Sensor and method of driving same

Abstract

A sensor according to one embodiment comprises: an elastic deformation unit capable of being elastically deformed; a force transfer unit which is positioned above the elastic deformation unit and receives external force; a first PCB positioned below the elastic deformation unit; and a second PCB which is positioned below the first PCB and is spaced apart from the first PCB, wherein the first PCB moves along a rotation axis by deformation of the elastic deformation unit, and force or torque against external force is measured on the basis of the change in capacitance according to the distance between the first PCB and the second PCB, and the rotation axis can be perpendicular to the ground.

Description

Sensor and method of driving the same

[0001] The following examples relate to sensors and methods of driving the same.

[0002] Global demand for robotic manipulation technology is growing rapidly, and the development of applicable robotic sensors is also accelerating. Due to the limited size and weight of robot joints and end devices, compact, lightweight, and high-performance sensors are required.

[0003] Conventional force / torque sensors utilizing capacitive sensing have inherent interference between measurement axes and radial stiffness variations, making calibration and maintenance challenging. Furthermore, the sensor's operation requires a sufficiently long housing, making it difficult to use in confined spaces.

[0004] Therefore, there is a need for a sensor that provides radially symmetric performance with a low radial error stiffness and uses a capacitive method with low inter-axial interference.

[0005] Patent No. 10-2229563 discloses a force / torque sensor that can be miniaturized.

[0006] An object of one embodiment is to provide a sensor capable of obtaining accurate force information by having radially symmetric performance by manufacturing an elastic deformation portion in a radially symmetrical shape.

[0007] An object of one embodiment is to provide a sensor that has less interference between measurement axes, thereby facilitating calibration work involved in the sensor manufacturing process.

[0008] According to one embodiment, a sensor includes an elastic deformation unit that can be elastically deformed, a force transmission unit located on an upper side of the elastic deformation unit and to which an external force or torque is applied, a first PCB located on a lower side of the elastic deformation unit, and a second PCB located on a lower side of the first PCB and spaced apart from the first PCB, wherein the first PCB moves along a rotation axis by deformation of the elastic deformation unit, and measures a force or torque in response to an external force based on a change in electrostatic capacitance according to a distance between the first PCB and the second PCB, and the rotation axis can be perpendicular to the ground.

[0009] According to one embodiment, the elastic deformation member may include a deformation element formed in a circular shape, a hole formed in the center through which a driving shaft can pass, and a plurality of slits arranged on the outside of the hole.

[0010] According to one embodiment, the elastic deformation member can transmit force in a direction parallel to the axis of rotation, or can rotate about a first axis or a second axis, wherein the first axis and the second axis can be parallel to the ground and perpendicular to the axis of rotation, and the first axis and the second axis can be perpendicular to each other.

[0011] In one embodiment, the deformation element may be radially symmetrical about the hole.

[0012] According to one embodiment, the thickness of the elastic deformation portion may correspond to the thickness at the optimal point where the maximum stress curve according to the thickness of the elastic deformation portion and the linear stiffness curve according to the thickness of the elastic deformation portion intersect.

[0013] According to one embodiment, the first PCB includes a first electrode at a lower portion, the second PCB includes a second electrode at an upper portion, and the cross-sectional area of ​​the first electrode may be wider than the cross-sectional area of ​​the second electrode.

[0014] A method of driving a sensor according to one embodiment may include a step of applying a force or torque to a force transmission unit, a step of deforming an elastic deformation unit by the applied force or torque, and a step of detecting a change in electrostatic capacitance as a change in a distance between a first PCB and a second PCB according to the deformation of the elastic deformation unit.

[0015] According to one embodiment, the step of deforming the elastic deformable part by the applied force includes a step of deforming the elastic deformable part in a direction parallel to the rotation axis or a step of rotating the elastic deformable part about a first axis or a second axis, wherein the first axis and the second axis are parallel to the ground, the rotation axis is perpendicular to the ground, and the first axis, the second axis, and the rotation axis may be perpendicular to each other.

[0016] According to one embodiment, a sensor has radially symmetric performance by manufacturing an elastic deformation portion in a radially symmetrical shape, thereby obtaining accurate force information.

[0017] According to one embodiment, a sensor may have less interference between measurement axes, making it easier to perform calibration work during the sensor manufacturing process.

[0018] Figure 1 illustrates a perspective view of a sensor according to one embodiment.

[0019] Figure 2 illustrates an exploded view of a sensor according to one embodiment.

[0020] FIG. 3 illustrates a cross-sectional view along line AA of FIG. 1 of a sensor according to one embodiment.

[0021] FIGS. 4A and 4B illustrate the driving mechanism when force and torque are applied to the elastic deformation member, according to one embodiment.

[0022] FIGS. 5A and 5B illustrate, according to one embodiment, how the first PCB moves when force and torque are applied to the elastic deformation portion.

[0023] FIGS. 6A and 6B illustrate experimental results verifying the radial symmetry performance of an elastic deformation member, according to one embodiment.

[0024] Figures 7a, 7b and 7c illustrate experimental results showing less axis interference along the first axis, the second axis and the rotation axis, according to one embodiment.

[0025] FIG. 8 illustrates a method for selecting the thickness of an elastic deformation portion according to one embodiment.

[0026] Fig. 9 is a flowchart showing a method of driving a sensor according to one embodiment.

[0027] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, the embodiments may be modified in various ways, and the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or alternatives to the embodiments are included within the scope of the patent application.

[0028] The terms used in the examples are for illustrative purposes only and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood to not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments pertain. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0030] In addition, when describing with reference to the attached drawings, identical components will be assigned the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing embodiments, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

[0031] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of the embodiments. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by the terms. When a component is described as being "connected," "coupled," or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but another component may also be "connected," "coupled," or "connected" between each component.

[0032] Components included in one embodiment and components with common functions will be described using the same names in other embodiments. Unless otherwise stated, the descriptions given in one embodiment may also apply to other embodiments, and detailed descriptions will be omitted to the extent of overlap.

[0033] Fig. 1 illustrates a perspective view of a sensor (1) according to one embodiment. Fig. 2 illustrates an exploded view of a sensor (1) according to one embodiment. Fig. 3 illustrates a cross-sectional view taken along line AA of Fig. 1 of a sensor (1) according to one embodiment.

[0034] Referring to FIGS. 1 to 3, a sensor (1) according to one embodiment may include an elastic deformation portion (100) that can be elastically deformed, a force transmission portion (200) located on the upper side of the elastic deformation portion (100) and to which an external force or torque is applied, a first PCB (310) located on the lower side of the elastic deformation portion (100), and a second PCB (320) located on the lower side of the first PCB (310) and spaced apart from the first PCB (310).

[0035] The first PCB (310) can move along the rotation axis (Z) by deformation of the elastic deformation part (100), and force or torque can be measured based on the change in electrostatic capacitance according to the distance between the first PCB (310) and the second PCB (320), and the rotation axis (Z) can be perpendicular to the ground.

[0036] In addition, it may further include a case (400) that can accommodate an elastic deformation portion (100), a force transmission portion (200), a first PCB (310) and a second PCB (320), and a case fixing ring (500) positioned on the upper portion of the case (400) and fixing the case (400).

[0037] The elastic deformation member (100) may be formed in a circular shape, and may include a hole (101) formed in the center, as described below, through which a driving shaft (not shown) may pass, and a deformation element (102) formed by arranging a plurality of slits on the outside of the hole (101). In addition, the deformation element (102) may be radially symmetrical with the hole (101) as the center.

[0038] Since the elastic deformation part (100) has a radially symmetrical shape, it can have radially symmetrical performance in which the radial stiffness or hysteresis can be constant, and also interference between the measurement axes (the first axis, the second axis, and the rotation axes (X, Y, Z)) can be reduced.

[0039] Meanwhile, the elastic deformation portion (100) is illustrated as having a circular shape, but this is only one example, and it is obvious that the elastic deformation portion (100) may have another shape having a radially symmetrical shape. For example, the elastic deformation portion (100) may have a regular hexagonal shape.

[0040] The force transmission unit (200) is located on the elastic deformation unit (100) and can transmit an external force or torque applied to the force transmission unit (200) to the elastic deformation unit (100).

[0041] The first PCB (310) may be positioned spaced apart from the second PCB (320). The first PCB (310) may be connected to the elastic deformation part (100), and the first PCB (310) may move according to a change in the shape of the elastic deformation part (100). That is, as described below, when a force is applied to the elastic deformation part (100) in the direction of the rotation axis (Z), the first PCB (310) may also move in the direction of the rotation axis (Z), and when a force in the direction of rotation is applied to the elastic deformation part (100), the first PCB (310) may also move in the direction of the rotation. The first PCB (310) may include a first electrode (not shown) on which a charge is accumulated at a lower portion.

[0042] The second PCB (320) may be fixed on the case (400). The electrostatic capacitance measured on the second PCB (320) may sensitively change depending on the change in the distance between the first PCB (310) and the second PCB (320). The second PCB (320) may include a second electrode (not shown) on the upper portion of which charge is accumulated. In this case, the charge stored in the second electrode may have an opposite polarity to the charge stored in the first electrode.

[0043] FIGS. 4A and 4B illustrate a driving mechanism when force and torque are applied to an elastic deformation member (100) according to one embodiment. FIGS. 5A and 5B illustrate a first PCB (310) moving when force and torque are applied to an elastic deformation member (100) according to one embodiment.

[0044] According to one embodiment, as shown in FIGS. 4a and 4b, the elastic deformation member (100) may include a hole (101) formed in the center through which a driving shaft (not shown) can pass, and a deformation element (102) formed by arranging a plurality of slits on the outside of the hole (101).

[0045] Additionally, referring to FIGS. 4a and 4b, the deformation element (102) can be radially symmetrical about the hole (101).

[0046] Meanwhile, although it is exemplified that a hole (101) is formed in the center of the elastic deformation part (100), this is only one embodiment, and it is obvious that the hole (101) may not be formed in the center of the elastic deformation part (100) as needed.

[0047] The elastic deformation member (100) can transmit force in a direction parallel to the rotation axis (Z), as illustrated in FIG. 4a, or can rotate about the first axis (X) or the second axis (Y), as illustrated in FIG. 4b. That is, the elastic deformation member (100) can have one degree of freedom in the direction of the rotation axis (Z) (i.e., in the normal direction) and two degrees of freedom in the rotational direction about the first axis (X) and the second axis (Y).

[0048] Specifically, referring to FIGS. 4A and 5A, when a force is applied to the force transmission unit (200) in the direction of the rotation axis (Z), deformation may occur in the elastic deformation unit (100), and the first PCB (310) may move in the direction of the rotation axis (Z) toward the second PCB (320) according to the deformation of the elastic deformation unit (100).

[0049] In addition, referring to FIGS. 4b and 5b, when a force or torque in the rotational direction about the first axis (X) or the second axis (Y) is applied to the force transmission unit (200), rotational deformation may occur in the elastic deformation unit (100), and the first PCB (310) may also rotate about the first axis (X) or the second axis (Y) according to the rotational deformation of the elastic deformation unit (100).

[0050] At this time, the first electrode (not shown) located at the lower end of the first PCB (310) may have a cross-sectional area that is sufficiently wider than that of the second electrode (not shown) located at the upper end of the second PCB (320). Therefore, since the cross-sectional area of ​​the first electrode is sufficiently wider than that of the second electrode, any change in cross-sectional area that may occur due to rotation can be ignored.

[0051] Since there is a distance between the force transmission unit (200) and the first PCB (310), parasitic displacement may occur due to rotation, but this can be completely canceled out during the calibration process. Therefore, there is an effect of reducing interference between the measurement axes (the first axis, the second axis, and the rotation axes (X, Y, Z)).

[0052] FIGS. 6A and 6B illustrate experimental results verifying the radial symmetry performance of an elastic deformation member (100) according to one embodiment.

[0053] The radial symmetry performance was verified by the difference between the expected and average values ​​of stiffness and hysteresis, and as shown in Fig. 6a, the maximum error of stiffness was 0.98%, and as shown in Fig. 6b, the maximum error of hysteresis was 0.2%, indicating that the radial symmetry performance was satisfactory.

[0054] Radially symmetric performance may refer to a performance in which the difference in stiffness or hysteresis at the same radial location centered on the hole (101) of the elastic deformation member (100) can be minimized. For example, as illustrated in FIGS. 5A and 5B, the radially symmetric performance may indicate that the error in the stiffness or hysteresis measured along the circumference of the elastic deformation member (100) is small. In other words, it may indicate that the value of the stiffness or hysteresis due to the pressure is constant regardless of which part along the circumference of the elastic deformation member (100) is subjected to pressure in the direction of the rotation axis (Z).

[0055] Here, hysteresis may refer to a phenomenon in which the output of the sensor (1) changes not only at a single point in response to an increase or decrease in the input value, but only when it exceeds or falls below a certain threshold. In other words, it may refer to a phenomenon in which the output values ​​appear different when the input value increases and decreases.

[0056] Figures 7a, 7b and 7c illustrate experimental results showing that there is less axis interference along the first axis (X), the second axis (Y) and the rotation axis (Z), according to one embodiment.

[0057] Figure 7a shows that when a force is applied in the direction along the rotation axis (Z) (i.e., in the normal direction), there is less axial interference along the first axis (X) and the second axis (Y).

[0058] Figures 7b and 7c show that when torque is applied along the first axis (X) and the second axis (Y), respectively, there is less axis interference along other axes.

[0059] The experimental results show that the maximum error between the measurement axes (the first axis, the second axis, and the rotation axes (X, Y, Z)) is 1.74%. Compared to the maximum error of 2.3% for conventional sensors, this shows that interference between the measurement axes is small.

[0060] Therefore, as seen in FIGS. 6a, 6b, 7a, 7b and 7c, the sensor (1) utilizes an elastic deformation portion (100) having a radially symmetrical shape, thereby having radially symmetrical performance and less interference between measurement axes (first axis, second axis and rotation axes (X, Y, Z)), and thus can provide accurate force information, and can have the feature of being easy to perform the calibration work that is essential in the process of manufacturing the sensor (1).

[0061] FIG. 8 illustrates a method for selecting the thickness of an elastic deformation portion (100) according to one embodiment.

[0062] The stiffness of the elastic deformation part (100) may have a characteristic of sensitively changing depending on the thickness of the elastic deformation part (100). Therefore, it may be desirable to manufacture the thickness of the elastic deformation part (100) by taking into consideration the maximum stress related to the stability of the sensor (1) and the stiffness related to the sensitivity of the sensor (1).

[0063] That is, as illustrated in Fig. 8, an elastic deformation portion (100) can be manufactured with a thickness at the optimal point where the maximum stress curve and the linear stiffness curve intersect based on the three degrees of freedom force and torque to be measured.

[0064] Existing sensors utilize soft deformation media, making it difficult to simulate and model them, making it difficult to derive optimal design points.

[0065] In contrast, the sensor (1) according to the present invention can be designed to be compact, thin, and hollow by utilizing an elastic deformation member (100), and the desired specifications can be derived and optimally designed through simulation and modeling prior to design. In other words, the difference between modeling and simulation is minimal, and by utilizing this, a model suitable for the desired specifications can be selected and manufactured.

[0066] Fig. 9 is a flowchart showing a method of driving a sensor (1) according to one embodiment.

[0067] A method of driving a sensor (1) according to one embodiment is as follows.

[0068] First, force or torque can be applied to the force transmission unit (200) (S101).

[0069] Next, the elastic deformation part (100) can be deformed by the applied force (S102). At this time, the elastic deformation part (100) can move in the normal direction along the rotation axis (Z) with three degrees of freedom and in the rotational direction about the first axis (X) and the second axis (Y).

[0070] Next, a change in electrostatic capacitance can be detected by a change in the distance between the first PCB (310) and the second PCB (320) according to deformation of the elastic deformation portion (100) (S103).

[0071] Meanwhile, the calibration task of the sensor (1) can be completed by performing the calibration in the form of applying an arbitrary force within the measurement range through a handle in combination with an external sensor, and deriving a calibration matrix through a comparison of the values ​​with the external sensor. After the calibration of the sensor, the force and torque measurement performance of each axis (X, Y, Z) can be evaluated using a high-resolution load cell.

[0072] In the case of the sensor (1) according to the present invention, the root mean square error in the direction of the rotation axis (Z) (normal direction) of the measurement result corresponds to 0.29 N, and the root mean square error in the direction of rotation about the first axis (X) and the second axis (Y) corresponds to 2.33 and 1.97 N·mm, respectively, so it can be confirmed that it has high accuracy even with easy calibration work.

[0073] In addition, when an experiment was conducted to measure the stiffness and weight of an object by placing the sensor (1) for which the calibration work was completed at the beginning of the robot finger in a narrow space, the root mean square error of the measured stiffness as a result of the experiment corresponded to approximately 0.0073 N / mm, the root mean square error of the measured weight corresponded to approximately 8.72 g, and the minimum measurement resolution corresponded to approximately 5 g, so it can be seen that it can be utilized with high accuracy even when placed in a narrow space.

[0074] As described above, the sensor (1) according to one embodiment has radially symmetric performance by manufacturing the elastic deformation portion (100) in a radially symmetrical shape, thereby obtaining accurate force information.

[0075] According to one embodiment, the sensor (1) has less interference between measurement axes, so that the calibration work involved in the manufacturing process of the sensor (1) can be made easy.

[0076] A sensor (1) according to one embodiment utilizes a capacitance measurement method, so it does not require a separate external signal processing device such as a strain gauge or an FBG (Fiber Bragg Grating) sensor, and does not require the attachment of a separate sensor, making it easy to manufacture. Therefore, it can be manufactured in a compact size, and can be installed and utilized in narrow spaces such as robot joints and end devices.

[0077] A sensor (1) according to one embodiment can be designed to be small, thin, and hollow by utilizing an elastic deformation part (100), and the desired specifications can be derived and optimally designed through simulation and modeling prior to design.

[0078] Although the embodiments described above have been described with limited drawings, those skilled in the art will appreciate that various technical modifications and variations can be applied based on the above. For example, appropriate results can still be achieved even if the described techniques are performed in a different order than described, and / or components of the described systems, structures, devices, circuits, etc. are combined or combined in a different manner than described, or are replaced or substituted with other components or equivalents.

[0079] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims described below.

Claims

1. Elastic deformation part that can be elastically deformed; A force transmission unit located on the upper side of the elastic deformation unit and to which force or torque is applied; A first PCB located below the elastic deformation portion; and A second PCB positioned below the first PCB and spaced apart from the first PCB; Including, The above first PCB moves along the rotation axis by deformation of the elastic deformation portion, Measures force or torque based on the change in electrostatic capacitance according to the distance between the first PCB and the second PCB, The above rotation axis is perpendicular to the ground, Sensor.

2. In paragraph 1, The above elastic deformation part is, It is formed in a circular shape, a hole formed in the center through which the drive shaft can pass; and A deformation element formed by arranging a plurality of slits on the outside of the above hole; A sensor including:

3. In paragraph 2, The elastic deformation member can transmit force in a direction parallel to the rotation axis, or can rotate about the first axis or the second axis, The first axis and the second axis are parallel to the ground and perpendicular to the rotation axis, The first axis and the second axis are perpendicular to each other, Sensor.

4. In paragraph 3, The above deformation element is a sensor that is radially symmetrical with respect to the hole.

5. In paragraph 4, The thickness of the above elastic deformation portion is A sensor corresponding to the thickness at the optimal point where the maximum stress curve according to the thickness of the elastic deformation portion and the linear stiffness curve according to the thickness of the elastic deformation portion intersect.

6. In paragraph 5, The first PCB includes a first electrode storing charge at the lower portion, The second PCB includes a second electrode for storing charge at the upper portion, The cross-sectional area of ​​the first electrode is wider than the cross-sectional area of ​​the second electrode, Sensor.

7. Step of applying force or torque to the force transmission unit; A step in which an elastic deformation portion is deformed by an applied force; and A step of detecting a change in electrostatic capacitance due to a change in the distance between the first PCB and the second PCB according to a deformation of the elastic deformation portion; A method of driving a sensor, including:

8. In paragraph 7, The step in which the elastic deformation part is deformed by the applied force is: A step in which the elastic deformation part is deformed in a direction parallel to the rotation axis; and A step in which the elastic deformation part is rotated about a first axis or a second axis; Including, The first axis and the second axis are parallel to the ground, The above rotation axis is perpendicular to the ground, The first axis, the second axis and the rotation axis are perpendicular to each other, How to drive the sensor.

Images