A Simple Control Method for Opening a Door with Mobile Manipulator

Transcription

1 ICCAS Ocober -5, Gyeongu EMF Hoel, Gyeongu, Korea A Siple Conrol Mehod for Opening a Door wih Manipulaor u-hyun Kang *,**, Chang-Soon Hwang **, and Gwi ae Park * * Deparen of Elecrical Engineering, Korea Universiy, Seoul, Korea (el : ; E-ail: ie9@kis.re) ** Inelligen Roboics Research Cener, KIS, Seoul, Korea (el : ; E-ail: cshwang@kis.re.kr) Absrac: he hoe service robo suppors huan beings by perforing various kinds of works a hoe. his paper presens a siple conrol ehod for opening a door fro he viewpoin of he obile anipulaion. he siulaion shows various resuls of pah planning and oion planning for opening a door. he oin raecories were generaed by he siulaion syse. In general, a six-axis force/orue sensor a an end-effecor is needed in order o ainain he saic euilibriu of he anipulaor. Bu we show anoher ehod. Fro hree coponens of applied forces which was direcly obained by he hree-axis force sensor and hree coponens of applied forces which was indirecly esiaed by he oin-orue sensors, all of oin orues ha will exacly balance forces a he end-effecor in he saic siuaion can be found. I is ore pracical ehod han using a six-axis force sensor in a wris. Experienal resuls have shown ha he opening a door can be realized ore effecively fro he suggesed conrol ehod of obile anipulaion. Keywords: service robo, anipulaor, copliance conrol, opening a door. Inroducion hese days, a new applicaion of roboics is appearing, e.g. he areas of field, hazard-work and service robo. Especially, a hoe service robo suppors huan beings a hoe by perforing various asks such as parolling roos, feching and carrying hings, opening a door, ec. he successful new area, when hese kinds of robos and huan beings live ogeher, depends on he developen of he safe and easy robo syses. For ha reason, he robos have o ensure enough obiliy and anipulaion []. Various conrol ehods are needed for diverse asks. Force conrol and copliance conrol for siple asks in indusry are well sudied and his echniue works uie well []. However, sufficien robus, accurae and siple conrol ehods are needed for real world asks. hese robos work obile anipulaion, he inegraed conrol of a obile base plafor and anipulaor, and hese anipulaors can perfor various kinds of asks like opening a door. Previous door opening approaches have been presened soe ehods. For insance, S. Yua in he Universiy of sukuba explains he ehod of opening a door. he robo previously copues he posiion of obile base and he oin angles of anipulaor for opening a door ask. Yaabico-, which was developed by Universiy of sukuba, assues ha paraeers of he door are well known [8]. L. Peersson presened anoher door opening syse. I is supposed ha door paraeers such as he posiion and radius are unknown and hese paraeers are esiaed by leas suare ehod fro he oion of he robo when a copliance conrol is used [9]. O. Khaib presens a conrol ehod conneced wih dynaics. An end-effecor dynaically decoupled oion and force conrol can be achieved by he conrol srucure []. Bu hose presened robos use a six-axis force/orue sensor a end-effecor of a anipulaor. In his paper, we show anoher ehod for opening a door wihou a six-axis force/orue sensor. We use six coponens of applied forces obained fro a hree-axis force sensor a he gripper and he oin-orue sensors a he firs, second and hird oins. his ehod has he advanage of design and cos. We use Hobo in an experien. Hobo, a hoe service robo which was developed by he KIS, can expand is scope of working space wih an euipped anipulaor. he discussion in his aricle focuses a siple ehod for opening a door fro he viewpoin of he obile anipulaion. his paper is organized as follows. Secion explains kineaics analysis. Secion presens experienal syse. Secion 4 deals wih he siulaion resuls and discussion. Secion 5 shows experien and is resul. Finally, conclusion is ade in secion.. Kineaic Analysis he relaionship beween saic forces and he corresponding oin orues is defined by he acobian arix []. Generally, ransforing he forces and orues acing on he end-effecor ino corresponding oin orues is described as follows: = f () where is he vecor of oin orues of he anipulaor and f is he vecor of force acing on he end-effecor. is he anipulaor acobian arix ransposebecause of he echanis ofdau (Double Acive Universal oin) in anipulaor [], E. () can be divided ino E. () and E. (4). E. () includes he echanis of DAU bu E. (4) dose no. f f and are he known paraeers and 4 5 f and arehe unknown. he forces and oens on he end-effecor can be convered o corresponding oin drive orues using appropriae acobian.

2 ICCAS he oin orues of anipulaor are and 4 as follows: Ocober -5, Gyeongu EMF Hoel, Gyeongu, Korea K K K K K4 K 5 = 7 f 4 K K K K K K f R = () 5 K5 K5 K5 K5 K54 K 55 ( p7 ) R7 R7 K K K K K4 K5 4 where R 4 is acobian arix [] such as z p7 p z z p7 p z z p7 p z z p7 p z ( ( )) ( ( )) = ( ( )) ( ( )) and f is a force vecor and is a oen vecor.he arix frae Σ fro frae posiion vecor of i () R denoes he roaion arix of Σi and he vecor i P denoes he Σ sorigin fro Σ i s origin. he noaion ( i ) denoes he cross produc arix of he vecor p. Furherore, 4 and 5 are he orues of fourh and fifh oins respecively. R diag(,,,,, ) ( ) 4 α = α 5 p7 R7 Rα (4) where diag(,,,,, ) is diagonal arix. I is deerined by ouer universal oin of DAU []. R is acobian arix [] such as and α R 7 f α α α ( p7 ) R7 R ( zα ( pα pα)) z α = ( z β ( pα pβ)) zβ A = C D (5) K K K K K4 K5 f K K K K K K f 4 5 B ( ) f f f (7) Hence, he unknownparaeers which are 4 5 f and are calculaed according o follow euaions. f f = B A f (8) 4 f f f = C f + D = ( C-DB A) C f + DB (9). Experienal syse he hardware configuraion of Hobo is divided ino wo pars, i.e. a obile base and an euipped anipulaor. he syse of Hobo is coposed of wo on-board copuers. One of he is for oion conrol, he oher is for vision. Hobo is inerfaced wih oion board using CAN-BUS in Windows syse and has a obile base wih wo-wheels driving. he obile base of Hobo is also euipped wih a sereo vision caera for visual servoing. he anipulaor ouned on a obile base of Hobo has six degree-of-freedo and has a hree-axis force sensor a he gripper and oin-orue sensors a he firs, second and hird oins shown in Fig.. Axis Axis 4, 5 Axis (DAU) oin orue Sensor 5 anφ sin an cos 5 + φ = an sin φ 5 an cos φ 5 + () where p = α pα p βα pβ = as he origins coincide. hus he ransfor arix K in E. (7) calculaed fro E. () and E. (4). he arix ransfors he forces and orues acing on he end-effecor ino corresponding oin orues. Gripper Force/orue Sensor Axis oin orue Sensor Axis oin orue Sensor Fig. Configuraion of he Manipulaor

3 ICCAS inor Axis Ar Base Base Ocober -5, Gyeongu EMF Hoel, Gyeongu, Korea base Buper raecory Sar Posiion of Iniial collison posiion aor axis..4 Final Collison Posiion Ellipical raecory Origin of Ellipse Door Origin { World } Doorknob Fig. Ellipical raecory of Base End Posiion of Door Fig. Collision Pah. In general, a six-axis force/orue sensor a an end-effecor is needed in order o ainain he saic euilibriu of he anipulaor. In Hobo, hree coponens of applied forces can be obained fro he hree-axis force sensor a he gripper, and hree coponens of applied forces can be esiaed fro he oin-orue sensor a he firs, second and hird oins. herefore, we can find all of oin orues ha will exacly balance forces a he end-effecor in he saic siuaion. he collision is defined ha a safe disance beween he obile base and a door is no ensure. 4. Siulaion Resuls he siulaion shows various resuls of pah planning and oion planning for opening a door. o realize his oion, we assued ha ) he anipulaor syse is rigid, ) he gripper of anipulaor follows he raecory of he doorknob during opening a door, ) he siulaor is reuired predefined paraeers such as he heigh, a radius and posiion abou a doorknob for his work 4) he obile base us avoid he collision wih a door. In siulaion, he collision is defined ha a safe disance beween he obile base and a door is no ensured. In he firs ehod, he posure of he anipulaor is changed and he obile base follows he predeerined an ellipical pah illusraed in Fig.. he ellipical paraeers like he lenghs of a aor axis and inor axis are deerined by he iniial posiion where he obile base is locaed in fron of a door. Bu here is no soluion for inverse kineaics during opening a door, because of he echanical characerisic of anipulaor. In he second ehod, he posure of he anipulaor is changed and he obile base follows he predeerined pah. his algorih is shown in Fig., Fig., Fig. 4, and Fig. 5. Fig. shows he collision pah before he siulaion. Fig. 4 illusraes he new collision free pah wih a door. Fig. 5 represens he oin angles of anipulaor during opening a door ask. he algorih of a new collision free pah is suarized as he following seps: SEP: Given a candidae posure of he anipulaor, he obile base follows he predeerined ellipical pah. If no soluion for inverse kineaics is found, he given Final Collision Poin Inerediae poin Manipulaor Doorknob Door Ellipical raecory Iniial Collision Poin raecory Doorknob raecory Fig. 4 New Collision Free Pah Creaed by Siulaion posure is infeasible. So, change he posure of he anipulaor. (Fig. ) SEP: Check he collision poins wih a door. (Fig. ) SEP: Draw a sraigh line fro an iniial collision poin o a final collision poin. And find a cener poin on he creaed sraigh line. SEP4: Draw a perpendicular line hrough he cener poin. SEP5: Generae a new pah via any poin on he perpendicular line SEP: Afer creae a new pah, i is needed o check ha all he presened assupions are saisfied. SEP7: If he new pah is no saisfied he supposed condiions, find anoher new pah by nex sep SEP8: If he obile base collides wih he door beween he iniial collision poin and he inerediae poin, he iniial collision poin is oved forward along he ellipical raecory. Also, if he collision occurs beween he iddle poin and he final collision poin,

4 4 ICCAS Ocober -5, Gyeongu EMF Hoel, Gyeongu, Korea oin Angle [dge] Roaion of Door [deg] (a) (b) Fig. 5 oin Angles of Manipulaor he final collision poin is oved backward. (Fig. 4) SEP9: Above seps are repeaed unil a new collision free pah which is saisfied wih he presened assupions is generaed. And an angular velociy of he obile base is influenced by a angenial angle. he speed of he obile is se by a differenial coefficien of he poin. 4. Experienal Resuls and Discussion In his secion, experienal resuls of he behavior are shown. Using he proposed siulaion, he process of opening a door follows nex seps. Firs, he obile base of Hobo is locaed in fron of a door using he sereo vision syse on he obile base. Before opening a door ask wih visual feedback, he robo ar is posed for an appropriae posiion shown in Fig. (a). Second, he visual syse on he obile base sends a signal o anipulaor conroller. Wih his signal, he anipulaor oves he end-effecor o desired posiion shown in Fig. (b). hird, afer visual servoing, he cener of gripper is aligned by he ar for closing a gripper. he anipulaor grasps he doorknob o urn i. I is illusraed in Fig (c). Fourh, Hobo ar pulls very lile a doorknob. Before execuing an acual oion, he siulaor checks he planned oion. Sixh, he siulaor akes a collision free pah. hen he oion of he robo is used coplian conrol. he new collision avoidance pah is generaed by he siulaor, again. Final, he robo obile follows he collision free pah generaed by he siulaor. he copliance conrol is begun o work for Hobo ar. I is represened on Fig. (d). We assued ha an end-effecor s posiion of anipulaor is fixed (perpendicular o a door), like Fig. (b), bu i is no used any siuaion. For exaple, he end-effecor is no perpendicular when visual servoing of obile base is a he wrong angle and he pulling raecory of doorknob is no perpendicular. In our ipleenaion, he pah planning algorih is very siple, here is no guaranee o find a pah, because of he liis of oin and collision avoidance wih a doorknob (c) Fig. Process of Opening a Door: (a) pose anipulaor before visual servoing. (b) afer visual servoing. (c) closing gripper. (d) urning and pulling a doorknob. 5. Conclusions In his paper, a siple conrol ehod for opening a door wih obile anipulaor was presened. he oin raecories were generaed by he siulaion syse. Fro hree coponens of applied forces which was direcly obained by he hree-axis force sensor and hree coponens of applied forces which was indirecly esiaed by he oin-orue sensors, all of oin orues ha will exacly balance forces a he end-effecor in he saic siuaion can be found. I is ore pracical ehod han using a six-axis force sensor in a wris. Experienal resuls have shown ha opening a door can be realized ore effecively fro he suggesed conrol ehod of obile anipulaion. References [].. Craig, Inroducion o roboics: echanics and conrol, Addison-Wesley, 989. []. Yoshikawa, Foundaions of roboics, he MI Press,99. [] S. Ryew and H. Choi, Double acive universal oin (DAU) : roboic oin echanis for huanlike oions. IEEE ransacions on Robo and Auoaion, (d)

5 ICCAS Ocober -5, Gyeongu EMF Hoel, Gyeongu, Korea Vol.7, pp.9-,. [4] K. Nagaani and S. Yua, Designing sraegy and ipleenaion of obile anipulaor conrol syse for opening door, IEEE Inernaional Conference on Roboics and Auoaion, Vol, pp 88-84, 99. [5] K. Nagaani and S. Yua, Designing a behavior o open a door and o pass hrough a door-way using a obile robo euipped wih a anipulaor, IEEE/RS Inernaional Conference on Inelligen Robo and Syses, Vol., pp , 99. [] K. Nagaani and S. Yua, An experien on opening-door-behavior by an auonoous obile robo wih a anipulaor. IEEE/RS Inernaional Conference on Inelligen Robo and Syse, Vol., pp 45-5, 995. [7] K. Nagaani and S. Yua, Designing sraegy and ipleenaion of obile anipulaor conrol syse for opening door. IEEE he Inernaional Conference on Roboics and Auoaion, Vol., pp , 99. [8] K. Nagaani, S. Yua, Designing a behavior of a obile robo euipped wih a anipulaor o open and pass hrough a door. ournal of Roboics and Auonoous Syse, Vol 7., pp 5-4, 99 [9] L. Peersson, M. Egersed. and H.I. Chrisensen, A hybrid conrol archiecure for obile anipulaor, IEEE/RS Inernaional Conference on Inelligen Robos and Syses, Vol., pp. 85-9, 999. [] L. Peersson, D. Ausin, D. Kragic High-level conrol of a obile anipulaor for door opening. IEEE/RS Inernaional Conference on Inelligen Robos and Syses, pp. -8,. [] L. Peersson, D. Ausine, D. Kragic. And H.I. Chrisensen, owards an inelligen service robo syse. Acceped for IEEE Inernaional conference on Inelligen Auonoous Syse, [] L., D. Ausine, and H.I Chrisensen, DCA: A disribued conrol archiecure for roboics. IEEE/RS Inernaional Conference on Inelligen Robos and Syse, Vol.4, pp -8, [] L. Peersson, P. ensfel, D. ell, M. Srandberg, D. Kragic. And H.I. Chrisensen, Syses inegraion for real-world anipulaion asks. IEEE Inernaional Conference on Roboics and Auoaion. Vol., pp 5-55, [4] O. Khaib. anipulaion: he roboic assisan, ournal of Roboics and Auonoous Syses, Vol., pp 75-8, 999 [5] C.. Rhee A hand-ar coordinaive anipulaion for indoor service robo PSR, M.S. hesis. Hanyang Universiy.