The disclosure of Japanese Patent Application No. 2018-192715 filed on Oct. 11, 2018 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
The disclosure relates to tactile sensors.
Recently, robots with human flexibility and a sense of touch have been increasingly developed. Such robots use a tactile sensor in order to achieve a human tactile function. Such a tactile sensor uses a soft material such as elastomer or rubber for human flexibility.
For example, Japanese Unexamined Patent Application Publication No. 2018-17536 (JP 2018-17536 A) proposes such a deformation measurement device 2 as shown in
In the deformation measurement device 2, as shown in
In the deformation measurement device 2 shown in
In the deformation measurement device 2, the distance between the first layer 4 and the sensing circuit layer changes with deformation of the flexible layer. Such a change in distance is detected based on a change in magnetic flux density of the magnetic field generated by the member 8 embedded in the sensing circuit layer.
When the deformation measurement device 2 shown in
The disclosure provides a tactile sensor having high sensitivity to deformation while having sufficient flexibility.
A tactile sensor includes: an element that changes an inductance of the element with deformation of the element and that includes a coil; a first deformation layer that has the element embedded in the first deformation layer and is elastically deformable together with the element; and an elastically deformable surface layer that is placed on the first deformation layer and contains a magnetic material. In this tactile sensor, when the surface layer is pressed and elastically deformed, the first deformation layer is also elastically deformed. Since the element is embedded in the first deformation layer, the element is also deformed when the surface layer is deformed. In this tactile sensor, the inductance of the element changes with deformation of the element itself, and the surface layer containing the magnetic material improves the rate of change in inductance. This tactile sensor thus has high sensitivity to deformation. Since deformation of the element itself is reflected on a change in inductance, the elastically deformable surface layer or the elastically deformable first deformation layer of the tactile sensor can have a sufficient thickness. In other words, the surface layer or the first deformation layer of the tactile sensor can have a sufficient thickness within such a range that does not inhibit deformation of the element itself. This tactile sensor thus has high sensitivity to deformation while having sufficient flexibility.
In the above tactile sensor, the magnetic material may have a flat shape. This configuration facilitates orientation of the magnetic material dispersed in the surface layer of the tactile sensor. The orientation of the magnetic material improves sensitivity to deformation. The tactile sensor thus has higher sensitivity to deformation while having more sufficient flexibility.
In the above tactile sensor, the element may include a core material comprised of an amorphous metal fiber, and the core material may be placed along the coil. Since amorphous metal fibers do not have crystal magnetic anisotropy, this configuration further increases a change in inductance associated with deformation of the element. This tactile sensor thus has further improved sensitivity to deformation. This tactile sensor therefore has higher sensitivity to deformation while having more sufficient flexibility.
The above tactile sensor may further include an elastically deformable second deformation layer, the first deformation layer may be stacked on the second deformation layer, and the second deformation layer may be more flexible than the first deformation layer. With this configuration, since the first deformation layer is sufficiently deformable, a force pressing the surface layer effectively acts on the element. Since deformation caused by the pressing force is sufficiently reflected on deformation of the element, this tactile sensor has further improved sensitivity to deformation. This tactile sensor thus has higher sensitivity to deformation while having more sufficient flexibility.
As can be seen from the above description, the disclosure provides a tactile sensor having high sensitivity to deformation while having sufficient flexibility.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
The disclosure will be described in detail based on a preferred embodiment with reference to the accompanying drawings.
The body 24 is soft as a whole. The body 24 is placed on a substrate 30. The substrate 30 is harder than the body 24. The substrate 30 of the tactile sensor 22 is not particularly limited as long as the substrate 30 can support the body 24.
In the tactile sensor 22, the body 24 is comprised of a plurality of layers stacked in the thickness direction. The body 24 includes a surface layer 32 and a first deformation layer 34.
The surface layer 32 forms the upper surface of the body 24. The surface layer 32 is placed on the first deformation layer 34. As shown in
The surface layer 32 is a sheet-like layer. In the tactile sensor 22, the surface layer 32 has a thickness of about 1 mm.
The surface layer 32 is comprised of a soft material and is elastically deformable. Examples of the soft material are rubber and elastomer. In the tactile sensor 22, the material of the surface layer 32 is not particularly limited as long as the surface layer 32 is elastically deformable. The surface layer 32 of the tactile sensor 22 is comprised of cross-linked rubber containing silicone rubber as a base material and having flexibility.
As used herein, the term “flexibility” means being so soft as to be easily deformable by, e.g., a pressing force of a human finger.
Although not shown in
The first deformation layer 34 is located under the surface layer 32 and is placed on a second deformation layer 36 described below. As shown in
The first deformation layer 34 is a sheet-like layer. In the tactile sensor 22, the first deformation layer 34 has a thickness in the range of 3 mm to 4 mm.
The first deformation layer 34 is comprised of a soft material and is elastically deformable. Examples of the soft material are rubber and elastomer. In the tactile sensor 22, the material of the first deformation layer 34 is not particularly limited as long as the first deformation layer 34 is elastically deformable. The first deformation layer 34 of the tactile sensor 22 is comprised of cross-linked rubber containing silicone rubber as a base material and having flexibility. In the tactile sensor 22, the first deformation layer 34 does not contain any magnetic material. The first deformation layer 34 has about the same flexibility as, or higher flexibility than, the surface layer 32.
In the tactile sensor 22, the body 24 includes an element 38. The element 38 is an elastically deformable, long string-like element. The element 38 changes its inductance with its deformation.
The element 38 includes at least a coil 40. The coil 40 is formed by winding an enamel wire (wire) into a helix. In the tactile sensor 22, the coil 40 has a diameter in the range of 0.3 mm to 0.4 mm. The wire of the coil 40 has a diameter of 0.1 mm or less. The coil 40 is a very small coil.
In the tactile sensor 22, the element 38 is embedded in the first deformation layer 34. In other words, the element 38 is covered by the first deformation layer 34. The element 38 is placed in the first deformation layer 34 so as to extend in a direction parallel to the upper surface of the first deformation layer 34 on which the surface layer 32 is stacked. In
Although not shown in the figure, the tactile sensor 22 includes a plurality of the elements 38. In the tactile sensor 22, the elements 38 may be arranged either at regular intervals or in a grid pattern in the first deformation layer 34. The number of elements 38 that are embedded in the first deformation layer 34 and their arrangement are determined as appropriate in view of the specifications of the tactile sensor 22.
In the tactile sensor 22, as shown in
In the tactile sensor 22, the detection unit 26 is connected to the coil 40 of each element 38. The detection unit 26 detects the inductance of each element 38. The detection unit 26 can output the detected inductance as a signal in a time series manner. An example of the detection unit 26 is an LCR meter.
As described above, in the tactile sensor 22, the inductance of the element 38 changes when the surface of the body 24 is pressed and the element 38 is deformed. The detection unit 26 detects this change in inductance associated with the deformation.
In the tactile sensor 22, the control unit 28 is connected to the detection unit 26. The output signal of the detection unit 26 is input to the control unit 28. The control unit 28 processes this input signal and calculates, e.g., the amount of depression of the body 24. In the tactile sensor 22, the control unit 28 is comprised of, e.g., an arithmetic processing unit such as a computer, a part of the arithmetic processing unit, etc.
As described above, the tactile sensor 22 includes the body 24, the detection unit 26, and the control unit 28. In the disclosure, the tactile sensor 22 may be comprised only of the body 24. In this case, the tactile sensor 22 comprised only of the body 24 is connected to, e.g., an LCR meter serving as a detection unit equivalent to the detection unit 26 and an arithmetic processing unit serving as a control unit equivalent to the control unit 28.
In the tactile sensor 22, when the surface layer 32 is pressed and elastically deformed, the first deformation layer 34 is also elastically deformed. Since the element 38 is embedded in the first deformation layer 34, the element 38 is also deformed as shown in
As shown in
Since deformation of the element 38 itself is reflected on a change in inductance, the elastically deformable surface layer 32 or the elastically deformable first deformation layer 34 of the tactile sensor 22 can have a sufficient thickness. In other words, the surface layer 32 or the first deformation layer 34 of the tactile sensor 22 can have a sufficient thickness within such a range that does not inhibit deformation of the element 38 itself. The tactile sensor 22 thus has high sensitivity to deformation while having sufficient flexibility.
In the tactile sensor 22, the surface layer 32 contains a magnetic material and a part of the magnetic material is exposed on the upper surface of the surface layer 32. Sticking of the surface layer 32 is thus effectively reduced. The tactile sensor 22 is thus effectively prevented from sticking to a human finger or similar objects.
As shown in
In the tactile sensor 22, the first deformation layer 34 is stacked on the second deformation layer 36, and the second deformation layer 36 is stacked on the substrate 30. The second deformation layer 36 is thus located between the first deformation layer 34 and the substrate 30.
The second deformation layer 36 is a sheet-like layer. In the tactile sensor 22, the second deformation layer 36 has a thickness of about 4 mm.
The second deformation layer 36 is comprised of a soft material and is elastically deformable. Examples of the soft material are rubber and elastomer. In the tactile sensor 22, the material of the second deformation layer 36 is not particularly limited as long as the second deformation layer 36 is elastically deformable. The second deformation layer 36 of the tactile sensor 22 is comprised of cross-linked rubber containing silicone rubber as a base material and having flexibility. In the tactile sensor 22, the second deformation layer 36 does not contain any magnetic material.
In the tactile sensor 22, the second deformation layer 36 is more flexible than the first deformation layer 34. Since the first deformation layer 34 is sufficiently deformable, a force pressing the surface layer 32 effectively acts on the element 38. Since deformation caused by the pressing force is sufficiently reflected on deformation of the element 38, the tactile sensor 22 has further improved sensitivity to deformation. The tactile sensor 22 thus has higher sensitivity to deformation while having more sufficient flexibility. In view of this, it is preferable that the tactile sensor 22 include the elastically deformable second deformation layer 36, the first deformation layer 34 be placed on the second deformation layer 36, and the second deformation layer 36 be more flexible than the first deformation layer 34.
As described above, in the tactile sensor 22, the surface layer 32 contains a magnetic material. In order to improve sensitivity to deformation, it is preferable that the magnetic material be soft magnetic metal powder. Examples of the metal powder are spherical atomized powder and flat atomized powder.
The magnetic material 42 in the surface layer 32 shown in
As described above, in the tactile sensor 22, each of the elements 38 is placed in the first deformation layer 34 so as to extend in a direction parallel to the upper surface of the first deformation layer 34 on which the surface layer 32 is stacked. Accordingly, in the case where flat atomized powder is used as the magnetic material 42 of the tactile sensor 22, the magnetic material 42 dispersed in the surface layer 32 is oriented so as to extend in the direction in which the element 38 extends. That is, in the tactile sensor 22, orientation of the magnetic material 42 dispersed in the surface layer 32 is facilitated.
The use of flat atomized powder as the magnetic material 42 of the tactile sensor 22 facilitates orientation of the magnetic material 42 dispersed in the surface layer 32. This orientation of the magnetic material 42 improves sensitivity to deformation. The tactile sensor 22 thus has higher sensitivity to deformation while having more sufficient flexibility. In view of this, in the tactile sensor 22, it is preferable that the magnetic material 42 have a flat shape, and more specifically, the magnetic material 42 be flat atomized powder.
In the tactile sensor 22, the element 38 may include a core material 46 in addition to the coil 40. The core material 46 is placed along the coil 40. Specifically, as shown in
In the tactile sensor 22, the core material 46 is comprised of an amorphous metal fiber. An example of the amorphous metal fiber is “Sency (registered trademark)” made by Aichi Steel Corporation.
Since amorphous metal fibers do not have crystal magnetic anisotropy, the use of an amorphous metal fiber as the core material 46 further increases a change in inductance associated with deformation of the element 38. The tactile sensor 22 thus has further improved sensitivity to deformation. The tactile sensor 22 therefore has higher sensitivity to deformation while having more sufficient flexibility. In view of this, in the tactile sensor 22, it is preferable that the element 38 include the core material 46 comprised of an amorphous metal fiber in addition to the coil 40 and the core material 46 be placed along the coil 40. In order to improve sensitivity to deformation, it is more preferable that the core material 46 be inserted through the center of the coil 40 in the case where the element 38 includes the coil 40 and the core material 46.
As can be seen from the above description, the disclosure provides the tactile sensor 22 having high sensitivity to deformation while having sufficient flexibility.
The embodiment disclosed herein is merely illustrative in all aspects and not restrictive. The technical scope of the disclosure is not limited to the above embodiment and includes all modifications that are made without departing from the scope of the claims.
The tactile sensor described above can be used in medical applications such as artificial hands. This tactile sensor is also applicable to automobile parts to be touched by humans, such as a steering wheel, and can be used as a communication tool between a driver and an automobile.
Number | Date | Country | Kind |
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2018-192715 | Oct 2018 | JP | national |