A New Robotic 3D Inspection System of Automotive Screw Hole

Transcription

1 740 Moon-Hong Baeg, Internatonal Seung-Ho Journal Baeg, of Control, Chanwoo Autoaton, Moon, Gu-Mn and Jeong, Sstes, Hun-Sk vol. 6, no. Ahn, 5, and pp , Do-Hun Otober K 2008 A New Robot 3D Inspeton Sste of Autootve Srew Hole Moon-Hong Baeg, Seung-Ho Baeg, Chanwoo Moon*, Gu-Mn Jeong, Hun-Sk Ahn, and Do-Hun K Abstrat: Ths paper presents a new non-ontat 3D robot nspeton sste to easure the prese postons of srew and punh holes on a ar bod frae. The newl developed sensor onssts of a CCD aera, two laser lne generators and LED lght. Ths lghtweght sensor an be ounted on an ndustral robot hand. An nspeton algorth and sste that work wth ths sensor s presented. In perforane evaluaton tests, the easureent aura of ths nspeton sste was about 200 μ, whh s a suffent aura n the autootve ndustr. Kewords: 3D sensor, frae nspeton, laser, srew hole, robot 3D nspeton sste, vson. 1. INTRODUCTION Produtvt and qualt of the fnshed ar are portant n autootve ndustr. To prove the, a hgh preson autoat sste whh nspets the qualt of welds and assebl, algnent of holes and bod ft s ndspensable, and varous nspeton sstes whh use oputer vson and laser sensor deves have been proposed [1-4]. Espeall, the algnents of holes and parts are portant, beause prese postonng of punhes and srew holes on a bod frae an twst the frae, loosen srews, produe vbraton and deterorate other qualtes. Therefore, these holes and parts need to be nspeted wth preson for hgh qualt ontrol. Pereptron, In. of USA released a non-ontat 3D vsual nspeton sste for the autootve ndustr [5], and two knds of nspeton ethods were proposed. The frst ethod uses ultple sensors whh are arranged all over the bod frae to easure the shape of the frae, but f the nspeton ponts are hanged, all sensors need to be rearranged. In the seond ethod, the sensor sste s ounted on a robot hand, and the robot nspets the target ponts whose postons are stored n advane. Manusrpt reeved June 5, 2007; revsed Januar 14, 2008; aepted Marh 20, Reoended b Edtoral Board eber Sangdeok Park under the dreton of Edtor Jae-Bok Song. Moon-Hong Baeg and Seung-Ho Baeg are wth the Appled Robot Tehnolog Dvson, KITECH, Sa 1-dong, Sangnok-gu, Ansan-s, Geongg-do, Korea (e-als: {hbaeg, shbaeg}@kteh.re.kr). Chanwoo Moon, Gu-Mn Jeong, Hun-Sk Ahn, and Do- Hun K are wth the College of Eletral Engneerng & Coputer Sene, Kookn Unverst, 861-1, Jeongneungdong, Seongbuk-gu, Seoul, Korea (e-als: {wnt, g1004, ahs, dhk@kookn. a.kr). * Correspondng author. The latter ethod s preferred beause of the flexblt of a robot sste, but ths sste has soe nonvenenes. Frstl, the gathered poston data are expressed wth respet to the sensor oordnate sste, not to the referene oordnate sste, and the nspeton sste onl opares the obtaned data wth the odel. Therefore, the bod frae ust be fxed at the exat poston to nspet the atual poston. Seondl, f the nspeton pont s not perpendular to the sensor sste, easureents beoe naurate. 3D laser sanners whh nspet the surfae of the objet were oeralzed b soe vendors, but the have nsuffent aura and requre long easureent te to easure the prese poston of a hole on-lne. Vson sstes whh easure the postons of holes were reported [6,7], but the were naurate for the autootve ndustr. As a result, a new sste to nspet the srews and punh holes of a frae was needed. Ths paper presents a new non-ontat 3D robot nspeton sste and an algorth to easure the prese postons of srews and punh holes on an autootve bod frae. A newl developed lghtweght sensor, whh onssts of a CCD aera, two laser lne generators and LED lght an be ounted on the robot s hand to ove fro an nspeton pont to another nspeton pont as the robot s taught. 2. PROPOSED SENSOR SYSTEM Not a few assebl operatons are nserton operatons of autootve parts nto holes, and these holes are postoned all over the bod frae. The holes loated on the underbod of the frae an not be nspeted wth the establshed ethods suh as stereo vson and the laser lght ut ethod [8,9]. To easure the prese 3D postons of these holes, a new sensor sste whh onssts of a CCD aera, 2 laser lne generators and LED lght s proposed. A

2 A New Robot 3D Inspeton Sste of Autootve Srew Hole 741 ud tanθ =, x x X x vd tanθ =, x x Y x fd tanθ =. x x Z x (4) Fg. 1. Modelng of the proposed sensor sste. oordnate odel of the proposed sensor sste s depted n Fg 1. The sensor oordnate s loated n the enter of the aera whh s odeled as a pnhole aera, and two laser lne generators, the X- laser and Y-laser, are loated on the Y and X axs, respetvel. A hole for nspeton s on plane p. Here, d x : Dstane between X-laser and the aera oordnate θ x : Angle between X-laser and the aera oordnate d : Dstane between Y-laser and the aera oordnate θ : Angle between Y-laser and the aera oordnate f : Effetve Foal Length S x : Slt bea of X-laser S : Slt bea of Y-laser. C C C A pont P( X, Y, Z ) on the objet whh s spotted b laser beas S x and S are projeted onto ( u, v ) of the aera age, and b trangulaton, the 3D poston of ths pont s obtaned as follows[10]. Frstl, the aera age ( u, v ) of ths pont s obtaned as (1) and (2). Usng the Y-laser and b the sae proedure, we fnd the poston of P b ud tanθ X =, f + u tanθ vd tanθ Y =, f + u tanθ fd tanθ Z =. (5) Proedure to alulate the 3D poston of a hole s as follows. Step 1: Fro the laser lne age, alulate the plane equaton of the surfae whh nludes the hole Step 2: Fro the aera age and result of Step 1, alulate the 3D postons of the boundar ponts of the hole Step 3: Wth the result of Step 2, alulate the enter poston of the hole Ths proedure an be desrbed ore n detal. Step 1: Laser lnes of X-laser and Y-laser are aptured b the aera, as shown n Fg. 2. The 3D postons of the ponts on the laser lnes an be found b (4) and (5). The plane equaton whh ontans suh ponts an be obtaned b the least squares fttng b AX ˆ + BY ˆ + CZ ˆ = 1, (6) u f X Z = (1) f Y v = (2) Z Now, the plane equaton of S x s gve as x x x sn θ ( Y d ) + osθ Z = 0. (3) Fro (1)-(3), the 3D poston of P s obtaned as Fg. 2. Laser lne age.

3 742 Moon-Hong Baeg, Seung-Ho Baeg, Chanwoo Moon, Gu-Mn Jeong, Hun-Sk Ahn, and Do-Hun K where 1 T = = 1 = 1 ˆ θ ϕϕ ϕ, Aˆ X ˆ θ ˆ = B, ϕ Y =. Cˆ Z (7) Step 2: Fro the aera age of the objet wth LED lghtng as shown n Fg. 3, and after proessng t, we get the boundar ponts of the hole ( u, v ). Sne ths pont les on the plane of (6), we obtan (8) and (9). ˆ Z ˆ Z A u ˆ + B v + CZ = 1 f f f Z = Au ˆ ˆ ˆ + Bv + Cf Z X = u f Z Y = v f (8) (9) Step 3: B projetng the boundar ponts of Step 2 onto the X-Y plane, we obtan an ellpse as gven b 2 ˆ 2 ax ˆ + bxy + Y ˆ + dx ˆ + ey ˆ + 1= 0. (10) B least squares fttng, eah paraeter an be alulated b 1 T e = = 1 = 1 2 aˆ X ˆ θ ϕϕ ϕ, ˆ b XY θ = = dˆ X eˆ Y ˆ ˆ, 2 e ϕ Y. (11) Beause ths ellpse s a projeton of a rle whh s rotated and translated, to alulate the enter of ths ellpse, the ellpse needs to be rotated b X = X osθ Y sn θ, Y = X snθ + Y os θ. (12) B (11), (12) and b settng the oeffent of the produt ter of XY to 0, relaton (13) s obtaned. ˆ tan 2 θ = b aˆ ˆ (13) After obtanng θ, and fro (11) and (12), the oordnate transfored rle s obtaned b (14) and (15). 2 2 ax + Y + dx + ey + 1= 0 (14) 2 2 ( d ) 2 ( e ) 2 d e a X + + Y + = + 1 (15) 2a 2 4a 4 Fro (8) and (15), ts enter s obtaned as n d e Aˆ d Bˆ e 1 (,, + ). 2a 2 Cˆ 2a Cˆ 2 Cˆ 3. DEVELOPMENT OF THE PROPOSED SENSOR SYSTEM (16) A sensor sste ust have suffent easureent aura, and t need to be suffentl lght n weght to be ounted on a oeral ndustral robot. And to nspet the underbod of ar frae, t needs to be sall. Fg. 4 shows the developed sensor sste. Two tpes of sensors are desgned aordng to workng dstane whh s the dstane between the aera and objet. The desgned workng dstanes are 100 and 150. Table 1 provdes the oponents lst of ths sensor sste. Fg. 3. Caera Iage of hole wth LED lghtng. Fg. 4. The developed sensor wth 100 workng dstane.

4 A New Robot 3D Inspeton Sste of Autootve Srew Hole 743 Table 1. The oponent lst of the developed sensor. Part Model Spefaton 1,300 (H) x 1,030 (V) pxels Area San BASLER 2/3 nh HAD nterlne CCD A101 transfer progressve san Caera CCD Workng dstane 100 Lens Laser Lne Generator Xenoplan F1.9/35 Lens Apo- Coponon F2.4/40 Lens 13LR Effetve Foal Length 34.9 Maxu dstorton 0.25% Workng dstane 150 Effetve Foal Length 41.5 Maxu dstorton 0.5% Workng dstane 100 Wave length 661n Fan angle 25 Lne length 74.7 Fous Range 100~205 Workng dstane 150 Wave length 661n Fan angle 12 Lne length55.9 Fous Range 205~415 Fg. 5. Construton of proposed nspeton sste. Lghtnng LED LDR-90B LED LED Color RED Power Consupton 9.5W Fg. 6. Experental Setup. 4. EXPERIMENT Fg. 5. shows a general vew of the proposed nspeton sste. A developed sensor s ounted on a robot s hand, and the entre nspeton proess s ontrolled b a proess ontrol PLC (Prograable Log Controller). The easureent data are gathered b PC. Fg. 6 shows an experental setup for the evaluaton of the nspeton perforane. The perforane s evaluated wth a gauge blok whh has test holes, as shown n Fg. 7. The gauge blok s ade of Al, tested prevousl wth a oeral 3D oordnate easureent ahne, and t has ahnng error of less than ±5μ. Fg. 8 shows a aptured nspeton age. To evaluate the repeatablt easureent aura of the sensor onl, the robot ar s fxed over a target hole of the gauge blok, and the sensor easures the poston of the target hole repettvel. In the frst experent, the target hole s perpendular to the sensor, and obtaned repeatablt easureent aura s nearl 0. In the seond experent, the target hole s not perpendular wth arbtrar angles, and repeatablt easureent aura s about 23 PH008 PH007 PH001 PH002 PH006 PH003 Fg. 7. CAD drawng of gauge blok for the perforane evaluaton. μ, whh s less than the error of 1 pxel, 40 μ. Table 2 suarzes the experental results. The easureent aura of the whole nspeton sste s evaluated n a slar wa. Frstl, the robot hand oves over the target hole, the sensor easures the poston of the hole, and then the aqured data are transfored to the base oordnate sste fro the sensor oordnate sste. Table 3 shows the results of the repettve experent, and shows that the

5 744 Moon-Hong Baeg, Seung-Ho Baeg, Chanwoo Moon, Gu-Mn Jeong, Hun-Sk Ahn, and Do-Hun K Fg. 8. Captured nspeton age. Table 2. Repeatablt easureent aura of the proposed sensor. Experent 1 () Experent 2 () Itera -ton SSR PX (Perpendular) SSR SSR PY PZ SSR D1 axu devaton s less than 40 μ. Table 4 suarzes the perforane of ths sensor sste. 5. CONCLUSION (Out of perpendular) SSR SSR SSR PY PZ D1 SSR PX Max Mn Range σ To prove the produtvt and qualt of autootve parts, a hgh preson nspeton sste s essental. In ths paper, a new sensor sste was developed, and an on-lne hgh speed and hgh aura 3D nspeton sste equpped wth ths sensor sste was presented. Ths nspeton sste an nspet the 3D postons of punhng holes and srew holes, whh are sattered all over the ar bod Table 3. Repeatablt easureent aura of the proposed nspeton sste. Iteraton PX () PY () PZ () Maxu Mnu Range σ Table 4. Spefaton of the proposed nspeton sste. Features Unt Spefaton Inspeton sste easureent aura μ ± 215 Measureent aura of sensor Inspeton sste repeatablt easureent aura μ 23 μ ±40 Workng Dstane 100, 150 Measureent te Seond/Pont 3.5 Weght of sensor kg 5.7 frae. The newl developed sensor, whh onssts of a CCD aera, 2 laser lne generators and LED lghtnng, was ounted on an ndustral robot, and nspeton ponts were prograed prevousl b teahng. The nspeton sste adoptng ths sensor sste s ontrolled b a proess ontrol PLC, and the easureent data are gathered and analzed b PC. Experents to easure the aura of ths sensor sste were onduted wth a presel anufatured gauge blok. The aura of the developed sensor was 23 μ, and n the experent usng the sensor nstalled on a robot, the aura of the nspeton sste was 215 μ. Ths deteroraton s due to the naura of the robot. Measureent aura of ±0.2 ~ 0.25 ust be guaranteed n the autooble ndustr, and these results show that our sensor sste s aeptable. Now, these sensors are under testng n

6 A New Robot 3D Inspeton Sste of Autootve Srew Hole 745 three autootve fatores, and as a future work, a researh on the albraton of the robot wll be studed to prove the easureent aura of the sensor sste. REFERENCES [1] P. Marno, M. Donguez, and M. Alonso, Inspeton of steel sheets based on CCD age sensors, Pro. of IEEE/SICE/RSJ Internatonal Conferene on Multsensor Fuson and Integraton for Intellgent Sstes, pp , August [2] M. Kondo, S. Tahk, M. Ishda, and K. Hguh, Autoat easurng sste for bod ft on the autooble assebl lne, Pro. of IEEE Internatonal Conferene on Robots and Autoaton, pp , [3] Q. Sh, N. X, H. Chen, and Y. Chen Calbraton of robot area sensng sste for densonal easureent of autootve part surfaes, Pro. of IEEE/RSJ Internatonal Conferene on Intellgent Robots and Sstes, pp , August [4] F. Shafat, M. S. Pervez, A. A. Qaz, J. Wollnak, and T. Trttn Real te two-step nspeton sste for assebled valve kes n autooble lnder heads, Pro. of thrd Internatonal Conferene on Iage and Graphs, pp , Deeber [5] Sanworks Datasheet, Pereptron, [6] B. Lara, K. Althoefer, and L. D. Senevratne Autoated robot-based srew nserton sste, Pro. of the 24th Annual Conferene of the IEEE, Industral Eletrons Soet, Volue 4, pp , Aug Sept [7] W. J. Pastorus, MACHINE vson for ndustral nspeton etrolog and gudane, Pro. of Prograable Control and Autoaton Tehnolog Conferene and Exhbton, pp. 13A2-1/1-5, Ot [8] R. Jan, R. Kastur, and B. G. Shunk, Mahne Vson, 1st edton, MGraw-Hll Sene/Engneerng/ Math, Marh 1, [9] F. Chen, G. M. Brown, and M. Song, Overvew of three-densonal shape easureent usng optal ethods, Optal Engneerng, vol. 39, no. 1, pp , [10] R. A. Jarvs, A perspetve on range-fndng tehnques for oputer vson, IEEE Trans. on Pattern Analss Mahne Intellgene, vol. 5, no. 2, pp , Moon-Hong Baeg reeved the B.S. and M.S degrees n Control Engneerng fro Seoul Natonal Unverst, and the Ph.D degree fro Unverst of Toko n 1982, 1984 and 1995, respetvel. Hs researh nter-ests nlude robots vson nspeton, 3-D sene analss and robot navga-tons. Seung-Ho Baeg reeved the B.S. and M.S degrees n Metallurgal Engneerng fro Korea Unverst n 1991 and 1993, respetvel. Hs researh nterests nlude ahne vson nspeton, 3D age aqus-ton and oble robot navgatons. Chanwoo Moon reeved the Ph.D. degree n Eletral Engneerng and Coputer Sene fro Seoul Natonal Unverst n Hs researh nterests nlude oble robot navgaton/loalzaton, ro anpulaton and otor ontrol. Gu-Mn Jeong reeved the Ph.D. degree n Eletral Engneerng and Coputer Sene fro Seoul Natonal Unverst n Hs researh nterests nlude ebedded sste, PDA applaton and vehle eletrons. Hun-Sk Ahn reeved the Ph.D. degree n Control and Instruentaton fro Seoul Natonal Unverst n Hs researh nterests nlude ebedded sste, vehle eletrons and ontrol. Do-Hun K reeved the Ph.D. degree n Eletrons Engneerng fro Seoul Natonal Unverst. He was a Presdent of IEEK n Hs nterests nlude ontrol and nstruentaton.