WO2011122536A1 - 変位計測方法及び変位計測装置 - Google Patents
変位計測方法及び変位計測装置 Download PDFInfo
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- WO2011122536A1 WO2011122536A1 PCT/JP2011/057560 JP2011057560W WO2011122536A1 WO 2011122536 A1 WO2011122536 A1 WO 2011122536A1 JP 2011057560 W JP2011057560 W JP 2011057560W WO 2011122536 A1 WO2011122536 A1 WO 2011122536A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
- B60L3/0076—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to braking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L50/00—Electric propulsion with power supplied within the vehicle
- B60L50/20—Electric propulsion with power supplied within the vehicle using propulsion power generated by humans or animals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L7/00—Electrodynamic brake systems for vehicles in general
- B60L7/10—Dynamic electric regenerative braking
- B60L7/12—Dynamic electric regenerative braking for vehicles propelled by dc motors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L7/00—Electrodynamic brake systems for vehicles in general
- B60L7/24—Electrodynamic brake systems for vehicles in general with additional mechanical or electromagnetic braking
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
- B60T17/18—Safety devices; Monitoring
- B60T17/22—Devices for monitoring or checking brake systems; Signal devices
- B60T17/221—Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62K—CYCLES; CYCLE FRAMES; CYCLE STEERING DEVICES; RIDER-OPERATED TERMINAL CONTROLS SPECIALLY ADAPTED FOR CYCLES; CYCLE AXLE SUSPENSIONS; CYCLE SIDE-CARS, FORECARS, OR THE LIKE
- B62K23/00—Rider-operated controls specially adapted for cycles, i.e. means for initiating control operations, e.g. levers, grips
- B62K23/02—Rider-operated controls specially adapted for cycles, i.e. means for initiating control operations, e.g. levers, grips hand actuated
- B62K23/06—Levers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M6/00—Rider propulsion of wheeled vehicles with additional source of power, e.g. combustion engine or electric motor
- B62M6/40—Rider propelled cycles with auxiliary electric motor
- B62M6/45—Control or actuating devices therefor
- B62M6/50—Control or actuating devices therefor characterised by detectors or sensors, or arrangement thereof
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D66/00—Arrangements for monitoring working conditions, e.g. wear, temperature
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2200/00—Type of vehicles
- B60L2200/12—Bikes
Definitions
- the present invention relates to a displacement measuring method and a displacement measuring device using optical interference, and more specifically to expansion of a measuring range.
- a state before braking when the brake lever is started that is, a state in which the tension of the brake wire is applied
- measuring a slight movement amount (displacement amount) proportional to the tension of the brake wire Necessary.
- FIGS. 16A and 16B show the relationship between the brake lever operation amount and the braking force of the electrically assisted vehicle.
- FIG. It is necessary to measure the amount of operation of the brake lever corresponding to the amount of movement of the brake wire in the idle section shown in (A).
- the time (brake operating point P1) at which the brake pad starts to apply braking to prevent the wheel from rotating by the extension of the brake wire. This is because if the control between the regenerative braking and the mechanical braking is not smoothly performed before and after braking, the driver including the passenger feels uncomfortable as if the driver suddenly applied the brake, or the braking force is insufficient. It is for feeling.
- a Michelson interferometer 200 shown in FIG. 17A includes a laser light source 202, a collimator lens 204 that converts laser light into parallel light, and divides the beam into two to irradiate a fixed mirror 208 with the other being a movable mirror. Irradiate 210. A splitter 206 that makes these two reflected lights interfere with each other and an optical sensor 212 are included.
- the Michelson interferometer 200 when the movable mirror 210 moves one wavelength in the beam direction with respect to the fixed side unit 214, light contrast is generated twice on the detector. The brightness of this light is shown in FIG.
- the interference fringes 216 are observed.
- the displacement of one wavelength or less at this time can be detected by reading the voltage value of this light / dark gradient.
- the measurement range is determined by the wavelength of the light, and if an attempt is made to measure a range that is greater than or equal to the wavelength of the light, the wavelength of the light that has passed is counted, and a resolution that is less than the wavelength of the light cannot be obtained.
- the positional accuracy of the optical component is very strict, and measurement may not be possible due to angular deviation (0.01 degree order) or positional deviation (sub- ⁇ m order). Therefore, it is necessary to take measures to prevent erroneous detection depending on the usage environment such as temperature change, humidity change, external vibration, and aging.
- the present invention pays attention to the above points, is not affected by the tilt accuracy of the optical element, can be simply configured and can be miniaturized, and is resistant to misalignment, and can adjust the optical resolution. It is an object of the present invention to provide a displacement measuring method and a displacement measuring apparatus capable of performing the above. Another object is to provide a displacement measuring method and a displacement measuring apparatus capable of performing displacement measurement at different detection sensitivities and detection positions simultaneously or in time series.
- the gist of the present invention is as follows. First, according to the first aspect of the invention, light emitted from a light source is converted into parallel light by a collimator lens, and the parallel light passes through a first diffraction grating disposed on the optical axis. Next, the light beam is advanced to a semi-transmissive semi-reflective mirror disposed on the optical axis so as to face the first diffraction grating. The semi-transmissive semi-reflective mirror reflects a part of the parallel light as first return light that returns to the first diffraction grating, and the rest of the parallel light is the same as that of the semi-transmissive semi-reflective mirror.
- the first return light is converted into zero-order light traveling in the same direction as the first return light by the first diffraction grating, and ⁇ n-order light (n Is a natural number of 1 or more).
- the diffracted light of a predetermined order of the ⁇ nth order light is received by the first optical sensor to detect the amount of light and pass through the transflective mirror.
- the parallel light that has traveled to the total reflection mirror is reflected by the total reflection mirror, passes through the transflective mirror, and returns to the first diffraction grating as second return light.
- the second return light that has reached the grating is divided into zero-order light and ⁇ n-order light by the first diffraction grating and travels. Subsequently, among the ⁇ n-order lights, the diffracted light of the predetermined order is received by the first diffraction grating and the amount of light is detected, and the relative movement amount of the total reflection mirror with respect to the first semi-transmission semi-reflection mirror is detected. It is an invention of a method that is summarized in that the first displacement amount in the axial direction of the parallel light is measured from a corresponding interference fringe or its signal, and is also an invention of an apparatus.
- the first diffraction grating is disposed between the first diffraction grating and the transflective mirror and disposed on the optical axis of the parallel light.
- the parallel light that has passed through the grating is divided into zero-order light and ⁇ n-order light that travel in the same direction as the parallel light.
- the second diffraction grating is disposed so as to be movable on the same optical axis so as to face the second diffraction grating, and the same as the second diffraction grating.
- the zero-order light that has passed through the second diffraction grating is further divided into zero-order light and ⁇ n-order light traveling in the same direction.
- diffracted light along the optical axis of the diffracted light of a predetermined order by the second diffraction grating is received by the second optical sensor. To detect the amount of light.
- a method of measuring the second displacement amount in the axial direction of the parallel light from the interference fringes corresponding to the movement amount of the third diffraction grating with respect to the second diffraction grating or the progress thereof is an invention and an invention of the device.
- the present invention it is not affected by the tilt accuracy of the diffraction grating, has little influence on the positional deviation of the diffraction grating in the plane direction, can be configured simply and downsized, and can adjust the optical resolution.
- a displacement measuring method and a displacement measuring apparatus can be provided. Also, displacement detection at different positions can be performed with one light source.
- FIG. 1 is a schematic diagram showing the basic structure of the displacement measuring apparatus according to the first embodiment of the present invention.
- FIGS. 3C and 3D are diagrams showing the interference between the optical path 4 and the optical path 5.
- FIG. This figure is an explanatory view showing the qualitative operation principle of displacement measurement by the wire elongation amount detection unit.
- These drawings are explanatory views showing quantitative operation principles of displacement measurement by the wire elongation amount detection unit.
- This figure is an explanatory diagram showing the qualitative operation principle of displacement measurement by the wire movement amount detection unit of the first embodiment.
- FIG. 1 is a diagram showing the quantitative operation principle of displacement measurement by the wire movement amount detector, and (B-1) to (B-3) are images of interference fringes detected by the optical sensor.
- FIG. This figure is a diagram showing the overall configuration of an electrically assisted bicycle to which the displacement measuring device of this embodiment is applied.
- These drawings (A) to (C) are schematic views showing the brake mechanism of the electrically assisted bicycle.
- These drawings (A) to ⁇ (C) are diagrams showing the braking operation of the electrically assisted bicycle and the operation of the displacement measuring device.
- This figure is a diagram showing a specific example of the displacement measuring unit of the present embodiment.
- FIG. 4D is a diagram showing a signal waveform of output 1 from the photodetection circuit
- FIG. 4D is a block diagram showing an outline of a processing procedure of output 1 from the photodetection circuit.
- FIG. 7 is a diagram showing a second embodiment of the present invention, in which (A) is a diagram showing a basic structure, and (B) is a diagram showing a configuration of a photodetection circuit.
- (A) and (B) in these figures are diagrams showing signal waveforms of outputs A and B from the photodetection circuit of the second embodiment, and (C) is a signal waveform showing calculation results of the outputs A and B. is there.
- (A) in these figures is a diagram showing the relationship between the brake lever operation amount and the braking force in the electrically assisted vehicle.
- (B) is an explanatory view when the brake operating point changes in the relationship between the brake lever operation amount and the braking force.
- Example 1 of the present invention is an example in which the displacement measurement of the present invention is applied to the measurement of the extension amount and the movement amount of a brake wire of an electrically assisted bicycle.
- FIG. 1 is a schematic diagram showing the basic structure of this embodiment
- FIG. 7 is a diagram showing the overall configuration of the electrically assisted bicycle
- FIG. 8 is a diagram showing an outline of the brake mechanism of the electrically assisted bicycle. As shown in FIG.
- the displacement measuring apparatus 10 of the present embodiment includes a laser light source 12 such as a laser diode, a collimator lens 14 that converts the laser light 13 from the laser light source 12 into parallel light 15 that travels straight, and the parallel.
- the components other than the total reflection mirror 24 are configured to be movable integrally as a displacement measuring unit 70, for example, as shown in FIG. On the other hand, as shown in FIGS.
- the electrically assisted bicycle 50 includes a handle 52, a brake lever 54, a brake wire 56 covered with a tube 58, a brake pad 60, and the like, a controller 64, a motor. 66, a battery 68, and the like.
- the displacement measuring unit 70 is provided in the vicinity of the brake lever 54 of the electrically assisted bicycle 50, for example, as shown in FIG.
- the brake mechanism has a known configuration in which tension is applied to the brake wire 56 and the brake pad 60 is pressed against the rim 62 by operating the brake lever 54.
- the brake wire 56 moves as shown in FIG. 8B, and the brake pad 60 contacts the rim 62 and is braked by the mechanical brake.
- the brake wire 56 extends.
- the extension amount of the brake wire 56 shown in FIG. 8C is detected by a wire extension amount detection unit comprising the diffraction grating 18, the third diffraction grating 20, and the optical sensor 26 (second optical sensor). The brake operation force corresponding to the amount is measured.
- the wire movement amount detection unit comprising the laser light source 12, the collimator lens 14, the first diffraction grating 16, the semi-transmission semi-reflection mirror 22, the total reflection mirror 24, and the optical sensor 28 (first optical sensor).
- the movement amount of the brake wire 56 shown in FIG. 8B is detected, and the brake operation amount is measured.
- the extension amount and the movement amount of the brake wire are measured simultaneously (or in time series) using one light source, so that FIG.
- the mechanical brake operating points P1 and P2 shown in FIG. 5 are directly detected to maximize the regeneration in the idle section and increase the efficiency of regenerative charging.
- ⁇ Wire elongation amount detection unit The wire elongation amount detection unit of the two displacement detection units described above will be described first.
- the parallel light 15 that has passed through the first to third diffraction gratings 16 to 20 actually includes zero-order light (zero-order diffracted light) that travels in the same direction as the parallel light 15 and the zero-order light.
- the light travels by being divided into ⁇ n-order light (or expressed as ⁇ n-order diffracted light, where n is a natural number of 1 or more) having a diffraction angle.
- the zero-order light traveling in the same direction as the parallel light 15 after passing through the first diffraction grating 16, the second diffraction grating 18, and the third diffraction grating 20 is gathered and travels straightly 30. It expresses.
- Fig. 2 (A) is a diagram showing the basic structure of the wire elongation detection unit.
- (B-1) and (B-2) are diagrams showing the optical path 4 and the optical path 5, respectively.
- (C) and (D) are diagrams showing how the optical paths 4 and 5 interfere.
- the second diffraction grating 18 divides the straight light 30 that has passed through the first diffraction grating 16 into a straight light 30 and a diffracted light 32 and travels.
- the third diffraction grating 20 has the same grating pitch P as the second diffraction grating 18, faces the second diffraction grating 18, and is on the optical axis of the straight light 30.
- the linearly traveling light 30 that has passed through the second diffraction grating 18 is further divided into the linearly traveling light 30 and the diffracted light 34 so as to travel relative to each other.
- the optical sensor 26 a photodiode or the like is used. More specifically, the diffracted light 32 is the same as the zero-order light of the first diffraction grating 16 and the first-order light of the second diffraction grating 18 after passing through the third diffraction grating 20. Zero-order light traveling in the direction.
- the first order light passing through the third diffraction grating 20 is the diffracted light 34.
- the primary light is used.
- the displacement amount described below may be measured using other predetermined orders of diffracted light.
- the second diffraction grating 18 and the third diffraction grating 20 have a large number of grooves 18A and 20A formed at the same predetermined pitch (grating pitch P in FIG. 1A), and two diffraction sheets
- the diffraction direction of the grating is set to be the same.
- the optical sensor 26 receives only the diffracted light along the optical axis of the diffracted light 32 by the second diffraction grating 18, including the diffracted light 34 diffracted by the third diffraction grating 20, and the light quantity of the interference light 36. Is detected. From the interference fringes corresponding to the relative movement amount (displacement amount X shown in FIG.
- the axial direction here refers to a direction orthogonal to the principal surfaces of the second diffraction grating 18 and the third diffraction grating 20.
- FIG. 2B-1 shows a state in which the optical path L4 is diffracted by the second diffraction grating 18, and FIG. 2B-2 shows that the optical path L5 is the third diffraction grating 20.
- the state of diffraction is shown.
- the optical path L4 shown in FIG. 2 (B-1) travels straight through the first diffraction grating 16 (0th-order light), and diffracted light through the second diffraction grating 18 (in this embodiment). In this case, only the diffracted light 32 (0th order light ⁇ first order light ⁇ 0th order light) traveling in the same direction after passing through the third diffraction grating 20 is shown.
- FIG. 2B-2 passes straight through the first diffraction grating 16 and the second diffraction grating 18 (0th-order light), and passes through the light incident on the third diffraction grating 20.
- first order diffracted light 34 (0th order light ⁇ 0th order light ⁇ first order light) traveling in the same direction as the diffracted light 32 shown in FIG. 2 (B-1) is shown.
- FIG. 2C shows a state in which these optical paths L4 and L5 are overlapped.
- the amount of displacement can be measured by measuring the amount of interference light 36 before and after the movement of the third diffraction grating 20 relative to the second diffraction grating 18, but FIG.
- the optical paths L4 and L5 share the same optical path, and further, the transmission diffraction light of the diffraction grating makes use of characteristics that are not easily affected by the tilt of the diffraction grating. For this reason, even if the third diffraction grating 20 vibrates due to tilt (vibration influence) or the like, the interference fringes are not adversely affected.
- the splitter which is the largest element in the above-described optical system of the background art, can be reduced, the apparatus can be reduced in size and cost.
- the operation principle of the wire elongation amount detection unit will be qualitatively described with reference to FIG. First, among the laser beams that have passed through the collimator lens 14 from the laser light source 12 and become parallel light 15 where the second diffraction grating 18 and the third diffraction grating 20 are opposed to each other at a predetermined interval.
- the straight light 30 that has passed through the first diffraction grating 16 is incident on the second diffraction grating 18.
- the incident light is divided into two light beams diffracted by the second diffraction grating 18 (path 1 and path 3) and straight light (straight light 30 in FIG. 2A), and is incident on the third diffraction grating 20.
- the straight traveling light is further diffracted by the third diffraction grating 20 (path 2), and the fixed side diffracted light and the movable side diffracted light interfere with each other, and the light sensor 26 detects the amount of light.
- the third diffraction grating 20 moves in the axial direction from the position shown by the solid line in FIG. 3 to the position shown by the dotted line
- the position of the diffracted light on the path 2 on the optical axis to be diffracted moves from the position P1 to P2.
- the interference light 1 Before the movement, the interference light 1 has no phase difference due to the interference of the diffracted light on the path 1 and the path 2, but after the movement, the interference light 1 becomes the interference light 2 of the diffracted light on the path 2 and the path 3. Will occur. Therefore, the interference fringes proportional to the amount of movement repeat light and dark, and the amount of movement can be detected.
- the operation principle of the wire elongation amount detection unit will be quantitatively described with reference to FIG.
- the path length of the path 2 changes by ⁇ d with respect to the movement of ⁇ d of the third diffraction grating 20, but the path length ⁇ d2 of the path 3 is expressed by the following equation (2). ).
- ⁇ d2 ( ⁇ d / cos ( ⁇ )) (2)
- the path difference ⁇ after the movement is expressed by the following equation (3).
- the generation interval of interference fringes depends on the diffraction angle ⁇ , and the diffraction angle
- the detection range can be expanded by ⁇ . Further, since the diffraction angle ⁇ is determined by the grating pitch P and the wavelength, it can be said that the generation interval of the interference fringes depends on the grating pitch P.
- the second diffraction grating 18 and the third diffraction grating 20 By miniaturizing the grating pitch P, it becomes possible to detect the displacement amount on the order of one wavelength or less. Thus, by expanding the detection range, it is possible to detect a linear portion and to detect a wide range of displacement from the sub- ⁇ m region to about 20 mm.
- the wire movement amount detection unit is constituted by the laser light source 12, the collimator lens 14, the first diffraction grating 16, the semi-transmissive / semi-reflective mirror 22, the total reflection mirror 24, and the optical sensor 28 (first optical sensor). .
- the first diffraction grating 16 is disposed on the optical axis of the parallel light 15 and has a 0-order light (0th-order diffracted light) that travels straight through the incident light and has a diffraction angle with respect to the 0th-order light.
- the transflective mirror 22 is arranged on the optical axis of the straight traveling light 30 so as to face the first diffraction grating 16 with the second and third diffraction gratings 18 and 20 sandwiched therebetween.
- An optical path L2 first return light Lrev1 that reflects a part of the straight light (optical path L1) that has passed through the first diffraction grating 16 and returns to the first diffraction grating 16; This is divided into the remaining straight light path L3.
- the total reflection mirror 24 is disposed so that its position can be changed relative to the transflective mirror 22 on the same optical axis, and the straight traveling light 30 (
- the second return light Lrev2 is reflected by the optical path L3) and returns to the first diffraction grating 16 after passing through the semi-transmissive / semi-reflective mirror 22.
- the second diffraction grating 18 and the third diffraction grating 20 described above are disposed between the first diffraction grating 16 and the semi-transmissive / semi-reflective mirror 22. For this reason, the optical path L1 shown in FIG.
- the first return light Lrev1 optical path L2
- the second return light L rev2 are both the 0th-order diffracted light of the third diffraction grating 20 and the second diffraction grating 18, and the first diffraction grating. 16 first-order diffracted lights, which are applied to the optical sensor 28.
- the optical sensor 28 receives the diffracted light of the first and second return lights Lrev1 and L rev2 and detects the amount of light, and the relative movement amount of the total reflection mirror 24 with respect to the transflective mirror 22 (
- the displacement Y between the transflective mirror 22 and the total reflection mirror 24 can be measured from the interference fringes proportional to the displacement Y in FIG.
- a photodiode or the like is used as the optical sensor 28.
- the first-order diffracted light from the first diffraction grating 16 is received by the optical sensor 28.
- the displacement Y may be measured.
- FIG. 6A is an explanatory view showing the operation of the wire movement amount detection unit
- FIGS. 6B-1 to 6B-3 are views showing images of interference fringes detected by the optical sensor 28.
- FIG. 6A shows a displacement measurement in which components other than the total reflection mirror 24 among the components constituting the displacement measurement apparatus 10 of the present embodiment can move relative to the total reflection mirror 24.
- a state in which the unit 70 is integrated is shown. As shown in FIG.
- FIG. 9 is a diagram showing the braking operation of the electrically assisted bicycle and the action of the displacement measuring device
- FIG. 10 is a diagram showing a specific example of the displacement measuring unit.
- FIG. 11A is a diagram showing a circuit configuration of a laser light source in the specific example.
- FIG. 11B is a diagram showing the configuration of the light detection circuit in the wire elongation amount detection unit;
- FIG. 11C shows a signal waveform of output 1 from the photodetection circuit.
- FIG. 11D is a block diagram showing an outline of the processing procedure of output 1 from the photodetection circuit.
- FIG. 11A is a diagram showing a circuit configuration of a laser light source in the specific example.
- FIG. 11B is a diagram showing the configuration of the light detection circuit in the wire elongation amount detection unit;
- FIG. 11C shows a signal waveform of output 1 from the photodetection circuit.
- FIG. 11D is a block diagram showing an outline of the processing procedure of output
- FIG. 12A is a diagram showing the dark spot count behavior on the optical sensor 28 of the wire movement amount detection unit in the play section in the specific example.
- FIG. 12B is a diagram showing the light amount behavior on the optical sensor 26 of the wire extension amount detection unit in the mechanical brake section.
- FIG. 13A is a diagram showing the relationship between the brake lever operation amount and the wire tension.
- FIG. 13B is a diagram showing the relationship between the brake lever operation amount and the braking force.
- the electrically assisted bicycle 50 and its brake mechanism are as described above.
- the displacement measuring unit 70 is provided in a housing 11 fixed to a brake handle (bicycle handle) 52 in the vicinity of the brake lever 54 so as to be movable along a brake wire 56 by a guide shaft (not shown). Yes.
- the total reflection mirror 24 is fixed to one side surface 11 ⁇ / b> B side of the housing 11.
- the brake wire 56 passes between the side surface 11A and the side surface 11B of the housing 11.
- the displacement measuring unit 70 includes a transparent resin molded body 72, a laser light source 12, a collimator lens 14, a first diffraction grating 16 to a third diffraction grating 20, a transflective mirror 22,
- the optical sensors 26 and 28 are accommodated.
- a through-hole 74 through which the brake wire 56 passes is provided on the upper side of the transparent resin molded body 72 from the side surface 72A to the side surface 72B.
- the brake wire 56 is transparent resin molded at two locations by screws 76A and 76B. Fixed to body 72
- the laser light source 12 is fitted in a circular concave space (not shown) provided on the side surface 72A, and the laser light source 12 is connected to a laser driving circuit 78 provided outside the transparent resin molded body 72.
- the collimator lens 14 is disposed in a space 80A penetrating the transparent resin molded body 72 in the thickness direction, and the periphery is fixed with an adhesive or the like.
- the space 80A may be a space formed by cutting.
- the first diffraction grating 16 is arranged in the space 80B
- the second diffraction grating 18 and the third diffraction grating 20 are arranged in the space 80C, and the back surfaces thereof are made of a transparent adhesive or the like. It is fixed.
- the transflective mirror 22 is disposed in the space 80D
- the optical sensor 26 is disposed in the space 80E
- the optical sensor 28 is disposed in the space 80F.
- the transparent resin molded body 72 includes a slit 86A provided above the second diffraction grating 18 side, and a space above the third diffraction grating 20 side, in addition to a space (not shown) serving as a light path.
- a provided slit 86B is formed.
- the slit 86A is continuous with the space 80C.
- These slits 86A and 86B are springs so that the transparent resin molded body 72 extends and contracts in the axial direction together with the brake wire 56 at the boundary between the second diffraction grating 18 and the third diffraction grating 20 (see arrow F10 in FIG. 10). It is for imparting sex.
- the third diffraction grating 20 can move in parallel to the second diffraction grating 18, and an accurate movement amount is measured. be able to.
- the transparent resin molding 72 shall not bend in the thickness direction.
- the optical sensors 26 and 28 are connected to I / V conversion circuits 82 and 84 provided outside the transparent resin molded body 72, respectively.
- the transparent resin molding 72 for example, a transparent resin such as acrylic or polycarbonate having a 15 mm square and a thickness of about 5 mm was used. Further, a laser diode LD having a wavelength of 650 nm and an output of 5 mW was used as the laser light source 12, and the optical axis was set in the direction parallel to the grooves 18A and 20A of the diffraction gratings 18 and 20 with the smaller emission angle.
- the collimator lens 14 has an NA of 0.65, an effective diameter of 4 mm, and a width of 1.5 mm, and the first diffraction grating 16 has a grating pitch of 0.72 ⁇ m and a grating groove depth of 216 nm. did.
- a grating having a grating pitch P of 1.6 ⁇ m, grooves 16A and 18A having a depth of 150 nm, and a groove width of 0.5 ⁇ m was used.
- the diffraction directions of the second diffraction grating 18 and the third diffraction grating 20 are set in the same direction, and the distance between the diffraction gratings is set within the coherence length (about 1 mm) of the laser light source 12. This is because if the distance between the two diffraction gratings 18 and 20 is increased, the coherence of the light is deteriorated, the brightness of the interference cannot be obtained, and the diameter of the incident light beam needs to be increased. Further, as the semi-transmissive and semi-reflective mirror 22, a mirror having a transmittance of 50% and a reflectance of 50% was used, and as the total reflection mirror 24, a mirror having a reflectance of 100% was used.
- the light sensor 26 that is a light receiving element has a size that allows a part of the interference light 36 to be captured, and the other light sensor 28 has a part of the interference light of the first return light Lrev1 and the second return light Lrev2. A size that can be taken in was used.
- the elongation (displacement X) can be detected.
- the displacement measuring unit 70 itself moves together with the brake wire 56 as shown in FIG. 9 (B), and the total reflection mirror 24 and the semi-transmissive / semi-reflective are compared with those before the brake lever operation start shown in FIG. 9 (A). Since the distance between the mirrors 22 changes, the amount of movement (displacement Y) of the brake wire 56 can be detected.
- FIG. 11A shows a circuit configuration of the laser light source 12.
- a laser diode LD is used as the laser light source 12, and the laser diode LD is connected to a power source via a current limiting resistor R1.
- FIG. 11B shows a light detection circuit of the wire elongation amount detection unit of this example.
- a photodiode PD is used as the optical sensor 26.
- a current is generated according to the amount of received interference light, which is input to the negative input terminal of the operational amplifier OP, converted into a voltage, and output as output 1. That is, the operational amplifier OP corresponds to the I / V conversion circuit 82.
- the operational amplifier OP corresponds to the I / V conversion circuit 82.
- resistors R2 and R3 are provided.
- One resistor R2 determines the operating point (output voltage when the optical signal is 0) of the operational amplifier OP, and the resistor R3 whose both ends are connected to the operational amplifier OP is the optical sensor 26 (photodiode PD).
- FIG. 11C shows the waveform of output 1 output from the operational amplifier OP.
- the horizontal axis indicates the displacement X
- the vertical axis indicates the detection voltage.
- the detection characteristic is a sin wave shape, so that the displacement X can be obtained from the intensity of the electric signal.
- the output 1 is amplified by an amplifier circuit 90 and binarized slice is performed by a slicer 92.
- the clock counter 94 counts the clock
- the arithmetic unit 96 calculates the count number ⁇ the wavelength ⁇ of the light source by a predetermined calculation firmware to obtain the displacement X. Note that the sine wave of the detection characteristic shown in FIG.
- 11C can use 100% of the entire amplitude, but assuming a shift in the detection range due to a shift in the origin position adjustment of the optical sensor 26, a margin of 20% And a range of about ⁇ 80% of the amplitude is preferably used.
- the light detection circuit, the output waveform, and the calculation processing procedure of the light sensor 28 of the wire movement amount detection unit are the same as those of the light sensor 26.
- the displacement measuring unit 70 configured as described above, when the driver starts pulling the brake lever 54 from the state shown in FIGS. 8A and 9A, as shown in FIG. As shown in FIG. 9B, the displacement measuring unit 70 moves together with the brake wire 56 as shown in FIG. Then, from the relative displacement Y of the total reflection mirror 24 with respect to the transflective mirror 22, the amount of movement of the brake wire 56, that is, the amount of operation of the brake lever 54 corresponding to the amount of movement can be measured in mm order. it can. Further, the displacement measuring unit 70 detects the displacement of the brake wire 56 by operating the brake lever 54 shown in FIG. 8C from the change in the distance I between the second diffraction grating 18 and the third diffraction grating 20 shown in FIG.
- the elongation (displacement X) is detected on the order of ⁇ m, and the transition from the idle section of the electrically assisted bicycle 50 to the mechanical brake section is detected.
- the controller 64 of the electrically assisted bicycle 50 determines an optimum regenerative braking force according to the output from the displacement measuring unit 70, and controls the motor 66 so that the optimum regenerative brake control works. Then, the motor 66 functions as a generator and charges the battery 68 with the generated electricity.
- the controller 64 detects the battery performance and status of the battery 68.
- the electrically assisted bicycle 50 equipped with such a displacement measuring device 10 it is possible to detect minute deformation due to the tension of the brake wire 56, and therefore, in the portion of play of the conventional brake shown in FIG. A regenerative brake can be applied to charge the battery 68 using the 66 as a generator. Furthermore, as shown in FIG. 13B, the regenerative brake is controlled and operated in parallel during mechanical braking (the region where the brake pad contacts the tire), so that the utility can be enhanced. According to the present embodiment, when the mechanical brake operating point is shifted due to the brake adjustment by the driver, for example, even if the brake operating point P1 is shifted from P1 to P2 in FIG. Since it can be sensed, high regeneration efficiency can always be maintained.
- FIG. 12 (A) shows the dark spot counting behavior on the optical sensor 28 in the play section.
- the horizontal axis represents the moving distance (displacement Y) (nm) of the displacement measuring unit 70
- the vertical axis represents the dark spot count.
- the amount of movement (displacement Y) in the order of ⁇ m and mm can be sensed by counting the dark spots on the optical sensor 28.
- the horizontal axis represents the movement amount (displacement X) of the wire elongation amount detection unit
- the vertical axis represents the light amount, and shows the change in the light amount on the optical sensor 26 in the mechanical brake section.
- a first diffraction grating 16, a semi-transmission semi-reflection mirror 22, and a total reflection mirror 24 are arranged in this order on the optical axis of parallel straight light from the laser light source 12, and the straight light is converted into the first light.
- the first diffraction grating 16 is allowed to pass through to the semi-transmissive / semi-reflective mirror 22, and is divided into a straight light 30 traveling to the total reflection mirror 24 and a first return light Lrev 1 returning to the first diffraction grating 16.
- the light that has reached the total reflection mirror 24 is reflected, passes through the semi-transmissive / semi-reflective mirror 22, and becomes second return light Lrev 2 that returns to the first diffraction grating 16. Since the diffracted light of a predetermined order by the first diffraction grating 16 of the first return light Lrev1 and the second return light Lrev2 is received by the optical sensor 28, the amount of light is detected. The movement amount (displacement amount) of the brake wire 56 corresponding to the relative position change between the total reflection mirrors 24 can be detected. (2) Since the displacement amount is detected by the optical path sharing method, the tilt effect is canceled and erroneous detection due to disturbance (vibration) can be prevented.
- the measurement range can be expanded to one wavelength or more, and a displacement from one wavelength or less to one wavelength or more can be continuously measured, and the optical resolution can be adjusted by the pitch of the diffraction grating.
- the second diffraction grating 18 and the third diffraction grating 20 having the same grating pitch P are relatively placed on the same axis between the first diffraction grating 16 and the transflective mirror 22.
- the diffracted light along the optical axis of the diffracted light of a predetermined order by the second diffraction grating 18 is arranged as an optical sensor. The light is received at 26 and the amount of light is detected.
- the amount of displacement corresponding to the amount of movement in the axial direction is detected from the interference fringes corresponding to the amount of movement (displacement X) of the third diffraction grating 20 relative to the second diffraction grating 18 or its signal, and the brake wire 56
- the mechanical brake start point can be directly detected from the measurement results of these two displacement amounts, the efficiency of regenerative charging can be improved.
- Embodiment 2 of the present invention will be described with reference to FIGS.
- symbol shall be used for the component which is the same as that of Example 1 mentioned above, or respond
- the present embodiment is a diagram showing a modification of the wire elongation amount detection unit in the above-described embodiment
- FIG. 14A is a diagram showing the basic structure of the wire elongation amount detection unit of this embodiment
- FIG. B) is a diagram showing a configuration of a photodetection circuit.
- 14A and 14B are diagrams showing signal waveforms of outputs A and B from the photodetection circuit
- FIG. 14C is a signal waveform showing calculation results of the outputs A and B.
- the detection position does not change even if the light amount of the laser light source is moved.
- the displacement measuring device 100 is provided with a phase plate 104 on the third diffraction grating 102 to form a step, and a two-part optical sensor instead of the optical sensor 26 of the first embodiment. Except for using 106, the configuration is the same as in the first embodiment.
- the phase plate 104 has a thickness d of about 3 ⁇ m, for example, and is formed of the same material as that of the third diffraction grating 102 by a step processing or a molding die.
- the straight light that has passed through the collimator lens 14 from the laser light source 12 and becomes parallel light passes through the first diffraction grating 16 and is divided into diffracted light and straight light by the second diffraction grating 18 on the fixed side.
- the straight traveling light enters the movable third diffraction grating 102 and is diffracted by the surface where there is no phase plate 104 (thick line in FIG. 14A).
- the phase plate 104 is also diffracted by the surface of the third diffraction grating 102 through the phase plate 104 (one-dot chain line in FIG. 14A).
- the two-split photosensor 106 uses a two-split photodiode composed of two photodiodes PD1 and PD2, as shown in FIG. 14B.
- the depth d of the step is expressed by the following formula (4), where n is the bending rate of the substrate.
- d ⁇ / (1 / cos ( ⁇ ) ⁇ 1) * (n ⁇ 1) (4)
- the light that has passed through the third 102 provided with the phase plate 104 whose thickness (step depth d) has been determined as described above is incident on each of the two-split optical sensors 106.
- a current is generated according to the amount of interference light received by one photodiode PD1 of the two-split optical sensor 106, and is input to the negative input terminal of the operational amplifier OP1. And output as an output signal A.
- the output signal A is output from the operational amplifier OP1 as a sine wave as shown in FIG.
- the interference light is received by the other photodiode PD2, a current is generated according to the amount of light, input to the negative input terminal of the operational amplifier OP2, converted into a voltage, and output as an output signal B.
- the output signal B is output as a sine wave that is 90 degrees out of phase with the output signal A with respect to the displacement X, that is, as a cosine wave as shown in FIG.
- the operation of the resistors R4 to R7 in the figure is the same as the resistors R2 and R3 of the first embodiment described above.
- TanX is obtained. Therefore, as shown in the following equation (5), the result of dividing the two signals is Atan, that is, Tan ⁇ 1 is calculated. A displacement X is determined. Tan -1 (A / B) Such calculation is performed by inputting the output signals A and B to the calculation device 108 shown in FIG. 14B and performing digital processing by AD conversion. FIG. 15 (C) shows the result. Also in this case, it is convenient to set the detection range to ⁇ 80% of the amplitude, as in the case of the detection method of the first embodiment described above.
- the phase plate 104 is provided with a step of depth d in the movable third diffraction grating 102 and the interference light is received by the two-part optical sensor 106.
- the characteristic can be linearized by the shift.
- the transparent resin molded body 72 is made springy by the slit 86A provided on the second diffraction grating 18 side and the slit 86B provided on the third diffraction grating 20 side. It was decided to grant.
- the design can be appropriately changed within a range in which a similar effect can be obtained, for example, by providing a slit (not shown) in the vicinity of an intermediate portion between the two diffraction gratings 18 and 20 to provide springiness.
- the displacement measurement is performed using the 0th-order diffracted light and the 1st-order diffracted light.
- diffracted light of any order other than the 1st-order diffracted light for example, 2 Secondary light etc.
- the laser light source 12 is used as the light source.
- an inexpensive LED (low coherence) light source may be used.
- the optical path difference ⁇ 0.36 ⁇ m. That is, the difference between two interfering paths is smaller than the coherence distance (spatial coherence length) of 10 ⁇ m, so that the measurement is within the measurement limit. Note that the diffraction angle ⁇ can be arbitrarily handled by changing the grating pitch P as described above.
- the brake force is detected by measuring the amount of displacement of the electrically assisted bicycle 50 due to the elongation (tension) of the brake wire, but the brake wire 56 is supported.
- the displacement measuring unit 70 may be sandwiched between the tubes 58, and the braking force may be detected from the stress in the length direction of the brake wire 56 to the displacement measuring unit 70.
- a first displacement amount detection unit (wire movement amount detection unit) including the first diffraction grating 16, the transflective mirror 22, the total reflection mirror 24, and the optical sensor 28,
- the second displacement detector (wire elongation detector) including the second diffraction grating 18, the third diffraction grating 20, and the optical sensor 26 is provided, this is only an example, and the second displacement is detected.
- the detection unit may be provided as necessary.
- a device that detects both the amount of extension and the amount of movement of the brake wire 56 in order to efficiently apply the regenerative brake in the electrically assisted bicycle 50 has been described as a specific example.
- the present invention can be applied to general measurement of a small displacement, calibration of a measuring device of a minute length, and the like, such as strain measurement of a mechanical system.
- the zoom and focus functions of a camera are currently performing position detection with a mechanical SW array, but by applying the present invention, it becomes possible to meet the demands for downsizing and flexureless position detection devices.
- linear detection can be performed with respect to movement beyond the wavelength, so that application to an optical microphone or the like is also possible.
- it is possible to detect minute vibrations and the like, and application to vibration sensors is also possible.
- the relative displacement amount of the total reflection mirror in the direction of the parallel optical axis can be measured over a wide range from sub- ⁇ m to around 20 mm, so that the displacement measuring device for measuring minute displacements It can be applied to any use.
- accurate measurement can be performed without correcting temperature and environment, it is possible to measure distortion and torsion of a mechanical system.
- it is suitable for the use which detects the movement amount or elongation amount of the brake wire of an electrically assisted bicycle.
- the displacement amount of the total reflection mirror in the axial direction of the parallel light can be measured, and at the same time, the total reflection mirror of the total reflection mirror can be measured with one light source.
- Displacement measurement between a pair of diffraction gratings can be performed simultaneously or in time series at a position different from the amount of displacement and a different detection sensitivity. For this reason, when there are a plurality of detection targets for displacement measurement, for example, it is suitable as a sensor for the amount of extension and movement of the brake wire of the electrically assisted bicycle.
- Displacement measuring apparatus 11 Housing 11A, 11B: Side surface 12: Laser light source 13: Laser light 14: Collimator lens 15: Parallel light 16: First diffraction grating 18: Second diffraction grating 18A, 18B: Groove 20 : Third diffraction grating 22: Transflective mirror 26: Total reflection mirror 26 and 28: Optical sensor 30: Straight light 32 and 34: Diffracted light 36: Interference light 50: Electric assist bicycle 52: Handle 54: Brake lever 56: Brake wire 58: Tube 60: Brake pad 62: Rim 64: Controller 66: Motor 68: Battery 70: Displacement measurement unit 72: Transparent resin molding 72A, 72B: Side surface 74: Through hole 76A, 76B: Screw 78: Laser drive circuit 80A to 80F: Space 80F: Passage 82: I / V conversion circuit 84: Screw 86A, 86B: Slit 90: Amplifying circuit 92: Slicer 94: Clock counter 96:
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Abstract
Description
(A)に示す遊び区間におけるブレーキワイヤの移動量に対応するブレーキレバーの操作量を測定することが必要である。次に、ブレーキパッドが車輪の回転を妨げようとして制動をかけ始めた時点(機械ブレーキ動作点P1)をブレーキワイヤの伸びで感知することが必要である。これは、制動がかかる前後において、回生制動と機械制動との間で制御がスムースに行われないと、搭乗者を含むドライバが急ブレーキをかけたような違和感を覚えたり、ブレーキ力の不足感を感じたりするためである。
(B)に示すように干渉縞216として観察される。このときの1波長以下の変位は、この明暗の傾斜の電圧値を読み取ることで検出できる。また、1波長以上の変位に対しては、この明暗(干渉縞)が何回発生したかを発生することで変位を計測できる。すなわち、ミラーの移動に対して往復で2倍の行路差が発生することから、図17(C)に示すように、変位(移動距離)=1波長×明暗数×2により算出できる(なお、どちらの方向に移動したかを検出する手段は別途必要となる)。このような光干渉を利用した技術としては、例えば、下記特許文献1に示す位相差検出器及び位相差検出方法がある。
(1)計測範囲が光の波長で決められてしまい、光の波長以上の範囲を計測しようとすると、通過した光の波長を数えるようになり、光の波長以下の分解能が得られない。
(2)光学部品の位置精度が非常に厳しく、角度ずれ(0.01度オーダ),位置ずれ(サブμmオーダ)により計測ができなくなることがある。従って、温度変化,湿度変化,外部振動,経時といった使用環境により誤検出を防止するための対策が必要となる。
(3)コリメータレンズ,ミラーの組み合わせ,スプリッタが必須であるため、小型化が困難である。
(4)異なる検出感度・検出位置での変位(例えば、上述した電動アシスト自転車のブレーキワイヤの移動量と伸び量など)を、同時ないし時系列的に測定することができない。
まず、第1の観点の発明は、光源から発射された光をコリメータレンズにより平行光とし、この平行光を、その光軸上に配置された第1の回折格子を通過させる。つぎに、前記光軸上に前記第1の回折格子に対向して配置された半透過半反射ミラーまで進行させる。前記半透過半反射ミラーにより、前記平行光の一部を反射させて前記第1の回折格子まで戻る第1の戻り光とし、前記平行光の残りを、前記半透過半反射ミラーに対して同一光軸上で相対的に位置変化可能に配置された全反射ミラーまで進行させる。前記第1の戻り光を、前記第1の回折格子により、前記第1の戻り光と同方向に進行する0次光と、この0次光に対して回折角を有する±n次光(nは1以上の自然数)と、に分けて進行させる。この±n次光のうちの所定次数の回折光を、第1の光センサで受光して光量検出するとともに、前記半透過半反射ミラーを通過させる。前記全反射ミラーまで進行した平行光を、該全反射ミラーで反射させて、前記半透過半反射ミラーを通過して前記第1の回折格子まで戻る第2の戻り光とし、前記第1の回折格子に達した第2の戻り光を、前記第1の回折格子により、0次光と±n次光とに分けて進行させる。つづいて、該±n次光のうち、前記所定次数の回折光を、前記第1の回折格子で受光して光量検出し、前半透過半反射ミラーに対する前記全反射ミラーの相対的な移動量に対応する干渉縞もしくはその信号から前記平行光の軸方向の第1の変位量を測定することを要旨とする方法の発明であり、また、装置の発明でもある。
なっている。前記ブレーキレバー54を引き始めた遊び区間では、図8(B)に示すように
ブレーキワイヤ56が移動し、ブレーキパット60がリム62に接触して機械ブレーキによる制動がかかっている状態では、図8(C)に示すように、ブレーキワイヤ56が伸びる。本実施例では、前記変位計測装置10のレーザ光源12,コリメータレンズ14,第2
の回折格子18,第3の回折格子20,光センサ26(第2の光センサ)からなるワイヤ伸び量検出部によって、図8(C)に示すブレーキワイヤ56の伸び量を検出し、該伸び量に対応するブレーキ操作力を計測する。
(B-1)及び(B-2)はそれぞれ光路4及び光路5を示す図,
(C)及び(D)は光路4及び5の干渉の様子を示す図である。前記ワイヤ伸び量検出部のうち、第2の回折格子18は、前記第1の回折格子16を通過した直進光30を、直進光30と回折光32に分けて進行させるものである。前記第3の回折格子20は、前記第2の回折格子18と同一の格子ピッチPを有しており、該第2の回折格子18と対向し、かつ、前記直進光30の光軸上で相対移動可能に配設されており、前記第2の回折格子18を通過した直進光30を、更に、直進光30と回折光34に分けて進行させるものである。前記光センサ26としては、フォトダイオードなどが利用される。前記回折光32は、より具体的には、第1の回折格子16の0次光、かつ、第2の回折格子18の1次光のうち、第3の回折格子20を経由した後も同方向に進行する0次光である。更に、前記第1の回折格子16,第2の回折格子18を経由した0次光(直進光30)のうち、第3の回折格子20を経由した1次光が、前記回折光34である。なお、本実施例では、1次光を利用することとしたが、他の所定次数の回折光を利用して、以下に説明する変位量の測定を行うようにしてもよい。
図2 (B-2)に示す光路L5は、第1の回折格子16及び第2の回折格子18を経由した後に直進して(0次光)、第3の回折格子20に入射した光のうち、前記図2(B-1)に示す回折光32と同方向に進行する1次回折光34(0次光→0次光→1次光)のみが示されている。また、図2(C)には、これら光路L4及びL5を重ね合わせた様子が示されている。本発明では、後述するように、第2の回折格子18に対する第3の回折格子20の移動前と移動後における干渉光36の光量測定によって変位量の測定が可能となるが、図2(D)に示すように、光路L4,L5が同じ光路を共有し、更に回折格子の透過回折光が回折格子の傾きの影響を受け難い特性を利用している。このため、チルト(振動影響)などで第3の回折格子20が振動したとしても、干渉縞に悪影響を与えることがない。また、上述した背景技術の光学系で最も大きな素子であるスプリッタの削減が可能であるため、装置の小型化及び低コスト化が可能となる。
sinφ + sinθ = λ/P ‥‥‥‥ (1)
Δd2 = (Δd/ cos(φ))‥‥‥‥ (2)
ここで、移動前は、可動側の行路2と固定側の行路1は行路差がないとすると、移動後の行路差Δは、下記の式(3)で表わされる。
Δ = Δd2 ― Δd
= Δd(1/cos(φ)-1)‥‥‥‥ (3)
回折角φ= ASIN(0.65/1.6)=24.0°
となる。そして、前記基板を回折格子に用いたときの回折角φは24度となることから、移動量Δdに対する行路2と行路3の行路差Δは、上記数式3から、
Δ=Δd(1/ cos(24°)-1)=0.094
となり、約11波長の移動で1回の干渉の明暗が発生することとなる。
sin波状となり、Gが大きくなると、検出範囲は、波長λ×倍率Gとなり、
sin波拡大によってリニア検出が可能となる。
Y=λ/4×(2n+1)(nは任意の整数)
となったときに、光センサ28上の明暗は「明」から「暗」に変化する(図6(B-3)の枠F3内参照)。また、「明」から「暗」に変化する途中段階である
0<Y<λ/4×(2n+1)
のとき、光センサ28上の干渉縞は、明暗の中間状態となる(図6(B-2)の枠F2内参照)。なお、前記図6(B-1)~(B-3)において、干渉縞全体を取り込むと、干渉縞は変化しても、光量の変化が微小になり検出感度が低下するため、本実施例では、同図に枠F1~F3で示す一部領域を取り込むことにより、高い検出感度を得ることとしている。
図11(A)は、前記具体例におけるレーザ光源の回路構成を示す図,
図11(B)はワイヤ伸び量検出部における光検出回路の構成を示す図,
図11(C)は前記光検出回路からの出力1の信号波形を示す図,
図11(D)は前記光検出回路からの出力1の処理手順の概略を示すブロック図である。
図12(A)は、前記具体例における遊び区間でのワイヤ移動量検出部の光センサ28上の暗点カウント挙動を示す図,
図12(B)は機械ブレーキ区間でのワイヤ伸び量検出部の光センサ26上の光量挙動を示す図である。
図13(A)はブレーキレバー操作量とワイヤ張力の関係を示す図,
図13(B)はブレーキレバー操作量とブレーキ力の関係を示す図である。
なお、電動アシスト自転車50及びそのブレーキ機構については、上述した通りである。
なお、図11(B)に示す回路では、2つの抵抗R2及びR3が設けられている。一方の抵抗R2は、オペアンプOPの出力の動作点(光信号が0の時の出力電圧)を決定し、両端がオペアンプOPに接続されている抵抗R3は、光センサ26(フォトダイオードPD)の入射光量に対して出力電圧の利得を決定する抵抗であって、抵抗が大きいほど、同じ光量で出力電圧が大きくなる。
一方、前記機械ブレーキ区間では、ワイヤ伸び量検出部の光センサ26上の干渉縞にも変化が発生する。図12(B)は、横軸がワイヤ伸び量検出部の移動量(変位X),縦軸が光量であって、機械ブレーキ区間における光センサ26上の光量変化を示している。同図
(B)に示す光量変化から、上述した定量原理に基づいて、機械ブレーキ開始を感知することができる。
(1)レーザ光源12からの平行な直進光の光軸上に、第1の回折格子16,半透過半反射ミラー22,全反射ミラー24を順に配置し、そして、前記直進光を、前記第1の回折格子16を通過させて半透過半反射ミラー22まで進行させ、全反射ミラー24まで進行する直進光30と、第1の回折格子16まで戻る第1の戻り光Lrev1に分割する。全反射ミラー24まで達した光は、反射されて半透過半反射ミラー22を通過し、第1の回折格子16に戻る第2の戻り光Lrev2となる。前記第1の戻り光Lrev1と第2の戻り光Lrev2の第1の回折格子16による所定次数の回折光を光センサ28で受光して光量検出することとしたので、半透過半反射ミラー22と全反射ミラー24間の相対的な位置変化に対応するブレーキワイヤ56の移動量(変位量)を検出できる。
(2)前記変位量の検出が、光路共有方式であるため、チルト影響がキャンセルされ、外乱(振動)による誤検出を防止することができる。
(3)スプリッタを利用しないため、部品点数を削減して小型化・低コスト化を図ることができる。また、構成が簡単なため、位置ずれに対しても強い。
(4)計測範囲を1波長以上に広げ、1波長以下の変位から1波長以上の変位までを連続的に計測でき、回折格子のピッチにより光学分解能の調整が可能である。
d=λ/(1/ cos(φ)-1)*(n-1)‥‥‥‥ (4)
例えば、波長λを0.65μm,基板の屈曲率nを1.58として、前記数式4に代入すると、段差の深さdは、
d=λ/(1/cos(φ)-1)/(n-1)/4
=0.65/0.094/(1.58-1)*1/4→2.98μm
と決定される。
Tan-1(A/B)
このような演算は、出力信号A及びBを、図14(B)に示す演算装置108に入力し、AD変換によるデジタル処理によって行われる。図15(C)には、その結果が示されている。この場合も、振幅の±80%を検出範囲とすると好都合であることは、上述した実施例1の検出方式の場合と同様である。このように、実施例2によれば、位相板104によって可動側の第3の回折格子102に深さdの段差を設け、干渉光を2分割光センサ106で受光することとしたので、位相シフトにより特性をリニア化することができるという効果がある。
(1)前記実施例で示した形状,寸法,材質は一例であり、同様の効果を奏するものであれば、必要に応じて適宜変更してよい。例えば、前記実施例1の変位計測ユニット70では、第2の回折格子18側に設けたスリット86Aと、第3の回折格子20側に設けたスリット86Bにより、透明樹脂成型体72にバネ性を付与することとした。だが、これも一例であり、2つ回折格子18,20の中間部付近に図示しないスリットを設けてバネ性を付与するなど、同様の効果を奏する範囲内で、適宜設計変更可能である。
(2)前記実施例1では、0次回折光と1次回折光を利用して変位測定を行うこととしたが、これも一例であり、1次回折光以外の任意の次数の回折光(例えば、2次光など)を利用してもよい。
(5)前記実施例1では、第1の回折格子16,半透過半反射ミラー22,全反射ミラー24,光センサ28からなる第1の変位量検出部(ワイヤ移動量検出部)と、第2の回折格子18,第3の回折格子20,光センサ26からなる第2の変位検出部(ワイヤ伸び量検出部)の双方を設けることとしたが、これは一例であり、第2の変位検出部は、必要に応じて設けるようにすればよい。
11:筐体
11A,11B:側面
12:レーザ光源
13:レーザ光
14:コリメータレンズ
15:平行光
16:第1の回折格子
18:第2の回折格子
18A,18B:溝
20:第3の回折格子
22:半透過半反射ミラー
24:全反射ミラー
26,28:光センサ
30:直進光
32,34:回折光
36:干渉光
50:電動アシスト自転車
52:ハンドル
54:ブレーキレバー
56:ブレーキワイヤ
58:チューブ
60:ブレーキパッド
62:リム
64:コントローラ
66:モータ
68:バッテリー
70:変位計測ユニット
72:透明樹脂成型体
72A,72B:側面
74:貫通孔
76A,76B:ネジ
78:レーザ駆動回路
80A~80F:スペース
80F:通路
82:I/V変換回路
84:ネジ
86A,86B:スリット
90:増幅回路
92:スライサ
94:クロックカウンタ
96:演算装置
100:変位計測装置
102:第3の回折格子
104:位相板
106:2分割光センサ
108:演算装置
200:マイケルソン干渉計
202:レーザ光源
204:コリメータレンズ
206:スプリッタ
208:固定ミラー
210:可動ミラー
212:光センサ
214:固定側ユニット
216:干渉縞
F1~F3:枠
L1~L5:光路
L rev1,L rev2:戻り光
LD:レーザダイオード
OP,OP1,OP2:オペアンプ
PD,PD1,PD2:フォトダイオード
R1:電流制限抵抗
R2~R7:抵抗
Claims (7)
- 光源から発射された光をコリメータレンズにより平行光とし、
該平行光を、その光軸上に配置された第1の回折格子を通過させ、更に、前記光軸上に前記第1の回折格子に対向して配置された半透過半反射ミラーまで進行させ、
前記半透過半反射ミラーにより、前記平行光の一部を反射させて前記第1の回折格子まで戻る第1の戻り光とし、前記平行光の残りを、前記半透過半反射ミラーに対して同一光軸上で相対的に位置変化可能に配置された全反射ミラーまで進行させ、
前記第1の戻り光を、前記第1の回折格子により、前記第1の戻り光と同方向に進行する0次光と、該0次光に対して回折角を有する±n次光(nは1以上の自然数)とに分けて進行させ、該±n次光のうちの所定次数の回折光を、第1の光センサで受光して光量検出するとともに、
前記半透過半反射ミラーを通過し、前記全反射ミラーまで進行した平行光を、該全反射ミラーで反射させて、前記半透過半反射ミラーを通過して前記第1の回折格子まで戻る第2の戻り光とし、
前記第1の回折格子に達した第2の戻り光を、前記第1の回折格子により、0次光と±n次光と、に分けて進行させ、該±n次光のうち、前記所定次数の回折光を、前記第1の回折格子で受光して光量検出し、
前半透過半反射ミラーに対する前記全反射ミラーの相対的な移動量に対応する干渉縞もしくはその信号から、前記平行光の軸方向の第1の変位量を測定することを特徴とする変位計測方法。 - 前記第1の回折格子と前記半透過半反射ミラーの間であって、前記平行光の光軸上に配置された第2の回折格子によって、前記第1の回折格子を通過した平行光を、該平行光と同方向に進行する0次光と±n次光とに分けて進行させ、
前記第2の回折格子と前記半透過半反射ミラーとの間に、前記第2の回折格子に対向して同一光軸上で移動可能に配置されており、前記第2の回折格子と同一の格子ピッチを有する第3の回折格子によって、前記第2の回折格子を経由した0次光を、更に、同方向に進行する0次光と±n次光とに分けて進行させ、
前記第2及び第3の回折格子を経由した±n次光のうち、前記第2の回折格子による所定次数の回折光の光軸に沿う回折光を、第2の光センサで受光して光量検出するとともに、
前記第2の回折格子に対する第3の回折格子の移動量に対応する干渉縞もしくはその信号から、前記平行光の軸方向の第2の変位量を測定することを特徴とする請求項1記載の変位計測方法。 - 光源と、
前記光源から発射された光を平行光にするためのコリメータレンズと、
前記平行光の光軸上に配置されており、前記平行光を、同方向に進行する0次光と、±n次光と、に分けて進行させる第1の回折格子と、
前記平行光の光軸上に、前記第1の回折格子と対向して配置されており、前記第1の回折格子を通過した平行光の一部を反射させて前記第1の回折格子まで戻る第1の戻り光とし、前記平行光の残りを通過させる半透過半反射ミラーと、
該半透過半反射ミラーに対して、同一光軸上で相対的に位置変化可能に配置されており、前記半透過半反射ミラーを通過した平行光を反射させて、前記半透過半反射ミラーを通過して前記第1の回折格子まで戻る第2の戻り光とする全反射ミラーと、
前記第1の回折格子によって回折された前記第1及び第2の戻り光の±n次光のうち、第1の戻り光の所定次数の回折光の光軸に沿う回折光を受光して光量検出する第1の光センサと、
を備えており、
前記半透過半反射ミラーに対する前記全反射ミラーの相対的な移動量に対応する干渉縞もしくはその信号から、前記平行光の軸方向の第1の変位量を測定することを特徴とする変位計測装置。 - 前記第1の回折格子と前記半透過半反射ミラーの間であって、前記平行光の光軸上に配置されており、前記第1の回折格子を通過した平行光を、該平行光と同方向に進行する0次光と、±n次光とに分けて進行させる第2の回折格子と、
該第2の回折格子と前記半透過半反射ミラーとの間に、前記第2の回折格子に対して同一光軸上で移動可能に配置されており、前記第2の回折格子と同一の格子ピッチを有するとともに、前記第2の回折格子を経由した0次光を、更に同方向に直進する0次光と、±n次光と、に分けて進行させる第3の回折格子と、
前記第2及び第3の回折格子を経由した±n次光のうち、前記第2の回折格子による所定次数の回折光の光軸に沿う回折光を受光して光量検出する第2の光センサと、
を備えるとともに、
前記第2の回折格子に対する第3の回折格子の移動量に比例する干渉縞もしくはその信号から、前記平行光の軸方向の第2の変位量を測定することを特徴とする請求項3記載の変位計測装置。 - 前記第3の回折格子が前記第2の回折格子と対向する面に段差を有する位相板を設け、前記第2の光センサとして、2分割光センサを用いるとともに、
前記2分割光センサから出力される2つの信号を合成する演算手段,
を備えたことを特徴とする請求項4記載の変位計測装置。 - 前記光源,コリメータレンズ,第1の回折格子,半透過半反射ミラー,第1の光センサが、透明樹脂成型体内に設けられた空間に設置されるとともに、
前記全反射ミラーが、前記透明樹脂成型体の外部に配置されており、
前記透明樹脂成型体と前記全反射ミラーが相対移動可能となるように、いずれか一方が軸に沿って移動可能に取り付けられたことを特徴とする請求項3記載の変位計測装置。 - 前記光源,コリメータレンズ,第1の回折格子,第2の回折格子,第3の回折格子,半透過半反射ミラー,第1の光センサ,第2の光センサが、透明樹脂成型体内に設けられた空間に配置され、
前記全反射ミラーが、前記透明樹脂成型体の外部に配置されており、
前記透明樹脂成型体と前記全反射ミラーが相対移動可能となるように、いずれか一方が軸に沿って移動可能に取り付けられるとともに、
前記透明樹脂成型体が、前記第2の回折格子と第3の回折格子が平行状態を保つように、これら2つの回折格子を境目に伸縮可能なバネ性を示すことを特徴とする請求項4又は5記載の変位計測装置。
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2010
- 2010-03-31 JP JP2010083537A patent/JP5424961B2/ja not_active Expired - Fee Related
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2011
- 2011-03-28 CN CN201180017720.3A patent/CN102834690B/zh not_active Expired - Fee Related
- 2011-03-28 KR KR1020127023588A patent/KR101390648B1/ko active IP Right Grant
- 2011-03-28 WO PCT/JP2011/057560 patent/WO2011122536A1/ja active Application Filing
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2012
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Also Published As
Publication number | Publication date |
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KR101390648B1 (ko) | 2014-04-30 |
CN102834690B (zh) | 2015-11-25 |
JP5424961B2 (ja) | 2014-02-26 |
JP2011215004A (ja) | 2011-10-27 |
US8922785B2 (en) | 2014-12-30 |
KR20120128669A (ko) | 2012-11-27 |
CN102834690A (zh) | 2012-12-19 |
US20130010305A1 (en) | 2013-01-10 |
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