure the tension on the plane and to realize the measurement of large deformation.

[0003] To solve the above technical problems, the prior art provides a capacitive tactile sensor for measuring tension, such as CN202010310831.4 (an integrated flexible stretchable tactile sensor based on super capacitor sensing principle), which includes a foam upper electrode layer, a foam electrolyte layer and a foam lower electrode layer arranged in sequence. Under the action of tension, physical contact is generated between the mesh-shaped electrolyte layer and the mesh-shaped electrode, and the contact area increases with the increase of the load. When the load disappears, the sensor returns to its original state, and the capacitance value returns to the initial value.

[0004] Such capacitive tactile sensor has high production cost and is currently in the research and development stage, which is not suitable for large-scale production. Therefore, a low-cost capacitive tension sensor is needed. SUMMARY

[0005] The present application aims to provide a capacitive tension sensor based on a mechanical superstructure to solve

[0006] To solve the above technical problems, the present application specifically provides the following technical solutions:

[0007] The present application provides a capacitive tension sensor based on a mechanical superstructure, which includes a first electrode sheet and a second electrode sheet parallel to the first electrode sheet; the first electrode sheet and the second electrode sheet are both flexible or elastic, and a three-dimensional dilatation structure is arranged between the first electrode sheet and the second electrode sheet, the edges of the first electrode sheet are connected to the edges of the second electrode sheet through the three-dimensional dilatation structure, and the three-dimensional dilatation structure is not conductive.

[0008] Preferably, the three-dimensional auxetic structure comprises hollow cells having cell walls, the cross-section of the hollow cells following a two-dimensional auxetic pattern.

[0009] Preferably, the hollow cells are several and abut each other.

[0010] Preferably, the two-dimensional auxetic pattern is a concave hexagon.

[0011] Preferably, the cell walls are made of a sheet.

[0012] Preferably, the cell walls connect the edges of the first electrode sheet and the edges of the second electrode sheet and form a sealed chamber.

[0013] Preferably, the sealed chamber is filled with a liquid inside.

[0014] Preferably, the liquid is an electrolyte.

[0015] Preferably, wires are connected on the first electrode sheet and the second electrode sheet respectively.

[0016] According to another aspect of the present application, the cell walls comprise fold lines parallel to a plane comprising the two-dimensional auxetic pattern, the cell walls form peaks and valleys by the fold lines, and the cell walls are foldable along the fold lines.

[0017] The present application has the following beneficial effects compared with the prior art:

[0018] When the first electrode sheet and / or the second electrode sheet are subjected to a pulling force parallel to themselves, the areas of the first electrode sheet and the second electrode sheet increase synchronously and equally in magnitude through the three-dimensional auxetic structure, the increase of the electrode areas leads to the increase of the capacitance values, the magnitude of the pulling force is calculated by measuring the change of the capacitance values, the electrode sheets and the three-dimensional auxetic structure can be manufactured through existing production lines, and the investment cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained from the provided drawings without creative labor.

[0020] Figure 1 a perspective view of the capacitive tension sensor provided for the embodiment 1 of the present application;

[0021] Figure 2 a top view of the capacitive tension sensor provided for the embodiment 1 of the present application;

[0022] Figure 3 is a sectional view along the A-A direction of Figure 2

[0023] Figure 4 is a schematic diagram of a capacitive tension sensor provided for Embodiment 1 of the present application;

[0024] Figure 5 is a perspective view of a three-dimensional tensile structure provided for Embodiment 2 of the present application;

[0025] The reference numerals in the drawings represent the following respectively:

[0026] 1 - first electrode sheet;

[0027] 2 - three-dimensional tensile structure; 2a - flat plate; 2b - concave plate; 2c - folding line;

[0028] 3 - second electrode sheet;

[0029] 4 - wire;

[0030] X - transverse tensile direction; Y - longitudinal expansion direction. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] As shown in Figures 1-4 , the present application provides Embodiment 1:

[0033] A capacitive tension sensor based on a mechanical superstructure, comprising a first electrode sheet 1 and a second electrode sheet 3 parallel to the first electrode sheet 1; the first electrode sheet 1 and the second electrode sheet 3 are both flexible or elastic, and a three-dimensional tensile structure 2 is arranged between the first electrode sheet 1 and the second electrode sheet 3, the edges of the first electrode sheet 1 are connected to the edges of the second electrode sheet 3 through the three-dimensional tensile structure 2, and the three-dimensional tensile structure 2 is not conductive.

[0034] Specifically, the first electrode sheet 1 comprises a flexible film, the edges of the flexible film are bonded to a frame formed by the three-dimensional tensile structure 2, and a flexible electrode is coated on the outer side of the flexible film, and the flexible electrode is tightly attached to the flexible film. The flexible electrode has the advantages of being light and thin, soft, bendable and stretchable, and can realize large deformation together with the substrate (flexible film) under the premise of ensuring signal stability.

[0035] ​Based on the above embodiments, the technical problem to be solved by the present application is how to measure the tension parallel to the electrode direction using a capacitive sensor.

[0036] To this end, the present application uses a first electrode sheet 1 and a second electrode sheet 3 to form a capacitor, when the first electrode sheet 1 and / or the second electrode sheet 3 is subjected to tension parallel to itself, the first electrode sheet 1 and the second electrode sheet 3 are deformed synchronously and equally in amplitude by the three-dimensional auxetic structure 2. Since the three-dimensional auxetic structure 2 has auxeticity, its volume increases when stretched and decreases when compressed, so that the area of the first electrode sheet 1 and the second electrode sheet 3 increases equally in amplitude.

[0037] According to the formula of the flat plate capacitor:

[0038]

[0039] Where C is the capacitance value of the flat plate capacitor, ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant, A is the area of the electrode, d is the distance between the electrodes, it can be found that the increase of the electrode area leads to the increase of the capacitance value, therefore, the magnitude of the tension can be calculated by measuring the change of the capacitance value.

[0040] Further:

[0041] The three-dimensional auxetic structure 2 includes hollow cells, the hollow cells have cell walls, the cross section of the hollow cells follows a two-dimensional auxetic pattern, the two-dimensional auxetic pattern is a regular structure, which is uniformly stressed and easy to calculate the theoretical capacitance value after shape change caused by loading.

[0042] In this embodiment, the hollow cell itself is an auxetic structure.

[0043] The hollow cells are several and adjacent to each other.

[0044] The plurality of hollow cells with auxeticity are adjacent to each other and also an auxetic structure, which is more uniform in expansion in each direction.

[0045] The two-dimensional auxetic pattern is a concave hexagon, specifically, it is a regular concave hexagon, which is symmetric up and down, left and right, and center, and θ0 is less than 45 degrees.

[0046] Specifically, the specific structure of the concave hexagonal auxetic pattern and its working principle are:

[0047] The three-dimensional auxetic structure 2 comprises two flat plates 2a arranged symmetrically around the center of the first electrode sheet 1, the two flat plates 2a being parallel to each other and perpendicular to the first electrode sheet 1; and two concave plates 2b connecting adjacent ends of the two flat plates 2a, the concave plates 2b being concave towards the center of the first electrode sheet 1, the concave plates 2b being composed of straight plates bent out obtuse angles; the flat plates 2a and the concave plates 2b are connected into a concave hexagon and connect the edges of the first electrode sheet 1 and the edges of the second electrode sheet 3.

[0048] When a pulling force F is applied to the three-dimensional auxetic structure 2 in the stretching direction X, the frame will be deformed in the direction of the pulling force with a size of x, and at the same time, the frame will be expanded and deformed in the direction Y which is perpendicular to F in the plane of the pulling force, that is, when the flat plates 2a are stretched outward, the obtuse angles of the concave plates 2b become larger.

[0049] The simultaneous expansion of the three-dimensional auxetic structure 2 in the XY direction causes the areas of the first electrode sheet 1 and the second electrode sheet 3 to increase, and at the same time, since the volume of the electrolyte in the sealed cavity does not change, the distance between the first electrode sheet 1 and the second electrode sheet 3 becomes smaller. The increase in the areas of the first electrode sheet 1 and the second electrode sheet 3 and the decrease in the distance between them result in an increase in the capacitance value of the flat plate capacitor formed by them.

[0050] Other auxetic patterns disclosed in the prior art are also applicable to the present embodiment.

[0051] Further:

[0052] The cell wall is made of a sheet.

[0053] The sheet can be a composite preform, a fabric or a unidirectional preform.

[0054] Further:

[0055] The cell wall connects the edges of the first electrode sheet 1 and the edges of the second electrode sheet 3 and forms a sealed cavity.

[0056] Since the first electrode sheet 1, the cell wall and the second electrode sheet 3 form a sealed cavity, when the three-dimensional auxetic structure 2 is auxetically stretched to cause the areas of the first electrode sheet 1 and the second electrode sheet 3 to increase, a vacuum is generated inside the sealed cavity, which causes the first electrode sheet 1 and the second electrode sheet 3 to collapse into the sealed cavity, thereby causing the distance between the first electrode sheet 1 and the second electrode sheet 3 to decrease slightly. As can be seen from formula (1), the decrease in the distance between the electrodes will cause the capacitance value to increase, thereby improving the sensitivity of the capacitive tension sensor.

[0057] Further:

[0058] The sealed cavity is filled with a liquid.

[0059] In the embodiment, since the volume of the liquid is constant, compared with the case that the sealed chamber is filled with gas, the increase of the area of the first electrode sheet 1 and the second electrode sheet 3 leads to a substantial decrease of the distance between the two, and further leads to a substantial increase of the capacitance value, thereby further improving the sensitivity of the capacitive tension sensor.

[0060] Further:

[0061] The liquid is an electrolyte.

[0062] Filling the sealed chamber with the electrolyte can not only increase the change of the distance between the first electrode sheet 1 and the second electrode sheet 3, but also increase the total amount of the capacitance value.

[0063] Further:

[0064] The first electrode sheet 1 and the second electrode sheet 3 are respectively connected with wires 4.

[0065] The wires 4 connected to the upper and lower membrane electrodes by the LCR instrument realize the measurement of the capacitance. The capacitance value is one-to-one corresponding to the tension F, and thus the determination of the tension can be realized by the measurement of the capacitance value.

[0066] The working principle of the capacitive tension sensor in the embodiment is as follows:

[0067] Figure 4 The solid line in the middle represents the initial shape of the frame, the four edges in the concave plate 2b are all of length a, the edges of the two flat plates 2a on the two sides of the tension are of length b, the complementary angle between the edge of length a and the edge of length b is θ0 shown in the figure, the distance between the two electrodes is d0, and the area of the flexible membrane coated with the flexible electrode on the outside is A0 in the initial state.

[0068] A0=2a·cosθ0(b-a·sinθ0) (2)

[0069] Therefore, the initial capacitance value is:

[0070]

[0071] When the tension F is applied in the transverse direction, it is assumed that the deformation of length x is caused in the transverse direction, and the shape of the structure is changed from the solid line to the dashed line. The area of the flexible membrane is changed to A1, and the distance between the flexible membranes is changed to d1. Since the length of each edge is constant, the complementary angle between the edge of length a and the edge of length b is θ1 shown in the figure. According to the liquid volume conservation, it can be obtained that

[0072] A0·d0=A1·d1(4)

[0073] Therefore,

[0074]

[0075] The corresponding capacitance value becomes

[0076]

[0077] wherein

[0078] A1=(2a·cosθ0+x)·(b-a·sinθ1) (7)

[0079] According to the geometric relationship

[0080] 2a·cosθ0+x=2a·cosθ1 (8)

[0081] It is obtained that

[0082]

[0083] Since x is greater than zero, θ is a monotonic decreasing function of x.

[0084] As the pulling force increases, x gradually increases and θ gradually decreases, so A1 monotonically increases, and since C0 and A0 are both constants, x and C1 are one-to-one, which means that C1 measured by formula (6) can determine the size of the pulling force F.

[0085] As Figure 5 shown, based on example 1, the application further provides example 2, which is different from example 1 in that:

[0086] The cell wall comprises a folding line 2c parallel to the plane comprising the two-dimensional auxetic pattern, the cell wall forms peaks and valleys through the folding line 2c, and the cell wall can be folded along the folding line 2c.

[0087] The cell wall can be folded in the Z direction (not shown in the Z direction diagram, the Z direction is perpendicular to the X direction and the Y direction), so that the first electrode sheet 1 and the second electrode sheet 3 are more easily close to each other when the three-dimensional auxetic structure 2 is auxetic.

[0088] The above examples are only exemplary embodiments of the application and are not used to limit the application, the protection scope of the application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the application within the spirit and protection scope of the application, and such modifications or equivalent replacements shall also be considered to fall within the protection scope of the application.

Claims

1. A mechanical superstructure based capacitive tension sensor, comprising a first electrode sheet (1) and a second electrode sheet (3) parallel to the first electrode sheet (1); characterized in that the first electrode sheet (1) and the second electrode sheet (3) are both flexible or elastic, a three-dimensional auxetic structure (2) is arranged between the first electrode sheet (1) and the second electrode sheet (3), edges of the first electrode sheet (1) are connected with edges of the second electrode sheet (3) through the three-dimensional auxetic structure (2), and the three-dimensional auxetic structure (2) is not conductive; the three-dimensional auxetic structure (2) comprises hollow cells, the hollow cells have cell walls, cross sections of the hollow cells follow a two-dimensional auxetic pattern, the cell walls connect the edges of the first electrode sheet (1) and the edges of the second electrode sheet (3) and form sealed chambers, and the sealed chambers are filled with electrolyte inside.

2. The mechanical superstructure based capacitive tension sensor according to claim 1, characterized in that the hollow cells are several and adjacent to each other.

3. The mechanical superstructure based capacitive tension sensor according to claim 1 or 2, characterized in that the two-dimensional auxetic pattern is a concave hexagon.

4. The mechanical superstructure based capacitive tension sensor according to claim 3, characterized in that the cell walls are made of sheet material.

5. The mechanical superstructure based capacitive tension sensor according to claim 1, characterized in that the cell walls comprise fold lines (2c), the fold lines (2c) are parallel to a plane comprising the two-dimensional auxetic pattern, the cell walls form peaks and valleys through the fold lines (2c), and the cell walls can be folded along the fold lines (2c).

6. The mechanical superstructure based capacitive tension sensor according to claim 1, characterized in that wires (4) are respectively connected to the first electrode sheet (1) and the second electrode sheet (3).

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