Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/12—Measuring force or stress, in general by measuring variations in the magnetic properties of materials resulting from the application of stress
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
  • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
  • G01L1/2268—Arrangements for correcting or for compensating unwanted effects
  • G01L1/2281—Arrangements for correcting or for compensating unwanted effects for temperature variations
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
  • G01L5/0061—Force sensors associated with industrial machines or actuators
  • G01L5/0076—Force sensors associated with manufacturing machines
  • G01L5/009—Force sensors associated with material gripping devices

Definitions

• the present invention relates to a magnetic force sensor that detects a force or a moment component and that detects a magnetic flux change in a magnetic flux generating source using a magneto-electric transducer.
• the present invention relates to a correction operation when a magnetic field generated at the magnetic flux generating source is changed.
• a force sensor is mounted to a wrist portion of the robot arm, detects a force or a moment component that is generated during an assembly work, and controls an
• Patent Document 1 Japanese Patent Laid-Open No. 2004-325328
• FIG. 5 A related structure that is discussed in Japanese Patent Laid-Open No. 2004-325328 is shown in Fig. 5.
• a permanent magnet 14 embedded in a resilient member and four magneto-electric transducers 15a to 15d opposing magnetic poles of the permanent magnet are disposed.
• the permanent magnet 14 is displaced, and the magneto-electric transducers 15a to 15d, such as Hall elements, detect a change in a magnetic field that is generated thereby. On the basis of the detected change in the magnetic field, it is possible to detect force
• a permanent magnet is used for a magnetic flux generating source.
• an absolute value of the strength of a magnetic field that is generated by a permanent magnet is changed by the temperature of the permanent magnet (that is, the absolute value has a predetermined temperature
• temperature compensation using a temperature compensation circuit that is provided with a temperature sensor is used.
• Fig. 6A shows a Hall element 16 provided at a position opposite to a permanent magnet 14.
• Fig. 6B shows a temperature compensation circuit connected to a constant voltage source (not shown) provided adjacent to the Hall element.
• the temperature compensation circuit provided adjacent to the Hall element causes a current value output to the Hall element from the temperature compensation circuit to increase in proportion to the temperature rise.
• the temperature compensation circuit needs to be provided separately from a sensor of, for example, the permanent magnet and the Hall element, thereby increasing costs and size.
• the present invention is carried out to overcome the aforementioned problems, and provides a compact magnetic force sensor that can precisely detect and correct
• the present invention provides a magnetic force sensor that detects a force on the basis of a position of an action portion and a position of a magnetic flux generating source relative to each other, the action portion being displaceable by the force that the action portion receives.
• the magnetic force sensor includes the action portion resiliently supported by a supporting member; a first magneto-electric transducer fixed to the action portion; the magnetic flux generating source disposed so as to face the first magneto-electric transducer; a second magneto-electric transducer disposed at a fixed position with respect to the magnetic flux generating source; and an operational
• processing section that corrects an output of the first magneto-electric transducer on the basis of an output of the second magneto-electric transducer.
• the present invention it is possible to provide a force sensor having a compact structure that does not use an additional structural component such as a temperature compensation circuit. According to the magnetic force sensor of the present invention, it is possible to correct variations in a magnetic field generated by a magnetic flux generating source caused by factors other than temperature variations.
• FIG. 1 shows a structure of a magnetic force sensor according to the present invention.
• Fig. 2 illustrates a temperature compensation method according to the present invention.
• Fig. 3 shows magnetic flux lines obtained from a simulation using a two-dimensional static magnetic field model that is symmetrical with respect to a Z axis.
• Fig. 4 shows magnetic flux lines obtained from a simulation using a two-dimensional static magnetic field model that is symmetrical with respect to a Z axis.
• Fig. 5 shows a structure of a related magnetic force sensor.
• Figs. 6A and 6B show a structure of a related force sensor .
• Fig. 1 shows most clearly the feature of the present invention, and is a sectional view taken along an X- Z axis of a magnetic force sensor.
• reference numeral 1 denotes an action portion to which a force is applied
• reference numeral 2 denotes a resilient member that resiliently supports the action portion 1 at a housing.
• the action portion 1 is resiliently supported so as to be displaceable when the force is applied to the action portion.
• Reference numeral 3 denotes a substrate for mounting magneto-electric
• Reference numerals 4a and 4b denote magneto- electric transducers (hereunder referred to as “displacement magneto-electric transducers").
• Reference numeral 5 denotes a magnetic flux generating source.
• Reference numeral 6 denotes a mount substrate that supports the magnetic flux generating source 5 and to which a magneto-electric
• Reference numeral 7 denotes the magneto-electric transducer that is provided on the mount substrate 6, and whose position relative to the magnetic flux generating source 5 is fixed (hereunder referred to as "fixed magneto-electric transducer").
• the magnetic flux generating source 5 may be a permanent magnet that is typified by a ND-Fe-B magnet, a Sm- Co magnet, a Sm-Fe-N magnet, and a ferrite magnet; or an electromagnet that generates a magnetic force by passing electricity through a coil that is wound upon a magnetic material.
• the fixed magneto-electric transducer 7 and the displacement magneto-electric transducers 4a and 4b are elements that output changes in a magnetic field as
• the action portion 1 need not be supported by the housing.
• the action portion 1 may be supported by a
• a method of calculating a force and a moment will be described with reference to Fig. 1.
• the action portion 1 receives a force Fz in a Z-axis direction and a moment My in a Y-axis direction.
• Amounts of changes in magnetic flux densities that pass through the displacement magneto-electric transducers 4a an 4b and the fixed magneto-electric transducer 7 are B4a, B4b and B7.
• kz and ky are sensitivity coefficients for
• My ky(B4a - B4b)
• the force and the moment applied to the action portion 1 can be calculated from the amounts of changes in the magnetic flux densities that pass through the displacement magneto-electric transducers 4a and 4b and the fixed magneto-electric transducer 7.
• the fixed magneto-electric transducer also functions as an output reference element not only when a temperature change is detected (described below) , but also when a force is detected.
• aforementioned displacement magneto-electric transducers and reference numeral 7 denotes a fixed magneto-electric
• Reference numerals 8 denote signal amplifiers for amplifying signals of the magneto-electric transducers.
• the signal amplifiers 8 are connected to the magneto-electric transducers.
• Reference numerals 9 denote signal converters for loading output signals into an operational section from the magneto-electric transducers, and are connected to the signal amplifier 8.
• Reference numerals 10 denotes signal adjusters that perform feedback operations to the
• the signal adjusters 10 are formed so that a signal for performing a correction operation can be output before outputs of the displacement magneto-electric transducers are input to the converters 9.
• a change in output of the fixed magneto-electric transducer 7 due to a variation in a generated magnetic field of the magnetic flux generating source 5 through the converter 9 is detected by the operational section.
• AVt GAV7.
• a detection resolution of the converter must allow satisfactory
• kd is a coefficient for converting from the magnetic flux change amount to the output voltage.
• ⁇ can be calculated from AVt, so that AVoff can be calculated.
• the adjusters 10 perform feedback operations to the signal amplifiers 8 connected to the displacement magneto-electric transducers 4a and 4b so that the AVoff is canceled. This makes it possible to correct in real time the offset of each
• each displacement magneto- electric transducer that is, the voltage value for when an external force is not applied to the action portion 1 may be canceled.
• a signal range that can be input to each converter 9 is a particular range. Therefore, when the output of any displacement magneto-electric transducer is offset, the range that can be detected by the sensor is narrowed.
• the above-described offset operation is significant for suitably using the signal range that can be input to each converter 9. ⁇ 4. Output Calculation Operation>
• kp (B - ⁇ ) /B is a correction sensitivity coefficient.
• the sensitivity coefficients are corrected on the basis of the magnetic field that is generated by the magnetic flux generating source. Therefore, it is possible to correct changes in the generated magnetic field caused by factors other than temperature, such as changes in the generated magnetic field caused by changes with time that could not be corrected by a related method using a temperature
• Figs. 3 and 4 show magnetic-field simulation
• a magnetic flux generating source 5 that was symmetrical with respect to a Z axis. Since the magnetic field that was generated was symmetrical in a left-right direction, in Figs. 3 and 4, a center line of magnetic poles is drawn on the left end, and only the right half is shown. [0039] In Fig. 3, a magnetic flux generating source 5 having a thickness of 4 mm in a Z-axis direction and a thickness of 2 mm in an X-axis direction is disposed in air. In Fig. 4, a magnetic material 13. having a thickness of 4 mm in the Z-axis direction and a thickness of 1 mm in the X- axis direction is wound upon the magnetic flux generating source 5.
• each magnetic flux generating source had characteristics of a Nd-Fe-B magnet having a residual flux density of 1.4 T and a coercive force of 1000 kA/m.
• the relative permeability of the magnetic material was set to 5000.
• Magnetic flux lines are dense near the two magnetic poles (the north (N) pole and the south (S) pole) of the magnetic flux generating source. It can be understood that, if the magneto-electric transducers are provided near the magnetic poles, changes in displacements of the magneto- electric transducers relative to the magnetic flux
• generating source can be sensitively detected.
• the magnetic poles of the rod-like magnetic flux generating source 5 have end sides, it is possible to fix the fixed magneto-electric transducer 7 to the end side of one of the magnetic poles, and to dispose the displacement magneto- electric transducers 4a and 4b at positions facing the other magnetic pole. It can be understood that such a structure makes it possible to most precisely detect the force and the variations in the magnetic field generated by the magnetic flux generating source.
• the present invention is suitably applicable as a force sensor used in an industrial robot arm.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Measuring Magnetic Variables (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 2009
  • 2009-11-26 JP JP2009269186A patent/JP5500957B2/ja not_active Expired - Fee Related
• 2010
  • 2010-11-11 WO PCT/JP2010/070522 patent/WO2011065267A2/en not_active Ceased
  • 2010-11-11 KR KR1020127015722A patent/KR101325542B1/ko not_active Expired - Fee Related
  • 2010-11-11 US US13/509,218 patent/US8978488B2/en active Active
  • 2010-11-11 CN CN201080052676.5A patent/CN102667433B/zh active Active
• 2014
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