Joural of Robotics ad Mechaical Egieerig Research The NC Machie Tool Roudess Error Test Method Based o EIB74 Su Yili, Hou Xuya *, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua Harbi Istitute of Techology www.verizoaoliepublishig.com Vol:, Issue: 3 *Correspodig author: Dr. Hou Xuya, Lecturer, School of Mechatroics Egieerig, Harbi Istitute of Techology, Room 427, Buildig 2F, Yi-kuag Street, Nagag District, Harbi, Heilogjiag, Chia, Tel: +86-045-8643857, Fax: +86-045-8643857; Email: hitrcamc@foxmail.com Article Type: Research, Submissio Date: 0 Jauary 206, Accepted Date: 2 Jauary 206, Published Date: 08 February 206. Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. Copyright: 206 Su Yili, Hou Xuya, et al. This is a ope-access article distributed uder the terms of the Creative Commos Attributio Licese, which permits urestricted use, distributio, ad reproductio i ay medium, provided the origial author ad source are credited. Abstract I order to achieve the detectio of the machie tool roudess error. Usig KGM gradig ecoder to obtai the measuremet sigal. Choosig sigal acquisitio card EIB74 to collect siusoidal icremetal sigals from KGM gradig ecoder. Usig TCP/IP commuicatio deal to coect the acquisitio card with persoal computer. The ecoder supportig software have licese that it ca oly istall o oe computer ad its operatio iterface is umodifiable i foreig laguage that is hard for workers to use. Labview software was used to develop programs for sigal processig o PC. The roudess error of acquisitio ad aalysis system based o virtual istrumet was studied. The program based o the roudess error s real time acquisitio, storage ad amedmet ad is desiged. The measure ad assessmet method of the machie tool roudess error is proved valid through the experimet. Keywords: Roudess error, Acquisitio card, Labview, Virtual istrumet. Itroductio The detectio of the machie tool s error has great relatioship with the accuracy of error mode, ad error of machie tool will affect result of error compesatio of machie tool [-2]. Error measuremet is ot oly the foudatio of machie error detectio, but also a importat techology of reactig machie accuracy ad error compesatio. Therefore, Experts ad scholars from home ad abroad have made a lot of effort o studyig lots of methods of measuremet error. Roudess error measuremet is oe of the most commo mechaical measuremets. The commoly small displacemet measuremet method is usig sesors to detect small displacemet, the coverted ito aalog sigal ad set to the data acquisitio card. Powerful aalysis fuctio of virtual istrumets is i base of software [3-6]. So, we ca establish a set of roudess detectio ad aalysis system usig virtual istrumets to measure roudess error, the achieved data acquisitio, data processig ad error display fuctios. Data acquisitio system hardware ad theory The virtual istrumet of the roudess error measure produces sigal by usig ecoder. It costruct with sigal acquisitio card EIB74 ad persoal computer, show as Figure. Figure : The system hardware structure The compositio ad priciple of gratig ecoder The high plae gratig ecoder KGM82 which is used to detect the machie tool s two-dimesio motio trail precisio is a kid of o-cotact optics measure istrumet. It is produced by Germay Heidehai Compay [7-9]. It is show i Figure 2. Figure 2: Heidehai KGM82 ecoder J Robot Mech Eg Resr (3). Page 22
Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. KGM82 ecoder s measures radius from mm to 5mm. It fits micro radius ad high speed feed measuremet ad uses twodimesio measuremet. It ot oly measure positio error, but also detects the reality velocity ad acceleratio via the relatio of time ad positio. Through the measured outlie data ad error graph, the machie tool s motio precisio ca be obtaied easily ad source of the machie error ca be judged easily. Gratig ecoder cosists of two parts, scale gratig ad gratig readig head. Gratig readig head icludes light source, photoelectric elemet, les, idicatig gratig. As show i Figure 3. the accurate displacemet of the movig parts. I the process of movig, the light itesity was chaged with siusoidal fuctio. Optical sigals as the moire frige which was received by photoelectric elemet is trasformed ito sie voltage sigal. Ad usig sigal processor to amplifyig ad differetial coefficiet processig the voltage sigal. The detected displacemet is proportioal to the outputted pulse voltage sigal. Usig the photoelectric elemet to trasform the optical sigals with siusoidal variatio to electrical sigals with siusoidal variatio, as show i Figure 5. Accordig to the phase relatioship of sigal which was output by the photoelectric elemet, we ca determie the gratig movig directio. The voltage is (2) Figure 3: The compositio of gratig ecoder The scale gratig ad idicative gratig ca be called as log gratig ad short gratig. I the test, two gratigs overlap with each other i parallel. Keep the clearace from 0.0mm to 0.mm. The log gratig rotatig a tiy agle θ relative the short gratig i its ow plae. Whe light hittig the gratig i parallel it causes the effect of the light trasmissio ad diffractio. I the vertical directio with the agle bisector of two gratig. There will be thick stripe of alteratig light ad shade, equal iterval. We call it moire frige. As show i Figure 4. Amplify the voltage sigal ad the sigal trasform to square wave, the coverted to pulse sigal. Fially usig digital form display physical displacemet. The displacemet is equal to the product of pulse ad lattice spacig. The resolutio measure is equal to the lattice spacig. To the mutual vertical two-axis o the plae of the machie tool, KGM outputs two 90 degrees phase differece ad 4µm Figure 5: The electrical sigals of light itesity Figure 4: Moire Frige Moire frige have displacemet amplificatio effects. The relatio betwee the space of moire frige B ad the stripe agle of two gratig θ is By the above formula, as the value of θ is too small, the space of moire frige B is much bigger tha W. Two gratig move a lattice spacig W, the the moire frige movig a frige spacig B. So the light o a fixed poit of the gratig chage the light itesity for oce. The photoelectric elemet ca acquire the umber of moire frige stripe, the we will kow how may lattice that the gratig moved. Thus to kow () period sigal, measurig sigal set to the persoal computer for subsequet processig. EIB74 acquisitio card is used to coect KGM ad the computer. EIB74 ca subdivide the siusoidal sigal for 4096 times. So every axis s measuremet step distace is about m. Data acquisitio card The EIB 74 is a exteral iterface box for precise positio measuremet. It is ideal for ispectio statios ad multipoit ispectio apparatuses as well as for mobile data acquisitio, such as i machie ispectio ad calibratio. The EIB 74 is ideal for applicatios requirig high-resolutio ecoder sigals ad fast data loggig. Etheret trasmissio also eables you to use switches or hubs for coectig more tha oe EIB 74. A maximum of four HEIDENHAIN ecoders, either with siusoidal icremetal sigals ( VPP) or with EDat iterfaces (EDat 2. ad EDat 2.2) ca be coected to the EIB 74[0-]. The EIB 74 subdivides the periods of the icremetal sigals 4096-fold for measured-value geeratio. The deviatios withi oe sigal period are automatically reduced by adjustig the siusoidal icremetal sigals (sigal compesatio). The itegrated measured-value memory eables the EIB 74 to save up to 250,000 measured values per axis i recordig mode. J Robot Mech Eg Resr (3). Page 23
Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. Figure 6: Basic circuit diagram of the EIB Iteral or exteral triggers ca be used for axis-specific storage of the measured values. A stadard Etheret iterface usig TCP or UDP commuicatio is available for data output [2-4]. This permits direct coectio to a PC, laptop or idustrial PC. The stadard Etheret based o TCP/IP commuicatio deal is used to output data. Therefore it ca cotact the laptop via ettig cable. Roudess error data processig algorithm KGM ecoder outputs two siusoidal sigal whose directios are differet ad sigal cycle legths both are 4µm. EIB74 data acquisitio card ca subdivide oe sigal cycle legth for 4096 times. Therefore the uit legth of the positio coordiates captured by the computer directly is: L =4μm/4096 =/024μm. While measurig the machie tool s circular arc iterpolatio precisio, the motio trail of the machie tool s x axis ad y axis is show i Figure 7. The motio trail starts from circle ceter, moves distace R alog x axis, ad returs to the circle ceter alog y axis after movig 450 degrees i clockwise directio Figure 7: The x axis ad y axis trajectory curve alog R radius circle. Ad the it moves distace R alog the egative axis y, ad returs to the circle ceter alog x axis after movig 450 degrees i aticlockwise directio alog R radius circle. Because the ceter of the machie tool motio arc is t i the absolute origi pf coordiates, so we eed acquisitio the actual circle ceter firstly. Eve though the machie tool does t operate, the positio coordiates captured by the data acquisitio card are fluctuated. Therefore the machie tool stay for T to obtai the mea coordiate O (a,b) of the circle ceter. a = b = x i i= y i i= Where xi ad yi are the actual coordiates of axis x ad axis y, is the umber of the acquired ceter coordiates. Startig from time T2, we ca obtai ew positio coordiates by subtractig the circle ceter coordiates from actual acquired positio coordiates. This ca guaratee that the circle ceter of circle trail is i the origi of the coordiate. x' = x x i i i i = y' = y y i i i i = While measurig, the ecoder ca acquire all the poits of the machie tool motio trail. However error aalysis just eeds oe forward circle ad oe reverse circle. This is show i Figure 8. The time θi= 330 is chose as the start poit ad the ed poit of sigal acquirig ad storig. Namely we start to acquire the positive arc trail while y'i -R/2, ad we termiate the acquirig while y'i -R/2 agai. Ad the the arc moves alog the egative (3) (4) (5) (6) J Robot Mech Eg Resr (3). Page 24
Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. k times. We also eed add the radius r of the base circle to the magified error. Ad the we trasform the chage relatio of phase positio ad amplitude back ito the positio chage relatio of the rectagular coordiate system, so we ca obtai the ew positio relatio curve about x''i ad y''i. Fially the machie tool roudess error is show visually. (7) Above formula: (8) Figure 8: Two set of trajectory curve directio. At this time we start to acquire the egative arc trail while y'i>-r/2, ad we termiate the acquirig while y'i>-r/2 agai. At last, achieve the fuctio of adjustig the acquirig arc trail. The positio coordiates set before ad after adjusted are show i Figure 9 ad Figure 0 respectively. I order to see the micrometer-level error of the cetimeter-level circle visually, we should magify the error. Firstly trasform the positio chage relatio of x'i ad y'i i the rectagular coordiate system ito the chage relatio of phase positio θi ad amplitude Ri. Obtai the roudess error by subtractig the radius R. The error level ca be see by magifyig the error Software programmig base o Labview (9) As show i Figure is the simulatio sigal geerator. Usig two sigal geerator with same frequecy ad amplitude, the phase differece is 90 degrees. The two sigals are correspodig to the X axis ad Y axis i the horizotal plae. Fially, the simulatio data of circular trajectory was displayed. I order to see the micrometer-level error of the cetimeter-level circle visually, we should magify the error. As show i Figure 2 is the program diagram of sigal amplificatio processig. Figure 9: The uadjusted coordiates collectio Figure 0: The adjusted coordiates collectio Figure : Sigal simulatio circle diagram Firstly trasform the positio chage relatio of x'i ad y'i i the rectagular coordiate system ito the chage relatio of phase positio θi ad amplitude Ri. Obtai the roudess error by subtractig the radius R. The error level ca be see by magifyig the error k times. We also eed add the radius r of the base circle to the magified error. Ad the we trasform the chage relatio of phase positio ad amplitude back ito the positio chage relatio of the rectagular coordiate system, so we ca obtai the ew positio relatio curve about x''i ad y''i. Fially the machie tool roudess error is show visually. As show i Figure 3 is the program chart of the simulatio sigal processig. Two sigal geerators geerate two siusoidal sigals with 90 degrees phase differece. Usig coversio module coverted the rectagular coordiates system to polar coordiates system. The subtract the amplitude of the simulatio J Robot Mech Eg Resr (3). Page 25
Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. a) Switch to polar coordiates system b) Obtai the error by subtractig the radius c) magifyig the error d)add the radius of the base circle to the magified error e) Switch back to Rectagular coordiates system Figure 2: The process of magify the error Figure 3: Sigal processig simulatio program block diagram J Robot Mech Eg Resr (3). Page 26
Citatio: Su Yili, Hou Xuya, Zhag Kailiag, Zhag Kaidi, Liag Pig ad Deg Zogqua (206) The NC Machie Tool Roudess Error Test Method Based o EIB74. J Robot Mech Eg Resr (3): 22-27. sigal. Amplitude of the uit from cetimeter to micrometer by magifyig the error 0000 times. We add the radius r of the base circle to the magified error. Ad the we covert the polar coordiates system back ito the rectagular coordiate system. Usig shift register is to store the simulatio sigals geerated by each axis. Otherwise we oly ca see the poit istead of showig the full circle. For example, the phase of two axes is 90.0degrees istead of 90 degrees. It is the simulatio of straight agle error of machie tool. We caot see the error size or error type o the origial trajectory because we did ot do ay processig. As show i Figure 4, we ca see the error size ad error type clearly after amplificatio. Figure 4: The graphics of the Roudess error The experimet of data acquisitio system ad result aalysis The KGM had its supportig software. We usig the supportig software to collected the data ad display the graph. The we test the Labview program. Whe we ope the Labview program, we eed to set up parameters at first, such as the error amplifier gai, the machie tool s ruig arc radius, size of the base circle. Ruig the software after settig the parameters, the roudess error graphics ad error magitude displayed. We compare the graph that usig the program desiged by Labview that savig by the ecoder to the graph that usig the ecoder supportig software. As show i Figure 5, the two graphs were exactly the same. Figure 5: Cotrast the error curve accordig to two software by the same set of data Coclusio ad Outlook Through the experimet. It is tested that software desiged by Labview ca achieve the fuctio of roudess error acquisitio ad error aalysis. The complete circle trajectory are extracted successfully ad displayed directly. The measure ad assessmet method of the machie tool roudess error is proved valid through the experimet. This method ca solve the reality problem that is coveiet for worker to use ad get rid of the limit of permissios. We ca also achieve further ew fuctio by Labview i the view of the sigal processig. Refereces. Kakio Y, Ihara Y, Nakatsu Y, et al. The Measuremet of Motio Errors of NC Machie Tools ad Diagosis of their Origis by Usig Telescopig Magetic Ball Bar Method[J]. CIRP Aals - Maufacturig Techology. 987; 36():377-380. 2. Kap W. Test of Three-Dimesio Ucertaity of Machie Tools ad Measurig Machies ad its Relatio to the Machie ErrorAals of the CIRP. 983; (32):459-464. 3. Su bao shou, Zha fa, Zhag Lei. Labview ad virtual roudess error measurig istrumet. J. Of ahui Uiversity of techology. 2005; 07:259-26. 4. Kalkma DCJ. LabVIEW: a software system for data acquisitio, data aalysis, ad istrumet cotrol. Joural of Cliical Moitorig. 995; ():5-58. 5. YE Huai chu, LI Zhi qiag, WANG Peg xiag, et al. Geometry ad positio error measurig system of CNC machies based o LabVIEW[J]. Joural of Mechaical & Electrical Egieerig. 200:26-28. 6. Wa W. Roudess Error Measuremet ad Aalysis System Study Based o LabVIEW[J]. Machie Tool & Hydraulics. 20:80-82. 7. Ochi T. Itroductio of update Heidehai absolute liear ecoder over 4m.The Maufacturig & Machie Tool Coferece. The Japa Society of Mechaical Egieers. 2004:83-84. 8. Che M, Xiog A, Fa Y. Uiversal Module for Sigal Measurig ad Processig of Heidehai Ecoders Based o FPGA ad DSP[J]. Microcotrollers & Embedded Systems. 204:28-3. 9. Warer M, Krabbedam V, Schumacher G. Adaptive periodic error correctio for Heidehai tape ecoders. Proc Spie. 2008; 702:7023N-7023N-8. 0. SUN Shi-wei, CHEN Xiu-cai, WANG Feg-rui. Reedig Method Study of Absolute Ecoder with Edat Iterface. Jiagsu Electrical Apparatus. 2008; 0:4-7.. Yao Jua, Zhag Zhijie, Li Lifag. Desig ad implemetatio of data acquisitio system based o LabVIEW ad TCP. Measuremet Cotrol Techology ad Istrumets. 202; 07:72-74. 2. Zhag dog, Shi Qi-feg, Wag Yu-bo. Developmet ad applicatio of data acquisitio system based o LabVIEW ad TCP. Metallurgical Idustry Automatio; 20; 03:36-40. 3. Yag H R, Liu G, Rog-Yu X U. TCP/IP techique applicatio i ispectig system[j]. Chia Measuremet & Testig Techology. 2008:42-44. 4. GAO Zha feg, DU Ya liag, LIU Yu hog, et al. Remote Data Acquisitio ad Trasmissio Based o LabVIEW[J]. Microelectroics & Computer. 2007; 24(3):02-04. J Robot Mech Eg Resr (3). Page 27