Drive device, method of controlling strain and computer readable medium storing program

A drive device includes a drive member, a light source, a marker, a detector, a signal processor and a strain controller. The drive member includes at least a material which generates a plasmon. The drive member generates strain in response to input energy. The marker is formed on a surface of the drive member. Strain occurs in the marker in accordance with a deformation of the drive member and the marker reflects or transmits light emitted from the light source. The detector detects a light intensity of light reflected from or transmitted through the marker. The signal processor calculates an amount of strain which occurs in the marker based on the light intensity. The strain controller controls an amount of strain of the drive member based on the amount of strain calculated by the signal processor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drive device, a method of controlling strain and a computer readable medium storing a program.

2. Description of Related Art

Recent years, the need for the technology to detect strain which occurs in a drive unit as typified by an actuator is growing. For example, in the case of a robot hand, the amount of strain needs to be strictly controlled for gripping an object more properly and accurately. Thus, a unit for detecting strain of a drive unit is necessary. Presently, electrical-type strain gages are major units for detecting strain. An electrical-type strain gauge is a mechanical sensor which can calculate the amount of strain by measuring the change of electrical resistance due to a deformation.

As an example of an electrical-type strain gauge, a technique is disclosed which reduces measurement errors to enable high precision uniaxial displacement measurement (for example, refer to JP H07-321385 A).

Also, a technique is disclosed which reduces the influence caused by the operation of an actuator to improve the detection accuracy of a sensor (for example, refer to JP 2011-072180 A).

In the techniques described in JP H07-321385 A and JP 2011-072180 A, a sensor is attached to a drive unit to detect the strain of the drive unit and the strain of the drive unit is controlled based on the detected value.

In order to detect strain, there is also a method called a moire method. In the moire method, a grid pattern is drawn on the surface of the drive unit, and strain is detected by carrying out an image analysis with respect to the change of the grid pattern.

In general, when strain of a drive unit is detected, transmitting the detected information on strain to a signal processing unit causing as small time lag as possible is important. Also, since a drive unit frequently undergoes impact resulting from external force or the like, countermeasure against impact is necessary. As described above, rapid detection and high impact resistance are required to a section for detecting strain in a drive unit.

However, in the prior art, there is no detection unit which satisfies the two performances described above (rapid detection and high impact resistance) at the same time.

For example, electrical-type strain gauges described in JP H07-321385 A and JP 2011-072180 A can detect strain rapidly. However, since these strain gauges are formed to be very fragile not to disrupt driving, they have low impact resistance and easy to be broken.

In case where moire method is adopted, since a grid pattern is directly inscribed on a drive body, high impact resistance can be expected. However, since carrying an image analysis takes time, there is a problem that detection rate is low.

SUMMARY OF THE INVENTION

The present invention is made considering the circumstances described above. An object of the present invention is to provide a drive device and a method of controlling strain while rapid detection and high impact resistance are realized at the same time.

To achieve at least one of the objects described above, according to one aspect of the present invention, there is provided A drive device including: a drive member which includes at least a material which generates a plasmon, the drive member generating strain in response to input energy; a light source which emits light; a marker formed on a surface of the drive member, wherein strain occurs in the marker in accordance with a deformation of the drive member and the marker reflects or transmits light emitted from the light source; a detector which detects a light intensity of light reflected from or transmitted through the marker; a signal processor which calculates an amount of strain which occurs in the marker based on the light intensity detected by the detector; and a strain controller which controls an amount of strain of the drive member based on the amount of strain calculated by the signal processing unit, wherein the marker includes, on the surface of the drive member, a periodic fine structure, a size of the fine structure being equal to or smaller than a wavelength of light emitted from the light source.

Preferably, in the drive device, the drive member and the marker are composed of a material including at least a hydrogen storage alloy.

Preferably, in the drive device, the hydrogen storage alloy is an alloy including palladium.

Preferably, in the drive device, the marker is formed integrally with the drive member.

Preferably, in the drive device, the marker includes a flat plate including a first medium and a second medium, a refractive index of the first medium and a refractive index of the second medium being different from each other, the second medium is periodically arranged in the first medium, and a maximum length of the second medium in a direction parallel with a light receiving surface of the marker is shorter than a wavelength of light emitted from the light source.

Preferably, in the drive device, the light source emits a plurality of light fluxes polarized in directions different from each other, the detector further detects a polarization direction of light reflected from or transmitted through the marker, and the signal processor calculates a direction of strain which occurs in the marker based on the light intensity and the polarization direction detected by the detection member.

Preferably, in the drive device, the second medium is arranged such that at least one second medium exists in a direction parallel with a direction of deformation of the marker.

Preferably, in the drive device, gas is accommodated in an area where the second medium is to be accommodated.

To achieve one of the objects described above, according to one aspect of the present invention, there is provided a method of controlling strain of a drive device including a drive member which includes at least a material which generates a plasmon, the drive member generating strain in response to input energy; a light source which emits light; a marker formed on a surface of the drive member, wherein strain occurs in the marker in accordance with a deformation of the drive member and the marker reflects or transmits light emitted from the light source and wherein the marker includes a periodic fine structure, a size of the fine structure being equal to or smaller than a wavelength of light emitted from the light source, the method including steps of: detecting a light intensity of light reflected from or transmitted through the marker; calculating an amount of strain which occurs in the marker based on the detected light intensity; and controlling an amount of strain of the drive member based on the calculated amount of strain.

To achieve one of the objects described above, according to one aspect of the present invention, there is provided a non-transitory computer readable storage medium storing a program thereon which causes a computer of a drive device including a drive member which includes at least a material which generates a plasmon, the drive member generating strain in response to input energy; a light source which emits light; a marker formed on a surface of the drive member, wherein strain occurs in the marker in accordance with a deformation of the drive member and the marker reflects or transmits light emitted from the light source and wherein the marker includes a periodic fine structure, a size of the fine structure being equal to or smaller than a wavelength of light emitted from the light source, to function as units, including: a detector which detects a light intensity of light reflected from or transmitted through the marker; a signal processor which calculates an amount of strain which occurs in the marker based on the light intensity detected by the detector; and a strain controller which controls an amount of strain of the drive member based on the amount of strain calculated by the signal processor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described in detail with reference to the drawings in the following. In the following description, the left to right direction inFIG. 1is defined as X direction, the down to up direction inFIG. 1is defined as Z direction, and the direction perpendicular to X direction and Z direction (rear to front direction) is defined as Y direction.

A drive device100according to the present embodiment is a sensor which is able to measure strain occurring in a drive unit1with use of light. As shown inFIGS. 1 and 2, the drive device100includes the drive unit1which generates strain passively or actively based on input energy (external source, external energy), a light source2disposed above the drive unit1in Z direction, a marker3which is integrally formed on the surface of the drive unit1by microfabrication and which reflects light emitted from the light source2, a detection unit4which is disposed above the drive unit1in Z direction and which detects light reflected by the marker3, a signal processing unit5which measures the strain of the drive unit1based on light detected by the detection unit4, and a controller6(refer toFIG. 2).

The drive unit1is a member which is able to output physical quantity such as strain, displacement and force by inputting the output from an external source P1as shown inFIGS. 3 and 4. Specifically, the drive unit1generates displacement by inputting the output from an external source P1as shown inFIG. 4and the displacement generates force P11resulting from the external source. The drive unit1generates displacement and force P11resulting from external source via strain. Strain D1is expressed by formula 1:
D1=Q1/L1  (1)
where Q1represents amount of displacement (resulting from the external source), L1represents a length before the displacement and L2represents a length after the displacement.

Since the amount of displacement Q1is obtained by subtracting the length L1before the displacement from the length L2after the displacement, the strain D1is expressed by formula 2:
D1=(L2−L1)/L1  (2)

FIG. 5shows an example of behavior when external energy P2occurs in the drive unit1other than the external source P1.FIG. 6are side views of the drive unit each shown inFIGS. 3 to 5. In the example shown inFIG. 5, the output from the external source P1and external energy P2are input to the drive unit1. The external energy P2means energy such as temperature and load other than the external source P1which causes the drive unit1to output strain and displacement. When the external energy P2is input to the drive unit1, strain and displacement are generated in the drive unit1and the occurrence of the strain and displacement generates force P21resulting from the external energy. Thus, as shown inFIG. 6, actual amount of displacement Q3when the external energy P2occurs is expressed by formula 3:
Q3=Q1+Q2  (3)
where Q1represents amount of displacement resulting from the external source and Q2represents amount of displacement resulting from external energy.

That is, in order to exactly output the actual amount of displacement Q3of the drive unit1, detecting the amount of displacement Q2resulting from external energy is necessary, and thus, a sensor which detects the strain of the drive unit1is necessary.

The drive unit1is a member formed of an alloy including palladium, for example. Palladium is one of hydrogen storage materials which is able to generate a plasmon phenomenon. A hydrogen storage material is a material which can undergo a volume change in accordance with adsorption and release of hydrogens corresponding to the external source P1(hydrogen adsorption accompanied by volume increase and hydrogen release accompanied by volume decrease). That is, the drive unit1can output desired amount of strain by controlling hydrogen amount and/or temperature of palladium which is a hydrogen storage material.

The light source2emits a linearly polarized light flux (incident light21) toward the marker3disposed below. The light source2emits a light flux having a wavelength of 1 μm or less.

The marker3has a nano hole array structure in which uniform nanometer-size fine pores are periodically arranged. The light intensity of the light reflected from the nano hole array changes in accordance with the amount of strain generated by external energy (load, weight, heat, magnetic force, pressure, for example). As shown inFIGS. 7 and 8, the marker3includes a first medium31and a second medium32which are integrally formed on the surface of drive unit1by microfabrication and reflects light flux emitted from the light source2. The refractive indices of the first medium31and the second medium32are different from each other.

The first medium31is a substantially square shaped plate member formed of an alloy including palladium, for example. The first medium31may be a metal such as aluminum, gold, silver, titanium and titanium oxide, a resin, an oxide semiconductor or the like. The areas which each accommodate the second medium32are formed in the first medium31so as to each have a true circle shape having the center axis in Z direction in a plan view.

The second medium32is formed of acrylic resin or the like. However, this is not limitative. For example, a gas may be accommodated in the area where the second medium32is accommodated. In this case, any gas may be tightly sealed. Air may be the second medium32by leaving the area for the second medium32empty.

As shown inFIGS. 9 and 10, the first medium31and the second medium32which constitute the marker3are deformed in response to external energy in parallel with the surface of the drive unit1(marker3).

For example, as shown inFIGS. 9A and 9B, in a case where deformation and/or strain in X direction occurs in the marker3(X strain711), strain and/or deformation in X direction is generated in the marker3. As shown inFIG. 9C, when320represents the second medium before the strain and/or deformation of the marker3, and321represents the second medium after the strain and/or deformation of the marker3, the amount of strain generated in the marker3can be calculated in accordance with formula (4):
εx=(X1−X0)/(X0)  (4)
where X0represents the diameter of the second medium320before the strain and/or deformation and X1represents the diameter of the second medium321after the strain and/or deformation.

FIGS. 10A, 10B and 10Cshows that, in a case where deformation and/or strain in Y direction occurs in the marker3(Y strain712), strain and/or deformation in Y direction is generated in the marker3. As shown inFIG. 10C, when320represents the second medium before the strain and/or deformation of the marker3, and321represents the second medium after the strain and/or deformation of the marker3, the amount of strain generated in the marker3can be calculated in accordance with formula (5):
εy=(Y1−Y0)/(Y0)  (5)
where Y0represents the diameter of the second medium320before the strain and/or deformation and Y1represents the diameter of the second medium321after the strain and/or deformation.

The detection unit4detects the light intensity of light flux reflected on the marker3(reflected light22). The light intensity of the reflected light22detected by the detection unit4is output to the signal processing unit5.

The signal processing unit5calculates the amount of strain of the drive unit1based on the light intensity of the reflected light22output from the detection unit4. Specifically, the signal processing unit5calculates the amount of strain based on the table data which shows the correspondence between the light intensity and the amount of strain (refer toFIG. 12).

The controller6includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM) and the like. The CPU opens in the RAM various programs stored in the ROM, and carries out the overall control of the operation of each component of the drive device100such as the drive unit1, the light source2, the detection unit4and the signal processing unit5(refer toFIG. 2).

Next, a method of calculating the amount of strain occurring at the marker3(drive unit1) in the drive device100according to the present embodiment will be described in reference toFIGS. 11 and 12. The range of the amount of strain which can be measured depends on the wavelength of light emitted from the light source2and the size of the diameter X0of the second medium32. Therefore, the amount of strain caused by a nanometer-size deformation can be measured by setting the nanometer-size wavelength of light emitted from the light source2and the nanometer-size diameter X0of the second medium32. Needless to say, the amount of strain caused by microscopic or larger deformation can be measured by properly setting the wavelength of light emitted from the wavelength2, the size of structures, the kind of material or the like.

EXAMPLE

In the example, such a marker3is used that the thickness Z0of the first medium31is 1000 nm, the thickness Z1of the second medium32is 200 nm, the diameter X0of the second medium is 300 nm and the period C0of the second medium32is 450 nm. Palladium (Pd) is used as the first medium31and air is used as the second medium32. The light source2is used which emits light linearly polarized in X direction (the direction of strain of the marker3) and whose peak wavelength is about 700 nm.

FIG. 11shows the change in the spectrum of the reflected light caused by the strain of the marker3. As shown inFIG. 11, when strain occurs in the marker3, the intensity of reflected light changes in accordance with the direction of strain of the marker3(in this example, X direction). This is because, when strain occurs in the marker3, the shape of the second medium32included in the marker3deforms, and the property (resonance condition) of surface plasmons generated on the surface of the marker3changes. That is, the amount of strain of the marker3and the intensity of reflected light are correlated. The amount of strain of the marker3can be calculated from the intensity of reflected light with use of this correlation.

FIG. 12shows table data which shows the correspondence between the amount of strain of the marker3in X direction and the intensity of reflected light. The intensity of reflected light is calculated in accordance with “light intensity of reflected light22/light intensity of incident light21”. In the example shown inFIG. 12, the intensity of reflected light at the wavelength 700 nm is plotted for each amount of strain. When the signal processing unit5has the table data shown inFIG. 12prepared (input) in advance, the amount of strain generated in the marker3in X direction can be calculated based on the intensity of reflected light detected by the detection unit4. For example, when the intensity of reflected light detected by the detection unit4is 0.50, the amount of strain (≈0.10) can be calculated corresponding to the intensity of reflected light 0.50 with reference to the table data shown inFIG. 12.

When the light source2is prepared which emits light polarizable in the direction of strain of the marker3and the signal processing unit5has table data for each of the direction of strain (polarization direction of light) in advance, the amount of strain generated in the marker3in any direction on XY plane can be calculated. For example, when calculating the amount of strain of the marker3in Y direction is necessary, by preparing the light source2which emits light linearly polarized in Y direction and the table data in which the correspondence between the amount of strain of the marker3in Y direction and the intensity of reflected light in the signal processing unit5is plotted in advance, calculating the amount of strain of the marker3in Y direction is possible.

Next, the operation of the drive device100according to the present embodiment will be explained with reference to the flowchart shown inFIG. 13.

The controller6controls the detection unit4to detect the spectral intensity of the light flux (reflected light22) reflected from the marker3(Step S101).

Then, the controller6controls the signal processing unit5to calculate the amount of strain generated in the marker3based on the spectral intensity detected in Step S101(Step S102).

The controller6determines if the amount of strain calculated in Step S102is a predetermined amount of strain which is set in advance (Step S103). The predetermined amount of strain is the amount of strain resulting from the external source which a user desires, and is set in appropriate in accordance with the material of the drive unit1, for example.

When the controller6determines that the calculated amount of strain is the predetermined amount of strain (Step S103; YES), the controller6ends the processing.

When the controller6determines that the calculated amount of strain is not the predetermined amount of strain (Step S103; NO), the controller controls the value input to the drive unit1based on the amount of strain calculated in Step S102(Step S104) where the value input to the drive unit1is the value of the output from the external source P1input to the drive unit1. That is, the controller6controls the value of the output from the external source P1input to the drive unit1such that the drive unit1outputs the predetermined amount of strain. The controller6functions as a strain controller of the present invention.

After the controller6controls the value input to the drive unit1at Step S104, the flow shifts the processing to Step S101to repeat the processing.

The drive unit1can output the predetermined amount of strain by the processes described above.

As described above, a drive device100according to the present invention, includes: a drive unit1configured to include at least a material which generates a plasmon, the drive unit1generating strain in response to input energy; a light source2which emits light; a marker3formed on a surface of the drive unit1, wherein strain occurs in the marker3in accordance with a deformation of the drive unit1and the marker3reflects or transmits light emitted from the light source2; a detection unit4which detects a light intensity of light reflected from or transmitted through the marker3; a signal processing unit5which calculates an amount of strain which occurs in the marker3based on the light intensity detected by the detection unit4; and a strain controller (controller6) which controls an amount of strain of the drive unit1based on the amount of strain calculated by the signal processing unit5. Also, the marker3includes, on the surface of the drive unit1, a periodic fine structure, a size of the fine structure being equal to or smaller than a wavelength of light emitted from the light source2.

Thus, according to the drive device100of the present embodiment, since strain can be detected based on the change in the intensity of reflected light, strain can be detected rapidly without a complicated process such as an image analysis. Also, since a fine structure is provided on the surface of the drive unit1itself, even when an impact occurs due to external force or the like, the marker3is not damaged or detached, and strain can be detected stably.

Therefore, according to the drive device100of the present embodiment, strain can be detected while rapid detection and high impact resistance are realized at the same time.

In the drive device100according to the present embodiment, the drive unit1and the marker3are composed of a material including at least a hydrogen storage alloy.

Thus, according to the drive device100of the present embodiment, since complicated parts such as a gear, a compressor and a motor are not necessary, the configuration of the drive unit1can be made smaller. Also, since a hydrogen storage alloy can generate a plasmon, the strain of small drive unit1can be detected only by forming the micrometer-size marker3on the surface of the drive unit1.

Therefore, according to the drive device100of the present embodiment, the feedback of strain to the controller6is possible while small drive unit1is realized.

In the drive device100according to the present embodiment, the hydrogen storage alloy is an alloy including palladium.

Thus, according to the drive device100of the present embodiment, since the coefficient of volume expansion of palladium is as large as about 300% when palladium storages hydrogen, palladium can output great force (strain) as the drive unit1. Also, since palladium generates surface plasmon in the visible light region, the strain of the drive unit1can be detected easily.

Therefore, according to the drive device100of the present embodiment, both the output function and the strain detection function can be realized at a high level.

In the drive device according to the present embodiment, the marker3is formed integrally with the drive unit1.

Thus, according to the drive device100of the present embodiment, since the elastic moduli of the drive unit1and marker3can be conformed to each other, even when the drive unit1is deformed, the occurrence of stress between the drive unit1and the marker3can be suppressed, and the fracture and degradation of the marker3can be suppressed. Also, since applying and fixing the marker3is not necessary, the uncertainty regarding the detachment of the marker3can be resolved and cost can be reduced owing to the reduction of members and/or process for fixing.

In the drive device100according to the present embodiment, the marker3is formed so as to be a flat plate including a first medium31and a second medium32, a refractive index of the first medium31and a refractive index of the second medium32being different from each other. Also, the second medium32is periodically arranged in the first medium31, and a maximum length of the second medium32in a direction parallel with a light receiving surface of the marker3is shorter than a wavelength of light emitted from the light source2.

Thus, according to the drive device100of the present embodiment, since the shape of the second medium32included in the marker3is deformed and the light intensity of light reflected from the marker3changes, the magnitude of strain generated in the drive unit1can be detected by converting the detected light intensity to the amount of strain. Also, since the detectable range of the amount of strain depends on the wavelength of light emitted from the light source2and the length of the diameter of the second medium32, strain caused by a nanometer-size deformation can be detected by setting the nanometer-sized wavelength of light emitted from the light source2and the nanometer-sized length of the diameter of the second medium32. Needless to say, the detection of strain caused by a micrometer-size or more deformation is possible by setting the wavelength of light emitted from the light source2, the size of structures, the material or the like appropriately.

In the drive device100according to the present embodiment, gas is accommodated in an area where the second medium is to be accommodated.

Thus, according to the drive device100of the present embodiment, since stress or the like does not occur between the first medium31and the second medium32, robustness can be insured with respect to the repetition of deformation.

Although the present invention is described based on an embodiment of the present invention, the present invention is not limited to the embodiment described above and can be modified within the scope of the present invention.

For example, in an example shown inFIG. 14, the configurations of a light source2A, a detection unit4A and a signal processing unit5A are different in comparison to the drive device100of the embodiment. For ease of explanation, same reference numeral is given and detailed explanation is omitted with respect to a configuration similar to that of the embodiment.

Specifically, as shown inFIG. 14, the light source2A of the drive device100A according to the modification emits light fluxes (incident light21A) linearly polarized in directions different from one another.

The detection unit4A detects the light intensity and polarization direction of light flux (reflected light22A) reflected from the marker3.

The signal processing unit5A calculates the direction of strain and the amount of strain based on the light intensity and the polarization direction of the reflected light22A output from the detection unit4A. Specifically, the signal processing unit5A calculates the amount of strain based on the table data which shows the correspondence between the light intensity and the amount of strain in the calculated direction of strain.

As described above, in the drive device100A according to modification, the light source2A emits a plurality of light fluxes polarized in a direction parallel with a light receiving surface of the marker3, the plurality of light fluxes being polarized in directions different from each other. Also, the detection unit4A further detects a polarization direction of light reflected from the marker3, and the signal processing unit5A calculates a direction of strain which occurs in the marker3based on the light intensity and the polarization direction detected by the detection unit4A.

Thus, according to the drive device100A of the modification, since the light intensity of reflected light of a plurality of directions of polarization can be detected, the direction of maximum strain can be detected based on the difference of the light intensity of each polarization direction. The amount of strain in the direction of maximum strain can be detected based on the light intensity of the detected direction of maximum strain.

Therefore, according to the drive device100A of the modification, the strain of the drive unit1can be retrieved as two-dimensional information.

In the embodiment described above, the second medium32is arranged in the first medium31in a grid-like pattern. However, this is not limitative. For example, like the marker3A shown inFIG. 15, the second media32adjacent to each other in X direction may be arranged so as to be shifted from each other by δy in Y direction.

In the marker3A, since the first medium31and the second medium32are arranged as described above, the direction of deformation and the periodic direction of the second medium32are not parallel with each other. Thus, when any cross-section is created along the direction parallel with the direction of deformation (X direction in the drawing), the ratio of areas of the media (the first medium31and the second medium32) on each of the cross-sections is substantially constant. For example, as shown inFIGS. 15 to 17, when the cross-section along line A-A inFIG. 15(cross-section A; refer toFIG. 16) and the cross-section along line B-B inFIG. 15(cross-section B; refer toFIG. 17) are compared with each other, the ratio of areas of the media is substantially the same. The fact that the ratio of area of each medium is substantially the same on each of cross-sections means that the apparent modulus of elasticity on each cross-section is substantially the same.

Most preferably, in the marker3A, the ratio of areas of media on each cross-section which is parallel with the direction of deformation is the same. However, this is not limitative. That is, if at least one second medium32is arranged along the direction parallel with the direction of deformation, the variation in the ratio of areas of media on each cross-section is reduced. Thus, the variation of the apparent modulus of elasticity at each position can be reduced.

As described above, by arranging at least one second medium32along the direction parallel with the direction of deformation of the marker3A, the variation of the ratio of areas of media along the direction parallel with the direction of strain (direction of deformation) of the marker3A can be reduced. Thus, the variation of the apparent modulus of elasticity at each position of the marker3A can be reduced.

Therefore, the maximum value of the amount of strain which can be detected by the marker3A can be increased.

In the embodiment described above, the drive unit1and the first medium31of the marker3is formed of an alloy including palladium. However, this is not limitative. For example, the drive unit1and the first medium31of the marker3may be formed of a hydrogen storage material other than palladium. The drive unit1and the first medium31of the marker3may be formed of a metal other than a hydrogen storage material (for example, a magnetic shape-memory alloy).

In the embodiment described above, the marker3is integrally formed on the surface of drive unit1. However, this is not limitative. For example, the marker3may be formed separately from the drive unit1and the marker3and the drive unit1may be welded with each other.

By forming the marker3separately from the drive unit1as described above, time and cost necessary for forming operation can be reduced because forming the marker3is made easier.

The drive unit1of the present invention may include a member associated with the drive unit1(such as a transmission member). That is, the marker3may be formed on the surface of a member associated with the drive unit1. Owing to this, even when the marker3is arranged indirectly with respect to the drive unit1, the strain can be detected while both rapid detection and high impact resistance are realized.

In the embodiment described above, the area which accommodates the second medium32is formed so as to have a true circle shape having a center axis in Z direction (direction perpendicular to the light receiving surface of the marker3) in a plan view. However, this is not limitative. The area which accommodates the second medium32may have any shape such as an ellipsoidal shape and a rectangular shape, if it has a shape whose maximum length parallel with the light receiving surface of the marker3is smaller than the wavelength of light emitted from the light source2.

In the embodiment described above, a material whose modulus of elasticity is smaller than that of the first medium31is used for the second medium32. However, this is not limitative. That is, a material whose modulus of elasticity is smaller than that of the first medium31is preferable for the second medium32. However, a material whose modulus of elasticity is comparable with or smaller than the modulus of elasticity of the first medium31may be used for the second medium32.

In the embodiment described above, the amount of strain is calculated based on a table data (refer toFIG. 12) which shows the correspondence between the light intensity and the amount of strain. However, it is not limitative. For example, the amount of strain may be calculated by a predetermined formula based on the light intensity detected by the detection unit4, for example.

In the embodiment described above, the configuration in which light flux emitted from the light source2is reflected from the marker3is explained as an example. This is not limitative. For example, by making the marker3and the drive unit1transparent, the marker3and the drive unit1transmits the light flux emitted from the light source2. In this case, the detection unit4is disposed at the destination of the light flux emitted from the light source2and transmitted through the marker3and the drive unit1, and detects the spectral intensity of light transmitted through the marker3.

Thus, since the amount of strain can be measured using the light transmitted through the marker3and drive unit1, measurement accuracy can be improved in comparison to the measurement using reflected light.

A temperature measurement unit which measures the temperature of the marker3and the drive unit1may be provided and the signal processing unit5may calculate Young's modulus of the marker3and the drive unit1based on the temperature measured at the temperature measurement unit.

Thus, since the measurement value can be compensated using the calculated Young's modulus, the measurement accuracy of the amount of strain can be improved further.

In the embodiment described above, as shown inFIG. 1, the light source2and the detection unit4are disposed distant from each other. This is not limitative. That is, the light source2and the detection unit4may be disposed adjacent to each other, and the light source2may emit light in the direction substantially perpendicular to the light receiving surface of the marker3.

Thus, since light incident on the marker3substantially perpendicular to the marker3, the spectral intensity of light flux due to the incident angle can be suppressed as small as possible, and the measurement accuracy of the amount of strain can be insured.

In addition, the detailed configuration and detailed operation of each device which constitutes the drive device can be modified without departing from the scope of the present invention.

According to one aspect of a preferred embodiment of the present invention, there is provided a drive device including:

a drive unit configured to include at least a material which generates a plasmon, the drive unit generating strain in response to input energy;

a light source which emits light;

a marker formed on a surface of the drive unit, wherein strain occurs in the marker in accordance with a deformation of the drive unit and the marker reflects or transmits light emitted from the light source;

a detection unit which detects a light intensity of light reflected from or transmitted through the marker;

a signal processing unit which calculates an amount of strain which occurs in the marker based on the light intensity detected by the detection unit; and

a controller which controls an amount of strain of the drive unit based on the amount of strain calculated by the signal processing unit, wherein

the marker includes, on the surface of the drive unit, a periodic fine structure, a size of the fine structure being equal to or smaller than a wavelength of light emitted from the light source.

In accordance with the drive device, strain can be detected while rapid detection and high impact resistance are realized at the same time.

The entire disclosure of Japanese Patent Application No. 2016-019387 filed on Feb. 4, 2016 is incorporated herein by reference in its entirety.