a INVA
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`(19) O
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`EuropeanPatent Office
`Office européen des brevets
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`a 1)
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`EP 1630 562 Al
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`(12)
`
`EUROPEAN PATENT APPLICATION
`published in accordance with Art. 158(3) EPC
`
`(43) Date of publication:
`01.03.2006 Bulletin 2006/09
`:
`
`(21) Application number: 04730008.2
`
`(22) Dateoffiling: 28.04.2004
`
`(51) Int CL:
`GOTP 21700 (1968.09)
`GOTC 19/00 (7966.99)
`
`GO1P 15/00 (1968.09)
`GO1B 11/00 08.03)
`
`-
`
`(86) International application number:
`PCT/JP2G04/0061 48
`
`(87) International publication number:
`WO 2004/097433 (11.11.2004 Gazette 2004/46)
`
`(30) Priority: 28.04.2003 JP 2003123417
`21.10.2003 JP 2003360287
`
`(74) Representative: Smith, Normanlan et al
`fJ CLEVELAND
`
`
` Designated Contracting States:
`Inventor: UMEDA, Akira
`DE Fl GB SE
`Tsukuba-shi,
`
`
`Ibaraki 3058563 (JP)
`
`
`\
`I
`
`ms a
`ee
`
`(71) Applicant: National Institute of Advanced
`Industrial Science
`and Technology
`
`Tokyo 100-8921 (JP)
`
`
`(54)
`DYNAMIC MATRIX SENSITIVITY MEASURING INSTRUMENTFORINERTIAL SENSORS, AND
`MEASURING METHOD THEREFOR
`
`40-43 Chancery Lane
`London WC2A 1JQ (GB)
`
`FIG.1
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`Tonetwork OO
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`interferometer— EP1630562A1
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`4p
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`-
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`opaneeneenee
`tttencereeeenenepotaser
`[mrt
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`A device for measuring the dynamic matrix sen-
`(57)
`sitivity of an inertia sensor is provided with a motion gen-
`erating machine or a vibrating table for inducing a trans-
`lational or rotary motion, an acceleration measuring unit,
`an angular velocity measuring unit or angular accelera-
`tion measuring unit, an output device for fetching an out-
`put from the unit, one or ,pre light reflectors, a displace-
`ment measuring device for seizing a multidimensional
`motion by using a laser interferometer radiating lightfrom
`a plurality of directions to the light reflectors, a data
`processing unit for processing a data indicating the state
`of motion and obtained from the displacement measuring
`unit, and a displaying device to display or a transmitting
`device to transmit the output of the data processing unit
`and the output of the acceleration measuring unit, angu-
`lar velocity measuring unit or angular acceleration meas-
`uring unit. Since the accelerometer is exposedto accel-
`eration in every conceivable direction and possibly fails
`to find a correct value of acceleration as encountered by
`the conventional one-dimensionalcalibration, it is actu-
`ally calibrated by applying acceleration from all possible
`directions thereto.
`
`~
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`BNSDOCID: <EP__
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`1630562A1_|_>
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`Printed by Jouve, 75001 PARIS (FR)
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`

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`EP 1 630 562 A1
`
`Description
`
`Technical Field:
`
`[0001] This invention relates to a device for measuring the dynamic matrix sensitivity of an inertia sensor and a method
`for the measurement. Particularly the invention relates to a device for the measurementof the dynamic matrix sensitivity
`of an inertia sensorfor a varying use suchas, for example, an inertia sensor relating to inertial navigation devices to be
`mounted on automobiles, submarines, missiles, and airplanes, an inertia sensor to be used for motion contro! of robots,
`an inertia sensor to be used for measuring the motion of a human body, the vibration exerted on a human body, and
`the motion of an animal, and an inertia sensor to be used for preventing image devices and screen imagesfrom blurring
`and a method for effecting the measurement.
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`BackgroundArt:
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`[0002] As one example of the inertia sensor, the accelerometer which is well known maybe cited. It is generally a
`one-axis accelerometer whichis furnished with one sensitive axis. When this one-axis accelerometer is calibrated, the
`calibration is effected by causing the direction of motion generated by a motion generating machine to coincide with the
`axis of sensitivity. The degree of freedom of motion to be used for calibrating accelerometers, therefore, is a single
`degree of freedom. The primary calibration using a laser interferometer which is reputed to have the highest precision
`also usesthis technique.
`[0003] However, since the device which calibrates the one-axis accelerometer mentioned above generally entails a
`three-dimensional motion, itis rare that the device will be limited to a one-dimensional motion. The fact that the calibration
`is carried out by causing the direction of motion generated by the motion generating machine to coincide with the axis
`of sensitivity as described above occurs in the calibration which resorts to the measurement of the amplitude of the
`acceleration when the direction of motion is known in advance.
`[0004] As concrete examples of the conventional one-axis accelerometer, a piezoelectric type accelerometer, an
`electromagnetic type servo accelerometer, an interference type optical fiber accelerometer and a strain gauge type
`accelerometer have been known. Owing to their structures and the natures of their materials, accelerometers areinflu-
`encedby the acceleration components notparallel to the sensitivity axis when the directions of application of acceleration
`to the acceleration sensors fail to coincide with the direction of sensitivity axis.
`[9005]
`itis, therefore, apparent that concerning practical motions, the calibration technique alone in the present state
`of affairs has notfully satisfactorily established a method for evaluating the performance of an acceleration sensor or
`perfected a measurement standard for the determination of acceleration.
`[0006]_Itis derived that in terms of vector space with three-dimensional transverse motion, even the cross ortransverse
`35
`sensitivities of one-axis accelerometers are expressed by two parametersaswill be subsequently explained. The practice
`of denoting the two kindsoftransversesensitivity by S,, and S,, and designating S,, as a magnitude of not more than
`5% and Sy as a magnitude of not more than 3%has never been in vogue heretofore.
`[0007]
`itis natural that the one-axis accelerometer generally emits an output signal in responseto an input component
`in the direction of the sensitivity axis thereof.
`It is also characterized by emitting output signals in response to input
`acceleration components from two directions perpendicular to the sensitivity axis thereof. The reason for this property
`is that the piezoelectric accelerometer, the electromagnetic servo accelerometer, the interferometer type optical fiber
`accelerometer, or the strain gauge type accelerometer mentioned aboveis provided with a mass capable of also moving,
`though slightly, in a direction other than the direction of sensitivity axis or something equivalent thereto and, therefore,
`is so configured as to detect the relative motion of this mass or detect a voltage or an electric current necessary for
`preventing this relative motion.
`[0008] Heretofore, the accelerometer is set on the one-axis motion generating machine and the sensitivity axis of the
`accelerometer is caused to coincide with the direction of the motion generated by a motion generating machine as
`illustrated in Fig. 3. The concept of enabling the accelerometer to be calibrated most accurately by measuring a motion
`with a laser interferometer under such set conditions as mentioned above and consequently establishing a standard for
`measurementof acceleration is officially approved by the Treaty of the Meter as well. Generally, the reference acceler-
`ometer is calibrated in accordance with the method embodying this concept.
`[9009]
`Then, in industries, it is supposed to calibrate a given accelerometer based on a reference accelerometer
`mentioned abovebyjoining in series connection the reference accelerometer which has undergone measurement by
`the method of Fig. 3 and the given accelerometer asillustrated in Fig. 4(b), causing the sensitivity axis to coincide with
`the direction of motion generated by a motion generating machine, and comparing the output signals from the two
`accelerometers.
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`[0010] The conventional methodofcalibration which resides in determining the transverse sensitivity from the output
`signal due to a motion only in one direction perpendicular to the sensitivity axis asillustrated in Fig. 4(a) and Fig. 4(b),
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`BNSDCCID:<EP.
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`1630562A1_|_>
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`EP 1 630 562 A1
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`however, is essentially in error in the elementary sense. In the sense that this method is an expedient and is capabie of
`determining only one transverse- sensitivity, the thought directed toward the decomposition and the synthesis of vector
`supports a judgment that this method views the phenomenon only in a two-dimensional space.
`[0011] The transverse sensitivity is determined by imparting vibration only in one direction perpendicular to the sen-
`sitivity axis as illustrated in Fig. 4(c).
`[0012]
`For the sake of surveying the transverse sensitivity more specifically, the behavior of the piezoelectric type
`accelerometer using a piezoelectric material, for example, will be explained below. The piezoelectric type accelerometer
`possesses transverse sensitivity because the piezoelectric constant comprises a shear component. Thatis, the piezo-
`electric substance generates an electric charge which transmits a signal via an electrode even to slippage. Generally,
`in the region in which the voltage (or electric current) generated in response to an input signal (acceleration) possesses
`linearity, the sensor sensitivity is defined by the ratio of their magnitudes. Thus, the following formula is established.
`
`Thesensitivity axis output voltage (a,,(w)exp(jwt)) of accelerometer
`
`= normalsensitivity x input componentofacceleration in normalsensitivity
`
`direction + cross (transverse) sensitivity 1 x input component of
`
`acceleration in direction 1 perpendicular
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`to normal + cross
`
`(transverse) sensitivity 2 x input component of acceleration in
`
`direction 2 perpendicular to main axis
`
`= Sxx(@)aixexp(jot) + S,,aiyexp(jot) + S,,a,exp(ja@t)
`
`[0013] When this formula is rewritten in the matrix form, the formula 1 is obtained. Here, the amplitude of the vector
`acceleration exerted on the accelerometeris denoted by(a;,, aiy, jz) and the time change component by exp(jat).
`
`(Mathematical 1)
`
`Bix exp(Jat)
`Aga(@ )OXP{JO t )=(S_zx(M) Szy(O) Sy2(@))| ay ExP( Jae)
`aj, exp(Ja t)
`
`[0014] The drawing of the acceleration vector A applied to the accelerometer and the decomposition of the vector in
`X, Y and Z axesis shownin Fig. 2.
`[0015]
`!t is well knownthat the acceleration is a vector which is expressed by amplitude and direction. Further, in order
`that the accelerometer maycorrectly measure the acceleration, the accelerometer must be calibrated with the acceleration
`as a vector. The conventional methodof calibration, however, effects the calibration with the magnitude of amplitude
`because the direction of the exerted acceleration is determined at the stage of setup.
`[0016] When the accelerometeris put to actual services, there are times when the direction of motion can be forecast
`and there are times when the forecast cannot be attained because of the possibility of the accelerator being exposed
`to application of acceleration in every direction.
`[0017]
`In the case of an earthquakeor accidental collision of ccars,it is not possible to know in advancethedirection
`of motion. When the calibration is made only in amplitude (one-dimensionally) as practiced conventionally, there are
`times when no correct magnitude of acceleration can be obtained. Thus, the desirability of calibrating the accelerometer
`by applying acceleration to the accelerometer in all actually conceivable directions has been finding general recognition.
`[0018] The technical backgroundofthis invention has been described heretofore. As concrete examples of the prior
`art of this invention, the following documents have been known.
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`EP 1 630 562 A1
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`(Non-Patent Document 1] Vibration Engineering Handbook, complied by Osamu Taniguchi, published in 1976 by
`Youkendo, Chapter 13 "Determination of Vibration," 13.3.2 "Calibration of vibration measuring device"
`[Non-Patent Document 2] ISO (the International Organization for Standardization) 16063-11: 1999 (E)
`(Non-Patent Document 3] FINAL REPORT ON KEY COMPARISON CCAUV. V-K1 Hans-Jurgen von Martens,
`ClemensElster, Alfred Link, Angelika Taubner, Wolfgang Wabinski, PTB-1.22 Braunschweig, October 1, 2002
`[Non-Patent Document4] ISO 5347 part 11 Testing of transverse vibration sensitivity
`[Non-Patent Document 5] ISO 5347 part 12 Testing of transverse shock sensitivity
`[Non-Patent Document6] ISO 8041 Human responseto vibration - Measuring instrumentation
`[Non-Patent Document 7] ISO 2631-1, 1997 Evaluation of human exposure to whole-bodyvibration Part 1: General
`requirement
`[Non-Patent Document 8] ISO 5349-1, 2001 Measurementand evaluation of human exposureto hand-transmitted
`vibration - Part 1: General guidelines
`
`Disclosure of the Invention:
`
`[0019] This invention relates to a device for measuring dynamic matrix sensitivity of an inertia sensor and serving to
`enable an inertia sensor to be calibrated by application thereto of a vibration possessing an acceleration component
`along the degree of not less than two degreesof freedom selected from amongthe degreesof six degrees of freedom
`of motion and a method for the measurement. The first aspect of this invention is characterized by being provided with
`a motion generating machine capable of inducing a translational motion or a rotary motion, an acceleration measuring
`device which as a device subject to calibration is at least temporarily fixed on the motion generating machine, an angular
`velocity measuring device or an angular acceleration measuring device, an output means for fetching an output from
`the device subject to calibration, a single or a plurality of light reflecting materials, a displacement measuring means
`capable of seizing a multidimensional motion by the use of a laser interferometer formed by radiating laser beams from
`a plurality of directions to the single or plurality of light reflecting materials, a data processing device for processing the
`data indicating a multidimensional state of motion obtained from the displacement measuring means and converting the
`resultant muitidimensional translational motion or multidimensional rotary motion into magnitudesfit for a predetermined
`coordinate system, and a display means for displaying or a conveying means for conveying the output of the data
`processing device and the output of an acceleration measuring device, an angular velocity measuring device, or an
`angular acceleration measuring device which is the device subject to calibration.
`[0020] The second aspect of this invention is characterized by the fact that the motion generating machine mentioned
`above generates a periodic motion. The term "periodic” as used herein meansthat the vibration produced in each cycle
`by the motion generating machine mentioned aboveis periodic within the period in which no influence is exerted on the
`measurementusing the vibration of the next cycle.
`[0021] The third aspect of the invention is characterized by the fact that the motion generating machine mentioned
`above generates a motion of the nature of the function of pulse. Here, the motion of the nature of the function of pulse
`may be a periodic motion in the general sense of the word. In this case, it is provided that the motion of the nature of
`the function of pulse produced in each cycle generated by the motion generating machine occurs within the period of
`such an extent as avoids exerting an influence on the measurement using the motion of the nature of the function of
`pulse producedin the next cycle. The aforementioned motion of the nature of the function of pulse may be followed by
`a motion for eliminating the displacement produced by the motion.
`[0022] The fourth aspectof the invention, besides the third aspectof the invention, is characterized by being provided
`with a first converting meansfor determining the Fourier component on the frequency axis of the motion of the nature
`of the function of pulse mentioned above and a second converting means for determining the Fourier component on the
`frequencyaxis of the output of an acceleration measuring device, an angular velocity measuring device, or an angular
`acceleration measuring device which is a device subject to calibration mentioned above and further provided with a
`means to display or a means to transmit the frequency characteristic of the correction of an acceleration measuring
`device, an angular velocity measuring device, or an angular acceleration measuring device whichis a device subject to
`calibration obtained from the outputs of the first and second converting means.
`[0023]
`The fifth aspect of the invention is characterized by the fact that the motion generating machine mentioned
`above is a motion generating machine which produces a random motion. The term "random motion" as used herein
`means that the motion can be handied as a white noise within the range of frequency band subjectto calibration.
`[0024] The sixth aspectof the invention, besides the fourth aspect of the invention, is characterized by being provided
`with afirst converting meansfor determiningthe Fourier component onthe frequencyaxis of the random motion mentioned
`above and a second converting meansfor determining the Fourier component on the frequencyaxis of the output of an
`acceleration measuring device, an angular velocity measuring device, or an angular acceleration measuring device
`which is a device subject to calibration mentioned above and further provided with a means to display or a means to
`transmit the frequency characteristic of an acceleration measuring device, an angular velocity measuring device, or an
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`EP 1 630 562 A1
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`angular acceleration measuring device which is a device subject to calibration obtained from the outputsofthe first and
`second converting means.
`[0025] Before the measurementby the useof a laser interferometeris started, the control to the extent aimed atis
`possibly blocked as by the parasitic vibration of the motion generating machine.
`In this case, by feeding back the
`information showing the state of motion of the motion generating machine, it is made possible to attain the control as
`aimed at and cope with the trouble so as to repress the influence of the variation with time of the device. The seventh
`aspectof this invention, therefore, is characterized by the fact that the motion generating machine mentioned aboveis
`provided with an accelerometerfor controlling a motion and a feedbackcircuit or a controlling device for controlling the
`drive device mentioned abovesothat the signal from the accelerometer may agree with a predetermined value.
`[0026] The eighth aspect of the invention is characterized by having as one object thereof the performance of the
`surveillance mentioned abovewith high precision and possessing a structure for imparting dynamic matrix sensitivity to
`the aforementioned accelerometer for controlling a motion and, in the control of the feedback or in the control of a
`calculating machine, estimating the motion of the sample mounting table of the motion generating machine from the
`output vector of the accelerometer for controlling the motion by using the dynamic matrix sensitivity mentioned above,
`and controlling the motion.
`.
`[0027] The ninth aspectof the invention is aimed at evaluating an error and is characterized by being provided with
`a meansto display for determining an error from the output of the data processing device mentioned above and the
`output of an acceleration measuring device, an angular velocity measuring device, or an angular acceleration measuring
`device whichis a device subject to calibration and displaying the value of this error or a meansto convey for transmitting
`this value.
`7
`[0028] Wherethe laser interferometer cannot be used easily, an alternate of high precision is used instead. This
`alternate at times abhors an appreciable degradation of measuring precision. The 10th aspect ofthe invention is directed
`toward coping with this situation and is characterized by being provided with a motion generating machine capable of
`inducing a translational motion or a rotary motion, an acceleration measuring device, an angular velocity measuring
`device, or an angular acceleration measuring device which is a device subject to calibration and is at least temporarily
`fixed on the motion generating machine, an output means for taking out the output from the device subject to calibration,
`an inertia sensor capable of seizing a multidimensional motion calibrated in advance by using a dynamic matrix sensitivity
`measuring device of the inertia sensor recited in claim 1, a data processing device for processing the data showing the
`state of multidimensional motion obtained from the inertia sensor and converting a multidimensionaltranslational motion
`ora multidimensional rotary motion to the value fit for the predetermined coordinate system, and a meansto display or
`a meansto convey the output of the data processing device and the output of the acceleration measuring device, the
`angular velocity measuring device, or the angular acceleration measuring device which is a device subjectto calibration.
`[0029] When an acceleration measuring device, an angular velocity measuring device, or an angular acceleration
`measuring device is calibrated on the ground, since the calibration is carried out in the presence of gravitational accel-
`eration, it is preferred to be capable of excluding the influence thereof from the measured value. The 11aspect of the
`invention, therefore, is characterized by being provided with a meansof adjustingthe direction of mounting an acceleration
`measuring device, an angular velocity measuring device, or an angular acceleration measuring device whichis a device
`subject to calibration so that the direction maybe varied relative to the direction of gravity and a meansfor obtaining an
`output from the aforementioned device subject to calibration temporarily fixed as set in a plurality of directions relative
`to the direction of gravity, finding dynamic matrix sensitivity for each of the plurality of directions-mentioned above, and
`estimating the dynamic matrix sensitivity liberated from the influence of gravity from the plurality of dynamic matrix
`sensitivities mentioned above.
`
`Particularly the aforementioned device subject to calibration which characterizesthe 12th aspectofthis invention
`[0030].
`is an acceleration measuring device, an angular velocity measuring device, or an angular acceleration measuring device
`which possesses the output thereof only in a specific direction. The motion generating machine which induces the
`aforementioned translational motion or rotary motion may be capable of producing a motion with a plurality of degrees
`of freedom.
`[0031] The 13% aspect of the invention is characterized by the whole of a device for measuring the dynamic matrix
`sensitivity of an inertia sensor being particularly installed in a room capable of intercepting noise or vibration from the
`exterior, the device for measuring acceleration which is a device subject to calibration being a seismograph, and the
`motion generating machine being a motion generating machine which generates a motion of the nature of the function
`of pulse or the function of cycle and imparts small vibration in a vibration frequency band or in a seismic zone detectable
`by the seismograph (strong motion seismograph). The seismic wave is knownin two kinds, a longitudinal wave and a
`transverse wave. Specifically, it is inherently a multidimensional motion which possibly occurs simultaneously in the
`vertical direction and the horizontal direction, which possibly occurs later in the horizontal direction, or which occurs in
`the form of a rotation of the ground and it is characterized by the fact that the direction of motion is an unknown factor.
`The motion mentioned above preferably conformsto this situation.
`[0032] The 14th aspect of the invention is characterized by the aforementioned motion generating machine being
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`EP 1 630 562 A1
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`particularly a motion generating machine which generates random motion and imparts vibration in an vibration frequency
`band detectable by the inertia sensor used for constant detection of vibration of a vibro-isolating bed, and the motion
`generating machine orthe vibro-isolating bed being provided with a cooling device or a thermostat. Here, the vibration
`of the floor surface for mounting the vibro-isolating bed comprises a horizontal motion and a vertical motion and is
`characterized bythe fact that the direction of motion cannot be known in advance. Thus,the aforementioned motion-gen-
`erating machine is preferred to be adapted to generate a motion conforming to this situation.
`[0033] The 15th aspect of this invention is characterized by the aforementioned motion generating machine being
`particularly a motion generating machine which gives a vibration in a vibration frequency band detectable by an accel-
`erometer used for controlling an automobile suspension or for controlling an automobile passenger protecting airbag,
`and the acceleration measuring device whichis a device subject to calibration being an accelerometer used for controlling
`the automobile suspension or for controlling the automobile passenger protecting airbag and being provided with a
`temperature controlling device for controlling the temperature environment of the acceleration measuring device which
`is a device subject to calibration. Since the vibration of the automobile suspension is characterized by simultaneously
`producing a translational motion in the direction of a spring and a rotary motion around the rotational axis of the link of
`the suspension mechanism, the aforementioned motion generating machine is preferred to be enabled to generate a
`motion conforming to this situation. Further, the accelerometer to be used for controlling the automobile passenger
`protecting airbag has an important requirement of possessing the following characteristic features andthe aforementioned
`motion generating machine is preferred to be capable of generating a motion conforming to this situation. First, the
`evaluation of safety laid out in the specification is stipulated to give results of calculation of the absolute values of
`acceleration in head-on collision and lateral collision below specified levels. The actual collision of cars does not always
`occur in the form of head-on collision. That is, the accelerometer which is used in the system for ensuring safety in
`collision must always detect correct acceleration without relying on the direction of acceleration The calibration, therefore,
`must be effected in termsof vector.
`[0034] The 16" aspectof this invention is characterized by the aforementioned motion generating machine being
`particularly a motion generating machine which simultaneously generates a motion of the nature of the function of pulse
`or the nature of the function of cycle and comprising a translational motion and a rotary motion and imparts a motion in
`a vibration frequency band detectable by an inertia sensor used for controlling the motion of a robot and the aforemen-
`tioned acceleration measuring device which is a device subject to calibration being an inertia sensor to be used for
`controlling the motion of the robot mentioned above. Since the motion of the robot is characterized by being capable of
`simultaneously generating a translational motion and a rotary motion with high accuracy, the motion mentioned above
`is preferred to conform to this situation.
`[0035] The 17% aspect of this invention is characterized by the aforementioned motion generating machine being
`particularly a motion generating machine which givesa vibration in a vibration frequency band detectable by aninertia
`sensor to be used for measuring a human body motion, a vibration exerted on a human body, or an animal behavior
`monitor and the aforementioned acceleration measuring device which is a device subject to calibration being an inertia
`sensor,i.e. distributed accelerometers, to be used for measuring a human body motion, a vibration exerted on a human
`body, or an animal behavior monitor and being provided with a multichannel signal output terminal for emitting a signal
`for the distributed accelerometers. Since the vibration exerted on the inertia sensor to be used for measuring a human
`body motion, a vibration exerted on a human body, or an animal behavior monitor is characterized as indicated herein
`below, the aforementioned motion generating machine is preferred to be enabled to generate a motion conforming to
`this situation.
`
`1) The specification laid down by ISO regarding the measurementof vibration exerted on a human body (Non-Patent
`Document 6, Non-Patent Document 7 and Non-Patent Document 8) defines use of a three-axis accelerometer for
`vibrations in hands and arms and useof a six-axis accelerometer for whole body vibrations. To be specific, since
`the process of judgment embraces an operation of exerting a weight on the X component, Y component, and Z
`component of given acceleration, squaring the respective responses, totaling the produced squares, and reducing
`the total to a square root(raising to the 1/2nd power), the specification evidently expects the measurement of the
`acceleration in terms of vector. The value of weightdiffers between whole body vibration and vibration of hands and
`arms. Meanwhile, the method for calibrating an accelerometer concerns the calibration of the amplitude of a one-axis
`vibration. Evidently, the human body possesses an ability to discern a direction of vibration. The fact that the
`accelerometer whichis used for investigating the influence of the vibration on ahuman bodyis calibrated exclusively
`with the amplitude of acceleration is irrational.
`2) The measurementof the motion of a human body yields a valuable basic data for the sports engineering and for
`the control of a humanoid robot.
`It is evidently irrational, however, to assume that the direction of a motion of a
`human bodyis constantly fixed. The fact that the accelerometer which is used for investigating the motion of a
`human bodyis calibrated exclusively with the amplitude of acceleration is irrational.
`3) The animal inhabits a real space and the translational motion occurs three-dimensionally. When the rotational
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`EP 1 630 562 A1
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`motion is also taken into account,it is logical to conclude that the animal inhabits a six-dimensional space. The fact
`that the inertia sensor for monitoring a behavior is not calibrated in six-dimensional space may well be judged
`senseless.
`;
`,
`4) In the measurement of the motion of a human body and the analysis of a human body motion in the sport
`engineering, while inertia sensors are attachedto joints, arms, and feét, the calibration must be made based on the
`motion of six degrees of freedom because the motion simultaneously inducesa vertical and a horizontal motion and
`entails a rotary motion producedin a joint.
`,
`
`[0036] The 18h aspect of the invention, besides the 10th aspect of the invention, is characterized by particularly the
`motion generating machine which induces the aforementioned translational motion or rotary motion generating a motion
`along one axis, the acceleration measuring device, the angular velocity measuring device, or the angular acceleration
`measuring device which is a temperarily fixed device subject to calibration being furnished with a one-axis output, and
`the output from the device subject to calibration being furnished with a multi-axis output.
`[0037] With the exception of the case in which the aforementioned device subject to calibration is one-axis, the ac-
`celerometer is expected to bé calibrated with a greater degree of freedom than the degree of freedom possessed by
`the motion generating machine. The number of axes which can be handled is possibly smallerthan the number of output
`axes of the accelerometer expected to be usedfor calibration. The 19th aspect of the invention, which concerns a method
`to be applied in such a case to the device for measuring the dynamic matrix sensitivity of the inertia sensor possessing
`the aforementioned characteristics, is characterized, onthe assumption thatthe aforementioned displacement measuring
`means producesoutputsof different N axes, the degree of freedom of the motion of the aforementioned motion generating
`_ machine is a natural number M of not more than 6, and the relation M x N = 1 is not satisfied, by dividing the M degrees
`of freedom into a plurality of groups allowed duplication,
`
`1) obtaining input vectors and corresponding output vectors for each of the groups mentioned above by m