英文翻译.pdf

97 8- 1- 4244- 8452- 2/11/$26.0 0 20 11 IEEE FPM 20 11 Experimental Res earc h of the Infl uenc e of Cons traint for Pneumatic Artific ial Mus c l e Charac teris tic Zang Kejiang, Ma Yan Col l ege of el ec tromec hanic al engineering Northeas t Fores try Univers ity Harbin, China kjzang163.c om Sun Ning, Li Xiuc hen, Zhang Lan Col l ege of mec hanic al engineering Jiamus i Univers ity Jiamus i, China AbstractPn e u ma t ic a r t ificia l mu scle ( PAM) is a n e w p n e u ma t ic a ct u a t o r . A lo t o f wo r k h a v e b e e n co mp le t e d a b o u t t h e p r in cip le , t h e o r e t ica l, e x p e r ime n t a l mo d e lin g a n d a p p lica t io n s o f p n e u ma t ic a r t ificia l mu scle . Re se a r ch e r s h a v e fo u n d t h a t PAMs e x h ib it n o n - lin e a r ch a r a ct e r ist ic. Ba se o n t h e p u b lish e d lit e r a t u r e s, n o n - lin e a r ch a r a ct e r ist ic r e la t e d t o e la st icit y, fr ict io n b e t we e n r u b b e r a n d b r a id a n d t h e co n st r a in t r in g . Th e fo r me r t wo a sp e ct s h a v e b e e n ma in ly st u d ie d in t h e p u b lish e d p a p e r s. Ho we v e r , st u d y o n t h e in flu e n ce o f co n st r a in s o n t h e e n d o f p n e u ma t ic a r t ificia l mu scle is st ill r a r e . Th is st u d y e st a b lish e s t h e PAM st a t ic ch a r a ct e r ist ic e x p e r ime n t a l syst e m, a n d t h e PAM ch a r a ct e r ist ics a b o u t mu lt ip le co n st r a in t s a r e t e st e d . Th r o u g h t h e a n a lysis o f e x p e r ime n t a l r e su lt s, t h e in flu e n ce is o b t a in e d wh ich co n st r a in t s t h e wo r k fo r p n e u ma t ic a r t ificia l mu scle wo r k in g ch a r a ct e r ist ics. Keywordsp n e u ma t ic a r t ificia l mu scle ( PAM) , co n st r a in t s, st a t ic ch a r a ct e r ist ics, e x p e r ime n t a l r e se a r ch I. INTRODUCTION Pneumatic artific ial mus c l e is a new kind of pneumatic ac tuator with the ad vantages of c l eannes s , l ightweight, l ow c os t, eas y maintenanc e, c ompac t s truc ture and high power/vol ume ratio. For this reas on, they are wid el y c onc erned by ac ad emic s tud y and engineering appl ic ation. The pneumatic mus c l e was invented in 195 0 s in ord er to provid e d rivers for pros thes is or rehabil itation mec hanic al . However, for the prac tic al probl ems , s uc h as pneumatic power s torage, avail abil ity and poor q ual ity val ve tec hnol ogy at that time, pneumatic artific ial mus c l e have not been d evel oped and appl ied . In the 1988s , engineers of the Japanes e type manufac ture Brid ges tone propos ed more powerful vers ion of the red es igned pneumatic artific ial mus c l e c al l ed Rubbertuator intend ed to motoris e though s oft yet powerful robot arms . They were c al l ed Soft- Arms and were c ommerc ial ized as s ervic e robots whic h have al s o been s tud ied . The artific ial mus c l e, whic h is s impl e in d es ign, is mad e of rubber inner tube c overed with a s hel l braid ed ac c ord ing to hel ic al weaving. The mus c l e is c l os ed by two end s , one being the air input and the other being forc e attac hment point. The braid fibers run hel ic al l y about the mus c l es l ong axis at an angl e c al l ed interweave angl e. When pres s ure is s uppl ied , the inner tube trans formed , together with s ets of rad ial movement d riving weaving, interweave angl e inc reas ing, the axial braid s l eeve s horting whic h pul l ing the end of the l oad and weaving s ets of fil aments prod uc ed tens ion at the s ame time, then the tens ion and internal pres s ure eq uil ibrium. Bec aus e of PAMs working c harac teris tic s s imil ar to animal mus c l e, it is c al l ed pneumatic ac tuator pneumatic artific ial mus c l e 1 2. Pneumatic artific ial mus c l e is a new pneumatic ac tuator. A l ot of work have been c ompl eted about the princ ipl e, theoretic al , experimental mod el ing and appl ic ations of pneumatic artific ial mus c l e. Res earc hers have found that PAMs exhibit non- l inear c harac teris tic . Bas e on the publ is hed l iteratures 3 4, non- l inear c harac teris tic rel ated to el as tic ity, fric tion between rubber and braid and the end c ons traints . The former two as pec ts have been mainl y s tud ied in the publ is hed papers . However, s tud y on the infl uenc e of the c ons traints on the end of pneumatic artific ial mus c l e is s til l rare. This s tud y es tabl is hes the PAM s tatic c harac teris tic experimental s ys tem, and the PAM c harac teris tic s about mul tipl e c ons traints are tes ted . Through the anal ys is of experimental res ul ts , the infl uenc e that c ons traints work for pneumatic artific ial mus c l e working c harac teris tic is obtained . II. EXPERIMENTAL PNEUMATIC SYSTEM A. Ex p e r i me n t a l r i g This pneumatic experimental s ys tem ?Fig.1?is d es igned to s tud y the rel ations hips of the pres s ure, c ontrac tion and forc e of PAMs with d ifferent c ons traints . The experimental s ys tem c ontains el ements s hown in the fol l owing tabl e. TABLE I. DETAIL SHEET Co mp o n e n t n a me Co mp o n e n t t yp e Co mp o n e n t t e ch n ica l d a t a air s ourc e Fuma- CEBM power:11KW maximum pres s ure: 0 .8MPa gas hol d er: 2L s ol enoid val ves FESTO- R10 7 s uppl y vol tage : DC24V out pres s ?0 - 0 .6MPa pres s ure s ens or SMC PSE5 40 A- R0 6 s uppl y vol tage : DC 12 24V pres s ure range:0 - 1MPa ac c urac y: 0 ?5 % l oad s ens or CZL- 3 s uppl y vol tage : DC 12 24V l oad range: 0 - 5 0 Kg ac c urac y: 0 ?0 3% PAM Home- mad e initial l ength: 17 6mm initial d iameter: 8mm 132 pres s ure range:0 - 0 .3 MPa s tepper motor 86BYGH45 0 B- 113 s tep angl e ac c urac y:2% s tep angl e:1.8? max torq ue?6.7 Nm guid e s c rew SFU160 5 nominal d iameter?16mm l ead :5 mm rated l oad :7 .65 KN d is pl ac ement s ens or KTC 5 0 0 l in:0 .0 5 8 R: 5 .3K? c omputer LEGEND 1+1 CPU: Pentium III 45 0 RAM : 25 6M d ata c ol l ec tor WS- USB res ol ution: 8 ac c urac y:0 .0 0 3%FS? 1LSB d river CW25 0 AC s uppl y Vol tage : DC1224V mod e of operation: 1/5? 1/10 ?1/25 ?1/40 ?1/5 0 ?1/10 0 ?1/20 0 pul s er MPTG s uppl y Vol tage :DC10 0 25 0 V output Freq uenc y : 6- 9999Hz weight c omponents of national s tand ard s 2Kg red uc ing val ve IR20 20 - 0 2G- R max s up pres s : 1MPa out pres s : 0 .0 1- 0 .8MPa Figure 1. Pneumatic experimental s ys tem The feed eq uipment is c ompos ed of four parts ? s tepper motor, pul s er, d river and guid e. The pul s er outputs pul s es to s tepper motors d rivers to d rive the s tepper motors forward or bac kward . The pul s er c an be meas ured in 1/4998. The s tepper motor turns a ful l c irc l e by 20 0 - s teps . The l ead of s c rew is 5 mm/r. The pos ition error is l ittl e (about 5 e- 6mm/r). Straight l ine l ead rail s are ad opted in the experimental s ys tem, with good ac c urac y and s tabil ization. Fig.1 s hows an ord inary pneumatic experimental s ys tem. The c omputer- c ontrol l ed s ol enoid val ves c an output a pred etermined gas pres s ure. When c ompres s ed gas enters PAM, it c ontrac ts and prod uc es a pul l ing forc e. The gas s ourc e is us ual l y a c ompres s or. Cl earl y the experiment s houl d inc l ud e both a s ol enoid val ves and PAM. Firs t we d is c us s the s ol enoid val ves . This is a c omputer- c ontrol l ed s ys tem outputs a pred etermined gas pres s ure within a d efinite fiel d whic h is proportional to the vol tage whic h as a s ol enoid val ves input, whos e q uantity c an be c ontrol l ed by the c omputer. The pneumatic experimental s ys tem c ons is ts of a pres s ure s ens or, a l oad s ens or and a d is pl ac ement s ens or. The pres s ure s ens or meas ures the output gas pres s ure, the l oad s ens or meas ures the output l oad , and feed thes e bac k to the c ontrol c irc uit. The magnitud e of the gas pres s ure output from the c ompres s or s houl d be l arger than the maximal gas pres s ure output from the s ol enoid val ves . B. Muscl e The artific ial mus c l e c ons is ts of the inner rubber tube where the natural rubber l atex through the vul c anizing proc es s has been us ed as s hown in Fig.2. In ord er to red uc e the infl uenc e of the rubber el as tic , the rubber us ed in the experimental is very thin. The outer s hel l is the braid ed s l eeve (s ee Fig.2). Figure 2. Rubber tube and braid ed s l eeve The as s embl y of the artific ial mus c l e is s hown in Fig.3, one s id e of whic h is the air inl et and the other s id e is the c l os ed end . In this experiment, four types of the number of the c ons traint rings (0 , 1, 2, 4) have been tes ted 5 . Figure 3. Pneumatic artific ial mus c l e with c ons traint rings III. ISOMETRIC-LOAD EXPERIMENT The experiment s etup is s hown in Fig.4. One end of PAM 5 is mounted tightl y to a metal frame. The other end of the mus c l e is tied by wire rope with d ifferent l oad s s us pend ed to it. Dis pl ac ement s ens or 8 is fixed to the metal frame; s l id e rod is c onnec ted to removabl e end of the mus c l e, s o that a prec is e meas urement is mad e. The pos ition d ata obtained from d is pl ac ement s ens or is s ent bac k to the PC through the A/D c onverter. To provid e the power for the mus c l e, air c ompres s or 1 c an s uppl y 0 .8MPa c ompres s ed air. The c omputer- c ontrol l ed s ol enoid val ves 2 c an output a pred etermined gas pres s ure. In this tes t, weights 7 are 4Kg and 6Kg. Compres s ed gas enters mus c l e, PAM c ontrac ts whil e the weight is abl e to maintain c ons tant pul l ing forc e. The real - time d ata through the s ens ors are l ogged to the PC. The experiment is repeated s everal times und er d ifferent c ons traints . Then we c an s tatis tic al l y anal yze rubber tube braid ed s l eeve 133 the res ul ts to find out the rel ations hip between the c ontrac tion ratio and pres s ure of the mus c l e for d ifferent l oad 6 7 8 9. Figure 4. Princ ipl e bl oc k d iagram of is ometric - l oad experimental s ys tem The l ength of mus c l e is meas ured by d is pl ac ement s ens or? 0 l is initial l ength, lis real - time l ength, then c ontrac tion ratio is c al c ul ated as 00 ()/l l l= (1) Fig.5 s hows the rel ation between c ontrac tion ratio and pres s ure. From this figure, we c an obvious l y c onc l ud e that the experimental c urve is a hys teres is c urve, this is bec aus e of a c hange in d irec tion of fric tion when the PAM working d uring a tes t period . And at l ow pres s ure, the experimental c urve s hows more hys teres is than at high pres s ure. This kind of phenomenon is referred to the internal fric tion c oeffic ient of PAM and fil l ing pres s ure 10 . Figure 5 . Pres s ure vers us c ontrac tion ratio In ord er to highl ight the infl uenc e of c ons traints , c ons traint ring d iameter s l ightl y l arger than the initial d iameter of PAM. When the c ontrac tion ratio reac hes a c ertain val ue, the c ons traint rings begin to work on the PAM. When c ons traint rings d ont work, the experiment c urves are s uperpos ition; when c ons traint rings und er working, the c ontrac tion is obvious l y s mal l er when inc reas ing the c ons traint rings in the s ame pres s ure. Cons traints red uc e the PAM c ontrac tion abil ity. IV. ISOMETRIC- PRESSURE EXPERIMENT Is ometric - pres s ure experiment s tud ies the rel ations hip between the c ontrac tion ratio and forc e und er c ertain c ons tant pres s ure. One end of PAM 5 is mounted tightl y to a metal frame through l oad s ens or 4. The other end of the mus c l e is attac hed on a s l id e pl ate s l id ing al ong l inear guid es , and the s l id e pl ate empl oys guid e s c rew 7 c ontrol l ed by a s tepper motor 6, thes e trans mis s ion c omponents are abl e to s imul taneous l y obtain high c ontrol ac c urac y and operating effic ienc y. In this tes t, Pres s ure val ve s et pres s ure at 0 .1MPa, 0 .15 MPa, 0 .2Mpa and 0 .25 MPa. Then by us ing the motor to c hange the l ength of the mus c l e und er the c orres pond ing pres s ures mentioned above. The d ata of pul l ing forc e and d is pl ac ement through the s ens ors ?4,6? are s ent to the PC. The experiment is repeated s everal times und er d ifferent c ons traints . We c an c arry out d ifferent c ons traint is ometric - pres s ure experiments und er the d ifferent pres s ure 11. Figure 6. Princ ipl e bl oc k d iagram of Is ometric - pres s ure experimental s ys tem Fig.7 s hows the rel ation between c ontrac tion ratio and forc e. The output forc e of PAM is rel ated to c ontrac tion ratio, the greater the c ontrac tion ratio, the greater the output forc e. As mentioned above, the PAM is ometric - pres s ure c urve is a hys teres is c urve d ue to the infl uenc e of fric tion. With the inc reas e in the number of c ons traints , there exis ts s ignific ant hys teres is phenomenon, the experimental c urves d rop as a whol e, the l inearity d egree bec ome poor, but the trend d o not c hange, whic h c l earl y ind ic ate that c ons traints are s ignific antl y impac ts the s tatic c harac teris tic s of PAM. Figure 7 . Contrac tion ratio vers us forc e V. ISOMETRIC-LENGTH EXPERIMENT The experiment rig is s hown in Fig.8. One end of PAM 5 is fixed on frame. The other end of the mus c l e c onnec ts a s l id e pl ate s l id ing al ong l inear guid es whic h is the s ame s truc ture as Is ometric - pres s ure experiment s ys tem. The s ys tem is c ompos ed of a s l id e pl ate, a guid e s c rew 7 and a s tepper motor 6 s el f- l oc k d evic e whic h is us ed to ac c uratel y c hange the l ength of mus c l e. The c omputer- c ontrol l ed s ol enoid val ves 2 c an make gas pres s ure c hange regul arl y. When c ompres s ed gas enters the mus c l e, a pul l ing forc e is prod uc ed and working on the l oad s ens or 4. The l oad d ata obtained from l oad s ens or is s ent bac k to the PC through the A/D c onverter. The guid e s c rew is c aus ed to rotate by means of s tepper motor to c hange l ength of the mus c l e. The experiment is repeated s everal times us ing d ifferent c ons traints (0 , 1, 2, 4). n t scon st r a i 44 t scon st r a i n 23 sn tcon st r a i 12 tcon st r a i n 01 n t scon st r a i 44 t scon st r a i n 23 sn tcon st r a i 12 tcon st r a i n 01 134 Fig.9 s hows the rel ation between pres s ure and forc e. The res ul t is a l oad c yc l e of ac tuator forc e in the range of operational pres s ure. Fig.9 s hows that forc e d ec reas es with ac tuator c ons traint. Tiny forc e is al mos t al ways meas ured d uring the d ec reas ing pres s ure phas e of the tes t 12. Figure 8. Princ ipl e bl oc k d iagram of is ometric - l ength experimental s ys tem Figure 9. Pres s ure vers us forc e Fig.9 al s o s hows that the output forc e of pneumatic artific ial mus c l e is proportional to infl ation pres s ure. However, d uring this tes t, fric tion between rubber tube and braid ed s l eeve is very s mal l ; the hys teretic behavior appears to d ec reas e. The rubber thic knes s , whic h is us ed in this experimental , is s mal l . The rubber el as tic forc e is s mal l . The graph c l earl y s hows that the s ys tem mentioned above have a l ittl e infl uenc e to this experiment. The l inear rel ations hip between pres s ure and output forc e d o not c hange when the number of c ons traints inc reas ing. However, there is a c hange in their s l ope. Without the infl uenc e of the rubber el as tic forc e and fric tion between rubber tube and braid ed s l eeve, the c ons traint infl uenc e is obvious . VI. COMPARISON OF MODEL TO EXPERIMENT In ord er to verify whether the res ul ts are reas onabl e, a theoretic al approac h is introd uc ed without c ons id ering the d etail ed geometric s truc ture mod ified from the work reported in. To find the eq uation of the mus c l e forc e by us ing the princ ipl e of virtual work, there mus t be an eq uil ibrium between the virtual work i n d W d one in the mus c l e by the pres s ure and the virtual work d one by the d is pl ac ement of the mus c l e out d W 11 (s ee Fig.10 ). Figure 10 . Sc hematic d iagram of the two interac ting virtual work c omponents . i n d Wc an be c al c ul ated with the hel p of the rel ative pres s ure p, the s urfac e of the pres s ure attac k i S, the normal vec tor on i d s, the working d irec tion of the res ul ting forc e i d land the c hange of the mus c l e vol umed V: i i i nii S ii S d Wp d s d l pd s d l p d V = = = ? ? (2) The axial forc e Fand the mus c l e axial d is pl ac ement d l prod uc e the outer virtual work d lFd Wout= (3) By eq uating both the virtual work c omponents and us ing (2) and (3), the eq uation for the mus c l e forc e is d erived . outi n d Wd W= (4) d l d V PF= (5)? By as s uming that the c ontrac ting mus c l e s urfac e ac ts the s imil ar as a c yl ind er, i n d Wc an be d ivid ed into an axial and a rad ial c omponents . The axial c omponent has the oppos ite working d irec tion to the rad ial c omponent, s ee Fig.10 . The forc e eq uation is found : 2 2 d r Fr r l prp d l = (6) A PAM is mod el ed as a c yl ind er and the wal l thic knes s is as s umed to be zero. The d imens ions of this c yl ind er are the l ength l and d iameter2Dr=. As s uming inextens ibil ity of the mes h material , the geometric c ons tants of the s ys tem are the thread l ength b and the number of turns for a s ingl e threadn. The final d imens ion us ed for this formul ation is the interweave angl e, whic h is the angl e between the thread