A Model of Multi-DOF Microrobot Manipulator Using Artificial Muscle

Transcription

1 st WSEAS ntrnatonal Confrnc on BOMEDCAL ELECTRONCS and BOMEDCAL NFORMATCS (BEB '8 Rhods, Grc, August -, 8 A Modl of Mult-DOF Mcrorobot Manpulator Usng Artfcal Muscl l OA, Adran ZAFU Unvrsty of tst, Elctroncs and Computrs Dpartmnt, Strt Targul dn Val, No., tst, Args, 4, Romana cpopa@upt.ro Abstract: - n ths papr, w dscrbd a nw typ of mult-dof manpulator usng a structur wth thr artfcal muscl (MC sgmnts. W dvlop th knmatc modlng of multlnk motons for th control of th manpulator usng a transposd Jacoban or an nvrs Jacoban usng as snsors lmnts of motons was ralzd by MC flm too, bcaus was usd th spcal actuator-snsor sgmnt (MC flms ar sparatd lctrcally by cuttng groovs and both th snsor and th actuator can b unfd n th sam structur. Th papr contan smulaton rsults of ths modl. Kywords: Elctroactv olymr Artfcal Muscl (EAM; onc olymr-mtal Compost (MC; Dgr- Of-Frdom (DOF, dual actuator-snsor flm; mcrorobot manpulator; mult-lnk knmatcs; transposd Jacoban control. ntroducton A bmorph-typ soft polymr gl actuator, whch w call an lctroactv artfcal muscl, s an onc polymr-mtal compost (MC consstng of a prfluorosulfonc acd mmbran wth chmcally platd gold or platnum as lctrods on both sds [, ]. t has som xcllnt charactrstcs for robotc applcatons compard wth othr soft polymr actuators [3, 4, 5] as follows: Low powr consumpton; Drvn wth low voltag (<3V; Fast rspons (> Hz n watr; Mchancally and chmcally durabl and stabl; Soft and complant; Works n watr (or n wt condtons. Morovr, t has an advantag for mnaturzaton wth ts smpl actuator structur. Wth ths charactrstcs, w xpct to apply t to mcromanpulatons n th bongnrng or mdcal flds. Our goal s to ralz bonsprd soft robots, for xampl a multdgr-of frdom (DOF mcrorobot manpulator [6, 7].t s asy to mnaturz th actuator bcaus of ts smpl structur. n th futur, s possbl to mak robots that can swm n thn tubs or n blood vssls, or varous knds of mcromanpulators n th bomdcal fld. n ths papr, w show som rsults from smulatons of th proposd manpulator control mthod of th mult-dof bndng moton and smulatd rsults for th dual actuator snsor sgmnt structur MC flm (s Fgur b. Bcaus Th MC artfcal muscl s not stabl whn work n ar, bat has a good stablty n aquous mdum [4, 5], hand-arm was sunkn n watr (s Fgur a. Th Mult-DOF Manpulator Structur Mcromanpulatons n bongnrng or n th mdcal fld can b on of th applcatons of th artfcal muscl. Our goal s to nvstgat th possblts to ralz a mult-dof mcrorobot manpulator that s automatcally controlld by a dual systm actuator-snsor, as shown n Fgur [8]. MC flms ar sparatd lctrcally by cuttng groovs and both th snsor and th actuator can b unfd n th sam structur. Ths arrangmnt s mor ffctv to sns moton than th paralll arrangmnt bcaus thr s lss ntrfrnc wth th actuaton by th snsor part [9]. Th sz of th strp s 3 [mm]. Th strp s sparatd nto th two sctons, th snsor part s mm wd, and th actuator part s mm wd. Two coupls of lctrods wr arrangd for th actuator and th snsor [9]. Th lasr dsplacmnt snsor was usd for MC snsor flm calbraton. SSN: SBN:

2 st WSEAS ntrnatonal Confrnc on BOMEDCAL ELECTRONCS and BOMEDCAL NFORMATCS (BEB '8 Rhods, Grc, August -, 8 Th block dagram of th control systm for ths modl of mult-dof composd by thr sgmnts MC actuator-snsor s showd n Fgur a. Th pattrnng of lctrods on an MC nabls th mult- DOF bndng motons of a manpulator wth a smpl structur. Command sgnals Currnt amplfr D/A convrtr Cnmatc modl Actuator controllr Snsors sgnals Currnt amplfr A/D convrtr and sral ntrfac C (Wndows X urfd watr Hand arm wth artfcal muscl and snsors MC a Fgur. a Applcaton of mult-dof artfcal muscls MC; b Structur of MC actuator-snsor flm. b Th proposd fdback control systm showd n Fgur ncluds a snsng systm, a Jacoban and rror stmaton componnt, a control componnt, and a mult-dof pattrnd artfcal muscl (MC. Th manpulator s hung n watr abov th lctrc connctor. 3 Modlng of Mult-Lnk Knmatcs To ralz th mult-dof moton of a manpulator, w can connct svral lnks n srs n th sam way as n convntonal sral-lnk manpulators. n ths study, as a frst stp n our rsarch, w rstrct th moton of th manpulator to a two dmnsonal spac, n whch two DOF for poston and on DOF for th tangntal drcton of th nd pont ar controlld. W can control all thr DOF ndpndntly by controllng th thr lnks of an MC. W now dfn coordnat systms,( = {,,,3 } on at th orgn, on at ach jont of th mult-lnk systm, and on at th nd pont of an arm, as shown n Fgurs and 3. A homognous transfr matrx A+ from + to s: A l cos( sn( ( cos l = sn( + cos( + sn α α (3. + whr th crtan lngth of a lnk s l, th curvatur s = r / l, and f th lnk has a crtan bndng angl ( SSN: SBN:

3 st WSEAS ntrnatonal Confrnc on BOMEDCAL ELECTRONCS and BOMEDCAL NFORMATCS (BEB '8 Rhods, Grc, August -, 8 at th jont, ths angl s rfrrd as α. W consdr that l and α ar known and α =. Fgur. On-lnk knmatc modlng (not that usually α =, as n ths study Fgur 3. Mult-lnk coordnat systm (jonts ar usually not bnt, as n ths study A transfr matrx from th bas to th nd pont s calculatd by multplyng ach matrx of th lnk from th frst to th last usng T 3= A A A3 (3. whch s shown n Fgur 3. From ths quaton, w can obtan th poston vctor and rotaton angl th nd pont n th bas coordnat systm follows xprssons (3.3, of as (whr x = (, = (,, : t t x Y = cos( + + cos( + + cos( + + α cos( + = Y (cos α = sn( + + sn( + + sn( + sn( + sn To control th poston and orntaton of th hand of th manpulator, w hav to solv an nvrs knmatc problm. Mor spcfcally, w hav to solv ˆ = ( by t = (,, from Eq. (3.3, whr ˆ dnots both th objctv poston and orntaton. Howvr, t s qut dffcult to solv Eq. (3.3; thus w us Jacoban mthods for controllng and dfn control varabls to convrg to objctv valus. Th Jacoban of wth s dfnd by followng xprssons: J J = [ J J J ] =, ( = {,,} (3.4 Usng th Jacoban, th followng control, whch s an nvrs Jacoban mthod, wll nduc th control varabl to convrg to an objctv valu ˆ xponntally: ' ' λ ˆ = J ( = λ J ε (3.5 whr λ, n ths xprsson, s a gvn constant. Usng th transposd Jacoban mthod, wll also nduc convrgnc to an objctv: (3.6 ' t ' t = λ J ( ˆ = λ Jε Ths s possbl f an approprat valu of a constant ' λ s chosn. J can b calculatd xplctly, but w omt such calculatons. SSN: SBN:

4 st WSEAS ntrnatonal Confrnc on BOMEDCAL ELECTRONCS and BOMEDCAL NFORMATCS (BEB '8 Rhods, Grc, August -, 8 4 Smulatons W prformd som smulatons to vrfy our control mthods. A block dagram of a control systm smulaton s shown n Fgur 4. s possbl to obtan rsults by th nvrs Jacoban or by th transposd Jacoban mthod but w prsnt, n ths papr, only th transportd mthod. Th rsults obtand by ths mthod ar shown n Fgur 5. Objctv poston and orntaton ˆ + - ε Transposd Jacoban: J t ntgral: s Knmatc modl Arm moton Fgur 4. Block dagram of smulaton systm Fgur 5. Rsults obtand by transposd Jacoban control (uppr lft: hand s kpt n uppr drcton, uppr rght: ts drcton s changd to rght, bottom lft: trackng a round trajctory, bottom rght: mov and swng SSN: SBN:

5 st WSEAS ntrnatonal Confrnc on BOMEDCAL ELECTRONCS and BOMEDCAL NFORMATCS (BEB '8 Rhods, Grc, August -, 8 All rsults show that ach sgmnt of an MC mmbran s proprly bnt to ralz th gvn trajctors of postons and orntatons of th nd ponts. By th nvrs Jacoban mthod, trajctors n Cartsan coordnats ar straghtforward and xponntally convrgd to th objctv, whr thy ar not by th transposd Jacoban. Howvr, an nvrs Jacoban s not stabl nar a sngular poston, n ths cas, at th uprght poston, whras a transposd Jacoban s dfnd and stabl at any pont. From ths rsults, t s confrmd that s possbl to control all thr DOF of a -D manpulator by ths mthods. 5 Conclusons n ths study, w dscrbd a nw typ of mult-dof manpulator usng a structur wth thr artfcal muscl (MC sgmnts, and proposd th knmatc modlng of multlnk motons for th control of th manpulator usng a transposd Jacoban or an nvrs Jacoban. Th snsors lmnts of motons was ralzd by MC flm too, bcaus was usd th spcal actuator-snsor sgmnts prsntd n Fgur a. Smulatons and xprmnts vrfy our approach. By usng th nvrs Jacoban and transposd Jacoban mthods, trajctors n Cartsan coordnats ar convrgd, but th nvrs Jacoban s not stabl nar a sngular poston whl th transposd Jacoban s dfnd and stabl at any pont. From th smulatd rsults, t s confrmd that s possbl to control all thr DOF of a -D manpulator by ths mthods. W consdr that s vry mportant to addrss th problm of th low conductvty of sgmnt ntrconnctons. t s possbl to ncras th wdth of th ntrconnctons and/or ncras th amount of gold platng, so that thr conductv layrs bcom thckr. Although bndng vlocty gnrally follows a gvn voltag sgnal, nonlnar charactrstcs, such as swng back moton, also contrbut to a dynamc rspons. Rfrncs [] K. Asaka and K. Oguro ( Bndng of polylctrolyt mmbran platnum composts by lctrc stmul art. Rspons kntcs. J. of Elctroanalytcal Chmstry, 48: [] K. Oguro, Y. Kawam, and H. Taknaka (99 Bndng of an on-conductng polymr flm-lctrod compost by an lctrc stmulus at low voltag. J. of Mcromachn Socty, 5:7 3. (n Japans [3] Y. Bar-Cohn (, Elctro-actv polymrs: currnt capablts and challngs. roc. of SE nt. Symp. on Smart Structurs and Matrals, EAAD [4]. opa, olymrs as Artfcal Muscl n Robotcs, Elctroncs, Computrs and Artfcal ntllgnc ECA 7 ntrnatonal Confrnc, Unvrsty of tst, Jun 9, 3, Romana. [5].opa, Usng of Elctroactv olymrs as Artfcal Muscl Smart Matrals, 3rd ARA Congrs, Brasov, Romana, 3 July 5 August, pp [6] Y. Nakabo, T. Muka, and K. Asaka (4, A mult- DOF robot manpulator wth a pattrnd artfcal muscl. Th nd Conf. on Artfcal Muscls. Osaka [7] Y. Nakabo, T. Muka, and K. Asaka (5 Knmatc modlng and vsual snsng of mult-dof robot manpulator wth pattrnd artfcal muscl. roc. EEE nt. Conf. Robotcs and Automaton, [8] A. unnng, Elctromcancal charactrzaton of onc olymr-mtal ompost snsng actuator, Tartu Unvrsty rss, 7. [9] Konyo M., Y. Konsh, S. Tadokoro, and T. Kshma, Dvlopmnt of Vlocty Snsor Usng onc olymr- Mtal Composts, roc. SE ntrnatonal Symposum on Smart Structurs, Confrnc on Elctro-Actv olymr Actuators and Dvcs, 3. SSN: SBN: