Use of Colour and Shape Constraints in Vision-based Valve Operation by Robot

Transcription

1 Use of Colour and Shae Constrants n Vson-based Valve Oeraton b Robot De Xu ; Mn Tan ; Zemn Jang & Huosheng Hu Ke Laborator of Comle Sstems and Intellgene Sene, Insttute of Automaton, Chnese Aadem of Senes, Bejng 00080, P.R. Chna, ude@omss.a.a.n Deartment of Comuter Sene, Unverst of Esse, Colhester CO4 3SQ, Unted Kngdom, hhu@esse.a.uk Abstrat: Ths aer rooses a new strateg for a humanod robot to aroah and oerate a valve based on olour and shae onstrants. It onssts of four stages, namel rough base aroahng, fne base aroahng, rough hand aroahng and fne hand aroahng and grasng. The robot estmates the objet s oston usng ts stereo-vson at the frst stage. A new vsual ostonng method s used to determne the valve s oston and ose n the robot s frame n the seond stage. When ts hands are near the valve, a vsual servong method s emloed to ath the handle of the valve va ameras n end-effetors. The advantages of both ee-n-head and ee-to-hand sstems are eloted. Eermental results are resented to verf the effetveness of the roosed method. Kewords: Vsual ostonng, vsual ontrol, hand-ee sstem, autonomous manulaton, humanod robot.. Introduton Hand-ee sstems s wdel used n robots alatons, whh nlude two tes: one s an ee-nhand sstem (EIHS that has ameras nstalled on and moved wth hands, and the other s an ee-to-hand sstem (ETHS that has ameras that do not move wth hands (Flandn 000. EIHS s ver oular n the area of ndustral robots. When a manulator aroahes a target, the dstane between the amera and the target s redued, and the measurement error of the amera s dereased. Vsual ontrol methods n an EIHS are dvded nto three tes, namel mage-based, oston-based or hbrd (a ombnaton of both. The mage-based vsual ontrol method an effetvel elmnate amera albraton error beause of the losed loo establshed n the mage sae. On the other hand, the absolute measurement error n ostonbased vsual ontrol s dramatall redued whle a manulator s lose to a target. The same stuaton haens under the hbrd vsual ontrol method (Hager 996, Chaumette 000, Corke 000, Zhu 000, Wells 00. However, EIHS has a vtal drawbak,.e. the objet annot be guaranteed n the vew feld of the ameras at all tme, eseall durng the ose adjustment of the hand at a long range (Hager 996. In ontrast, ETHS an be effetvel used n humanod robots and moble manulators that oerate n a large work sae. When the robot s far from a target, t travels toward t and stos at a lose range. Then, aordng to vsual measurements, the manulator aroahes the target and manulates t. To ensure that the end-effetor an reah the target auratel, some researhers have desgned seal marks whh are nstalled on the endeffetor and the target (Han 00, Cardenas 003. The aroahng task s realed through losed loo ontrol of end-effetors. However, beause the target or markers ma be artall bloked durng aroahng or manulaton, mage-based or hbrd vsual ontrol methods ma not be able to brng the manulator to the target auratel. As we know, the oston of an objet n 3D sae an be alulated from two mage onts usng stereo ameras and aordng to the rojetng vew lnes. The lak of onstrants, errors n albraton and errors n mage oordnates of mathng onts result n large errors durng objet ostonng and ose estmaton. B usng shae onstrants of an objet and ts multle magng onts, ostonng aura, eseall ose estmaton aura, an be nreased and the nfluene of the last fator an be artl elmnated (Bartol 00. B ombnng ETHS and EIHS, a humanod robot ould use ts hands to reah and manulate an objet auratel. In ths aer, the advantages of both ee-to-hand and ee-n-hand sstems are full eloted n the develoment of a new ostonng method. The blokng roblem for the ee-to-hand sstem s effetvel avoded sne ameras on the head are atve. The roblem of losng targets n the feld of vew for an ee-n-hand sstem s resolved, and end-effetors onl adjust ther oston n a small range. The rest of ths aer s organed as follows. Seton ntrodues our humanod robot and the Internatonal Journal of Advaned Robot Sstems, Vol. 3, No. 3 (006 ISSN ,

2 Internatonal Journal of Advaned Robot Sstems, Vol. 3, No. 3 (006 four-stage roess for fndng and manulatng a valve. The amera models are desrbed n Seton 3. Seton 4 rooses a new vsual ostonng method based on retangle onstrants, whh auratel rovdes the oston and ose of the valve. Sstem albraton s onduted n Seton 5 to verf the aura of the roosed ostonng method. Seton 6 resents the alaton eerment that s desgned for the humanod robot to aroah and oerate the valve autonomousl, and results show the effetveness of the roosed method. Fnall, Seton 7 rovdes a bref onluson.. The robot and ts ontrol strateg As shown n Fg., our humanod robot onssts of a head, a bod wth two arms and a wheeled moble base. The robot bod has three degrees of freedom (DOFs,.e. twst, th and aw. The two arms/manulators have s DOFs and are fed, one on eah sde of the bod. Eah has an end-effetor as ts hand, and ts wrst s equed wth a mn amera and fore sensors. Note that we treat the end-effet, grer and hand as the same n ths aer from now on wthout further elanaton. Fg.. The humanod robot Camera Head Arm Hand Moble base The robot head has two ameras as ees and a PC04 omuter to roess mages used to oston the valve. One the robot fnds the valve, t moves towards t and oerates t usng ts hands, as shown n Fg.. Oeratons nlude turnng on or turnng off the valve. These oeratons an be remotel ontrolled b an oerator usng audo ommands sent va rado. The roess of fndng and oeratng the valve onssts of four stages as follows: o Stage The robot frst uses ts stereo vson to estmate the rough oston of the valve relatve to ts own oston n order to aroah the valve. At ths stage, the entre of the mage area for the red olour marker s seleted as the feature ont, and the ose of the valve s not mortant. When the dstane between the valve and the robot s less than two meters, the frst stage of the ostonng method s ended and the seond stage begns. A new strateg s develoed for measurng the oston and ose of the valve, n the robot frame, based on the shae onstrant of the marker. o Stage Aordng to the oston and ose of the valve n the robot frame, the robot moves near to t at a range that s reahable b ts arm. The oston and ose of the valve, alulated at the end of the nd stage, s used for the movement ontrol of ts arm n the 3rd stage of the ostonng method. The gven ose of the end-effetor of the robot arm s alulated, and s ket for later stages. o Stage 3 The oston that the hand should reah at ths stage s alulated aordng to the oston of the valve (b onsderng the oston of the mark and handles. Based on knemats and nverse knemats, the hand s ontrolled to move to the handle whle the amera n the hand measures the green olour mage se of the handle marker. It wll sto when the marker se s large enough or a gven oston s reahed. o Stage 4 An mage-based vsual servong method s adoted to gude the end-effetor to reah and ath the handle. Fnall hbrd ontrol wth fore and oston s emloed to rotate the valve usng two hands. Fg.. Valve wth a retangle mark Camera Grer Handle mark Valve mark Handle mark Wth regard to ontrol, man methods are emloed n the roess desrbed above. The ontrol methods n the st and nd stages emlo oston-based vsual servong. Control n the 3rd stage emlos models and ontrol n the 4th stage nvolves mage-based vsual servong. The oston-based vsual servong methods n the st and nd stage and the model based ontrol method n the 3rd stage are tradtonal. The are omtted here beause of length lmtaton. The ose of the valve, gven at the end of the nd stage, s an mortant arameter beause t ensures that the end-effetor an ath the handle wth orret orentaton. The vsual ostonng method n the nd stage wll be desrbed n the net seton. 68

3 Xu et al. / Use of Colour and Shae Constrants n Vson-based Valve Oeraton b Robot 3. Camera model To enlarge the feld of vew, 8mm fous lenses are seleted for the ameras n the robot head. However, ths knd of lenses has the dstorton roblem, whh needs to be orreted. In ths researh, the roess of dstorton orreton s arred out b sml hangng a non-lnear mage to a lnear one. In other words, the magng urve of a lne should be orreted to a lnear lne. To smlf the roess, the non-lnear model shown n ( s used to denote the radal dstorton. u u0 ( u u0( + ku r ( v v0 ( v v0( + kvr where [u, v] are the oordnates of a ont n a ratal mage. [u 0, v 0 ] denote the mage oordnates of the entre of the otal as. [ u, v ] are the oordnates n the mage after dstorton orreton, and [k u, k v ] are the one order orreton oeffents of the radal dstorton n u and v dretons. r ( u u0 + ( v v0 s the radus. The ntrns and etrns arameter models of the ameras are shown n ( and (3. ud k 0 0 / / v / d 0 k 0 / M ( 0 0 where u d u u, 0 v d v v, and [ 0,, ] are the oordnates of a ont n the amera frame. M s the ntrns arameter matr, and [k, k ] are the magnfaton oeffents from the magng lane oordnates to the mage oordnates. n n n o o o a a a w w M w w w w where [ w, w, w ] are the oordnates of a ont n the objet frame, and M s the etrns arameter matr. In M, v n [ n ] T n n s the dreton vetor of the -as, v o [ o ] T o o s the dreton vetor of the -as, v a [ a ] T a a s the dreton vetor of the -as, and v [ ] T s the oston vetor. 4. Vsual ostonng method A red retangular olour marker s attahed to the valve, as shown n Fg.. The measurement of the oston and ose for the valve s smlar to that for the red marker. A frame s establshed as a target frame based on the retangle entre, whh takes the retangle lane as a XOY lane. The lne between two handle markers ats as the X as, as shown n Fg. 3. The retangle se s X w n wdth and Y w n heght. The oordnates of the four (3 vertees P to P 4 are also known n ths frame. Obvousl, an ont on the lane should satsf w 0. Y 4. The dervaton of vetor n v Aordng to the orthogonal onstrants of M, we have (4 that s derved from (3 wth the ondton w 0. o + o + o w + o + o + o a + a + a a + a + a Let A w + o + o + o B a + a + a Sne A 0, B 0 and 0, we have where C A /B, (4 (5 o + o + o a + a + a C and / / (6.. Note that an be obtaned from ( and ( aordng to the magng oordnates [u, v]. All onts on the lne arallel to the X as have the same oordnate w, so A and B are onstants. Takng two onts on the lne arbtrarl, suh as ont and ont j, and alng them to (6, we obtan (7 and also ts smlfed form (8 whh results from ts smlfaton usng the orthogonal restrton of the rotaton matr M. o + o + o o j + o j + o (7 a + a + a a + a + a n ( + n ( + n ( 0 (8 j j j j An two onts on the same lne arallel to the X as should math (8. Therefore, we an obtan two equatons for one amera from the two lnes arallel to the X as,.e. four suh equatons for two ameras. If the amera s otal as s not vertal to the target lane, then n 0, (8 an be dvded b n and beome (9. where n + n ( j j j ( (9 n n and n n / n n / P X O P 3 P 4 Fg. 3. The objetve frame of a retangle wth n v after alulatng n / n j j. n s alulated and n / n j. Then n and n an be obtaned easl. If the amera s otal as s vertal to the target lane, we have n 0 and (8 has two unknown varables. (0 s obtaned wth n v after transoston and the square P 69

4 Internatonal Journal of Advaned Robot Sstems, Vol. 3, No. 3 (006 of (8, wth the results of n and n. n s ostve, and the sgn of n deends on (8. ( j n ( + ( (0 j n n 4.. The dervaton of vetor a v Aordng to (3 and the orthogonal restrton of the rotaton matr M, we have n + n a + a + n + a where A + n + n + n. w A B ( In a lne arallel to the Y as, w s onstant, so A s a onstant too. Beause A 0, B 0 and 0, ( beomes a + a + a C ( n + n + n ( where C B /A. Consderng that n v and a v are orthogonal, and a 0, we have n a + n a (3 n where a a / a and a a / a. If ( s dvded b a, and then ombned wth (3, a s removed. A new equaton wth varables a and C s formed as follows: n a n( n + n + n C ( n n n (4 where C C / a. As for onts on the lne arallel to the as Y, C s a onstant. Takng an two onts from the lne, we alulate both a andc b usng (4. B alng a to (3, a s alulated, followed b the results of a, a and a, wth a v. To mrove aura, onts on two lnes arallel to the Y as are used to alulate the results of a, a and a. It should be noted that eah lne arallel to the Y as has a dfferent onstant C n (4. o v s determned from v v v o a n after obtanng the vetors n v and a v. The rotaton matr an be ensured as an orthogonal matr sne n v and a v are unt orthogonal vetors The dervaton of vetor v Rough Postonng: Two onts are taken from two lnes, one on lne Y w and the other on lne Y w. The orresondng onstants C for the lnes are alulated from (6, denoted as C and C resetvel. C orresonds to Y w. To enhane the reson, more onts on eah lne are needed. C and C are alulated from the average of C for eah lne resetvel. From C and C, two equatons (5 and (6 wth and are obtaned. Equaton (7 s derved from them. ( o + o + o C + C (5 a + a + a Yw a + a + a C C (6 (o Dh a + (o Dh a + (o Dh a 0 (7 Dha + Dha + Dha Yw where Dh C + C, Dh C C. Smlarl, two equatons are formed from lne X w and X w as n (8. Combnng (7 and (8, and are alulated. (n Dv a + (n Dv a + (n Dv a 0 Dv a + Dv a + Dv a X w (8 where Dv / C + / C, Dv / C / C. C and C orresond to lnes X w and X w, resetvel. Fne Postonng: In the amera frame, v s a oston vetor of the orgnal ont n the target frame. Obvousl, usng v and (, the mage oordnates of the target orgnal ont, [u b, v b ], are obtaned easl. X Fg. 4 shows the relaton between the sae ont and ts magng ont. Aordng to the amera s nhole model, the target ont P n the sae and the ont P on the lane Z share the same magng oordnates. Usng the magng oordnates P and angle β, the -oordnate of the ont P n the target frame s obtaned as follows: P OP OP (9 β sn β os + ( P / where β s the angle between rojetons of the Z as n the target frame and the Z as n the mage frame on the lane X O Z, as shown n (0. P / / s obtaned from ( usng the magng oordnates. OP s the offset on the X as between the onts P and O on the lane Z, as n (. β a tan ( a, a (0 P Q P O Fg. 4. Sae oston and magng Q O P β P Z 70

5 Xu et al. / Use of Colour and Shae Constrants n Vson-based Valve Oeraton b Robot u u OP k b ( Alng (0 and ( to (9, P, the oordnate for P on the as X n the target frame s alulated. ( u u a + a ( b P m ak + a ( u u0 Smlarl, the oordnate for P on the Y as n the target frame, P, s also obtaned. ( v v a + a (3 b P m ak + a ( v v0 where m and m n ( and (3 are the oordnates of P n the vrtual target frame, whh s n the normaled fous magng lane,.e.. In the target lane, oordnates offset on the as Y of both to brm and bottom brm of the retangle are ntegrated along the as X, obtanng the area S of the target retangle. S [ M M ( P ( m P ( P + m ( m + P m ] S (4 where S s the target area on the normaled fous magng lane. M s the samle numbers along the X as n the target frame. m, m are oordnates on the Y as of the -th edge ont of the retangle, whh have the same oordnates on the X as. / S (5 S S X wyw / and are realulated b alng to (7 and (8, to obtan more rese target oston vetor v. 5. Sstem albraton 5.. Camera Calbraton The two ameras on the robot head were well albrated usng the method desrbed n (Zhang 000, Hekkela 000. Ther ntrns arameters are shown n Table. The etrns arameters of the left amera relatve to the end of the ndustral robot are gven n (6. T m Item Left Camera Rght Camera K u 4.80e e-007 K v e e-007 K.083e+003.5e+003 K.0678e e+003 u v Table. Camera arameters (6 5.. Verfaton of the vsual measurement An eerment was desgned and onduted to verf the roosed method wth a retangular olour marker attahed to a anel. A red retangle was vewed as the valve, and had a dmenson of 98mm 00mm. Two green arts are used to smulate valve handles. The robot head was nstalled on the end of an ndustral robot as shown n Fg.5 (a. The target was lad on the ground under the head. Images atured b two MINTRON 8055MK ameras n the head are as shown n Fg.5 (b. (a The eerment sene (b Image Fg. 5. The eermental sene and target mage In the eerment, the target was fed on the ground under the robot head. The oston and ose of the robot s hand was hanged so that the ameras ould ature the fed target. The oston and ose of the target relatve to the left amera at the -th samlng s denoted as T, that of the robot s hand as T e, and that of the target n the world frame of the ndustral robot as T w. The edges of the red retangle were deteted usng a Hough transformaton (Tv 990 after dstorton orretons. Two onts were then seleted from eah lne to alulate, T, the oston and ose of the target aordng to the method desrbed n Seton 4. Four vertees were omuted usng the nterseton of these lnes, then the fne oston vetor v was obtaned and T was modfed. Table shows verfaton results A omarson wth tradtonal stereovson To omare the roosed method wth a tradtonal stereo vson method, another eerment was onduted. Four onts that the retangle ntersets wth the -as and -as of the objet frame were seleted as feature onts for stereovson. Ther ostons n Cartesan sae were omuted, and were used to 7

6 Internatonal Journal of Advaned Robot Sstems, Vol. 3, No. 3 (006 Tmes T e (robot end-effetor T (vsual measurement T w (target n the world frame Table. Verfaton Eerment Results alulate the orgn oston, the X as and Y dreton vetors of the objet frame. Thus the oston and ose of the target relatve to left amera was obtaned. Measurements were taken three tmes under the same ondtons. Table 3 shows measurng results for the oston and ose of an objet. The frst olumn shows the results for the oston and ose of the objet omuted wth a tradtonal stereovson method, whle the nd olumn shows the results for the roosed method. Poston values are shown n mm. The results wth stereo vson were dfferent, and the results wth our method were unhangng. Tmes 3 Results wth stereovson Results wth the roosed method Table 3. Measurng results for the oston and ose of an objet usng stereovson and retangle onstrant Table 4 shows the ostonng results for four feature onts P to P4 n terms of the stereovson method and our roosed method. The results wth the roosed method are formed usng the oordnates of the feature onts n the objet frame, and the oston and ose of the objet frame. It an be found that the ostonng results wth our method are ver stable. Results wth the roosed Results wth stereovson Tmes method P P P P P P P P Table 4. Postonng results for the feature onts usng stereovson and retangle onstrants It should be noted that the method roosed n ths aer omutes the oston and ose of the target wth the magng onts on edge lnes of the retangle (these are deteted through a Hough transformaton. Even f there were errors n some magng onts, the edge lne would be aurate enough for the Hough transformaton, whh an elmnate the nfluene of random errors. Furthermore, t does not need to emlo feature ont mathng. Measurng results for the roosed method are 7

7 Xu et al. / Use of Colour and Shae Constrants n Vson-based Valve Oeraton b Robot stable and nsenstve to random nose. In other words, the roosed method s more robust than the tradtonal stereovson method n terms of nose resstane. Errors whh est n the measurements taken wth the roosed method manl our due to sstem errors suh as amera albraton errors and so on. Errors n oses should be less than those n ostons,.e. the objet ose measurements have hgher aura. 6. Eermental results Based on the roosed method, eerments were desgned and onduted for our humanod robot to aroah and oerate a valve wth a retangular oloured marker attahed on ts anel, as shown n Fg.. The red retangle was 00mm n heght and 00mm n wdth. The ose of the valve handles was marked b green olour, whose dreton was onsstent wth the X as n Fg. 3. The head wth two MINTRON 8055MK ameras s shown n Fg.. Two mn ameras were fed on the wrsts of the two manulators. The ameras on the head were well albrated, but the ones on the wrsts are not albrated. 6. Aroahng the Valve b the moble base At the begnnng, the robot searhed for the target valve n the laborator. When the valve was found, the st stage desrbed n Seton was started. When the valve was wthn two meters of the robot, the nd stage began and the method desrbed above was n oeraton. The oston and ose of the moble base was adjusted aordng to that of the valve untl the robot was n an adequate oeratonal area. When the robot stoed movng, the oston and ose of the valve relatve to the head was measured agan b usng the roosed method. The oston and ose of the target valve relatve to the hest of the humanod robot ould be obtaned through oordnate transformaton. Table 5 shows the oston and ose of the target relatve to the referene frame at the hest. The ose and oston of the target relatve to two end-effetors ould also be alulated resetvel through oordnate transformaton. At the st and nd stages, both arms were not n oeraton and were ket n a stat oston and ose. In the roess of aroahng the target b the humanod robot, two arms were ostoned so that the dd not blok the head feld of vew of the target valve. n v o r a v v (mm Table 5. Poston and ose of the Valve 6.. Movng the end-effetors near to the Handle One the robot was n an adequate oeratonal area, the hands of both arms would move, one to eah of the handles of the valve. At the same tme, the ameras on the head were natve. The goal oston and ose of the two end-effetors were determned aordng to the ose and oston of the valve gven above. The goal ostons of the hands, eseall n the ameras vew dreton, had an offset added n order to avod ollsons between the end-effetors and the valve as a result of an error. The movng aths were lanned to satsf ostons wth a hgh rort so as to avod ollsons, eet for the ameras vew dreton. The movements were ontrolled usng knemat and nverse knemat models of manulators. Therefore, end-effetors ould move to the gven goal qukl. At the same tme, the amera at eah hand was n oeraton to measure the se of mage areas of the valve handle (the green olour marker on both sdes of the valve. The se of the green markers nreases as eah hand moved loser to the handle. If the se was large enough or a gven oston was reahed, oston adjustment was ended and the roess hanged to the 4th stage of the roosed ostonng method. (a The left mage (b The rght mage Fg. 6. Images atured b the ameras on the robot head Fg. 6 rovdes a ar of mages of one hand, atured at the end of the 3rd stage. Both mages,.e. Fg. 6(a and Fg. 6(b, were atured b the left and the rght ameras of the robot head resetvel. It an be seen that the endeffetor s at the lae near to the handle wth an arorate ose. Ths means that the ose alulated b the roosed method has good aura Aroahng and Cathng the Handle An mage-based vsual servong method n the 4th stage was aled to gude the end-effetors to reah and ath eah handle. As onted out n (Hager 996, magebased vsual servong methods for an ee-n-hand sstem 73

8 Internatonal Journal of Advaned Robot Sstems, Vol. 3, No. 3 (006 have the drawbak that a target objet ma be out of the amera s feld of vew durng ose adjustment of the endeffetor, whh results n servong falure. If ostons were onl adjusted n a statonar ose, ths drawbak would be overome. However, to ensure that the ose s statonar n the servong roess and the end-effetor an ath the handle wth arorate ose, the ose of the end-effetor should be gven auratel at the begnnng of vsual servong. Ths s wh the ose of the valve needs to be measured auratel n the 3rd stage of the roosed ostonng method and ket unhanged n the 4th stage. The goal of mage-based vsual servong s that the mage of the green marker, reresentng the handle, should math a gven referene mage as muh as ossble. The oston adjustments of end-effetors were gven a hgh rort, eet for one (n the ameras vew dreton, to avod ollson wth valve handles. The end-effetor was oen durng the vsual servong roess. The goal was to adjust the end-effetor oston at a small range, and the grer reahed the handle wth an arorate ose when guded b the amera n hand. The fnal art of the roess nvolved the grer losng to gras a handle. A hbrd ontrol method usng fore and oston was emloed to rotate the valve wth the robot s two hands. It s omtted here. In a seres of eerments, the humanod robot was able to autonomousl fnd, reah and oerate the valve suessfull. These eerments show that the oston and ose of the valve alulated usng the roosed methods are aurate enough to gude two arms n order for them to oerate the valve. The advantages of usng both ee-to-hand and ee-n-hand sstems are learl demonstrated. 7. Conlusons A new vsual servong strateg for a humanod robot to aroah and gras a valve s roosed. It onssts of four stages, namel rough base aroahng, fne base aroahng, rough hand aroahng and fne hand aroahng and grasng. As an mortant art n the roess of autonomous valve manulaton, a vsual ostonng and ontrol method was roosed n ths aer (for a hand-ee sstem and retangular shae onstrants. It emlos multle magng onts, whh le on lnes wth re-known arameters n the objetve frame. Postonng aura and robustness, eseall the ose, were nreased, and the nfluene of oston errors n mages was elmnated. Based on the oston and ose of the valve beng alulated usng the roosed method, end-effetors ould smoothl reah valve handles, under the gudane of a hand-ee sstem. The end-effetors of our humanod robot ould ath the handles suessfull and rotate the valve. The results verf the effetveness of our roosed methods. The relablt and robustness of the sstem were sgnfantl mroved. The methods em-loed an be wdel aled n real-world alatons of humanod robots and moble manulators. Aknowledgement: The authors would lke to thank the Natonal Hgh Tehnolog Researh and Develoment Program of Chna for suortng ths work under grant 00AA460. We would also lke to thank the Natonal Ke Fundamental Researh and Develoment Projet of Chna (973, No.00CB300 for ther suort. 8. Referenes Bartol, A., Sturm, P. & Horaud, R. (00. Struture and moton from two unalbrated vews usng onts on lanes, Proeedngs of the 3rd Internatonal Conferene on 3D Dgtal Imagng and Modellng, Cardenas, A.; Goodwne, B.; Skaar, S. & Seelnger, M. (003. Vson-based ontrol of a moble base and onboard arm. The Internatonal Journal of Robots Researh, Vol., No. 9, Chaumette, F. & Mals, E. (000. -/D vsual servong: a ossble soluton to mrove mage-based and oston-based vsual servong, Proeedngs of IEEE Internatonal Conferene on Robots & Automaton, Corke P. I. & Huthnson, S. A. (000. A new arttoned aroah to mage-based vsual servo ontrol, Proeedngs of the 3st Internatonal Smosum on Robots, Montreal. Flandn, G.; Chaumette, F. & Marhand, E. (000. Ee-nhand /ee-to-hand ooeraton for vsual servong, Proeedngs of IEEE Internatonal Conferene on Robots and Automaton, San Franso Hager, G. D.; Huthnson, S. & Corke, P. I. (996. A tutoral on vsual servo ontrol. IEEE Transaton on Robots and Automaton, Vol., No. 5, Han, M.; Lee, S.; Park, S.-K. & Km. M. (00. A new landmark-based vsual servong wth stereo amera for door oenng, Internatonal Conferene on Control, Automaton and Sstems, Muju Resort, Jeonbuk, Korea, Hekkela, T.; Sallnen, M.; Matsushta, T. & Tomta, F. (000. Fleble hand-ee albraton for mult-amera sstems, Proe. of IEEE/RSJ Internatonal Conferene on Intellgent Robots & Sstems,.9-97 Tv, D. B. & Sandler, M. B. (990. A ombnatoral Hough transform. Pattern Reognton Letters, Vol., No.3,.67-74, Wells, G. & Torras, C. (00. Assessng mage features for vson-based robot ostonng. Journal of Intellgent and Robot Sstems, Vol.30,.95 8 Zhang, Z. (000. A fleble new tehnque for amera albraton. IEEE Transatons on Pattern Analss and Mahne Intellgene, Vol., No., Zhu, S. & Qang, X. (000. Analss of 3-D oordnate vson measurng methods wth feature onts on workee. Journal of Ots and Preson Engn-eerng, Vol.8, No.,