The Implementation of PID Controller in the Pick and Place Robot

Transcription

1 Th Impmnttion of PI ontror in th Pick nd Pc Robot H. Frdinndo, H. Wicksono nd R. Wibowo pt. of Ectric Enginring, Ptr hristin Unirsity, Indonsi bstrct contro systm for pick nd pc robot is impmntd. Th contro gorithm ss th PI (Proportion-Intgr-riti). Th systm 3-OF robot with spcific tsk, i.. to pick crtin ttr bocks nd pcs it to th dsird oction. Th robot is controd with th T89S51 microcontror. Th commnd for th spcific ttr bocks coms from comptr. Th comptr nd th T89S51 r connctd i RS-232. Th tim smping of th systm is 5ms. ftr tning th PI s constnts, th rtio of th constnt for P, I nd is 2:.1:34. Th xprimnts show tht th ris tim of th systm is 1.41s; th stting tim is 4.3s nd th mximm orshoot is 1.62%. It is rcommndd tht th constnt for Proportion contror is btwn 2 nd 7, th grtr th constnt th ongr th ris tim. Big of th constnt so contribts to th nmbr of oscition. For th Intgr contror, it is 1 nd 5, th grtr th constnt th mor th oscition occrrd. This mks th motor rn brpty. Kywords PI, pick nd pc robot, T89S51 I. II. INTROUTION Th PI (Proportion-Intgr-riti) contror is th most popr contro gorithm in indstris. Th powr of this contror is on th simpicity of th contro gorithm. thogh thr r mny nw contro gorithms dopd nowdys, this contror sti xists. Thr r mny ppictions of th PI contror in indstris,.g. robotic rm, conyor, hting procss, tc. Th go is on, i.. to rch th stting point fst with sm orshoot. This ppr discsss th ro of th PI contror in controing pick nd pc robotic rm. Th robot wi pick crtin bock of ttr nd thn pc it in th dsird pc. Th contro gorithm is ppid to th momnt of th min body. Th contror is th T89S51 microcontror. It rcis commnd from comptr i RS-232. Th fin go is to gt systm with fst ris tim, fst stting tim nd minimm orshoot. This ppr is orgnizd s foow; th first sction gis introdction to th projct. Th PI contror is discssd brify on th nxt sction. For thos who do not fmiir with pick nd pc robot cn rd th foowing sction, thn it coms th dsign of th systm for mchnics, hrdwr nd softwr prt. It contins with xprimnt for th systm nd concsion coss this ppr. III. THE PI ONTROLLER BRIEF INTROUTION Th PI contror combins thr contro gorithms, i.. Proportion, Intgr nd riti contrors. Ech contror hs its own constnt to djst th otpt of th contror bsd on th rror sign. Ech contror hs diffrnt contribtion to th rspons of th systm. To gt good PI contror systm, on mst tn th constnts. thogh it sms indpndnt, th constnts do not. This gis compxity in tning thm. Th tn procss, howr, cn b don i sr gorithms sch s Zigr-Nichos, ohn-on, tc [1]. Ech gorithm hs its own dntgs nd disdntgs. Th powr of th PI contror is on its simpicity. On ony st thr constnts in ordr to gt good rspons. It is simp for th nmbr of prmtr is ony thr. Bsids, it cn b impmntd withot digit contror. On cn mk th PI contror with Oprtion mpifir nd sr pssi componnts. Off cors this kind of PI contror hs imitd cpbiitis, bt on cn s it to contro simp systm. Th mor compx PI contror ss digit contror sch s microcontror, P (prson comptr) or PL (progrmmb ogic contror). Ths qipmnts gi bttr PI contror bt with highr cost. Th chosn contror is bsd on th compxity of th pnt. IV. PIK N PLE ROBOT pick nd pc robot is mtri hnding robot tht cn work 24 hors dy withot worris or ftig [2]. This robot is common robot in indstris. Th tsk is to pick som objct nd pc it in th dsird pc. Whn it is controd, thn th position contro is th min iss. It mst b controd sch tht th robot cn pick th objct t crtin pc ccrty nd pc it t th dsird pc ccrty s w. It is th ro of th contror to chi this go. On cn s mny gorithms to chi it bt th go is on, i.. to pick nd pc objct ccrty, fst nd with sm orshoot.

2 Th ppiction of th pick nd pc robot is in ssmbing prodction procss, for xmp. Hr, th robot mst pick crtin prt nd pc it to th spcific pc. Th ssmbing procss of th csstt ss this robot. nothr ppiction is insrt mchin for th ctronic printd circit bord (pcb). Hr, th robot picks th componnt, insrts it to th ho, cts th d nd bnds it. Th insrt mchin cn finish th who componnt in pcb fst, compr to th hmn. rm ttr V. MEHNIS ESIGN Th mchnic dsign is bsd on figr 1. Th primry nd scondry rms cn rott 3 o nd th grippr cn mo p nd down (s figr 2). pc/sot Fig. 3. Bs pc (top iw) VI. HRWRE ESIGN motor 2 scondry rm gr box primry rm motor 1 Figr 4 shows th bock digrm of th systm. Th systm ss sr ddition circits. Thy r discssd in this sction. Potntiomtr2 9 Potntiomtr1 motor 3 min body P RS-232 T89S51 Limit switchs Fig. 1. Mchnic digrm of th robot 8 omprtor H-bridg 2 3 Fig. 2. How th robot mo Th robot is spportd by min body. Th min body hs bs pt. On th bs pt th ttr bocks r pcd. Figr 3 shows th who bs pt from top. Th ttr bock is pickd on by on nd pcd t th dsird pc 1 Tring w gnrtor Fig. 4. Bock digrm of th systm Th position snsor for th systm is potntiomtr. It is inr tn trn potntiomtr. Th PI contror is impmntd in microcontror MS-51 fmiy, i.. T89S51 [3]. Th nmbr of position snsors is two, on for th primry rm nd th othr for th scondry rm. Th grippr ss two imit switchs. Figr 1 shows th position of th potntiomtr (cos to th motor 1 nd 2) To rd th crrnt position, th T89S51 nds / conrtr. Th 9 is sd. Th signs, howr, cnnot b rd dircty for th sign rng dos not mtch to th rng of th 9 [4]. For this rson, n ddition circit is sd. It is cd zro nd spn circit. Th rms mst b b to trn W nd W. For this prpos, n H-bridg is sd to dri th motors. Th H- brid ss LM298N [5]. This chip cn proid crrnt p to 3.

3 Th momnt of th rms mst b b to b controd. It mns whn th crrnt position is fr from th dsird position, thn th rm mst mo fst, nd ic rs. For th motor is motor, it nds to contro th otg drop t th motor trmin. This ds to th PWM (Ps Width Modtion) systm. Th PWM circit sing simp tring w gnrtor, n inpt rfrnc sign nd comprtor. Th comprtor wi gi otpt ithr HIGH or LOW ccording to th stts of both inpts. Th inpt rfrnc sign is prodcd by th T89S51 i 8. For th otpt of th 8 is crrnt [6], thn th crrnt to otg conrtr is sd. Th 8 gts dt from th T89S51. Figr 5 shows th simpifid PWM circit. Th frqncy of th PWM sign is 1kHz. This frqncy dpnds on th frqncy of th tring w. This is chosn for th motor wi trn brpty in ow frqncy of PWM. th systm is id, witing for th nxt intrrpt timr. Figr 6 shows th prt of intrrpt timr rotin. oid Initontr(oid){ ontr=; E=; // disb intrrpts TH=256-18;// TL = 238 TMO=x22; // chos mod 2 stip timr PT=1; // bit priorits timr ET=1; // nb intrrpt of timr TR=1; // strt timr E=1; // nb intrrpts oid ontr_bit() intrrpt 1 sing 1 { ontr++; if (ontr==){ SmpingPI=1; Fig. 6. Prt of intrrpt timr rotin Th fg SmpingPI grds th min progrm sch tht whn th tim is com, thn th PI procss wi rn. s soon s th procss strts, thn this fg wi b crd. This mks th min progrm wits nti th nxt tim smping. B. PI ontror Fig. 5. Simpifid PWM circit VII. SOFTWRE ESIGN Th softwr in th T89S51 is writtn in [7] for th compttion ss foting point nmbr. To s ssmby ngg cn ngthn th dopmnt tim. Th T89S51 rcis commnd from comptr. Usr inpts th commnd sing th HyprTrmin. Th commnd is simpy on ttr. It mns th robot mst pick tht ttr nd pc it t th pr-st pc. Th robot mos its rm on by on instd of simtnosy. This mks th impmnttion simp.. Tim Smping Th contro gorithm ss PI. For this prpos, thr r thr constnts for th contror. It so nds tim smping in th compttion. Th tim smping is 2ms. It is ssmd tht th motor hs sow rspons for th od is big. Th T89S51 mst b st sch tht it wi rpt bnch of tsk ry 2ms. Th intrrpt timr is sd for this prpos. Thos tsks r rding th crrnt position of th primry rm, compr it with th dsird position from P (i RS-232), cct th PI contro ction nd dri th robot. Whn thr is tim rmining, thn Th constnts of PI prmtr cod h foting point. For this rson, th impmnttion ss ngg. To mk th systm simp nd sy for modifiction, th constnts r foting point. Figr 7 shows th PI contror impmnttion in th T89S51. oid tpi(oid){ YN1=Y; ErrN2=ErrN1; ErrN1=Err; Err=StPoint-rPoint; T=.5; Y= YN1 + KP*(Err-ErrN1) + KI*Err*T + ((K/T)*(Err+ErrN2-2*ErrN1)); if (Y>255) Y=255; if (Y<-255) Y=-255;. PWM ircit Fig. 7. PI contror in th T89S51 VIII. EXPERIMENTS Th frqncy of th PWM sign is Hz (priod = 1.85ms). It dpnds on th tring w. Figr 8 shows sr PWM sign with rios dty cyc, 25%, 5%, 75% nd 1%.

4 () Ris tim, stting tim nd mximm orshoot r 3.36s, 32.62s nd 3% rspctiy. This rst is not good. Th ris tim mst b sm nd so mst th stting tim. Th mximm orshoot is too big for contro position. To chng th constnt to 2.3, 7 nd.1 for P, I nd rspctiy dos not gi bttr rsts. This combintion mks th oscition contin forr. Figr 1 shows it. (b) (c) (d) Fig. 8. PWM sign for dty cyc () 25% (b) 5% (c) 75% (d) 1% Th xprimnts show tht th dty cycs do not fit to th dsign. For 25%, 5%, 75% nd 1%, th impmnttion rsts 25.34%, 5.23%, 75.57% nd 99.53% rspctiy. Th probm of thos ditions is tht thr is sm rror in th frqncy of th tring w. If th tring w is 1 khz xcty thn th dty cyc of both dsign nd impmnttion wi b th sm. This dition is not mjor probm sinc th contror wi compnst it. Th probm is how to find good combintion of PI s constnts which cn compnst tht dition. Good compnstion is shown whn th systm cn rch th go of th dsign rtd to ris tim, stting tim nd mximm orshoot. B. PI ontror Th initi constnt for PI contror in 2ms tim smping is 2.3, 3.5 nd.26 for P, I nd rspctiy. Figr 9 shows th rst. Tim Fig. 9. Rspons of th systm Fig. 1. Bd combintion of PI prmtrs This combintion shod not b sd for th stting tim is t infinity, thogh th ris tim is good. Th systm bcoms nstb for th riti constnt is too sm.. Smping Tim Ths rsts indict tht th PI constnts mst b tnd in ordr to gt good prformnc. It is so intrsting to s how th smping tim infncs th systm. It ss th bst combintion of th PI contror. Tim Smping 2ms: Th PI constnts r 9, 8.5 nd.26 for P, I nd rspctiy. Figr 11 shows th rst. Th oris tim is 2.98s with stting tim nd mximm orshoot r 6.28s nd.9%. Th rst is bttr thn tht of figr 9. Bt th ris tim, howr, is sti not stisfying. so th stting tim is considrd sow. 1 2 Tim Kp=9 Ki=8.5 Kd= Tim Fig. 11. On of rspons systm with smping tim 2ms From mny xprimnts tr, it is diffict to find good combintion of PI s prmtr in ordr to h

5 good prformnc. Th hypothsis is tht th smping tim is too sow. With smping tim 2ms, th systm gts contro ction ry 2ms. This mks th systm cnnot rspons s fst s possib. Thrfor, to choos 2ms s smping tim is not good. It is ncssry to s smr smping tim. Tim Smping 5ms: from th prios sb-sction, th nw smping tim is 5ms. 5ms is chosn for th motor is odd with its rm. Th rm is itt bit hy. So 5ms is nogh to gt bttr prformnc. Th PI constnts r 15, 1 nd.1. Figr 12 shows th rst. Kp=15 Ki=1 Kd= Fig. 12. Rspons of th systm with smping tim 5ms; Kp=15, Ki=1 nd Kd=.1 Th ris tim is 2.43s, th stting tim is 5.82s nd th mximm orshoot is 2.43%. Th rst is bttr compr to th prios sb-sction. Bt it is sti importnt to impro its prformnc. Figr 13 shows nothr xprimnt with diffrnt combintion of th PI s prmtr. Th chosn prmtrs r 2, 34,.1. Th ris tim of th systm is 1.41s with stting tim 4.3s nd mximm orshoot 1.62%. Th prformnc of th systm is improd gin. thogh th PI s prmtrs sm indpndnt, thy do not. This mks th tning procss mor diffict Tim Kp=2 Ki=34 Kd= Tim Fig. 13. Rspons of th systm with smping tim 5ms; Kp=2, Ki=34 nd Kd=.1. PI s Prmtrs Exportion It is ncssry to xpor th PI s prmtrs on this robot. Th prpos of this xprimnt is to gt som insight bot th PI s prmtrs in th pick nd pc robot. On prmtr wi b rid whi th othr two prmtrs r constnt. Th smping tim is 2ms. Proportion Prmtr: th strting point of this xprimnt is th rst from figr 13. Th I nd prmtrs r 34 nd.1 rspctiy with rition in P prmtr. Figr 14 shows th rst of this rition. Th xprimnt shows tht th smr th of P prmtr, th bttr th ris tim. It is shown tht th ris tim is bttr thn Kp=2 with smping tim 5ms, it is rond.4s. Th stting tim is so improd, i.. rond.5s Tim (ms) Fig. 14. Rst of th P prmtr rition (bck: Kp=2, whit: Kp=35, gry: Kp=7) Intgr Prmtr: th strting point of this xprimnt is th rst from figr 13. Th P nd prmtrs r 2 nd.1 rspctiy with rition in I prmtr. Figr 15 shows th rst of this rition. From ris tim point of iw, th systm with big I prmtr hs fst rspons. Sm nds ongr tim to rch th stting point Tim (ms) Fig. 15. Rst of th I prmtr rition (drk gry: Ki=1, whit: Ki=2, ight gry: Ki=5) riti Prmtr: th strting point of this xprimnt is th rst from figr 13. Th P nd I prmtrs r 2 nd 34 rspctiy with rition in prmtr. Figr 16 shows th rst of this rition. Th pot of th rspons for sr xprimnts is diffict to s. Th rsponss r most th sm, xcpt tht th prmtr cnnot b grtr thn 1. With prmtr is q to 1; th rspons hs rg stdy-stt rror.

6 E. Or Rspons Tim (ms) Fig. 16. Rst of th prmtr rition ftr xportions of th PI prmtr, it is ncssry to s th or rspons of th systm. For th robot is positiond to pick nd pc ttr bock, th xprimnts is bot th prformnc of th robot to pick th ttr bock for ch ttr ony. Th initi position is btwn 5 th nd 6 th sots in th bs pt (s figr 3). Th sot is pc whr th ttr bock is pcd. Th primry rm wi mo to th trgt ttr nd th prformnc is msrd. Th prformnc of th systm is rprsntd by ris tim (- 9%), stting tim (5%) nd mximm orshoot. Tim Smping 2ms: Tb 1 shows th smmry of this xprimnt with tim smping 2ms. Th PI prmtrs r from sb-sction 7.3.1, i.. Kp=9, Ki=8.5 nd Kd=.24. From tb 1, it shown tht th frthr th ttr, th ongr th ris tim. Bt this is not wys th cs. nd Z s th frthst ttr do not h th rgst ris tim. Th rgst ris tim for th ft hnd sid is for ttr B. If ttr B is omittd, thn th ris tim is incrsing from ttr M to. This is th dsird sittion. Th nomy of ris tim for ttr B cod b d to th mchnic, sinc th mchnic is not bnc. Th mximm orshoot of th systm for th ft hnd sid is so rid. Lttr M hs th rgst. This is d to its position. To st th P prmtr smr wi so this probm bt th rst of th ttr wi h bd prformnc. For th stting tim, thr is no spcific informtion, xcpt tht th stting tim for ttrs btwn J nd hs sm. Th ris tim for th right hnd sid ttrs is wor thn th ft hnd sid is. Hr, th ris tim chngs brpty from ttr to ttr. Th stbiity of th mchnic gis its contribtion for this probm. Th mximm orshoot is intrsting. Th is rg for th ttr cos to th initi point. To rdc th P prmtr wi so this probm bt th or prformnc wi b bd. Th stting tim for th right hnd sid sms rndom. Thr is no spcific pttrn. TBLE 1 PERFORMNE OF THE SYSTEM FOR EH LETTER WITH TIME SMPLING 2ms Lttr position Ris Tim Mx. Or Shoot (%) B E F G H I J K L M N O P Q R S T U V W X Y Z Stting Tim Tim Smping 5ms: Tb 2 shows th smmry of this xprimnt with tim smping 5ms. Th PI prmtrs r from sb-sction 7.3.2, figr 13, i.. Kp=2, Ki=34 nd Kd=.1 Th or prformnc is bttr thn th prios xprimnt. From th xprimnts, it ws known tht smping tim 5ms hs bttr prformnc thn tht of with smping tim 2ms. Hr th ris tim for both sids sms rndom, i.. thr is no spcific pttrn. Bt th rgst ris tim for th ft hnd sid is sti ttr M. Th ris tim for th right hnd sid hs most th sm pttrn s in th sb-sction Tht phnomnon is so hppnd for th mximm orshoot nd th stting tim. This mks th nysis bot mchnic instbiity mst b considrd. IX. ONLUSIONS Th tim smping of th systm dtrmins th prformnc of th systm. hoosing sitb tim smping mks th tning procss sir. Th comprison btwn 2ms nd 5ms shows tht tim smping 5ms is bttr thn th othr.

7 TBLE 2 PERFORMNE OF THE SYSTEM FOR EH LETTER WITH TIME SMPLING 5ms Lttr position Ris Tim Mx. Or Shoot (%) Stting Tim B E F G H I J K L M N O P Q R S T U V W X Y Z REFERENES [1] Ktshiko Ogt. Modrn ontro Enginring 5 th d. Prntic- H Inc. [2] Pick nd Pc Robot Work [ [3] tm orportion. T89S51 tsht. Jnry 3, 25 [ df] [4] Ntion orportion. 9 tsht. Octobr 18, 1999 [ [5] L298 tsht. Ity: StMicroctronics. Octobr 6, 2 [6] Ntion orportion. 8 tsht. Jnry 3, 25 [ [7] Hrtnto, Bdi. Pmbtn Progrm, Yogykrt: NI, 23 iffrnt tim smping hs diffrnt PI prmtr combintion. So, to chng th tim smping mns to tn th combintion of th PI prmtrs. Th mchnic gis contribtion d to its stbiity. Sm instbiity cn b compnstd by th contror bt it is diffict to compnst th rg instbiity. Lrg P prmtr mks th systm hs rg ris tim. This is intrsting for mny itrtrs stt tht rg P prmtr wi gi sm ris tim [1] Th I prmtr mst b rg in ordr to gt smr stting tim. I prmtr contribts to th imintion of th stdy-stt rror. Th prmtr dos not h big infnc, xcpt tht th mst b smr thn 1. Th combintion of PI prmtrs for tim smping 5ms is Kp=2, Ki=34 nd Kd=.1.