JP2009276127A - Tactile sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tactile sensor having high durability and reliability, can detect simultaneously the vertical stresses and shear stresses received from an object. <P>SOLUTION: Concerning light entering optical fibers 38, 44 constituting an X-direction shearing stress sensor section 32 and a Y-direction shearing stress sensor section 34, each light comprising a wavelength following a strain amount to the X, Y-directions of the X-direction shearing stress sensor section 32 and the Y-direction shearing stress sensor section 34 is reflected by gratings 40, 46. As for the light entering an optical fiber 50 constituting a Z-direction stress sensor section 36, a light comprising a wavelength that follows a strain amount in the Z-direction of the Z-direction stress sensor section 36 is reflected by gratings 52. The shearing stress and the vertical stress are calculated based on each reflected light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tactile sensor that detects a contact state of an object.

  For example, when a predetermined operation is performed by gripping an object with a manipulator, the object may be damaged if an excessive gripping force is applied to the object. On the other hand, if sufficient gripping force is not applied to the object, the object may fall off the manipulator.

  Therefore, as a sensor that can detect the gripping state of an object by a manipulator or the like, a tactile sensor that detects a vertical stress received from the object as a gripping force and detects a shear stress received from the object as a sliding state has been developed ( Patent Document 1).

  A tactile sensor disclosed in Patent Document 1 includes a pressure-sensitive element that detects pressure from an object as a change in resistance value on a flexible printed circuit board, and a piezoelectric that generates a differential voltage when pressure is applied from the object. It is configured by stacking elements. Normal stress can be detected by a pressure sensitive element and shear stress can be detected by a piezoelectric element.

  However, since pressure sensitive elements and piezoelectric elements detect stress based on electrical signals, they are susceptible to electromagnetic noise in adverse environments such as outdoors or in factories and are not suitable for precise stress detection. . Also, if the tactile sensor is damaged, there is a risk of leakage.

  On the other hand, strain sensors using optical fibers have been developed as sensors for monitoring the behavior of various structures such as tunnels and bridges, or the ground (see Patent Document 2).

  The strain sensor disclosed in Patent Document 2 is an FBG sensor (Fiber Bragg Grating Sensor) made of an optical fiber in which a grating (diffraction grating) is formed on a core, and the FBG sensor is laid on a measurement object. The distortion of the measurement object is detected by utilizing the phenomenon that the wavelength of the reflected light due to the grating of light introduced into the optical fiber changes when distortion occurs in the grating portion.

  In this case, the FBG sensor not only has high durability but also does not use an electric signal, so that it is not affected by electromagnetic noise and can detect distortion generated in the measurement object with high accuracy. .

  However, the FBG sensor disclosed in Patent Document 2 can only detect the strain of the measurement object and is not configured to simultaneously measure the stress in the shear direction and the vertical direction received from the measurement object.

JP 2006-10407 A JP 2002-131023 A

  The present invention has been made to solve the above-mentioned problems, and provides a tactile sensor that has high durability and reliability, and can simultaneously detect normal stress and shear stress received from an object. Objective.

In order to solve the above-described problems, the present invention provides a shear stress detection sensor unit including an optical fiber in which gratings that reflect light of a specific wavelength are arranged along a plane parallel to a direction in which shear stress applied from an object is applied. ,
A vertical stress detection sensor unit comprising an optical fiber in which gratings that reflect light of a specific wavelength are arranged along a plane parallel to a direction in which a normal stress received from the object is applied,
It is characterized by providing.

  In the tactile sensor of the present invention, shear stress and normal stress received from an object can be detected independently and simultaneously based on an optical signal. In this case, by using an optical signal, there is no influence of electromagnetic wave noise and there is no fear of electric leakage. Therefore, high durability and reliability are realized, and shear stress and normal stress are highly accurate. Can be detected.

  FIG. 1 is a configuration diagram of a robot system 10 to which a tactile sensor of the present invention is applied. The robot system 10 is disposed in a manipulator 14 that grips the object 12 and performs a predetermined process, and the hand portions 16 a and 16 b of the manipulator 14, and is in contact with the object 12 and moves the object 12 by the hand portions 16 a and 16 b. The tactile sensors 18a and 18b for detecting the gripping state, the tactile sensors 18a and 18b for controlling the tactile sensors 18a and 18b, and acquiring the shear stress and the vertical stress, which are information related to the gripping state of the object 12, and the tactile sensor controller 20 A manipulator controller 22 for controlling the manipulator 14 based on the acquired shear stress and normal stress.

  In this case, the sliding state of the object 12 with respect to the hand portions 16a and 16b can be detected based on the shear stress detected by the touch sensors 18a and 18b when the object 12 is gripped. Further, the gripping force of the object 12 by the hand portions 16a and 16b can be detected based on the vertical stress detected by the touch sensors 18a and 18b when the object 12 is gripped. Therefore, by controlling the hand portions 16a and 16b according to the shear stress and the vertical stress, it is possible to perform an operation such as gripping with an appropriate gripping force and moving it to a desired position without dropping the object 12. .

  Next, the operation principle of the FBG sensor 24 used for the tactile sensors 18a and 18b will be described with reference to FIG.

  The FBG sensor 24 is configured by forming gratings 30 </ b> A and 30 </ b> B using ultraviolet rays on a part of the core 28 of the optical fiber 26. In FIG. 2, an FBG sensor 24 having two gratings 30A and 30B is illustrated.

When the periods of the gratings 30A and 30B are Λ _A and Λ _B and the effective refractive index of the core 28 is n _eff , the gratings 30A and 30B have wavelengths λ _A and λ that satisfy the following expressions (1) and (2). Reflects light of _B (Bragg wavelength) and transmits light of other wavelengths.

λ _A = 2n _eff Λ _A (1)
λ _B = 2n _eff Λ _B (2)
Therefore, when light having a wavelength λ in a predetermined range shown in FIG. 3 is incident on the core 28 of the optical fiber 26, reflected light having wavelengths λ _A and λ _B is obtained from the incident end side as Λ _A ≠ Λ _B. The light of other wavelengths is output from the emission end side.

Here, as shown in FIG. 4, when a shear stress in the direction of the arrow X1 along the longitudinal direction of the optical fiber 26 is applied between the gratings 30A and 30B, the period Λ _{A of the} grating 30A is shortened, while the grating 30B Period Λ _B becomes longer. Accordingly, as shown in FIG. 5, the wavelength lambda _A of the light reflected by the grating 30A ^-, while shifting in the direction of shorter than the wavelength lambda _A, the wavelength lambda _B ⁺ of the light reflected by the grating 30B, It shifts in a direction longer than the wavelength λ _B.

Further, as shown in FIG. 6, when a shear stress in the direction of the arrow X2 along the longitudinal direction of the optical fiber 26 is applied between the gratings 30A and 30B, the period Λ _{A of the} grating 30A becomes longer, while the period of the grating 30B Λ _B becomes shorter. Accordingly, as shown in FIG. 7, the optical wavelength lambda _A ⁺ is a reflected by the grating 30A, while shifting in the direction longer than the wavelength lambda _A, the wavelength of the light reflected by the grating 30B lambda _B ^- is Shift in a direction shorter than wavelength λ _B.

From the above results, the direction and magnitude of the shear stress can be obtained by detecting the shift direction and shift amount of the wavelengths λ _A and λ _B of the light reflected by the two adjacent gratings 30A and 30B.

The magnitude of the stress (vertical stress) applied in the longitudinal direction of the optical fiber 26 can be obtained by detecting the shift amount of the wavelength λ _A or λ _B of the light reflected by one grating 30A or 30B. .

  FIG. 8 is an exploded perspective view of tactile sensors 18a and 18b using the FBG sensor 24 shown in FIG.

  The tactile sensors 18a and 18b include an X-direction shear stress sensor unit 32 that detects shear stress in the X-axis direction of the orthogonal triaxial coordinate system, a Y-direction shear stress sensor unit 34 that detects shear stress in the Y-axis direction, and a Z-axis. A Z-direction stress sensor unit 36 that detects a vertical stress in the axial direction is laminated.

The X-direction shear stress sensor unit 32 arranges one optical fiber 38 so that a large number of gratings 40 formed at regular intervals along the longitudinal direction of the optical fiber 38 are arranged in the X-axis direction. The optical fiber 38 is formed as a sheet body molded on a pressure-sensitive member 42 having flexibility such as plastic or resin. It should be noted that the periods of the gratings 40 (see periods Λ _A and Λ _{B in} FIG. 2) are all different.

The Y-direction shear stress sensor unit 34 arranges one optical fiber 44 so that a large number of gratings 46 formed at regular intervals along the longitudinal direction of the optical fiber 44 are arranged in the Y-axis direction. The optical fiber 44 is formed as a sheet body molded on a flexible pressure-sensitive member 48 such as plastic or resin. Note that the periods of the gratings 46 (see periods Λ _A and Λ _{B in} FIG. 2) are all different. FIG. 9 is an explanatory plan view of the X direction shear stress sensor unit 32 and the Y direction shear stress sensor unit 34.

The Z-direction stress sensor unit 36 arranges one optical fiber 50 so that a large number of gratings 52 formed at regular intervals along the longitudinal direction of the optical fiber 50 are arranged in the Z-axis direction. The fiber 50 is formed as a sheet body molded in a pressure-sensitive member 54 having flexibility such as plastic or resin. It is assumed that the periods of the gratings 52 (see periods Λ _A and Λ _{B in} FIG. 2) are all different. FIG. 10 is a YZ plane cross-sectional explanatory view of the Z-direction stress sensor unit 36.

  In addition, as shown in FIG. 11, the Z direction stress sensor part 36 arrange | positions the two optical fibers 56a and 56b in zigzag form, and thereby the Z direction stress of the grating 52 formed in each optical fiber 56a, 56b. The mounting density in the sensor unit 36 can be increased.

  As shown in FIG. 12, the tactile sensors 18a and 18b may be configured by laminating an X direction shear stress sensor unit 32, a Y direction shear stress sensor unit 34, and a Z direction stress sensor unit 36. As shown, a shear stress sensor unit 35 in which the X direction shear stress sensor unit 32 and the Y direction shear stress sensor unit 34 are integrated and a Z direction stress sensor unit 36 may be laminated.

  The tactile sensors 18a and 18b can be used by being attached to the surface of the hand portions 16a and 16b having an arbitrary shape by being formed from a flexible sheet.

  The X-direction shear stress sensor unit 32, the Y-direction shear stress sensor unit 34, and the Z-direction stress sensor unit 36 are each composed of a single continuous optical fiber 38, 44, and 50. You may divide and comprise.

  FIG. 14 is a configuration block diagram of the robot system 10 using the tactile sensors 18a and 18b configured as described above.

  The light output from the light source 58 passes through one of the half mirrors 62a to 62c selected in a time division manner by the beam switch 60, and the X direction shear stress sensor unit 32 constituting the tactile sensors 18a and 18b, the Y direction. The shear stress sensor unit 34 or the Z direction stress sensor unit 36 is supplied.

  A portion of the light incident from one end of the optical fiber 38, 44 or 50 (FIG. 8) of the X direction shear stress sensor unit 32, the Y direction shear stress sensor unit 34, or the Z direction stress sensor unit 36 is a grating 40. , 46 or 52 while the remaining light is transmitted through the grating 40, 46 or 52, and then guided to the transmitted light terminators 64a to 64c.

  The light reflected by the grating 40, 46 or 52 is guided to the reflected light detector 66 of the tactile sensor controller 20 via the half mirrors 62a to 62c, and is converted into an electrical signal. The reflected light detector 66 is constituted by a spectroscope that spectrally detects incident light for each wavelength. Electric signals relating to light from the X-direction shear stress sensor unit 32 and the Y-direction shear stress sensor unit 34 are supplied to the shear stress calculation unit 68. In addition, an electrical signal related to light from the Z-direction stress sensor unit 36 is supplied to the vertical stress calculation unit 70.

  The shear stress calculation unit 68 is obtained from the adjacent gratings 40 as shown in FIGS. 5 and 7 based on the electrical signal for each wavelength of the light reflected by each grating 40 of the X direction shear stress sensor unit 32. According to the shift amount and the shift direction of the wavelength of the reflected light with respect to the X direction, the magnitude and direction of the shear stress generated in the portion are calculated. Similarly, the shear stress calculation unit 68 calculates the magnitude and direction of the shear stress generated in the portion according to the shift amount and the shift direction of the wavelength of the reflected light from the Y direction shear stress sensor unit 34 with respect to the Y direction. And from these, the slipping state of the object 12 in the XY plane can be detected.

  Since the gratings 40 and 46 are arranged in a matrix in the XY plane, the X and Y directions are determined based on the sliding state detected by the gratings 40 and 46 and the positional information of the gratings 40 and 46. The distribution of the sliding state in the −Y plane can be obtained.

  Based on the electrical signal for each wavelength of the light reflected by each grating 52 of the Z-direction stress sensor 36, the vertical stress calculation unit 70 applies the wavelength shift amount of the reflected light obtained from each grating 52 to that portion. The magnitude of the generated normal stress is calculated. From this vertical stress, the gripping force of the object 12 in the Z direction can be detected. Since the grating 52 is arranged in a matrix in the XY plane, it is possible to obtain the distribution of gripping force in the XY plane.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change freely in the range which does not deviate from the main point of this invention.

  For example, in the robot system 10 shown in FIG. 14, instead of supplying the light output from the light source 58 to the tactile sensors 18a and 18b in a time-division manner by the beam switch 60, shearing in the X direction constituting the tactile sensors 18a and 18b is performed. While supplying light from three independent light sources to the stress sensor unit 32, the Y direction shear stress sensor unit 34, and the Z direction stress sensor unit 36, respectively, the X direction shear stress sensor unit 32 and the Y direction shear stress sensor unit The reflected light from 34 and the Z-direction stress sensor unit 36 may be detected by three independent reflected light detectors. With this configuration, the shear stress and the normal stress received from the object 12 can be detected simultaneously.

  The tactile sensors 18a and 18b are not limited to the detection of the gripping state of the object 12 by the hand portions 16a and 16b, but can be applied to the detection of the surface state of the object, for example.

It is a block diagram of a robot system to which the tactile sensor of the present invention is applied. It is operation | movement principle explanatory drawing of a FBG sensor. It is an explanatory view of the relationship between the wavelength of light incident on the FBG sensor and the wavelength of light reflected by the grating. It is explanatory drawing of the detection principle of the shear stress by a FBG sensor. FIG. 5 is an explanatory diagram of the relationship between the wavelength of light incident on the FBG sensor in the state shown in FIG. 4 and the wavelength of light reflected by the grating. It is explanatory drawing of the detection principle of the shear stress by a FBG sensor. FIG. 7 is a diagram illustrating the relationship between the wavelength of light incident on the FBG sensor in the state shown in FIG. 6 and the wavelength of light reflected by the grating. It is a disassembled structure perspective view of the tactile sensor of this embodiment. It is plane explanatory drawing of the X direction shear stress sensor part which comprises the tactile sensor of this embodiment, and a Y direction shear stress sensor part. It is a section explanatory view of the Z direction stress sensor part which constitutes the tactile sensor of this embodiment. It is a structure perspective view of other embodiment of the Z direction stress sensor part which comprises a tactile sensor. It is a composition perspective view showing the lamination state of the tactile sensor of this embodiment. It is a structure perspective view which shows the lamination | stacking state of the tactile sensor of other embodiment. 1 is a configuration block diagram of a robot system using a tactile sensor according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Robot system 12 ... Object 14 ... Manipulator 16a, 16b ... Hand part 18a, 18b ... Tactile sensor 20 ... Tactile sensor controller 22 ... Manipulator controller 24 ... FBG sensor 26, 38, 44, 50, 56a, 56b ... Optical fiber 30A , 30B, 40, 46, 52 ... grating 32 ... X direction shear stress sensor 34 ... Y direction shear stress sensor 35 ... shear stress sensor 36 ... Z direction stress sensor 42, 48, 54 ... pressure sensitive member 58 ... Light source 60 ... Beam switchers 62a-62c ... Half mirrors 64a-64c ... Transmitted light terminator 66 ... Reflected light detector 68 ... Shear stress calculator 70 ... Vertical stress calculator

Claims (6)

A shear stress detection sensor unit comprising an optical fiber in which gratings that reflect light of a specific wavelength are arranged along a plane parallel to a direction in which shear stress is applied from an object,
A vertical stress detection sensor unit comprising an optical fiber in which gratings that reflect light of a specific wavelength are arranged along a plane parallel to a direction in which a normal stress received from the object is applied,
A tactile sensor comprising: The tactile sensor according to claim 1,
The tactile sensor, wherein the shear stress detection sensor unit and the vertical stress detection sensor unit are formed as a flexible sheet. The tactile sensor according to claim 1,
The tactile sensor according to claim 1, wherein the shear stress detection sensor unit includes an optical fiber in which gratings are arranged in two orthogonal directions within a plane parallel to the direction in which the shear stress is applied. The tactile sensor according to claim 1,
The shear stress detection sensor unit has gratings arranged at a plurality of different positions in a plane parallel to the direction in which the shear stress is applied, and each grating reflects light having a specific wavelength different from each other. A tactile sensor. The tactile sensor according to claim 1,
The shear stress detection sensor unit includes two adjacent gratings, and detects the direction and magnitude of the shear stress based on the shift direction and shift amount of the wavelength of light reflected by the two gratings. Tactile sensor characterized by The tactile sensor according to claim 1,
The vertical stress detection sensor unit includes gratings arranged at a plurality of different positions in a plane orthogonal to the direction in which the vertical stress is applied, and the gratings reflect light having specific wavelengths different from each other. A tactile sensor.

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