JP2010054359A - Optical fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber sensor for improving measurement precision of a stress. <P>SOLUTION: Optical fibers 38, 44, 50 includes elastic materials 56 as stress direction changing means for changing a direction of a stress. Each of the elastic materials 56 includes a flat part 58 extending along a longitudinal direction of each of the optical fibers 38, 44, 50, joint parts 64a, 64b connected to the optical fiber 38 and inclination sections 62a, 62b respectively bridged between the joint parts 64a, 64b and the flat part 58. When a shear stress F is applied to each of the optical fibers 38, 44, 50 in a direction roughly perpendicular to the longitudinal direction thereof, the flat part 58 is expanded. Accordingly, the inclination parts 62a, 62b are further inclined so as to be separated from each other. As a result, the joint parts 64a, 64b are separated from each other so that the optical fibers 38, 44, 50 also gratings 40, 46, 52 are expanded. In the expanded gratings 40, 46, 52, intervals between adjacent gratings are roughly equalized. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical fiber sensor having an optical fiber in which gratings that reflect light of a specific wavelength are arranged and detecting stress with the optical fiber.

  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, it has been attempted to provide a sensor that can detect the gripping state of an object by a manipulator or the like. As this type of sensor, for example, as disclosed in Patent Documents 1 and 2, an FBG (Fiber Bragg Grating) in which a plurality of gratings (diffraction gratings) are provided in an optical fiber core embedded in a sheet body is used. It is recalled to use a fiber optic sensor called sensor). As described in Patent Documents 1 and 2, in the FBG sensor, when distortion occurs in the grating portion corresponding to the stress received from the object, the wavelength of the reflected light from the grating changes. It is considered that this phenomenon can be used to detect the occurrence of distortion and to detect the application of stress from the object.

  By the way, in the optical fiber sensors described in Patent Documents 1 and 2, when the shape of the object to be gripped, the contact position with respect to the optical fiber, and the like are different, the distribution state of the stress on the grating portion is different, and thus accurate stress is detected. There is a disadvantage that it is not easy to do.

  FIG. 20 is a state explanatory view schematically showing before and after stress is applied to the grating 1 from a direction orthogonal to the extending direction of the optical fiber 2. When the stress F is applied to the grating 1 so as to be substantially equal, the adjacent lattices are also stretched substantially equally. In this case, as shown in FIG. 21, only the wavelength of the reflected light changes.

  However, when the shape of the object to be gripped, the gripping angle, or the like is different, the stress may act on the grating 1 non-uniformly. In this case, as shown in FIG. 22, the gaps between adjacent gratings are unevenly stretched, and as a result, reflected light appears at a plurality of wavelengths according to the difference in the spacing between the gratings as shown in FIG. Will do.

  From this point of view, as proposed in Patent Document 3, the FBG sensor portion is formed by inserting an optical fiber into the fixed layer and sandwiching the fixed layer with an elastic sheet, while one end surface of the FBG sensor portion. It is recalled that the measured portion is closely attached to the other end through an adhesive layer and a pressing plate is provided on the other end surface through a buffer layer.

JP 2002-131023 A JP 2002-71323 A JP 2005-134199 A

  Even if the configuration described in Patent Document 3 is adopted, if the shape of the object to be gripped, the contact position with respect to the optical fiber, and the like are different, the distribution state of the stress on the pressing plate and thus the grating portion will be different. For this reason, it is not easy to obtain an accurate magnitude of stress, in other words, to sufficiently improve measurement accuracy.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide an optical fiber sensor capable of improving the measurement accuracy of stress.

In order to achieve the above object, an optical fiber sensor according to the present invention includes a stress detection sensor unit including an optical fiber in which gratings that reflect light of a specific wavelength are arranged;
A stress direction converting means for converting the direction of stress applied in a direction different from the longitudinal direction of the optical fiber into a direction parallel to the longitudinal direction and transmitting it to the grating;
It is characterized by providing.

  When the optical fiber is stretched by the stress direction changing means, the grating formed inside the optical fiber is stretched so that the intervals between adjacent lattices are substantially uniform. That is, the optical fiber is stretched with the contact point with the stress direction changing means as a base point, and for this reason, the stress is distributed substantially uniformly with respect to the optical fiber.

  Therefore, according to the present invention, the intervals between adjacent lattices in the extended grating are substantially equal. For this reason, since it is observed that the reflected light by the grating shifts before and after the extension, it is possible to accurately detect the stress acting on the optical fiber from the shift result.

  Note that the stress direction conversion means includes, for example, a flat portion extending in a direction parallel to the longitudinal direction of the optical fiber, and a stress transmission portion bridged from the flat portion to the optical fiber. can do.

  In this case, it is preferable that the flat portion is highly elastic compared to the stress transmission portion. As a result, the flat portion first expands, and the stress transmission portion expands without being bent along with the expansion. That is, it becomes easy to extend the optical fiber.

  According to the present invention, the grating portion of the optical fiber is equipped with stress direction conversion means for converting the direction of stress applied in a direction different from the longitudinal direction of the optical fiber into a direction parallel to the longitudinal direction. In the optical fiber, stress acts on the contact points between the optical fiber and the stress direction changing means.

  For this reason, in the extended grating, the intervals between adjacent gratings become substantially equal, and it is observed that the reflected light from the grating shifts before and after extension. Based on this shift result, the stress acting on the optical fiber can be accurately detected.

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

  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 optical fiber 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 optical fiber 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 in the optical fiber 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 period of each grating 30A, 30B is Λ _A , Λ _B , and the effective refractive index of the core 28 is n _eff , each grating 30A, 30B has a wavelength λ _A , which satisfies the following expressions (1) and (2): Reflects light of λ _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 the optical fiber sensors 18a and 18b using the FBG sensor 24 shown in FIG.

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

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.

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.

  The optical fiber 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.

  In the above configuration, an elastic body 56 as stress direction changing means is attached to each of the optical fibers 38, 44, 50 so as to straddle the gratings 40, 46, 52.

  As shown in FIG. 9 illustrating the optical fiber 38, the elastic body 56 includes a flat portion 58 extending in parallel to the longitudinal direction of the optical fiber 38, and bridges from the flat portion 58 to each end of the grating 40. The stress transmission part 60 is provided. In the present embodiment, the stress transmission part 60 is connected to the flat part 58 and inclined toward the optical fiber 38, and the joined part that is connected to the inclined parts 62a and 62b and surrounds the optical fiber 38. 64a and 64b. In this case, the angles θ1 and θ2 formed by the inclined portions 62a and 62b and the joint portions 64a and 64b are set to be equal to each other.

  The material of the elastic body 56 is not particularly limited as long as it can be elastically deformed, but rubber and resin can be cited as suitable examples. It may be a liquid crystal polymer, carbon fiber reinforced plastic (CFRP), or the like. Furthermore, it is preferable to set the elastic modulus of the flat portion 58 to the highest among the flat portion 58, the inclined portions 62a and 62b, and the joint portions 64a and 64b.

  Of course, the elastic bodies 56 provided in the remaining optical fibers 44 and 50 are similarly configured.

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

  The light output from the light source 68 passes through one of the half mirrors 72a to 72c selected in a time division manner by the beam switch 70, and the X direction shear stress sensor unit 32, Y constituting the optical fiber sensors 18a, 18b. The directional 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 74 a to 74 c.

  The light reflected by the grating 40, 46 or 52 is guided to the reflected light detector 76 of the optical fiber sensor controller 20 through the half mirrors 72a to 72c, and is converted into an electric signal. The reflected light detector 76 is configured by a spectroscope that spectrally detects incident light for each wavelength. Electrical 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 78. In addition, an electrical signal related to light from the Z-direction stress sensor unit 36 is supplied to the vertical stress calculation unit 80.

  The shear stress calculation unit 78 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 78 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. 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 unit 36, the vertical stress calculation unit 80 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.

  Here, in the optical fibers 38 and 44, as shown in FIG. 11, shear stress first acts on the flat portion 58 of the elastic body 56. Thereby, the flat part 58 expand | extends.

  As described above, in this case, the inclined portions 62 a and 62 b and the joint portions 64 a and 64 b are set to be less elastic than the flat portion 58. Therefore, the inclined portions 62a and 62b are inclined so as to be separated from each other with the boundary with the flat portion 58 as a fulcrum without being curved, and accordingly, the angle formed by the flat portion 58 and the inclined portions 62a and 62b increases. . In other words, the inclined portions 62a and 62b are expanded, and as a result, the joint portions 64a and 64b are displaced so as to be separated from each other, and the angle formed between the inclined portions 62a and 62b and the joint portions 64a and 64b is reduced.

  As the joint portions 64a and 64b are separated from each other, the optical fibers 38 and 44 expand. As a result, the spacing between the gratings in the gratings 40 and 46 is also extended. The intervals between the lattices thus extended are substantially equal to each other. This is because the optical fibers 38 and 44 are stretched by both the joint portions 64a and 64b as the joint portions 64a and 64b are separated from each other.

  Thus, the elastic body 56 operates to convert the direction in which the shear stress acts from a direction substantially orthogonal to the longitudinal direction of the optical fibers 38 and 44 to a parallel direction.

As shown in FIG. 13, when the shear stress is F, the stress acting on each of the inclined portions 62a and 62b is F1 and F2, and the stress acting on each of the joint portions 64a and 64b is F3 and F4, the gratings 40 and 46 The force for extending is F3 and F4. When the angle formed between the direction in which the shear stress F acts and the inclined portions 62a and 62b is α, the following equation (3) is established.
F1 = F2 = Fcosα (3)

Since the angle formed by F2 and the longitudinal direction of the optical fibers 38 and 44 is 90 ° −α, the force F4 acting on the optical fibers 38 and 44 and the joint portions 64a and 64b is obtained by the following equation (4). .
F3 = F4 = F2cos (90-α)
= F2sinα
= Fcos α sin α (4)

In this case, since the angle θ1 formed by the inclined portion 62a and the joint portion 64a is equal to the angle θ2 formed by the inclined portion 62b and the joint portion 64b, F1 = F2 and F3 = F4. Accordingly, when the elastic constant of the optical fibers 38 and 44 is E and the strain is ε, the following equation (5) is established.
ε = (2 / E) Fcosαsinα (5)

When the number of lattices in the gratings 40 and 46 is N and the lattice interval is Δ, the following relational expression (6) is established between Δ and N.
Δ = ε / (N−1) (6)

Substituting equation (5) into equation (6) yields the following equation (7).
Δ = 2Fcos αsin α / [E × (N−1)] (7)

Therefore, the wavelength shift amount λ can be obtained by the following equation (8).
λ = 2 × n _eff × Δ
= 4 × n _eff × Fcos αsin α / [E × (N−1)] (8)

  That is, the peak waveform is uniquely determined with respect to the shear stress F.

  This phenomenon also occurs when the shear stress is deviated from the middle part in the longitudinal direction of the flat part 58, for example, when it acts on the end part close to the inclined part 62b as shown in FIG. That is, when a shear stress acts on this part, the flat part 58 expands toward the inclined part 62a. Following this, the inclined portions 62a and 62b are further inclined so as to be separated from each other, and the joint portions 64a and 64b are displaced so as to be separated from each other with the inclination. As a result, the optical fibers 38 and 44 are extended, and the interval between the gratings in the gratings 40 and 46 is also extended. Of course, also in this case, as shown in FIG. 12, the distance between the expanded lattices is substantially equal.

  Although not shown in the drawings, the same applies when a shear stress acts on the end portion of the flat portion 58 close to the inclined portion 62a.

  Thus, as a result of the gratings 40 and 46 extending so that the intervals between the gratings are substantially equal to each other, the appearance of reflected light at a plurality of wavelengths (see FIG. 23) is avoided, as shown in FIG. In this way, reflected light having a wavelength different from that before the extension of the gratings 40 and 46 is obtained.

  When the angle θ1 formed by the inclined portion 62a and the joint portion 64a is different from the angle θ2 formed by the inclined portion 62b and the joint portion 64b, the calculation may be performed as follows.

When the angle between the direction in which the shear stress F acts and each of the inclined portions 62a and 62b is α and β, and the strain on the inclined portions 62a and 62b side is ε1 and ε2, the following equations (9) and (10) are obtained. To establish.
ε1 = F3 / E
= Fcos αsin α / E (9)
ε2 = F4 / E
= Fcosβsinβ / E (10)

In this case, since the total distortion ε is equal to ε1 + ε2, the following equation (11) is established.
ε = ε1 + ε2
= (Fcosαsinα + Fcosβsinβ) / E (11)

Hereinafter, the following formula (12) is obtained by substituting the formula (11) into the above formula (6).
Δ = (Fcosαsinα + Fcosβsinβ) / [E × (N−1)] (12)

Therefore, the wavelength shift amount λ is obtained by the following equation (13).
λ = 2 × n _eff × Δ
= 2 × n _eff × (Fcosαsinα + Fcosβsinβ) / [E × (N−1)] (13)

  Of course, the above operation is similarly performed when a normal stress is applied to the optical fiber 50. And the peak waveform according to a normal stress is obtained by the formula according to said formula (4)-(13).

  As described above, according to the present embodiment, when the gratings 40, 46, and 52 are expanded, the intervals between adjacent gratings are substantially equal, and the wavelength to be shifted is uniquely determined according to the stress. For this reason, the measurement accuracy of stress improves.

  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, as illustrated in FIG. 14, the joint portions 64 a and 64 b of the adjacent elastic bodies 56 may be continuous. Further, as shown in FIG. 15, the elastic body 56 (stress direction changing means) may be configured to surround the optical fibers 38, 44, 50 from both the upper surface and the lower surface. Of course, also in this case, as shown in FIG. 16, the joint portions 64 a and 64 b of the adjacent elastic bodies 56 may be connected to each other.

  Furthermore, as shown in FIG. 17, the elastic body 56 is disposed on either the upper surface or the lower surface of the optical fibers 38, 44, 50, or the joint portions 64 a, 64 b of the adjacent elastic bodies 56 are connected to each other. You may make it do.

  Furthermore, as shown in FIGS. 18 and 19, the flat portions 58 of the adjacent elastic bodies 56 may be connected to each other.

  In the robot system 10 shown in FIG. 10, instead of supplying the light output from the light source 68 to the optical fiber sensors 18a and 18b by time division by the beam switch 70, X constituting the optical fiber sensors 18a and 18b is configured. While supplying light from three independent light sources to the direction shear 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 You may comprise so that the reflected light from the sensor part 34 and the Z direction stress sensor part 36 may be detected with three independent reflected light detectors. With this configuration, the shear stress and the normal stress received from the object 12 can be detected simultaneously.

  Further, the optical fiber 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.

1 is a configuration diagram of a robot system to which an optical fiber 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 perspective view of the optical fiber sensor according to the present embodiment. It is a schematic whole perspective view of two elastic bodies. 1 is a configuration block diagram of a robot system using an optical fiber sensor according to the present embodiment. It is a plane explanatory view showing typically a shape change of an elastic body before and after stress acts on a substantially middle part in a longitudinal direction of a flat part. It is a plane explanatory view showing typically a shape change of an elastic body before and after stress acts on an end near an inclined part in a flat part. It is plane explanatory drawing which showed typically the relationship of the stress which acts on a flat part, an inclination part, and a junction part. It is a general | schematic whole perspective view of the elastic body of another shape. It is a schematic whole perspective view of an elastic body of another shape. Furthermore, it is a general | schematic whole perspective view of the elastic body of another shape. Furthermore, it is a general | schematic whole perspective view of the elastic body of another shape. Furthermore, it is a general | schematic whole perspective view of the elastic body of another shape. Furthermore, it is a general | schematic whole perspective view of the elastic body of another shape. It is a state explanatory diagram schematically showing the state of the grating before and after the stress is applied from the direction orthogonal to the extending direction of the optical fiber. It is typical explanatory drawing which shows the change of the wavelength of the reflected light in the case of FIG. It is a state explanatory diagram schematically showing the state of the grating before and after the stress is applied from the direction orthogonal to the extending direction of the optical fiber. It is typical explanatory drawing which shows the change of the wavelength of reflected light in the case of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Robot system 12 ... Object 14 ... Manipulator 16a, 16b ... Hand part 18a, 18b ... Optical fiber sensor 20 ... Optical fiber sensor controller 22 ... Manipulator controller 24 ... FBG sensor 26, 38, 44, 50 ... Optical fiber 30A, 30B , 40, 46, 52... Grating 32... X-direction shear stress sensor section 34... Y-direction shear stress sensor section 36 .. Z-direction stress sensor section 42, 48, 54 ... pressure-sensitive member 56 ... elastic body 58. Stress transmitting parts 62a, 62b ... inclined parts 64a, 64b ... joints 68 ... light source 70 ... beam switchers 72a-72c ... half mirrors 74a-74c ... transmitted light terminator 76 ... reflected light detector 78 ... shear stress calculating part 80 ... Vertical stress calculator

Claims (3)

A stress detection sensor unit comprising an optical fiber in which gratings that reflect light of a specific wavelength are arranged;
A stress direction conversion means for converting the direction of stress applied in a direction different from the longitudinal direction of the optical fiber into a direction parallel to the longitudinal direction and transmitting it to the grating;
An optical fiber sensor comprising:   2. The optical fiber sensor according to claim 1, wherein the stress direction converting means includes a flat portion extending in a direction parallel to the longitudinal direction of the optical fiber, and a stress transmission portion bridged from the flat portion to the optical fiber. And an optical fiber sensor.   3. The optical fiber sensor according to claim 2, wherein the flat portion has higher elasticity than the stress transmission portion.

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