Research on error compensation and measurement technology in robot flexible measurement

Transcription

1 Reserch on error compenston n mesurement technology n robot flexble mesurement Yong-Je Ren, J-Gu Zhu, Xue-You Yng, Sheng-u Ye Stte Key Lbortory of Precson Mesurng Technology n Instruments Tnjn Unversty, 37, hn Tel.: + 86 [] Fx: +86[] ml: yongjeren@tju.eu.cn bstrct Focusng on the coornte mesurng mchne s ncpblty of crrng on rel tme mesurng of cr boy, the reserch of flexble mesurng mchne bse on robotcs ws propose. Through controllng the pose of the robot n spce, the stereovson sensors mounte t the en of robot coul rrve t the gven ponts to collect mge nformton one by one, n then the three menson coornte t coul be obtne fter processng the mge t. y usng lser trcker n one precson trget, together wth the whole clbrton metho, the reltonshp between sensor coornte system n user evlutton coornte system coul be estblshe. t the sme tme, the error cuse by the chngng of temperture of envronment n robot boy ws compenste. stsfyng mesurement result ws cheve fter collectng n clcultng the expermentl t. Ths system cn meet the nees of mult-moel vehcle mesurement n vrtue of ts flexblty n perfect mesurng wthout e ngle. Keywors: Lser trcker; flexble three coornte mesurng mchne; whole clbrton; temperture compenston; vrtul sensorntroucton. Introucton More n more ttenton s p to the on-lne etecton technology of pvotl qulty control ponts of cr boy by omestc n foregn utomoble mnufcturers. The three-mensonl poston n sze of the key ponts shoul be ensure. The flexble lser vson nspecton system wth nustrl robot s crrer n non-contct vson sensors s consttutor, not only cn mke full use of the flexblty n smll-re occupyng of robots, but lso cn vry ts progrm convenently so s to meet the nees of mult-type n mult-seres mesurement. It s prtculrly sutble for non-contct, rp n ccurte mesurement of lrge-scle specl-shpe prts on mult-moel vehcle proucton lnes.. omposton of the flexble on-lne lser mesurng system Uner norml crcumstnces, the robot vson nspecton system s compose of hgh-precson robot, vsul sensors whch re mounte t the en of robot, mesurement control cbnet, PL control cbnet n other prts. Fgure shows the lyout of the scene n Fg. shows the network topology. Inustrl robot s crrer for the movement of three-mensonl vsul sensor, not only gretly expns the workng spce of vson sensors, but lso retns the fetures of non-contct n rpty of vsul etecton system. The process of flexble lser mesurng system cn be explne s follows: the cr boy slps to the nspecton stton n fxes poston exctly, n the mn controller stton sens n plce sgnl to the nspecton PL controller PL controller checks the sgnl of boy postonng, sens boy type n strt sgnl to the robot fter recevng the sgnl, robot sens mesurement request n mesurement pont ID to PL controller t ech mesurng pont, wts for "mesurement completon" sgnl from PL controller -83

2 FIPIO us thernet Mesurng system gets mesurement request n mesurement pont ID sgnl from the PL,n strts mesurng n recorng t, n then elver t to the nlyss softwre, mesurement completon sgnl s sent to the robot when fnshng mesurement Robot receves the mesurement completon n moves to the next pont, here full mesurement s complete. Fg.. Lyout of scene. Offce 车间以太网 结果数据 omputer Sensor control sgnl Server R bnet Sensor Mesurng R bnet Sensor bnet R3 bnet Sensor 3 R4 bnet Sensor4 P utton PL RFID System Mn Lne PL ommuncton Sgnl PL bnet Sfe System Z sensor Fg.. etwork topology. Through plnnng the robot trjectory n vnce to mke ech mesurement pont locte n the optml vew fel of vsul sensor, n then three-mensonl mesurement cn be complete pont by pont. Three-mensonl vson sensors mounte t the en of robot's jont cnnot obtn -84

3 coorntes n workpece coornte system, but n the vsul sensor coornte system. Snce the robot three-mensonl poston mesurement s me t gettng pont s coornte n the workpece coornte system, the trnsformton between vsul sensor coornte system n workpece coornte system must be estblshe. Dgrm 3 s sketch mp for reltonshp mong coornte systems. There re four coornte systems: the bsc coornte system ( OR X RYR Z R ) n the en jont coornte system ( O X Y Z ) whch re estblshe whle nstllng the robot, the cr boy coornte system ( O W X W Y W Z W ) whch s etermne by the proucton lne n the vsul sensor coornte system ( O XY Z ). The mesurement results re the coornte PW of pont P n the boy coornte system ( O W X W Y W Z W ). X O X Y Z O X Y Z P P P W Vsul pose. Lser trcker Trget Vsul pose n O R X R Y R Z R work pece coornte system Z O W X W Y W Z W Fg. 3. Sketch of robot coornte systems. s cn be seen from Fg. 3 P Z X P () W Fg. 4. lbrton of lser on-lne mesurng system. Where P s the coornte of pont P n the vsul sensor coornte system; X s the robot hn-eye reltonshp, tht s trnsformton between the robot en jont coornte system n vsul sensor coornte system; s for trnsformton between the robot en jont coornte system n robot s bsc coornte system, whch cn be obtne through the robot knemtcs moel n the vrbles of ll jonts; Z s for trnsformton between robot s bsc coornte system n cr boy coornte system. In formul (), X n Z re unknown vrble, for the rg connecton of the vsul sensor n the robot en jont, the reltve poston of whch s nvrnt whle mesurng, thus X s constnt n mesurement. Smlrly, robot bsc coornte system s reltvely chngeless to the cr boy coornte system, tht s to sy, the Z vlue s lso constnt. Therefore, X n Z cn be clculte before mesurement. s long s coornte( P ) of pont P n the vsul sensor coornte system cn be got, ccorng to formul (), P coornte( P W ) n the cr boy coornte system cn be resolve. evertheless, f the robot theoretcl knemtcs moel ws use for clcultng ccorng to formul (), the fnl error coul be cuse ue to the lrge bsolute error of robot postonng. The whole clbrton metho s opte to vo ths svntge. 3. Whole clbrton metho When robot wth vsul sensor reches every effectve poston, the sensor cn only gther one pont s correltve nformton, n other wors, ll mesurng ponts re mppng to spce pose of robot. s t s s before, the trnsformton between vson sensor coornte system -85

4 n the workpece coornte system n ech locton must be bult n orer to get the ponts coornte n the workpece coornte system. Ths cn be relze by usng lser trcker n pre-clbrton precson trget (s shown n Fg. 4). For the clbrton of ech mesurement locton, frstly, trget shoul be fxe n the vew fel of vsul sensor, by usng vsul sensor to mesure the stnr holes on the trget, the reltonshp between sensor coornte system n trget coornte system cn be solve. Seconly, by usng lser trcker to mesure the trget, the reltonshp between trget coornte system n lser trcker coornte system cn be obtne. Thrly, through usng lser trcker to mesure the work pece, the reltonshp between lser trcker coornte system n work pece coornte system cn be got n the sme wy. Fnlly, through the trnsformton chn: sensor coornte system -> trget coornte system -> lser trcker coornte system -> work pece coornte system, the trnsformton between vsul sensor coornte system n work pece coornte system cn be receve. Repet the bove steps for the mesurement of ech locton, n then the whole robot clbrton cn be eventully cheve. Dfferent from fxe-mesurement system, the sensor n every poston s clle vrtul sensor. 4. Temperture error compenston prncple For the robot repete movement mong fxe poses n the flexble boy vsul etecton system, hgh repettve postonng ccurcy s requre. owever, the mesurement results wll be ffecte by the chngng of mbent temperture n the temperture of the on robot. In orer to ensure the stblty of the system, t s necessry to crry out effectve temperture error compenston for the robot. Whle robot s runnng, the en jonts n sensors on t tke reltve movement, tht s, hn-eye reltonshp wll not chnge once estblshe. ssumng tht evton exsts n one of the jont prmeters, then reltve trnsformton between the sensor coornte system n the robot bsc coornte system s: n n n n n n n ) ( n n n ) n ( () Dfferentl trnsformton exts: (3) In ths wy, expn formul () n leve out the hgh-orer tems we cn get: 3 (4) Usng D- moel, the homogeneous coornte trnsformton mtrx from jont - to jont cn be expresse s ths: sn sn sn sn sn sn mong them, re the lever prmeters of jont. Gettng fferentl trnsformton ccorng to formul (3): ( sn ) (5) -86

5 -87 sn sn sn sn (6) So formul (4) cn be wrtten s: (7) ccorng to the compenston moel, lner equtons cn be estblshe. Wthout tkng the nfluence of nose nto conserton, through smultve experment, the chngng of prmeters cn be entfe very ccurtely. Whle ntroucng nto of the rnom nose (smultve vlue rnge s from -.mm to +. mm), some of the prmeters wll chnge gretly. In orer to reuce the nfluence of nose, unknown elements cn be solve by ng more mesurement ponts to bul super-set equtons n pplyng generlze nverse mtrx. 5. pplcton of on-lne mesurement system Detecton work stton completes tsks wthout mnul work. The results (t) re shown n the form of chrts n curve n the etecton stton termnls. If ultr-poor etecton ws obtne, lrm sgnl woul be exporte by the stton. t the sme tme, the result cn be lnke nto plnt nformton systems through the locl re network (L), qulty ssurnce n relte eprtments my ccess n nlyze the t t ny tme by the network termnl n ech offce. In orer to mke better nlyss of the t, goo t mngement n nlyss softwre s neee. The functon hve Dtbse lnng,query n nlyss of vehcle t n other functons. 6. oncluson The current system wth the vntge of convenent, tme-svng n esy-to-use meets the prctcl requrements. If there s n ncrese n the cr type n the future, only re-progrmmng n re-emrctng re necessry, gretly reucng the t. Through n bsolutely on-lne mesurement of the boy, problems n the mnufcturng process cn be scovere erler n bss for the justment of boy processng cn be prove so s to crete better vehcles. References. Jose Murco S.T. Mott, Gulherme. e rvlho, R.S. McMster. Robot clbrton usng 3D vson-bse mesurement system wth sngle cmer. [J]. Robotcs n omputer Integrte Mnufcturng., 7, pp hng-je Lu. Flexble coornte mesurement system bse on nustrl robot for cr boy-n-whte. Journl of Optoelectroncs Lser. 6, 7(), pp. 7- (n hnese). 3. Yong-Je Ren, J-Gu Zhu. The esgn n relzton of sort of robot vson mesure system. Proc of SPI. 6, vol. 6344, 6344Z Z R.Y. Ts, n R.K. Lenz. new technque for fully utonomous n effcent 3D robotcs n hn/eye clbrton. I Trnsctons on Robotcs &utomton. 989, 5(3), pp