Tactile sensor

Abstract

To provide a tactile sensor which can attain high resolution and high sensitivity.SOLUTION: The tactile sensor includes: an exterior body including an elastic deformable part having an outer surface and an inner surface; a plurality of rod-shaped members extending from the inner surface of the elastic deformable part and displaced according to deformation of the elastic deformable part; and a camera for observing respective tips of the plurality of rod-shaped members. The camera is disposed to face the tips of the plurality of rod-shaped members.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a tactile sensor. [Background technology]

[0002] For example, sensitive tactile sensing technology is essential for robots that have contact points that come into contact with objects, so tactile sensors that combine high resolution and high sensitivity are required for the contact points of robots.

[0003] Patent Document 1 discloses a tactile sensor that estimates the force applied to an elastically deformable cap placed at the contact point of a robot by observing the deformation of the cap with a camera. In this tactile sensor, multiple pins (i.e., rod-shaped members) are provided on the inner surface of the cap. The force applied to the cap is estimated by observing the positions of the tips of the multiple pins, which displace in response to the deformation of the cap. In particular, when the pins tilt in response to the deformation of the cap, the positions of the pin tips are amplified and displaced. This can improve the sensitivity of the tactile sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2022-546642 Summary of the Invention [Problem to be solved by the invention]

[0005] The tactile sensor disclosed in Patent Document 1 is configured to observe the tips of multiple pins using a camera installed to the side of the multiple pins. Increasing the number of pins is desirable to improve the resolution of the tactile sensor. However, with the tactile sensor disclosed in Patent Document 1, as the number of pins increases, the pins overlap when observed from the side. This poses a problem in that it is difficult to observe the tips of the pins using a camera installed to the side of the multiple pins. To address this problem, for example, the length of the pins located closer to the camera can be shortened so that the tips of the pins are exposed to the camera's field of view. However, in this case, the sensitivity decreases with shorter pins. Thus, the tactile sensor disclosed in Patent Document 1 has a problem in that it is difficult to achieve both high resolution and high sensitivity. The present specification aims to provide a tactile sensor that can achieve both high resolution and high sensitivity. [Means for solving the problem]

[0006] One embodiment of the tactile sensor disclosed herein may include an exterior body having an elastically deformable portion that includes an outer surface and an inner surface, a plurality of rod-shaped members extending from the inner surface of the elastically deformable portion and displacing in response to deformation of the elastically deformable portion, and a camera that observes the tips of the plurality of rod-shaped members. The camera may be disposed in a direction directly facing the tips of the plurality of rod-shaped members.

[0007] In the tactile sensor, the camera is positioned facing the tips of the rod-shaped members, so even if the number of rod-shaped members increases, the tips of the rod-shaped members are positioned within the field of view of the camera without overlapping, allowing the tactile sensor to achieve both high resolution and high sensitivity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a tactile sensor system. [Figure 2] FIG. 2 is a perspective view of a contact portion. [Figure 3]FIG. 2 is a cross-sectional perspective view of a contact portion. [Figure 4] 10A and 10B are diagrams illustrating a state when an object comes into contact with an elastically deforming portion of the contact portion. [Figure 5] 10A and 10B are diagrams for explaining the amount of displacement of the tip of a rod-shaped member in an in-plane direction perpendicular to the line of sight of the camera. [Figure 6] 10A and 10B are diagrams illustrating contact portions of modified examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] Figure 1 shows the configuration of a tactile sensor system 1. The tactile sensor system 1 is not particularly limited, but may be mounted on a robot having a contact unit for grasping an object and used to estimate the force applied to the contact unit. The tactile sensor system 1 includes a contact unit 10, a camera 20, and a control device 30. The contact unit 10 and the camera 20 constitute a tactile sensor. The control device 30 may be mounted on the robot, or may be provided external to the robot in a state capable of communicating with the tactile sensor.

[0010] The contact unit 10 has an exterior body 11 that forms the exterior of, for example, a robot fingertip. The exterior body 11 has a generally cylindrical shape and includes an elastically deformable portion 12 that is flexible and elastically deformable. The elastically deformable portion 12 has a cylindrical body with one axial side closed by a convex curved surface and the other side open. In this example, the convex curved surface is configured as a hemisphere. The open end 12a of the elastically deformable portion 12 is fixed to a rigid spacer (not shown) that forms part of the exterior body 11. As shown in FIGS. 2 and 3 , the elastically deformable portion 12 is not particularly limited, but may be formed, for example, from a polymer with a mesh structure. The internal space of the elastically deformable portion 12 is filled with a fluid (e.g., air). This allows the elastically deformable portion 12 to elastically deform in any direction toward the internal space when an object comes into contact with the outer surface. The outer surface of the elastically deformable portion 12 may be covered with a rubber cover, if necessary.

[0011] The contact portion 10 further has a plurality of rod-shaped members 14 extending from the inner surface of the elastically deformable portion 12. Each of the plurality of rod-shaped members 14 extends from a corresponding one of a plurality of positions distributed on the inner surface of the elastically deformable portion 12. A base 13 of the rod-shaped member 14 is located on the inner surface of the elastically deformable portion 12, and a tip 15 of the rod-shaped member 14 is located in an opening of the elastically deformable portion 12. The plurality of rod-shaped members 14 are not particularly limited, but may be formed of a polymer, for example, or may be formed integrally with the elastically deformable portion 12 using 3D printer technology.

[0012] The multiple rod-shaped members 14 include one rod-shaped member 14 extending from the inner surface of the apex of the hemispherical surface of the elastic deformation portion 12, and multiple rod-shaped members 14 extending from the inner surface of the hemispherical surface of the elastic deformation portion 12 other than the apex. Here, the tangent plane at the apex of the hemispherical surface of the elastic deformation portion 12 is a plane perpendicular to the axial direction of the elastic deformation portion 12, and as will be described later, is a plane perpendicular to the line of sight of the camera 20. In this specification, a portion of the elastic deformation portion 12 that is not perpendicular to the line of sight of the camera 20, in this example, the portion other than the apex of the hemispherical surface of the elastic deformation portion 12, is referred to as a non-orthogonal portion. The rod-shaped member 14 extending from the inner surface of the apex of the hemispherical surface of the elastic deformation portion 12 is linear and extends parallel to the axial direction of the elastic deformation portion 12, i.e., the line of sight of the camera 20. The multiple rod-shaped members 14 extending from the inner surface of the non-orthogonal portion of the elastic deformation portion 12 have a bent portion 16 bent between a base 13 and a tip 15. In this example, the rod-shaped member 14 having the bent portion 16 has only one bent portion 16, but instead of this example, it may be configured to have a plurality of bent portions 16.

[0013] The rod-shaped member 14 having the bent portion 16 extends from the base 13 to the bent portion 16 in a direction inclined with respect to the axial direction of the elastic deformation portion 12 so as to approach the central axis of the elastic deformation portion 12, and extends from the bent portion 16 to the tip 15 in the axial direction of the elastic deformation portion 12, i.e., parallel to the line of sight of the camera 20. The tips 15 of the multiple rod-shaped members 14 are dispersed and arranged on the opening surface of the elastic deformation portion 12 (a plane perpendicular to the axial direction of the elastic deformation portion 12 and in contact with the opening edge of the opening end 12a of the elastic deformation portion 12). In this way, some of the multiple rod-shaped members 14 are bent according to the shape of the elastic deformation portion 12, so that they extend from a wide range on the inner surface of the elastic deformation portion 12 and the tips 15 are gathered and arranged on the opening surface of the elastic deformation portion 12.

[0014] FIG. 4 shows what happens when an object comes into contact with the outer surface of the elastically deforming portion 12. When an object comes into contact with the outer surface of the elastically deforming portion 12, the elastically deforming portion 12 deforms according to the position of the object and the magnitude of the force at which the object comes into contact. When the elastically deforming portion 12 deforms, the multiple rod-shaped members 14 tilt with respect to the axial direction of the elastically deforming portion 12. The tilt of the multiple rod-shaped members 14 amplifies and displaces the positions of the tips 15 of the multiple rod-shaped members 14 in the radial direction of the elastically deforming portion 12. In this way, the multiple rod-shaped members 14 function as amplifier pins that convert the deformation of the elastically deforming portion 12 into the displacement of the positions of the tips 15.

[0015] As shown in FIG. 1 , the camera 20 is disposed a predetermined distance from the open end 12a of the elastically deformable portion 12 and is fixed to a rigid spacer (not shown) that constitutes part of the exterior body 11. The camera 20 is disposed facing the tips 15 of the rod-shaped members 14. That is, the line of sight of the camera 20 is parallel to the extension direction of the tips 15 of each of the rod-shaped members 14 (the direction extending from the tip 15 to a predetermined length). In this example, the line of sight of the camera 20 is also parallel to the axial direction of the elastically deformable portion 12. The camera 20 captures images of the tips 15 of the rod-shaped members 14. The tips 15 of the rod-shaped members 14 may be painted (e.g., black) so that the tips 15 of the rod-shaped members 14 can be clearly identified. The camera 20 outputs captured image data to the control device 30.

[0016] The control device 30 has an input / output port 32, a CPU 34, a ROM 36, and a RAM 38. The input / output port 32 is connected to the camera 20 and inputs image data from the camera 20. The CPU 34 is connected to the input / output port 32, the ROM 36, and the RAM 38 and executes a process for estimating the force applied to the elastic deformation unit 12 from the image data. The ROM 36 stores various programs for estimating the force applied to the elastic deformation unit 12 from the image data. The various programs include, for example, a program for extracting a position coordinate data set of the tips 15 of the multiple rod-shaped members 14 from the image data and a program for estimating the force applied to the elastic deformation unit 12 from the position coordinate data set. The program for estimating the force applied to the elastic deformation unit 12 from the position coordinate data set is not particularly limited, and may utilize, for example, a neural network model. This neural network model may be a model trained using as training data a combination of a force map, which describes the positions on the outer surface of the elastically deformable portion 12 to which force is applied and the magnitude of that force when a force is applied to the outer surface of the elastically deformable portion 12, and a position coordinate data set. The RAM 38 temporarily stores data required when the CPU 34 executes various programs. In this way, the control device 30 is configured to estimate the force map of the elastically deformable portion 12 from image data of the tips 15 of the multiple rod-shaped members 14 photographed by the camera 20.

[0017] As described above, in the tactile sensor system 1, the camera 20 is disposed facing the tips 15 of the multiple rod-shaped members 14. Therefore, even if the number of rod-shaped members 14 is increased, the tips 15 of the multiple rod-shaped members 14 are disposed within the field of view of the camera 20 without overlapping. Therefore, the tactile sensor system 1 has a structure suitable for achieving high resolution. Furthermore, the tips 15 of the rod-shaped members 14 can extend to the observation plane of the camera 20 without being substantially restricted by the positions of the other rod-shaped members 14, i.e., with a high degree of freedom. Therefore, the rod-shaped members 14 can be ensured to have sufficient length, allowing the tactile sensor system 1 to have high sensitivity characteristics. In this way, the tactile sensor system 1 can achieve both high resolution and high sensitivity.

[0018] In the tactile sensor system 1, the multiple rod-shaped members 14 can function as amplifying pins. This amplifying function is due to the tilt of the rod-shaped members 14 when the elastic deformation section 12 is deformed, and appears as an in-plane displacement of the tips 15 of the rod-shaped members 14 perpendicular to the line of sight within the field of view of the camera 20. Furthermore, the displacement of the tips 15 of the rod-shaped members 14 becomes larger as the rod-shaped members 14 extend longer in the line of sight of the camera 20. In the tactile sensor system 1, the camera 20 is positioned facing the tips 15 of the rod-shaped members 14, so it is possible to observe the displacement of the tips 15 in any in-plane direction. Therefore, the tactile sensor system 1 can have high sensitivity.

[0019] Here, this increased sensitivity will be further explained with reference to FIG. 5. The rod-shaped member 14 in FIG. 5 is shown with a complex structure to explain that the increased sensitivity can occur in any shape. When the rod-shaped member 14 is tilted (here, an example is shown in which the rod-shaped member 14 is rotated at an angle θ around the base 13), the displacement of the tip 15 of the rod-shaped member 14, i.e., the amount of displacement Δx in the in-plane direction perpendicular to the line of sight of the camera 20, can be expressed by the following equation: p1-p0 is a vector connecting the base 13 to the tip 15 of the rod-shaped member 14, and v Cam is the line of sight vector of the camera 20, and is a vector whose value increases when the rod-shaped member 14 extends in this direction.

number

[0020] For example, when observing with camera 20 from a direction perpendicular to the vector p1-p0, the vector p1-p0 and v Cam The vectors are orthogonal to each other, and their dot product is zero. In this case, the displacement Δx cannot be observed. The conventional tactile sensor described in the background art has a camera installed to the side of a linearly extending pin, resulting in this relationship. In contrast, in the tactile sensor system 1 disclosed in this specification, the camera 20 is positioned facing the tip 15 of the rod-shaped member 14, and the rod-shaped member 14 extends long in the line of sight of the camera 20. Therefore, it is possible to observe the displacement of the tip 15 of the rod-shaped member 14 in any direction within a plane perpendicular to the line of sight of the camera 20, and the displacement Δx of the tip 15 of the rod-shaped member 14 also becomes large. Therefore, the tactile sensor system 1 has high sensitivity.

[0021] In rod-shaped member 14 having bent portion 16, the angle formed by the vector connecting tip 15 to base 13 and the line-of-sight vector of camera 20 may be 45 degrees or less. Furthermore, in rod-shaped member 14 having bent portion 16, the angle formed by the portion from base 13 to bent portion 16 and the portion from tip 15 to bent portion 16 may be an obtuse angle, and the length of the portion from base 13 to bent portion 16 may be shorter than the length of the portion from tip 15 to bent portion 16. In such a case, rod-shaped member 14 having bent portion 16 extends long in the line-of-sight direction of camera 20, and therefore can exhibit a high amplification function when tilted in accordance with the deformation of elastically deformable portion 12.

[0022] Furthermore, the tips 15 of the rod-shaped members 14 are arranged in the same plane. This allows the camera 20 to focus well and obtain clear images. This allows the tactile sensor system 1 to have high sensitivity. Note that the same plane here refers to a plane that allows a width equal to the focal depth of the camera 20.

[0023] FIG. 6 shows a modified contact unit 10. In this example, the elastically deforming portion 12 extends in a direction away from the line of sight of the camera (not shown), and at least a portion of the elastically deforming portion 12 is not located within the field of view of the camera (not shown). Even with this type of elastically deforming portion 12, by employing a rod-shaped member 14 having a bent portion 16, the tip 15 of the rod-shaped member 14 can be displaced in response to the deformation of the elastically deforming portion 12. Therefore, the tactile sensor system 1 can estimate a force map of the elastically deforming portion 12 from image data of the tips 15 of multiple rod-shaped members 14.

[0024] The features of the technology disclosed in this specification are summarized below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness either alone or in various combinations.

[0025] (Feature 1) an exterior body including an outer surface and an inner surface and having an elastically deformable portion that is elastically deformable; a plurality of rod-shaped members extending from the inner surface of the elastic deformation portion and displacing in response to deformation of the elastic deformation portion; a camera for observing the tip of each of the plurality of rod-shaped members, The tactile sensor is configured such that the camera faces directly toward the tips of the plurality of rod-shaped members.

[0026] (Feature 2) 2. The tactile sensor according to Feature 1, wherein the tips of the plurality of rod-shaped members are disposed in a dispersed manner within a plane perpendicular to the line of sight of the camera.

[0027] (Feature 3) At least some of the plurality of rod-shaped members have a bent portion bent between a base located on the inner surface of the elastic deformation portion and the tip, the elastic deformation portion has a non-orthogonal portion that is not orthogonal to the line of sight of the camera, 3. The tactile sensor according to feature 1 or 2, wherein the rod-shaped member having the bent portion extends from the inner surface of the non-orthogonal portion.

[0028] (Feature 4) 4. The tactile sensor according to Feature 3, wherein the rod-shaped member having the bent portion extends in a direction parallel to the line of sight of the camera from the tip to the bent portion.

[0029] (Feature 5) 5. The tactile sensor according to Feature 3 or 4, wherein the elastically deforming portion is configured with the convex curved surface.

[0030] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0031] 1: tactile sensor system, 10: contact portion, 11: exterior body, 12: elastic deformation portion, 13: base, 14: rod-shaped member, 15: tip, 16: bending portion, 20: camera, 30: control device, 32: input / output port, 34: CPU, 36: ROM, 38: RAM

Claims

1. an exterior body including an outer surface and an inner surface and having an elastically deformable portion that is elastically deformable; a plurality of rod-shaped members extending from the inner surface of the elastic deformation portion and displacing in response to deformation of the elastic deformation portion; a camera for observing the tip of each of the plurality of rod-shaped members, The tactile sensor is configured such that the camera faces directly toward the tips of the plurality of rod-shaped members.

2. The tactile sensor according to claim 1 , wherein the tips of the plurality of rod-shaped members are arranged in a dispersed manner within a plane perpendicular to the line of sight of the camera.

3. At least some of the plurality of rod-shaped members have a bent portion bent between a base located on the inner surface of the elastic deformation portion and the tip, the elastic deformation portion has a non-orthogonal portion that is not orthogonal to the line of sight of the camera, The tactile sensor according to claim 1 , wherein the rod-shaped member having the bent portion extends from the inner surface of the non-orthogonal portion.

4. The tactile sensor according to claim 3 , wherein the rod-shaped member having the bent portion extends in a direction parallel to the line of sight of the camera from the tip to the bent portion.

5. The tactile sensor according to claim 3 , wherein the elastically deforming portion is configured by the convex curved surface.

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