A torque sensor based on the capacitance edge effect

Abstract

The present invention discloses a torque sensor based on the capacitance edge effect, which is composed of a sensor outer ring, a trapezoidal beam, a sensor inner ring, a moving electrode of the sensing capacitor, a static electrode of the sensing capacitor, and a substrate. Among them, the static electrode of the sensing capacitor is connected to the substrate and is perpendicular to the moving electrode of the sensing capacitor, located at the outermost end of the moving electrode of the sensing capacitor, and the static electrode of the sensing capacitor is placed along the axial direction of the sensor, that is, perpendicular to the substrate, to form a capacitor based on the capacitance edge effect. The substrate is connected to the sensor outer ring, and its relative position can be adjusted to change the initial distance between the moving electrode of the sensing capacitor and the static electrode of the sensing capacitor, so as to realize the adjustability of the sensor range and sensitivity. The present invention provides a torque sensor based on the capacitance edge effect, and the static electrode of the sensing capacitor is vertically distributed at the maximum deformation of the moving electrode of the sensing capacitor. This design has the characteristics of high sensitivity, high linearity, adjustable range, sensitivity, etc., and can quickly and accurately realize torque detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, relates to a torque sensor, and particularly relates to a torque sensor based on the capacitance edge effect installed on a robot joint. Background Art

[0002] Currently, in torque measurement, sensors for detecting torque are widely used. According to the way of generating torque signals, they can be divided into optical, optoelectronic, magnetoelectric, and strain types, etc. Among them, the more mature torque sensors on the market are mainly electromagnetic and strain types. The essence of the output signal of the magnetoelectric torque sensor is two angular displacement signals with a phase difference. After combining and processing the signals, torque information is obtained. It is a non-contact sensor without wear. However, it has a large volume, is not suitable for measuring the torque transmitted by robot joints in the field of serial robots, and is not easy to install; the strain torque sensor usually has a complex structure, difficult torque decoupling, and requires additional signal amplification circuits, A / D converters, etc. Currently, such sensors are relatively expensive.

[0003] Currently, for capacitive torque sensors, such as a dynamic torque sensor based on capacitance proposed in Chinese Patent CN201344846Y, when the relative position between the shaft and the housing changes, the capacitance signals at both ends of the shaft will generate a phase difference. By detecting this capacitance difference, the relationship between the capacitance difference and the torque is established to achieve torque measurement. This capacitive torque sensor has a large structural size, can only be used in specific occasions, and is not easy to detect torque in the field of serial robots. Some scholars have developed a vertical electrode type capacitive sensor based on the capacitance edge effect, and its sensitivity is less affected by the electrode spacing compared with the traditional parallel electrode type capacitive sensor. However, there are still problems such as poor linearity, low sensitivity, and non-adjustable sensitivity and range.

[0004] Therefore, the present invention will address the above existing problems, propose a new type of torque sensor based on the capacitance edge effect for detecting torque signals, which is easy to be applied in various fields such as serial robots, and the torque sensor has the characteristics of high sensitivity, high linearity, adjustable range, and sensitivity. Summary of the Invention

[0005] The purpose of the present invention is to overcome problems such as low sensitivity and linearity of the sensor, and design a torque sensor based on the capacitance edge effect to improve the sensitivity and linearity of torque detection, and to achieve the adjustable ability of sensitivity and range.

[0006] To achieve the above objectives, the main technical solutions of the present invention are as follows:

[0007] A torque sensor based on the capacitance edge effect, characterized in that it at least includes a capacitor part and a mechanical body part.

[0008] The capacitor part at least includes the static electrode 7 of the inductive capacitance and the moving electrode 6 of the inductive capacitance. The static electrode 7 of the inductive capacitance at least includes a metal sheet 10 and a second substrate 4-2. The static electrode 7 of the inductive capacitance is connected to the first substrate 4-1 and is located at the outermost end of the moving electrode 6 of the inductive capacitance, that is, the maximum deformation position of the moving electrode 6 of the inductive capacitance, so as to obtain a larger capacitance change amount. And the static electrode 7 of the inductive capacitance is placed along the axial direction of the sensor and is perpendicular to the moving electrode 6 of the inductive capacitance, thereby forming a capacitor 3 with a large deformation amount, that is, high sensitivity, and a uniform change in the distance between the moving electrode 6 of the inductive capacitance and the static electrode 7 of the inductive capacitance. The moving electrode 6 of the inductive capacitance is a part of the mechanical body, in the form of a thin cantilever beam, and is located between the inner sensor ring 1 and the outer sensor ring 2, and is fixedly connected to the inner sensor ring 1 as a whole. As the inner sensor ring 1 rotates, the maximum deformation occurs at the end of the moving electrode 6 of the inductive capacitance. The substrate 4-1 is connected to the outer sensor ring 2 through the fixing hole 9 and the adjusting hole 13. The relative position between the first substrate 4-1 and the outer sensor ring 2 can be adjusted through the adjusting hole 13 of the first substrate 4-1, so as to change the initial distance between the moving electrode 6 of the inductive capacitance and the static electrode 7 of the inductive capacitance, that is, to realize the adjustment of the sensor range and sensitivity.

[0009] The static electrode 7 of the inductive capacitance of the capacitor 3 is placed on the same side as the moving electrode 6 of the inductive capacitance, and there are at least two capacitors 3, and they are distributed in central symmetry, forming a differential measurement structure based on the capacitance edge effect, so as to improve the linearity of the sensor.

[0010] The mechanical body part at least includes the inner sensor ring 1, the outer sensor ring 2 and the trapezoidal beam 5. The trapezoidal beam 5 has at least four and is distributed in a spoke-like manner, and is connected to the inner sensor ring 1 and the outer sensor ring 2. The outer sensor ring 2 is connected to the output end through the outer sensor ring connection hole 12, and the inner sensor ring 1 is connected to the input end through the inner sensor ring connection hole 11; the trapezoidal beam 5 transmits the torque from the inner sensor ring 1 to the outer sensor ring 2 and generates a certain deformation, thereby changing the distance between the moving electrode 6 of the inductive capacitance and the static electrode 7 of the inductive capacitance. The capacitance signal of the capacitor is detected by the sensing element, and then the torque value is obtained through corresponding conversion.

[0011] The beneficial effects of the present invention are as follows:

[0012] 1. The torque sensor described in the present invention uses capacitance as the measured value. Compared with the traditional method of pasting strain gauges on the elastic beam, the torque sensor based on the capacitance edge effect described in the present invention has the advantages of low requirements for the elastic beam, low requirements for the surface processing of the elastic beam, and simple measurement circuit.

[0013] 2. The static electrode and the moving electrode of the sensing capacitance of the torque sensor according to the present invention are arranged perpendicular to each other. Compared with the parallel electrode plate type capacitance sensor, whose sensitivity is greatly affected by displacement changes and the capacitance output has serious non-linearity, the sensitivity of the torque sensor according to the present invention is less affected by the electrode spacing and has the advantages of high linearity and the like.

[0014] 3. The static electrode of the sensing capacitance of the torque sensor according to the present invention is arranged at the outermost end of the cantilever beam of the moving electrode of the sensing capacitance. Compared with the parallel distribution method or the method in which the static electrode of the sensing capacitance is distributed radially, the torque sensor based on the capacitance edge effect according to the present invention can detect the maximum deformation of the moving electrode of the sensing capacitance, that is, the maximum capacitance change can be obtained, and the spacing between the static electrode of the sensing capacitance and the moving electrode of the sensing capacitance changes uniformly everywhere, greatly improving the sensitivity of the sensor.

[0015] 4. For the torque sensor based on the capacitance edge effect according to the present invention, the initial spacing between the moving electrode and the static electrode of the sensing capacitance can be changed by adjusting the relative positions of the substrate and the outer ring of the sensor, thereby realizing the adjustable ability of the initial spacing, that is, the range and sensitivity of the sensor can be changed. Brief Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of a torque sensor based on the capacitance edge effect.

[0017] Figure 2 It is another schematic structural diagram of a torque sensor based on the capacitance edge effect.

[0018] Figure 3 It is a schematic structural diagram of a capacitor.

[0019] Figure 4 It is a schematic working principle diagram of a capacitor.

[0020] In the drawings: 1 - inner ring of the sensor; 2 - outer ring of the sensor; 3 - capacitor; 4 - substrate; 5 - trapezoidal beam; 6 - moving electrode of the sensing capacitance; 7 - static electrode of the sensing capacitance; 8 - substrate groove; 9 - fixing hole; 10 - metal sheet; 11 - inner ring connection hole of the sensor; 12 - outer ring connection hole of the sensor; 13 - adjustment hole. Detailed Description of the Invention

[0021] The present invention will be further described below with reference to the drawings.

[0022] Embodiment: As shown in Figure 1 , Figure 2 , Figure 3 and Figure 4As shown in the figure, a torque sensor based on the capacitance edge effect according to the present invention includes a capacitor part and a mechanical body part. The capacitor part at least includes a static electrode 7 of the sensing capacitor and a moving electrode 6 of the sensing capacitor; the static electrode 7 of the sensing capacitor at least includes a metal sheet 10 and a second substrate 4-2; the mechanical body part at least includes a sensor inner ring 1, a sensor outer ring 2 and a trapezoidal beam 5.

[0023] In the Figure 1 and Figure 2 illustrated embodiment, the first substrate 4-1 is connected to the sensor outer ring 2 through the adjustment hole 13 and the fixing hole 9. The relative position between the first substrate 4-1 and the sensor outer ring 2 can be adjusted through the adjustment hole 13 of the first substrate 4-1, so as to change the initial distance between the moving electrode 6 of the sensing capacitor and the static electrode 7 of the sensing capacitor, thereby realizing the ability to adjust the initial distance, that is, the range and sensitivity of the sensor can be changed. The sensor outer ring 2 is connected to the load. When the sensor inner ring 1 is subjected to an input torque, the trapezoidal beam 5 deforms, causing the moving electrode 6 of the sensing capacitor to rotate accordingly, so that the vertical distance between the moving electrode 6 of the sensing capacitor and the static electrode 7 of the sensing capacitor changes, resulting in a change in the capacitance value. The capacitance signal of the capacitor is detected by the sensing element, and the torque value is obtained through corresponding conversion.

[0024] In the Figure 3 and Figure 4 illustrated embodiment, based on the principle of the capacitance edge effect, the static electrode 7 of the sensing capacitor is perpendicular to the moving electrode 6 of the sensing capacitor and maintains a certain initial distance. The static electrode 7 of the sensing capacitor is connected to the first substrate 4-1 and is located at the outermost end of the moving electrode 6 of the sensing capacitor. By using the maximum deformation of the moving electrode 6 of the sensing capacitor, a large capacitance change amount can be obtained, which has the advantage of high sensitivity. At the same time, compared with the static electrode 7 of the sensing capacitor being placed radially, the static electrode 7 of the sensing capacitor described in the present invention being placed axially has the advantages that the vertical distance between the moving electrode 6 of the sensing capacitor and the static electrode 7 of the sensing capacitor can change uniformly and the change amount of the distance is the largest.

[0025] In the Figure 3 illustrated embodiment, the static electrode 7 of the sensing capacitor at least includes a metal sheet 10 and a second substrate 4-2, and the metal sheet 10 is located in the middle of the second substrate 4-2 or on either side; Figure 3 In, two metal sheets 10 are respectively located on both sides of the second substrate 4-2 and are connected in parallel. When the vertical distance between the moving electrode 6 of the sensing capacitor and the static electrode 7 of the sensing capacitor changes, the capacitance change amount can be increased, that is, the sensitivity of the sensor can be increased.

[0026] In the Figure 1 and Figure 2In the illustrated embodiment, the trapezoidal beam 5 of the present invention has a trapezoidal structure. When it is deformed, the stress change on the side parallel to the axis is relatively uniform, which can improve the strength and reliability of the trapezoidal beam 5.

[0027] In the attached Figure 2 In the illustrated embodiment, the adjusting hole 13 of the present invention is an annular hole. Other shaped holes can also be used to achieve this adjusting function, such as rectangular holes, elliptical holes, U-shaped holes, etc.

[0028] In the attached Figure 2 In the illustrated embodiment, the present invention uses the adjusting hole 13 to adjust the vertical distance (up and down position) between the moving electrode 6 and the static electrode 7 of the sensing capacitor, so as to achieve the adjustment of the measuring range and sensitivity; other methods can also be used, such as using a larger circular hole to adjust both the vertical distance (up and down position) and the horizontal position (left and right position) at the same time; or using an annular hole arranged along the direction of the moving electrode 6 of the sensing capacitor to adjust the horizontal position (left and right position), all of which can achieve the adjustment of the measuring range and sensitivity of the sensor.

[0029] The present invention uses a vertical electrode capacitor based on the principle of capacitance edge effect. Specifically: According to the principle of electromagnetism, when a very thin electrode plate is placed perpendicular to another electrode plate and a certain gap is maintained, if a voltage is applied between the two electrode plates, an electric field will be formed between the two electrodes, which is called an edge field. This phenomenon is called the edge effect, and the generated capacitance is called the edge capacitance.

[0030] According to the mirror image principle and the theory of complex functions, the mathematical relationship between the electrode plate gap and the capacitance between the electrode plates can be established:

[0031]

[0032] Where h is the distance between the two electrodes; H is the height of the vertical electrode; W is the width of the vertical electrode; ε is the dielectric constant of the packaging electrode sheet base.

[0033] It can be seen from the above formula that when the initial distance h0 between the electrode plates changes by Δh, the initial capacitance C0 changes by ΔC, that is:

[0034]

[0035] The capacitance change amount ΔC is:

[0036]

[0037] When the initial gap between the electrode plates is very small, expand it according to the Taylor formula:

[0038]

[0039] Among them, ΔC is the changed capacitance, Δh is the changed displacement between the plates, and h0 is the initial distance between the plates.

[0040] When Δh << h0, can be used for

[0041] linear fitting, and ΔC and Δh are approximately linearly related; it can be known from finite element analysis and mechanics of materials that when the material is within the elastic deformation range, the amount of deformation and the magnitude of the force applied are linearly related; when subjected to torque, the angle of rotation and the torque are linearly related.

[0042] Δθ = A·ΔT

[0043] where Δθ is the change in the angle of rotation, ΔT is the change in torque, and A is the coefficient.

[0044] It can be obtained that:

[0045] Δh = Δθ·L = A·ΔTL

[0046] where L is the distance between the static electrode 7 of the sensing capacitor and the center of the sensor.

[0047] From this, it can be obtained that:

[0048]

[0049] Sensor sensitivity:

[0050]

[0051] From the above formula, it can be obtained that the sensor sensitivity K is proportional to L and inversely proportional to h0. When the static electrode 7 of the sensing capacitor is placed at the outermost end of the moving electrode 6 of the sensing capacitor, that is, when L is the largest, the maximum sensitivity can be obtained; when adjusting the initial distance between the static electrode 7 of the sensing capacitor and the moving electrode 6 of the sensing capacitor, the sensor sensitivity can be adjusted; when the initial distance h0 changes, the difference between the limit distance that the static electrode 7 of the sensing capacitor of the sensor can reach and the initial distance h0 will also change, that is, the maximum deformation amount Δh that the sensor can reach will also change. From Δh = A·ΔTL, the maximum torque will also change accordingly, that is, the adjustment of the measuring range is realized.

[0052] The working principle of the torque sensor based on the capacitance edge effect described in the present invention is as follows: The outer ring 2 of the sensor is fixedly connected to the load. When the inner ring 1 of the sensor is subjected to an input torque, it is transmitted to the outer ring 2 of the sensor through the trapezoidal beam 5 to realize the output of the torque. At the same time, the trapezoidal beam 5 undergoes elastic deformation, so that the vertical distance between the moving electrode 6 and the static electrode 7 of the sensing capacitor changes. The capacitance signal of the capacitor is detected by the sensing element, and then the torque value is obtained.

[0053] The above are only specific application examples of the present invention and do not constitute any limitation to the protection scope of the present invention. In addition to the above embodiments, the present invention may also have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A torque sensor based on the capacitance edge effect, which at least includes an inner sensor ring (1), an outer sensor ring (2), a capacitor (3), a first substrate (4-1) and a trapezoidal beam (5); characterized in that: The capacitor (3) comprises at least a mutually perpendicular moving electrode (6) of the sensing capacitor and a stationary electrode (7) of the sensing capacitor; the stationary electrode (7) of the sensing capacitor comprises at least a metal sheet (10) and a second substrate (4-2); the stationary electrode (7) of the sensing capacitor is connected to the first substrate (4-1) and is located on one side of the moving electrode (6) of the sensing capacitor, and the stationary electrode (7) of the sensing capacitor is placed along the sensor axis, i.e., perpendicular to the first substrate (4-1), thereby forming a capacitor (3) based on the capacitor edge effect; the stationary electrode (7) of the sensing capacitor is located at the outermost end of the moving electrode (6) of the sensing capacitor, so that the torque sensor can detect the maximum deformation of the moving electrode of the sensing capacitor to obtain the maximum capacitance change; The static electrode (7) of the sensing capacitor is located at the first substrate groove (8) and is perpendicular to the first substrate (4-1); the first substrate (4-1) is connected to the sensor outer ring (2) through the adjustment hole (13) of the first substrate (4-1) and the fixing hole (9) of the sensor outer ring (2).

2. The torque sensor based on the capacitance edge effect according to claim 1, characterized in that: A certain initial spacing is left between the moving electrode (6) of the sensing capacitor and the stationary electrode (7) of the sensing capacitor. By adjusting the relative position of the first substrate (4-1) and the sensor outer ring (2) through the adjustment hole (13), the initial spacing between the moving electrode (6) of the sensing capacitor and the stationary electrode (7) of the sensing capacitor can be changed, thereby achieving adjustment of the sensitivity and range of the sensor.

3. The torque sensor based on capacitive edge effect according to claim 1, characterized in that: The static electrode (7) of the inductive capacitor comprises at least one metal sheet (10) and a second substrate (4-2), and the metal sheet (10) is located in the middle or on either side of the second substrate (4-2).

4. The torque sensor based on capacitive edge effect according to claim 1, characterized in that: The adjustment hole (13) is an annular hole and is connected to the fixing hole (9) of the sensor outer ring (2).

5. The torque sensor based on the capacitance edge effect according to claim 1, wherein: The static electrode (7) of the sensing capacitor can move toward the center of the sensor along the surface of the moving electrode (6) of the sensing capacitor.

6. The torque sensor based on the capacitance edge effect according to claim 1, wherein: The movable electrode (6) of the inductive capacitor is located between the sensor inner ring (1) and the sensor outer ring (2) and is integrally connected to the sensor inner ring (1).

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