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I E E E T r a n s a c t i o n s o n P o we r D e l i v e r y , V o l . P W R D - 1 , N o . 3 , J u l y 1 9 8 6 R O B O T I C M A I N T E N A N C E O F O V E R H E A D TRANSMISSION L I N E S

John H . D u n l a pS e n i o r MemberE l e c t r i c P o w e r R e s e a r c h I n s t i t u t eP a l o Alto C A

J o s e p h M . V an N a m eS en io r M em be rP hi la de lp hi a E le ct ri c C om pa nyP h i l a d e l p h i a , PA

Jerry A . HenkenerSouthwest Research InstituteSan A n t o n i o , T X

Abstract - T h i s p a p e r covers t h e d e s i g n ,a s s e m b l y , a n d fie ld t e s t i n g of t h e TOMCAT C o m p o n e n tEvaluation Unit ( C E U ) . T O M C A T i s an acronym f o rT e l e o p e r a t o r f o r O p e r a t i o n s , M a i n t e n a n c e , andConstruction u s i n g A d v a n c e d T e c h n o l o g y . The u n i twas d e v e l o p e d i n t h e p e r f o r m a n c e of Phase 2 of EPRIP r o j e c t N o . R P 1 4 9 6 7 - 1 , R e m o t e ControlledMaintenance D e v i c e s y s t e m d e v e l o p m e r i t p r o g r a m . T h eo b j e c t i v e of t h i s effort wa s t o d e s i g n , f a b r i c a t e ,a s s e m b l e , a n d e v a l u a t e a r e m o t e l y c o n t r o l l e dmanipulator system f o r t h e maintenance a n d r e p a i r ofoverhead transmission l i n e s b a s e d u p o n t h eu ti li za ti on o f a s many o f f - t h e - s h e l f c o m p o n e n t s asp r a c t i c a l . T h e m a j o r i n t e n t w a s t o d e v e l o p t h edesign i n f o r m a t i o n necessary f o r a f i e l d o p e r a b l ep r o t o t y p e . T h e c o m p o n e n t evaluation unit w a sa s s e m b l e d and then e va lu at ed u nd er e n e r g i z e d and d e -e n er g iz e d c o nd i ti o ns . Information g a t h e r e d f r o m t h eevaluation w i l l f o r m t h e d e s i g n cr iter ia f o r t h efollow-on prototype s y s t e m .

INTRODUCTIONThe maintenance o f o v e r h e a d transmission l i n esystems i s r o u t i n e l y performed b y e x p e r i e n c e dl in em en w ho make u s e of a wide v a r i e t y of s p e c i a ltools and adhere t o s t r i c t , w e l l - d e v e l o p e dprocedures. M o s t o f t h e s e t o o l s and p r o c e d u r e scannot b e e m p l o y e d d u r i n g i n c l e m e n t weather

c o n d i t i o n s . M a i n t e n a n c e o f t h e m o r e c o m p l e x , h i g h e rvoltage s y s t e m s c a n b e t a x i n g e v e n f o r e x p e r i e n c e dlinemen. I n h ea v il y p op ul a te d are as l o a d l e v e l s a r eincreasing and t h e c o m p a c t i n g of transmission l i n e si s being given serious c o n s i d e r a t i o n . A remotemaintenance system f o r use i n these c o n d i t i o n s i sv e r y attractive s ince d i f f e r e n t i a l energy costsassociated w ith an out of service l i n e can b eprohibitively e x p e n s i v e . I n an e f f o r t t o a u g m e n tt h e l i n e m a n ' s w o r k i n g a b i l i t y and t o g i v e h i m t h ea b i l i t y t o work d u r i n g inclement w e a t h e r , e s p e c i a l l yi n an e m e r g e n c y , t h e E l e c t r i c P o w e r R e s e a r c hInstitute ( E P R I ) initiated a research program a i m e da t d e v e l o p i n g a r e m o t e l y c o n t r o l l e d m a n i p u l a t o r w o r ks y s t e m . The b a s i c c o n c e p t w a s d e m o n s t r a t e d b yPhiladelphia Electric i n 1 9 7 9 o n a de-energized l i n eusing an a v a i l a b l e manipulator. After the interestg e n e r a t e d b y t h a t d e m o n s t r a t i o n , E P R I p r o c e e d e d w i t ht h e f i r s t P h a s e o f their research program b ycontracting w i t h Southwest Rese ar ch Institute( S w R I ) . S w R I wa s t e a m e d w i t h P h i l a d e l p h i a Electric8 6 WM 163-0 A paper recommended a nd a pp ro ve dby t he I E E E Transmission and Distribution Committeeof t h e IEEE Power Engineering Society f o r presenta-tion a t t h e IEEE/PES 1 9 8 6 Winter M e e t i n g , N ew Y o r k ,New Y o r k , February 2 - 7 , 1 9 8 6 . Manuscript s u b m i t -t e d September 3 , 1 9 8 5 ; made available f o r printingN o v e m b e r 1 2 , 1 9 8 5 .

Company ( P E C O ) , a n d A . B . Chance i n conducting t h eP h a s e 1 e f f o r t . T h e objectives f o r t h e P h a s e 1f e a s i b i l i t y s t u d y were ( 1 ) D e v e l o p requirements f o rm a i n t a i n i n g high v o l t a g e ( 1 3 8 kV t o 7 6 5 k V ) overheadt r a n s m i s s i o n l i n e s ; ( 2 ) Determine t h e technical a n deconomic f e a s i b i l i t y of d e v e l o p i n g a system t o meett h e r e q u i r e m e n t s ; ( 3 ) D e v e l o p a system conceptuald e s i g n . T h e P h a s e 1 o b j e c t i v e s were met and t h eresults were d o c u m e n t e d i n E P R I final report EL-3 2 9 6 , d a t e d N o v e m b e r 1 9 8 3 . E P R I continued t h econtract with S w R I a n d P E C O f o r P h a s e 2 i n which t h em a j o r o b j e c t i v e of t h e work wa s t o d e s i g n , a s s e m b l e ,and evaluate a f u n c t i o n a l , remotely operateds y s t e m . The system was n a m e d T O M C A T ( T e l e o p e r a t o rf o r O p e r a t i o n s , M a i n t e n a n c e , and C o n s t r u c t i o n usingA d v a n c e d T e c h n o l o g y ) . F i g u r e 1 s h o w s the completedC o m p o n e n t E v a l u a t i o n U n i t ( C E U ) a s s e m b l y . T h eemphasis i n P h a s e 2 w a s t o u ti li ze o f f- t he -s h el fcomponents t o t h e greatest e xtent possible.Development e f f o r t s w e r e divided i n t o seven t a s k s .This P a p e r summarizes t h e accomplishments of t h eP h a s e 2 e f f o r t .

C o m p o n e n t E v d I u a t i U n i t M I a n i p u l . t o r

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F i g u r e 1 . T O MC A T C om p on e nt Evaluation U n i tAssembly0 8 8 5 - 8 9 7 7 / 8 6 / 0 0 0 7 - 0 2 8 0 0 1 . 0 0 1 9 8 6 IEEE

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S Y S T E M DESIGNThe s e l e c t i o n o f an a p pr o pr i at e m a ni p ul a to r forth e T O M C A T S y s t e m was the f irst task of the Phase 2ef f ort. The m a jor goal was t o conduct ane n gi n ee r in g t r ad e- of f analys is, and select the mosta p p r o p r i a t e m a n i p u i l a t o r based upon t he c r i t e r i a

de fi ned dur i ng Phase 1 and the manufacturer sw i l l i n g n e s s to p a r t i c i p a t e in t he program on acooper ative b a s is . C a n d i d a t e s were r e e v a l u a t e d i nterms of the req u irements as shown in Tab le 1 .Kraf t O ce an S yst em s was the m a n u f a c t u r e r that mos tn ea rl y s at i sf i ed the T O M C A T CE U s y st e m r e qu i re m en t s.The s e l e c t e d m a n i p u l a t o r oper ates i n a m a s t e r -slave, s pa t ia l ly c o rr e sp on d en t m o d e . T he m anipu-lator was deve loped f or use i n th e harsh, u n d e r s e ae n v i r o n m e n t a nd ha s a proven t r a c k r e c o r d f orr e l i a b i l i t y under t h e roug h t re at me nt of o f f s h o r eoperations. T he m a n i p u l a t o r was e s p e c i a l l ya t t r a c t i v e for t r a n s m i s s i o n l i ne a p p l i c a t i o n sbecause of t h e r o b o t i c f eatures. I t i s c o n t r o l l e dby a compu ter w i t h the ability to r e m e m b e r t hem o t i o n sequence of each joint in a t e a c h m o d e .The motion sequences can then be repe ated in ar o b o t i c fashion. T h i s f eature can be especiallyimpor tant f or repe titive w o r k ta s ks a n d o t h e rrepe titive m o v e m e n t s s u c h as retrieving or s tow ingspecial t ool s.A m ajor m o d i f i c a t i o n over c o n v e n t i o n a lm a n i p u l a t o r s i s the use of f i b e r optics to provides a fe e l e c t r i c a l i s o l a t i o n b e t w e e n th e o p e r a t o r a n dthe m a n i p u l a t o r w h e n t he m a n i p u l a t o r is ener gized atl i ne potential. T he f ib e r optic components werepowered by a 1 2 Vdc l e a d - a c i d b attery. A s c h e m a t i cof t h e manipulator c o n t r o l system i s s h o w n i n Figure2 . The prototype includes a h yd ra ul ic p ow ere da l t e r n a t o r to m i n i m i z e b a t t e r y weig ht.T e l e v i s i o n was used for oper ator f eedback. TheT V camera pan and tilt m e c h a n i s m was controlledthrou gh t he use o f t h r e e p o s i t i o n (spr ing-loadedc e n te r o f f ) to ggle s w i t c h e s fo r b o t h t he p a n a n dtilt f unctions. Hydrau lic c o n t r o l for e a c h f u n c t i o nwas o b t a i n e d b y u s e o f four-way (center p o s i t i o nlocked) 1 2 V d c s o l e n o i d valves. T he pan a n d t i l tsystem was des igned to c o m m u n i c a t e over a s i n g l efib e r c o m m u n i c a t i o n s l i n k fr o m t he oper ator sc o n t r o l panel t o t he b o o m e n d c o n t r o l box .

Table I Manipulator Requirements

Highly Desired Features

o M a s t e r - s l a v e designo Force and p o s i t i o n feedb acko A ll w ea th er , w a t e r p r o o f designo Externally clean des ign to p r e v e n t / r e d u c e

corona dischargeo M i n i m u m of 7 de grees of fr eedom ( 6 plus g r i p )o H y d r a u l i c a l l y poweredo Weight less than 300 l b .o R e a c h a t l e a s t 5 f t . P o s i t i o n a l a c c u i r a c y of 1 / 8 i n . G ri p o pe ni ng o f 4 t o 6 i n . Corona s h i e l d i n g t o 765 kVo G r i p f orce 1 0 0 l b . m i n i m u mo W ri st t or qu e 5 0 ft-lb. A r m l i ft i ng c a pa b il i t y 1 0 0 l b .O P o s i t i o n hold i n e vent of power losso 1 0 0 0 hr m tb f (mean tim e b e t w e e n f a i l ] u r e )1 2 h r m t t r (mean t i m e to repair)48 h r m t b m (mean t i me b e t w e e n m aintenance )

o Symme tr ic w o rk i ng e nv e lo peo U s e r fr iendliness (quick t o l e a r n a nd easy forn o v i c e t o p e r f o r m r e l a t i v e l y c o m p l e x tasks, an a t u r a l e x t e n s i o n t o the h u m a n hand)o I n t e r c h a n g e a b l e end e f f e c t o r so Able t o be reconfigured in d i f f e r e n t lengths inthe f ieldo Lo w p o w e r consumptiono V a r i a b l e f or ce f ee db ac k at e a c h jointo Some de gree o f p r o g r a m m a b i l i t y or compu terass is t for r e p e t i t i v e taskso N o n c o n d u c t i n g o u t e r s k i no M o d u l a r des ign f or ease o f m a i n t e n a n c e

KM C 900-HTF i g u r e 2 . E v a l u a t i o n U ni t M a ni p ul at or ontrol System

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2 8 2T h e operator control c o m p o n e n t s c o n s i s t o f amanipulator m a s t e r , a manipulator hand t e r m i n a l , ac o n t r o l panel with p a n control a n d t i l t c o n t r o ls w i t c h e s , d u a l T V m o n i t o r s , and a control box f o rhousing t h e m a i n p ri nt ed c ir cu it b o a r d f o r datat r a n s m i s s i o n . T h e s e components a r e located i n theb a c k of t h e bucket t r u c k . E a c h T V camera was

mounted i n a sealed aluminum h o u s i n g f o r s h i e l d i n ga n d protection purposes. T h e c amer a wa s p o w e r e d b yt h e 1 2 Vdc b a t t e r y .A t t h e b e g i n n i n g of t h i s P h a s e 2 e f f o r t , i t w a sdecided t h a t only one of t h e camer as r e q u i r e d a pana n d t i l t c a p a b i l i t y . T h e decision was m a d e t oassemble a h y d r a u l i c p a n a nd tilt m e c h a n i s m u s i n gr e a d i l y available 1 2 V d c 4 - w a y solenoid v a l v e s andt w i n rotary a c t u a t o r s f o r t h e t w o d e g r e e s off r e e d o m . T h e mechanism was n o t o p t i m a l f o r t h eapplication b u t functioned s u f f i c i e n t l y w e l l t ol e a r n t h e critical r e q u i r e m e n t s needed f o r t h ef u t u r e prototype system i n w h i c h electric p o w e r e du n i t s w i l l b e u s e d .C O MP O NE N T E V AL U AT I ON UNIT

T h e CE U c o n s i s t e d o f a n insu lated bucket t r u c k ,m a n i p u l a t o r , s tru ctur al m o u n t i n g s y s t e m , televisionviewing s y s t e m , control s y s t e m , insulator c h a n g e - o u tt o o l s , a n d h y d r a u l i c power s u p p l y . T h e a b o v e s e v e ns u b s y s t e m s were i n d i v i d u a l l y d e s i g n e d , p u r c h a s e d a n d

f un ct io na ll y c he cke d p r i o r t o t h e f i n a l , t o t a lsystem assembly a t P E C O . A n i n s u l a t e d bucket tru ckw as provided b y P E C O f o r test purposes. I t shouldb e noted t h a t t h e g o a l o f t h e TOMCAT system i s t o b em o d u l a r , a n d t h e r e f o r e adaptable t o various t r u c kconfigurations o r other t y p e s of h o s t platforms s u c has conductor c a r t s . T h e b a s i c subsystem e l e m e n t s ,e xcept f o r t h e i n su l at o r c h an g e- o ut t o o l s , a r e showni n t h e t e s t a ss em bl y s ys te m configuration i n Figure3 . T h e boom mount ed components were initiallydesigned t o b e h e l d i n place by an aluminum mountingstructure. T h e mounting structure w a s purposelymade a s a bolt-together construction t o allow f o rr e l a t i v e l y e a s y modifications. T h e aluminum f r a m ew as designed t o straddle t h e boom a n d be pinned t o asolid steel shaft t h a t connects t o t h e booml e v e l l i n g s y s t e m . T h e levelling system m a i n t a i n st h e manipulator i n a vertical position regardless o ft h e boom p o s i t i o n . A mounting structure wasdesigned t o house t h e batteries a n d control b o x o neither s i d e of t h e b o o m . The c a m e r a s were i n i t i a l l ymounted behind t h e manipulator. A t o o l rack w a smounted o f f t o t h e l e f t s i d e o f t h e m a n i p u l a t o r .T h e i n i t i a l structural design p r o v e d t o b e t o ob u l k y . Modifications m a d e t o r e d u c e t h e s i z eincluded: s i d e brackets s h o r t e n e d , battery mountedon t h e s a m e p l a t e a s t h e m a n i p u l a t o r , c o n t r o l b o xrelocated t o a position b e h i n d t h e b a t t e r y .

- - I _ _ T _ T _ _ r _ Ii T - - 7 - -

F i g t u r e 3 . Co m p o n e n t Evaluation I J n i t A s s e m b l y

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2 8 3The Kraf t s e v en - f un c t io n m a n ip u l at o r w as b ol te dt o t h e s tru cture at t h e end of t h e boom. T h e onlym o d i f i c a t i o n t o t h e s ta nd ar d m an ip ul at or a rm w as t h ea d d i t i o n o f special j a w s specifically designed t ohandle t h e tools. Initially, t h e m a n i p u l a t o r wa smounted a t a 1 5 bias a ngl e t o perm it t h emanipulator t o ea si ly rea ch a tool rack w i thou t

req u ir in g t h e tool ra ck s tr uc tu re t o b e forw ard oft h e a r m i n i t s folded position. T h e manipulator w a slater m ou nt ed s tr ai gh t when t h e t o o l r ack conceptwas modified.The t e l e v i s i on v i ew i n g syst em u t i l i zed t w oCharge Couple Device ( C C D ) c a m e r a s w ith automatici r i s a n d fixed focus lenses. A 1 6 mm ( 0 . 6 3 i n )lense w as used f o r close viewing an d a n 8 . 5 m m ( 0 . 3 5i n ) lense was used t o provide an overall picture.T h e 1 6 mm c am er a wa s mounted on a hydraulicallyoperated pan and tilt m e c h a n i s m while t h e 8 . 5 m mcamera w as f i x e d . Each c a m e r a ha d i t s o wn monitorw ith a single f iber cab le linking e ach c a m e r a w i t hi t ' s monitor.T h e operator s cont rol panel a lso housed t h ef iber o p t i c transmitter and receiver f o r t h emanipulator controls and t h e sw itches f o rcontrolling pan and tilt and t h e electro-opticalrece ivers f o r both television cameras.

F IE LD E VA L UA T IO NAfter t h e b as ic f u n c t i o n a l checkout of the CE Ua s s e m b l y , d e- en er gi ze d t es ti ng w a s conducted pri-m a r i l y i n t h e following s tudy areas: reach, de x-t e r i t y , and s t a b i l i t y ; tool and task i n t e r f a c e ;insu lator work p r o c e d u r e ; change-out tool d e v e l o p -m e n t ; T V c a m e r a p l a c e m e n t ; system demonstration.Reach and dexterity tes ts were conducted i n asubjective m a n n e r w ith emphasis placed on t h e changeout o f a v e r t i c a l 2 3 0 k V insulator s t r i n g . For mos toper ations, t h e manipulator appeared t o havesu fficient reach. F o r t h e operation at the PECOtest s i t e , i t w as relatively e asy t o reposition t h e

b o o m . A p p l i c a t i o n s where l a r g e , f u l l y extendedbooms wi ll b e used m ay b e more difficult. I n thosea p p l i c a t i o n s , a n additional o n e t o two f o o t longerre ach c o u l d b e b e n e f i c i a l , especially when operatingon t h e hot end. The possibility of adding o n e ortwo a d d i t i o n a l degrees o f freedom t o the manipulatormounting f rame wa s explored, but was considered tob e an unnecess ary complexity f o r t h e C E U . Provisionf o r a d d i n g t h e additional d e g r e e s of freedom at alater date w ill b e p a r t of t h e p r o t o t y p e mountingstructure.T h e b as ic philosophy f o r t h e C E U was t os i m p l i f y t h e tools and procedures t o perm itf u n c t i o n i n g without f orc e f eedba ck. Manipulatordexterity appeared adequate i n terms of havingp o s i t i o n feedback o n l y . O n e of t h e tasks req u ir in gs i g n i f i c a n t d e x t e r i t y wa s the pulling of t h e cotterk e y . When adequate vis ion could b e p r o v i d e d , thek e y cou ld b e pu lled a s shown i n Figure 4 . T h e r e i sno doubt t h a t the addition of f o r c e f ee dba ck w il ls i g n i f i c a n t l y enhance t h e o p e r a t o r s a b i l i t y t om a n e u v e r p a r t s and t o control t h e work tools. T h i sw ill l e a d t o significant i m p r o v e m e n t s i n d e x t e r i t yand e f f i c i e n c y when f orce fe edb ack i s u s e d . T h i sapproach also provides t h e option t o u se a lesse x p e n s i v e system i f a utility ca n j u s t i f y reducede f f i c i e n c y or has less complex work tasks i n mind.

Stability o f the CE U w as r ev ie we d. I t was nota problem dur ing this Phase since the m a x i m u m he ightoff the ground f o r the m a n i p u l a t o r w as only 3 5 t o 4 0f e e t . F o r tr ansm iss ion line f i e l d conditions,however, the m a ni pu l at or he i ght cou ld e as i ly b e 1 5 0t o 2 0 0 f e e t . A t thes e heights, wi nd and boomr e p o s i t i o n i n g w ill undoubtedly cause t h e m a n i p u l a t o rt o s w a y . U nder these sit uations, one o r twostabilizing arms may b e des ir ab le . One a rm i sprefered t o minimize the m a n i p u l a t o r handlinge ffor t. These stabil izing arms can also b eintegrated with the l ock-on fe at ure wh en oper a ti ngat line p o t e n t i a l o r u nd er c lo se c le ar an ces . I t i slikely the stabilizing a rm w i l l be mos t effective i fi t can te les cope out from t h e m o u n t i n g s tru cture.If this i s the case, then the s ta bi li zi ng a rm w ou ldb e des igned t o clamp o n t o the conductor o r o t h e rpar t w hen w orkin g ener gized. Wh en w or ki ng on thecold end clamping t o t h e pole a rm or tower s tru cturew ou ld p ro vi de s tab ility.

CONCLUSIONST h e EPRI de ve lopment program f o r remotetransmission line m a i n t e n a n c e i s now i n the m iddleof Phase 3 , t h e prototype phase. T h e conclusions ofPhase 1 were that suc h a system wa s t e c h n i c a l l yfe as ib le and cou ld b e e co no m ic al ly j us ti fi ed f o rrou tine and e me rg en cy usea ge if the s ys te m c os t wa she ld t o around 3 0 0 k . Dur ing t he P h a s e 2 componentevaluation phase te chnical feasibility w asdemonstrated and t h e potential problem a r e as w er eidentified where t h e bulk of the p r o t o t y p edevelopment ef fo rt ne ed s t o b e concentr ated. Thesemajor a r e a s are ( 1 ) the v i e w i n g sy stem, ( 2 ) toolhandling and modification, 3 ) minimization ofweight an d s i z e ; response t o b o o m movements, and 1 4 )effective shielding from el ectric f ieldinterference. I t wa s demonstrated t h a t the u s e ofmultiple a r m s wou ld b e t o o bulky a s we ll as

significantly increasing t h e cost. I t was a l s odemonstrated that m any conventional hot stick toolscou ld b e used without the fiberglass poles. E v e r yo p e r a t i o n , h o w e v e r , i s l i k e l y t o require s o m es p e c i a l tools that a re u n i q u e and designed t ointerface w i t h the transmission l i n e hardw are. Amajor c on cl us i on f rom the Phase 2 e ffor t w a s t odemonstrate that a l in ema n c oul d operate t h e systemt o change out a string of 2 3 0 kV vertical insulatorsunder field-simulated conditions. T h e objectives ofthe P r o t o t y p e P h a s e n o w underway i s t o prove t h a tt h e s y s t e m c a n o p e r a t e i n t h e field under t h eexpected rugged abuse and harsh environmentalconditions.

F UT UR E W OR KDesign and construction of the field-operableprototype i s we ll u n d e r w a y and shoul d b e r e a d y f o rfie ld evaluations i n t h e fall o f 1 9 8 5 . Afterc o m p l e t e t e s t i n g f o r mechanical and electricalp e r f o r m a n c e , the prototype TOMCAT w ill b e m adeavailable t o EPRI member u t l i t i e s t o e v a l u a t e thepotential u s e s i n transmission lin e a c t i v i t i e s .

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Figure 4 . M a n i p u l a t o r P u l l i n g C otter K e y on C o l d E n d