United States
`(19)
`a2) Patent Application Publication (0) Pub. No.: US 2008/0195353 Al
`Igasaki et al.
`(43) Pub. Date:
`Aug. 14, 2008
`
`
`US 20080195353A1
`
`(54) PROFILING CONTROLLING METHOD AND
`CONTROLLER FOR CONTACT TYPE
`rereaN CONTACT TYPE MEASURING
`
`(75)
`
`Inventors:
`
`Shiro Igasaki, Kawasaki-shi (JP);
`Masaoki Yamagata, Kawasaki-shi
`(JP)
`
`Correspondence Address:
`RANKIN, HILL & CLARK LLP
`38210 Glenn Avenue
`WILLOUGHBY,OH 44094-7808
`
`(73) Assignee:
`
`MITUTOYO CORPORATION
`Kawasaki-shi (JP)
`
`°
`
`(21) Appl. No.:
`
`12/022,556
`
`(22)
`
`Filed:
`
`Jan. 30, 2008
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 14,2007
`
`(IP) w.ceeccessesseeesteseeenes 2007-032933
`
`Publication Classification
`
`(51)
`
`Int.Cl.
`(2006.01)
`GOIB 5/20
`(52) US. Cl. ssanmcnrenvinnvemnncanentmten 702/168
`(57)
`ABSTRACT
`Inprofiling control of a contact type probe in which a contact
`point is moved along a surface of an object to be measured,
`while being in contact with the object by a constant measure-
`ment force F, a contact determination level is provided for
`detecting a predetermined force smaller than a target mea-
`surementforce is applied to the contact point, contact deter-
`mination is performedat the time when force applied to the
`contact point reaches the contact determination level during
`approach, and the contact point is shifted from position con-
`trol to force control for bringing the contact point into contact
`with the object by the target measurement force. Thereby
`contact trace is prevented from occurring onthe object to be
`measured without reducing approach speed as much as pos-
`sible and lowering measurementefficiency. In this case, a
`commandvalue of the force control maybeinterpolated and
`gradually increased from the contact determination level to
`the target measurement force, and thus impact increase and
`over-shoot can be prevented from causing due to high-re-
`sponse.
`
`’(30
`
`Controller
`
`Switchin
`Target a
`measurement
`control
`+ Force|force control
`
`force
`command
`S
`0
`control
`compensator
`Target
`position|Acceleration .Position
`
`andreduction
`control
`processing
`compensator) Switch in
`position
`control
`
`Time
`differential
`
`Contact|,Contact
`evel
`Petmmabiot
`
`Position detection value
`
`Position feedback
`
`counter
`
` 40
`
`Measurementforce
`
`Digital calculation controlling part
`
`1
`
`Shenzhen Tuozhu 1017
`
`1
`
`Shenzhen Tuozhu 1017
`
`

`

`Patent Application Publication
`
`Aug. 14,2008 Sheet 1 of 11
`
`US 2008/0195353 Al
`
`Fig. 1
`
`PRIOR ART
`
`Fig. 2
`PRIOR ART
`
`—-
`
`.
`
`Input amplitude Pi
`
`46
`
`
`
`iL.
`
`+}.
`
`Output amplitude Po
`
`2
`
`

`

`Patent Application Publication
`
`Aug. 14,2008 Sheet 2 of 11
`
`US 2008/0195353 Al
`
`Fig. 3
`
`PRIOR ART
`
` an enh adeeb denfn
`
`hg.
`
`yoy fe
`yoy yoyooA
`<
`-
`Wesmearerrnaeleresrrcersecssee
`
`}j
`
`Output amplitude Py
`
`Fig. 4
`PRIOR ART
`
`50
`
`‘S
`
`©c
`
`00
`
`110
`= 100
`om
`he 90
`=o
`3°
`23 70
`og
`
`0
`
`50
`«6100
`6150
`200
`250
`Measurementforce F [uN]
`
`300
`
`3
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 3 of 11
`
`US 2008/0195353 Al
`
`Fig. 5
`
`PRIOR ART
`
`Approach f
`
`2 W
`
`ork shape
`
`Constantforce profiling operation
`
`4
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 4 of 11
`
`US 2008/0195353 Al
`
`Fig. 6
`PRIOR ART
`
`easurement
`
`Target
`measurement.,
`force
`
`M 14 “
`fj
`“
`ii
`A
`a
`
`Se
`value
`
`force
`
`
`
`a
`
`
`
`
`
`
`i+Contacts
`i
`|
`start/
`t
`"
`r *,
`ij
`
`—
`
`pneganeocatepeeeeeennyepeneene
`~~ Contact determination
`™{
`“ends and the mode }
`\ switches to force control}
`
` Impact in
`contactis strong
`Occurrence of
`
`
`
`ontact determination
`
`Approach
`8
`t od a
`cos,
`
`
`aN Contact
`start position®
`
`it
`i
`|
`|
`| Goniactsta)
`syAeonaetart)
`
`Push-in
`amount by
`
`
`
`
`ANpeernersnngeamaan’anneneanesene
`
`
`measurement ateeeeenrsennnenerent
`
`i
`
`
`
`
`Occurrence of push-in
`mare than push-in by
`measurementforce by
`
`delay time of contact
`determination
`
`Occurrence of contact trace
`
`5
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 5 of 11
`
`US 2008/0195353 Al
`
`Fig. 7
`
`PRIOR ART
`
`Force control command
`
`Target measurementforces |-----------ssssesssscceeseeeeeni -
`“PO
`
`“A,
`
`“se
`
`‘Contact determination
`ends and the mode
`switches to force control
`“’ Set force control
`command to target
`
`Measurementforce
`
`Target measurement force =>
`
`Position detection value
`
`Contact start position =
`
`
`
`naggrestamarens,
`— Qa9°
`=iY)g ad
`iJ
`A Start.
`
`Measurement position a |...-—--------ssscc-cccesscongenes
`
`more than push-in
`amount by measurement
`force
`Contact trace
`
`measurementforce
`
`esseeemnaera
`
`
`
`Time
`‘Contactdetermination}
`weet
`ends and the mode
`:
`4____Switchtoforcecontrol
`
`Impact in
`contact is small
`Contadt trace
`hardlyoccurs
`
`hardly occurs
`
`6
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 6 of 11
`
`US 2008/0195353 Al
`
`Fig. 8
`
`Force control command
`
`
`
`Target measurementforce = {-------~------<
`
`Contact determination
`
`«| ends and the mode
`
`“..\switches to force control
`
`Set force control
`command totarget
`measurement force
`
`Contact determination level =
`
`Measurementforce
`
`Contact determination level =
`
`/
`i:i;;
`powrennnnennmennneceeeany,
`(Contactstart
`Mcscusss
`sateeah hy
`
`Contactstart position =»
`
`Measurementposition = }----------------
`
`
`
`Target measurement force = }--...----.---.
`POTorcacreecatnenecarenesmemmameenention,
`
`J Contact determination ends and}
`
`Seemsenneweennmeneenneenewewesmeeneunroreeeeeeewem
`_“+ the mode switchesto force control
`}
`Yr Perform contact determination
`
`at contact determinationlevel
`
`
`
`
`
`
`Delay time of
`contact determination
`
`y dela
`us|
`time of contact determination
`smaller than push-in amount
`by measurement force
`
`
`
`No occurrence of push-in
`more than push-in amount
`
`by measurementforce
`!
`
`
`No occurrence
`of contact trace
`
`
`7
`
`

`

`icat
`
`ion
`
`Aug
`
`. 14, 2008
`
`Sheet 7 of 11
`
`US 2008/0195353 Al
`
`
`[eqoigeeJ9]]0.U05
`
`
`Oe’04
`
`
`
`Jonuose040}|_20t0+PUsoUCDuewenseeut
`tsUoISOg:+uogelejacoy|UOILISOd
`Ne9010-4yobuel
`
`IOJoujU09C)uonsnpa:pue
`UlYDUMSGfioesuedwoo}Burssaooid
`
`
`yoeqgpas)UonIsogSNICAUONDEIEpUOIISOYg
`
`
`
`
`a”Joyesusdwoo4OjO1]U09
`_yobiey
`
`UBLULWUOO9Di104}
`
`Patent Application Publ
`
`111
`
`1uoisod
`JOsJU09
`
`8
`
`
`
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 8 of 11
`
`US 2008/0195353 Al
`
`Fig. 10
`
`Force control command
`
`Target measurementforce =>
`
`Contact determination level >
`
`
`
`
`
`Force control commandset to
`target measurementforce at
`step when contact determination
`ended and the mode switched
`to force control
`
`
`
`
`
`
`Contact determination level=>
`
`
`Increase of impact and
`..
`
`
`Tree occurrence of over-shoot
`
`by high-responseof
`
`
`
`force control
`nnnContactdetermination
`
`
`a ¢ Contact; ends andthe mode
`
`semepangan!
`eneeemeenaeeetemeeseenne
`‘| determination}, switches to force control}
`
`Time
`_.f Delaytime of
`
`«~*~\contact determination
`
`
`Increase of impact an
`occurrenceof over-shoot
`i
`.
`SP
`pancemnnwennnanan enen.
`Measurement positionfo---m---mmm--rmm-PpPETAEAPAsmn by high-responseofforce control
`
`
`Occurrence of contact trace
`
`
`
`
`
`reneneatomarenmananaes
`‘.
`{ Contact start
`
`{
`
`Contactstart positions }--i--+-- Seneteewannanemennsasdensncadsecececeas:
`
`*
`{Contact determination ends
`:and the mode switches to}
`'};
`i force control =push-in amount}
`i at this time smaller than
`:i{
`i
`
`“
`“
`
` A
`
`9
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 9 of 11
`
`US 2008/0195353 Al
`
`Fig. 11
`
`Force control command
`
`Target measurementforce =
`
`Measurementforce
`
`Target measurement force =>
`
`.
`
`
`
`
`switched to force control Contact determination level =
`
`Interpolate and slowly make force
`
`contro! command approach target
`measurement force when contact
`determination ended and the mode
`
`
`.
`
`Contactdetermination ends and }
`
`the mode switchesto force control}
`Nannenmnereeetearaarrnacmmenemeserenesenscee:—
`
`
`
`Contact determination level=>
`
`Reduction of impact
`1
`and over-shoot by
`in
`&
`at UE interpolation of force
`{ deelan }
`control command
`aeaceranebongee
`
`
`
`Delay
`time of
`contact determination
`
`--""\_
`
`
`
`“ ,
`
`woednne genet
`
`
`
`¥
`f Contact
`\determination»,
`
`Contact start position=>
`
`7!
`
`+
`
`
`
`
`
`frnnasenenanncencncnsnnnnedencnadfenennnnecensconnand
`
`
`
`daeeneunncennaccnensecanaasnenseewemensannacbwerneabenfemiemepecuacncan|
`t 1iaH1Wiisancenecenennentcacsceneccensenshm
`
`
`
`\
`f
`=|
`{ends andthe mode
`i switchesto force control|
`1
`4
`i> Push-in amountat this;
`time smaller than push-in
`:
`i
`amount by measurement
`i
`:
`
`
`
`
`
`Reduction of
`impact and over-shoot
`4
`Ne-oreultenceof¥ contact trace
`
`Measurementposition =|.----.-.-.-.-_--------eeeeneneeteeneeeee
`
`10
`
`10
`
`

`

`Patent Application Publication
`
`Aug. 14, 2008 Sheet 10 of 11
`
`US 2008/0195353 Al
`
`
`
`
`
`[eqoldeeJ9]]04{U0D
`
`Oe’07
`
`ZL“Bis
`
`BAG;
`
`
`JO1]U098910}eoI0F4UEWUWUODBIO}
`SmarsUCD(uogejodiayul
`
`on20104jyuslueinseew
`
`a’ediDUISSaOO/C
`
`
`UtYOUMS|O1JUOS
`
`yohiel
`
`Joyydwe
`
`‘1I
`
`jul
`
`|[oa,U0D;UoRIsod
`
`%YOUMSHoVeStcdiiCeCyeoeared
`
`
`
`™,abineod+UuOnBIEJEI0yuonisod
`
`yobiey
`
`rs
`
`OL
`
`|
`
`i
`
`uOHeulUWS}ep
`
`J@A9|
`
`
`
`BJO)JUSLUDINSBSWY
`
`‘1
`
`yoejuog seqyunog
`
`
`
`
`yoeqpes)UdHISOdaNnjeAUooe}JepUOHISOd
`
`
`
`
`
`“edBuljjoyjuoouoHejngjeojeybig
`
`11
`
`11
`
`
`
`
`
`
`
`
`

`

`kK— T —
`Target measurement FOFCE ap }---—yra.-—---enennrnrenenenenneee
`
`
`
`
`
`
`
`Patent Application Publication
`
`Aug. 14,2008 Sheet 11 o0f11
`
`US 2008/0195353 Al
`
`Fig. 13
`
`(a) Lineartype
`
`Contact determination level
`
`(b) Exponenttype
`Force control command
`
`Target measurementforce «=
`
`
`
`}-.....
`
`
`
`Contact determination level =*
`
`(c) S-shapetype
`
`Force control command
`
`Target measurementforce = }-----.--.-----.------a-nes-05
`
`kK— T—
`
`
`
`Contact determination levels
`
`12
`
`12
`
`

`

`US 2008/0195353 Al
`
`Aug. 14, 2008
`
`PROFILING CONTROLLING METHOD AND
`CONTROLLER FOR CONTACT TYPE
`PROBES, AND CONTACT TYPE MEASURING
`MACHINE
`
`
`
`
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`[0001] The disclosure of Japanese Patent Application No.
`2007-32933filed on Feb. 14, 2007 including specifications,
`drawings and claims1s incorporated herein by referencein its
`entirety.
`
`
`
`BACKGROUNDOF THE INVENTION
`
`1. Field of the Invention
`[0002]
`[0003] The present inventionrelates to a profiling control-
`ling method and controller for contact type probes, and a
`contact type measuring machine. Moreparticularly,it relates
`to a contacttype probeprofiling controlling method and con-
`troller capable of measuring a shape, roughnessof a surface
`or the like of a soft object to be measuredsuchasa plastic lens
`or aluminum product while leaving noncontact trace on the
`object, and a contact type measuring machine equipped with
`the contact type probe whichis profiling-controlled bythe
`controller.
`
`2. Description of the Related Art
`[0004]
`[0005] As a touch sensor for probes used in the case of
`measuring a fine surface shape of an object to be measured
`with a fine shape measuring machineor a surface roughness
`measuring machine, or measuring an inner shape of a hole
`with a small hole measuring machine,the applicant proposes
`an excitation type force sensor shown in FIG. 1, the sensor
`being disclosed in Japanese Published Unexamined Patent
`Application No. 2001-91206 (Patent document 1). In the
`force sensor 10, piezoelectric elements 20 is adhered to both
`surfaces of a metallic base 12 integrated with a stylus 14, the
`piezoelectric element being separated into an exciting elec-
`trode (referred to as an exciting piezoelectric element) 22 and
`a detecting electrode (referred to as a detecting piezoelectric
`element) 24. Additionally, a contact point 16 constituted bya
`diamondchip or rubyballis fixed to a tip (lower end in FIG.
`1) of the stylus 14.
`[0006] An example ofa relationship between input ampli-
`tude and output amplitude ofthe force sensor 10 is shown in
`FIG.2. In the case where the contact point 16 is in noncontact
`with a work 8 which is an object to be measured, when a
`specified input amplitude Piis applied to the exciting piezo-
`electric element 22, the stylus 14 vertically ultrasonically
`vibrates at an amplitudeof, for example, several nm to several
`tens nm,and a signalof an output amplitude Po appears in the
`detecting piezoelectric element 24.
`[0007] Whenthe contact point 16 comes into contact with
`the work 8, as shown in FIG.3, the magnitude of the output
`amplitude decreases from Po to Px. When an output ampli-
`tude ratio kO=(Px/Po)x100=90%, 135 [UN] is obtained as
`measurementforce F in an example ofa relationship between
`the output amplitude ratio kO and the measurementforce F.
`When the force sensor 10 connected to an actuator (not
`shown)is controlled so that the output amplitude ratio k0 is
`constantly kept, measurement force (F) fixed profiling mea-
`surement (referred to as force fixed profiling measurement)
`can berealized that is capable of measuring a shapeor rough-
`ness ofthe work 8.
`
`In the case of measuring the work with use of a
`[0008]
`contact type probe, as shown in FIG. 5, approach (operation
`of shifting the probe, at low speed, for contact with the object
`to be measured, detecting the contact, and stabilizing the
`contact by a target measurementforce) to the work 8, which
`is the object to be measured,is required. Since, in sucha force
`sensor 10, there occurs no measurement force unless the
`sensor comes into contact with the object to be measured,
`approach drive before contact with the force sensor and the
`object to be measured is normally performed by position
`control, etc., using a scale detector, and the position controlis
`switched to force control after the contact with the sensor and
`the work 8. Then, the work 8 or probe (force sensor 10)
`attachmentsideis driven, and the sensor scans a surface ofthe
`work in a force controlstate. During the scan,a scale value of
`the probe and a position of the work are read as a shape
`measurement position. Then, after the force fixed profiling
`measurement ends,the force control 1s switched to the posi-
`tion control, and the sensorretractsto a retraction position.
`[0009] During the approach operation, the target measure-
`ment force (force judged at which contact is stabilized) is
`compared, for detecting the contact, with the measurement
`force detected by the force sensor 10, andthe position control
`is switched to the force control at the time when the measure-
`mentforce exceedsthe target measurementforce. In this case,
`a delay time, e.g. about 100 1s, is caused to contact determi-
`nation due to delayof an electric circuit, delayof calculation
`time of a digital controller, or the like. Consequently, as
`shown in FIG. 6, the probe is pushed into the work more
`deeply (over-push) than a position (measurementposition)
`where the sensor is pushed into the work by the target mea-
`surement force. Further, when an approach speed1s increased
`for raising measurementefficiency, not only does the amount
`of over-push become large but an impact in the contact
`becomelarge, and, a contact trace remains on the object to be
`measured, which may cause problem especially in the case
`wherethe object is a lens or metal mold.
`[0010]
`In order to prevent a contact trace from occurring
`due to approach, as shown in FIG. 7, a method has been
`conventionally employed that reduces, by reducing the
`approach speed as much aspossible, the push-in amount, as
`muchas possible, caused bythe delay time in the contact
`determination and simultaneously reduces the impact in the
`contact, and thus prevents the contacttrace from occurring on
`the object to be measured.
`[0011] However, inthe method, the approach speed must be
`reduced as muchas possible, and the measurementefficiency
`is conspicuouslylowered.
`
`SUMMARYOF THE INVENTION
`
`[0012] The present invention was made in order to solve the
`above problem, and aims at preventing a contact trace from
`occurring on an object to be measured without reducing an
`approach speed as muchas possible and lowering measure-
`mentefficiency.
`[0013]
`In order to solve the above problem, in the present
`invention,in profiling control of a contact type probe in which
`a contact point is moved along the object to be measured,
`while being in contact with the object by a fixed measurement
`force, a contact determination level is provided for detecting
`a predetermined force lower than the target measurement
`force is applied to the contact poit, contact determination is
`performedat the time when the force applied to the contact
`point reaches the contact determination level during the
`
`13
`
`13
`
`

`

`US 2008/0195353 Al
`
`Aug. 14, 2008
`
`approach, and the contactpointis shifted from position con-
`trol to force control for bringing the contact point into contact
`with the object to be measured by the target measurement
`force.
`
`
`
`[0014] The predetermined force can be considered to be a
`force at which contact can be predicted for the object to be
`measured and the contact point begins.
`[0015] The approach speed can be selected so asto satisfy
`the following inequality:
`[0016]
`(push-in amountat contact determination level
`[0017]
`+push-in amount by delay time of contact determi-
`nation)
`[0018] =push-in amount by measurementforce.
`[0019] A commandvalueof the force control is interpo-
`lated and gradually increased from the contact determination
`level to the target measurement force, and thus an impact
`increaseor over-shoot can be prevented from causing due to
`high response.
`[0020] Additionally, an interpolation curve of the force
`control commandvalue can beclassified into a linear type,
`exponent type or S-curvetype.
`[0021] Additionally, an interpolation timeofthe force con-
`trol commandvalue can be made variable.
`
`[0022] Thepresent invention providesa profiling controller
`for contact type probes, in which the contact point is moved
`along the surface of
`the object to be measured, while being in
`contact with the object by a fixed measurement force, the
`controller including:
`[0023]
`contact detecting means for detecting a predeter-
`mined contact determination level force lower than thetarget
`measurement force is applied to the contact point;
`[0024]
`position controlling meansfor controlling a position
`of the contact point;
`[0025]
`force controlling means for controlling measure-
`mentforce applied to the contact point; and
`[0026] means for performing the contact determination at
`the time whenthe force applied to the contact point reaches
`the contact determination level during the approach, and
`shifting the contact pointfrom the position controlto the force
`control for bringing, by the target measurement force, the
`contact point into contact with the object to be measured.
`[0027] Additionally, the present invention provides a con-
`tact type measuring machine equipped with the contact type
`probeprofiling-controlled bythe controller.
`[0028] According to the presentinvention, the contact trace
`can be prevented from occurring on the object to be measured
`without reducingthe approach speed as muchas possible and
`lowering measurementefficiency.
`[0029] These and other novel features and advantages of
`the present invention will becomeapparent from the follow-
`ing detailed description of preferred embodiments.
`
`
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`FIG. 3isa graph indicating an example of change in
`[0033]
`the output amplitude at contact, disclosed in patent document
`1.
`Tr
`FIG. 4 is a graph indicating an example ofa rela-
`[0034]
`tionship between an output amplitude ratio and measurement
`force, disclosed in patent document1.
`[0035]
`FIG. 5is a view showing an exampleofforce fixed
`profile measurement using the force sensor.
`[0036]
`FIG. 6 is a view showing a state where a contact
`trace occurs, due to approach, on an object to be measured,
`disclosed in patent document 1.
`[0037]
`FIG. 7 is a graph indicating a state where an
`approach speed is low, disclosed in patent document1.
`[0038]
`FIG. 8 is a graph indicating operation of a first
`embodimentof the present invention.
`Td
`[0039]
`FIG. 9 is a block diagram illustrating a constitu-
`tional example of a probe system for carrying out thefirst
`embodiment.
`
`FIG. 10 is a graph indicating a problem ofthe first
`[0040]
`embodiment.
`Td
`[0041]
`FIG. 11 is a graph indicating operation of a second
`embodimentof the present invention solving the problem of
`the first embodiment.
`
`
`
`
`
`TI
`
`FIG. 12 is a block diagram illustrating a constitu-
`[0042]
`tional example of a probe system for carrying out the second
`embodiment.
`
`FIG. 13 is a graph indicating an example of an
`[0043]
`interpolation curveof a force control commandofthe second
`embodiment.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`
`
`invention will be
`[0044] Embodiments of the present
`described below in detail with referenceto the drawings.
`[0045]
`a first embodiment of the present invention, as
`shownin FIG.8, a contact determination level is provided for
`approach to an object to be measured,the level for detecting
`a predetermined force (force that it can be predicted contact
`begins) lower than the target measurementforce (force thatit
`is judged contactis stable for measurement) is applied to a
`contact point, the force being, contact determination is per-
`formed at the time when force applied to the contact point
`reaches the contact determination level during the approach,
`and the contact point is quickly shifted from position control
`to force control for bringing, by the target measurementforce,
`the contact point into contact with the object to be measured.
`[0046] Here, the contact determination levelis set as a state
`where measurement force smaller than the target measure-
`mentforce is generated. The push-in amountof a position of
`the probe at the contact determination level is smaller than
`that of a position of the probe pushed into the object by the
`target measurement force. When the force applied to the
`contact point reaches the contact determination level, the
`contact determination is performed, and position control is
`switched to force control.
`
`[0030] The preferred embodimentswill be described with
`reference to the drawings, wherein like elements have been
`denoted throughout the figures with like reference numerals,
`mination level, and the position control is switched to the
`and wherein;
`force control. Therefore,ifan approach speeds selected so as
`to satisfy the following inequality:
`
`[0031] FIG.1is a perspective view of a force sensor dis-
`closed in patent document1.
`[0048]
`(push-in amountat contact determination level
`[0049]
`+push-in amountby delaytime of contact determi-
`[0032]
`FIG. 2 is a graph indicating an example of a rela-
`nation)
`tionship between excitation amplitude and output amplitude,
`disclosed in patent document1.
`[0050] =push-in amount by measurementforce,
`
`In the method, the contact determination is per-
`[0047]
`formed at the time when the force exceeds the contact deter-
`
`14
`
`14
`
`

`

`US 2008/0195353 Al
`
`Aug. 14, 2008
`
`over push-in doesnot occur, and noncontacttrace remains on
`the object to be measured.
`[0051]
`FIG. 9 showsa constitutional example of a contact
`type profiling probe system employing a digital controller, to
`carry out the embodiment. In FIG. 9, a probe 30 includes: a
`force sensor 10 for detecting the measurement force, the
`sensor being similar to a conventional sensor; a drive actuator
`32 for driving a tip of the probe in positioning control and
`force fixed profiling control; anda scale 34 andscale detector
`36 for performing position feedback and counting a shape
`position detection value.
`[0052] Additionally, a controler 40 includes: a drive ampli-
`fier 42 for supplying powerto the drive actuator 32 of the
`probe 30 side; a counter 44 for counting a position of the
`probe based on output of the scale detector 36; an analog/
`digital (A/D) converter 46 for converting an analog signal
`from the force sensor 10 into a digital signal; and a digital
`control calculating part 48 capable of controlling the switch-
`ing ofthe position control and force control.
`[0053] Moreover, in the case of the probe system for per-
`forming the forcefixed profiling as shown in FIG.9, in terms
`of improvement of measurement efficiency, the probe is
`desired to followshape variation, as fast as possible, of the
`object to be measured. Accordingly,it is requiredto set a loop
`gain of a force control loop high and to make high-response.
`In this state, whenthe first embodimentis applied, as shown
`in FIG. 10, impact increase and over-shoot occur due to the
`high response, and there 1s a possibility that the contacttrace
`remains on the object to be measured.
`[0054]
`In order to solve such problemsofthe first embodi-
`ment, in a second embodimentof the present invention, as
`shownin FIG.11, a force control command whentheposition
`control is switchedto the force controlis not raised at once to
`
`being used for an acceleration curve ofthe position control,
`and can be arbitrarily selected in accordance with a measure-
`ment condition or the like.
`[0059]
`In the case ofthe linear type interpolation curve in
`FIG. 13(a), controlis simple. On the other hand,in the case of
`the S-curve type interpolation curve in FIG. 13(c) being used,
`calculation is difficult, but extremely smooth control can be
`performed. Additionally, in the exponent type interpolation
`curve in FIG. 13(6), control can be performed more smoothly
`than that when the linear type interpolation curve in FIG.
`13(a) is used, and calculation can be performed moreeasily
`than that when the S-curve type interpolation curve in FIG.
`13(c) is used.
`[0060] Additionally, an interpolation time T of shift from
`the contact determination level to the target measurement
`force can be arbitrarily selected, the time being shownin FIG.
`13. For example, in the case of an object to be measured on
`which a contact trace easily occurs, the interpolation time is
`lengthened, and in the case of an object to be measured on
`which a contact trace hardly occurs, the interpolationtime is
`shortened. Thus, the measurementefficiencycan be raised.
`[0061] Alternatively,
`in place of the interpolation time,
`increase (inclination) offorce for unit time maybeset like the
`acceleration commandofthe position control.
`[0062] A user thus can select a proper interpolation pro-
`cessing in accordance with properties of the object to be
`measured, and can perform approach operation excellent in
`the measurementefficiency without causing a contact trace.
`[0063] Moreover, though the applicant used, in the embodi-
`ments, the force sensor disclosed in patent document 1, a
`probe of the present invention is not limited thereto. The
`present invention can be similarly applied to any probe as
`longas it can observe fine measurement force. Additionally,
`the probe system is not limitedto a digital constitution.
`[0064]
`It should be apparentto those skilled in the art that
`the above-described exemplary embodiments are merely
`illustrative which represent the application of the principles
`of the present
`invention. Numerous and various other
`arrangements can be readily devised bythose skilled in the art
`without departing from the spirit and the scope of the inven-
`tion.
`
`the target measurementforce, but interpolated and gradually
`raised so as to approachthe target measurement force. Thus,
`the impact and the over-shoot in contact are reduced, and the
`contact trace can be prevented from occurring.
`[0055]
`FIG. 12 showsa constitutional example of a probe
`system of the embodiment.
`[0056] The probe system is different fromthe probe system
`shown in FIG. 9 in the point that a force control command
`Whatis claimedis:
`interpolation processing part for subjecting the target mea-
`1.Aprofiling controlling method for contact type probes,
`surementforce to interpolation processing and makingit into
`in which a contact point is moved along a surface of an object
`the force control commandis provided inthe digital control
`to be measured, while being in contact with the object by a
`calculating part 48. The system is similar to that shown in
`specified measurement force, comprising the steps of:
`FIG. 9 in other points, therefore, description of the points is
`omitted.
`providing a contact determination level for detecting a
`predetermined force smaller than a target measurement
`force is applied to the contact point;
`performing contact determination at the time when force
`applied to the contact point reaches the contact determi-
`nation level during approach; and
`to force
`shifting the contact point from position control
`control for bringing the contact point into contact with
`the object by the target measurementforce.
`2. Theprofiling controlling method for contact type probes
`according to claim 1, wherein
`the predetermined force is a force at which contact can be
`consideredto be predicted for the object to be measured
`and the contact point begins.
`3. Theprofiling controlling method for contact type probes
`according to claim 1, wherein
`speed of the approachis selected so as to satisfy the fol-
`lowing inequality:
`
`[0057] Here, occurrence ofthe contacttrace on the object to
`be measured depends on conditions such as properties, such
`as shape and hardness, of a contact part of the force sensor,
`approach speed, magnitude of impact in contact, properties
`such as hardness of a surface of the object to be measured,
`control performanceofthe position control and control per-
`formanceofthe force control. Thus, force control command
`interpolation processing may include the following perfor-
`mances.
`
`[0058] That is, as shown in FIG. 13, an interpolation curve
`ofthe force control commandcan beselected and used from
`
`arbitrary curves. In FIG. 11, the interpolation curve is shown
`by a straight line connecting the contact determination level
`and the target measurement force as shown in FIG. 13(a).
`However, interpolation curves of various types such as the
`exponent type shown in FIG. 13(), S-curve type shown in
`FIG. 13(c) and the like can be used, the interpolation curve
`
`15
`
`
`
`15
`
`

`

`US 2008/0195353 Al
`
`Aug. 14, 2008
`
`(push-in amountat contact determination level
`+push-in amountby delay time of contact determination)
`“Spush-in amount by measurementforce.
`4. Theprofiling controlling method for contact type probes
`according to claim 1, wherein a
`a command value of force control is interpolated and
`gradually increased fromthe contact determination level
`to the target measurementforce.
`5. Theprofiling controlling method for contact type probes
`according to claim 4, wherein
`an interpolation curveof the force control command value
`is linear.
`
`6. The profiling controlling methodfor contact type probes
`according to claim 4, wherein
`the interpolation curve ofthe force contro] commandvalue
`is an exponenttype.
`7. The profiling controlling method for contact type probes
`according to claim 4, wherein
`the interpolation curve ofthe force contro] commandvalue
`is a S-curve type.
`8. The profiling controlling method for contact type probes
`according to claim 4, wherein
`
`an interpolation time ofthe force control commandvalueis
`variable.
`9. Aprofiling controller for contact type probes,in which a
`contact point is moved along a surface of an object to be
`measured, while being in contact with the object by a speci-
`fied measurementforce, the controller comprising:
`contact detecting meansfor detecting a predetermined con-
`tact determination level force lower than a target mea-
`surementforce is applied to the contact point;
`position controlling meansfor controlling a position ofthe
`contact point;
`force controlling meansfor controlling measurement force
`applied to the contact point; and
`means for performing contact determination at the time
`when the force applied to the contact point reaches the
`contact determination level during approach, and shift-
`ing the contact point fromposition control to force con-
`trol for bringing the contact point into contact with the
`object by the target measurementforce.
`10. A contact type measuring machine comprising a con-
`tact type probe profiling-controlled bythe controller of claim
`9.
`
`Hoe ee
`
`16
`
`16
`
`