Automatic Control of an Overhead Crane

Copyright © IFAC Control Science and Technology (8th Triennial World Congress) Kyoto. Japan . 1981

AUTOMATIC CONTROL OF AN OVERHEAD CRANE E. Ohnishi*, I. Tsuboi*, T. Egusa* and M. Uesugi** ·Computer Systems Development Department, Fukuyama Works, NIppon Kokan Kabushiki Kaisha, Fukuyama 721, japan ··Systems and Research Department, Technical Research Cent er, NIppon Kokan Kabushiki Kaisha, Kawasaki 210, japan

Abstract. In the iron and steel industry, the autonation and computer control of each nanufacturing process has been promoted in order to improve productiv ity. lloweve r, the auto"'\.1tion of transportation between manufacturing processes is laggin~ beh ind. In the Fukuyama Works of :I.K.K., transprotation using the overhead crane in the cold strip mill which required a large amount of labor was chased anc! enr,ineers began to develop technology aimed at crane autcmation. Crane operation and functions were investigated in oreer to achieve autOll'ation with minimum amount of remodelling of the existin g cralles. Subseqeuntly, engineers decided on the r.evelopment of a single cycle automatic operation system incorporating anti-swing control. One of the cranes now in use was remodelled and experiments were carried out t o Jetermine control function accuracy. It was confirmed that this model crane satisfi0d the required control accuracy with the possibility that labor saving a~d automation could b~ realized. l(eywo r ,ls. Cranes; conputer control; anti-swi.nG control feedback ; material handling. I:
HAT:; POI -IT" OF OLVELOP1:!::;:T

In the iron and steel industry, automation and computer control of each M
h~vc

J'cgr~

position control

~)phin{l

in automation

amI no-rr.an operatioL, becallse ma t erial s have heen hancle~ hv versatile overhead cranes. This probleM was successfully solve'! at the newly establishe,' Ooris11l'nCl J:ot Strip '!ill in tit:! Keihin "orl's 1,y cy:a~inhg anc. re .~esil;11in3 t)lf' Y.'lrd l3yout tin(1 the tictun J constructi ol~ of t~lC' cranp itself. l ) T!('Iwever,in existing "'''rk s, su~'1 basic L modell Lt; is impossible, and ~ .. refore, it is necess3"j' to rCP.1o de l existing cr:.nes
1885

In a olJ strip mill , o'-erh",,,C: CT:mes
1886

E. Ohnishi et al.

bance during the operation. (5) T',e ti1"e require,' for transfer

/ilttern of this control system. S l lOU1d

he

as sl10rt as possi]-]e. Ton~e

ston-position control an~ coil grasp/ release control. It ~ s necessary that the tonc:s' c1m,:s n, rasp t 11e roil secur"lv "ithout collidinc: a",:linst the coil an~ r elease it onlv at t he specified p0siti0n . (1) Stop-nosition of hoistin~ and ton~ openin" should Le controllf'" wit'lill ::!,lrnn, ::10~1". respectively. (~) !"evera1 sensors to ,'f'tect coil 10'ld and reco~nize coil position should he developed in orier to hold an d release the coil safely. Safety 1'11eaSllres an(1 crime operation route control. In most cases, in the existin~ yard, buildings such as motor rooms anJ ro11in~ mill e'lnin-:lent are instill1ed wit')ir. thp ccme' s ran ge of 1'11ovement. It is Absolutely essentiel to operate the crane only alon~ a safe route avoi,iing these hnildings.

Anti-swing control system. The general equation of motion of the overhead crane is as follows 'e"

6=

tjme and control accnracy. In sin~le cycle ilutomatic operation, includinr. the ahove 1"entioned controls, it is necessary to deri~e on a practical cycle tim" and to create a balance hetween the re'luire(\ ilccuracy ancl the operation efficiency of each control device.

CO"TROL SYSTf'! ~nti-swing

ilnd Stop-position C0ntrol.

In the past, an anti-swing and stop- position controls by the program control system had chiefly been proposed, a method to give operation pattern previol:sly, a method to learn operation method 2 ) and a method of operating the crane in the shortest motion time on maximum principle 3),4) and 5). However, these methods have various 2isaJvantage such as the lack of adaptability to external factors, difficulty of speeJ pattern determination, etc. ,\ fee ,'back control syst,,1" was "ls,) proposed. lIo',leve r, thi s me thod hall t he ,li sildvan tage of difficulty in adjusting anti-swing and stopposition a10u a longer transfer ti!:le in order to keep the swing angle at zero Juring 1; oth acceleraLiqi.";

'll '~d

d . . . ceJel",'1tio:....

·... hc rcfore,

botlo 3et',0 1s are no t vet ilct\lal1y in use in the fie l d o f over~ead cranes requirin~ delicate control. The a10 ti- swing and s top-posit ion con t rol systerr propose~ here adopts a feed back co~ trol system to specify the crane spee~ at every i710rnei:l :: (~cf'cI1Jing on the ~·'2."lS_n·\~ ( ! s~·: i:~.-~. ang1e, cca ,le SPeed a:1~! .:ran(' (1CCCler9tion. In aUl:i~ion,

t.:it i l t 11e prerequisite of t~lP. ;h:o:')tio n of D fecJback cOi~ trol syst ei.l , t~lC u!lLi-s"~i;Jg :::ont rol SYSl".!rr', \o;{lS prc;.ctically and rationally ad .~ustc,~

t ~ "',

t~le

Fit:; l :~' (:'

s~("'1~.:s

stop-~·.:S :itiO:i

co'ltrol syste;.-: al~l; , ::It thQ s~~e '-i~(', ,'1 ~ro~.;.:.ln contro l syste~o v:as 3dopt2 ,1 for t~c cO!1 trol (If tl:.e crailC ~uri:1~ sto pp i ;lE . ~

:~:~

\: :::d:r~1.f.:'

of

Ll, ,"",: ':--;")cr~tto:1

(1)

SHins ang l e (6«1) ('ran", position l.'ire rope length Gravitational acce1er3tion

1.= g T~is

is a 2nd order vibration system used to input the crane ~cceleration ~ and to output the sHinh anf>le This system is ant to cause SHinning hy acceleration an~ deceleration of t 1)e crane. The swin l';inf t hu s cause J is verv difficult to dilmp. To solve this nrohlern, it is necessary to ildjust the coefficient 0f t~n swinr an~ul~r v~locity ~ and that of the swing angle -e . In this control SysteM. suc~ a(l i11stment "'as "1ade by feeding hack the crane acceleration i as a function of the sl,ling angle 3nd the swing angular sp-'

e.

\.:~ e(~, Cvc1~

+ ryl& -R. -f4"B=k .2, l'

as e:~pr('ssed in the cqllacior. (2).

;: = -2(i'Sw

-i)Sn

,.',p

c,:"ati,on r l) equation ('1) + 2'51,,' +

e

:1

e

r.

,

ry

(~'v --g)&+11' -eset n

(2)

n

is transformed into tlle

e

, =

I,'

n

-

e

(1)

s('t

'5 = ','.1'''l'in:; factorWn = !at ural anzular frequency 8set = Swing a:~f,le set vallle The eq'lation (1) shows the stan(lard 2nd orcler systeM to il1~ut the s""ing angl!' set value eS 2t an": to output ti,e J"in..: ,,,,,,1,,, -:'l<~n scttinr tll(> lamping f
e

e~ 'e t C.:.l n 1'. 02 o: ) taillt:(~ .

T:lis auti-sT.\7il<~ con~-

ro} syster.-, can he adapted to change(! in the ro pe 1en~1.L;: . l'owe ver, in pr3ctice, for S<1fet\' the wirf' rope is not wound up while the cra~e is in motion (i=O). Stop-position control system. Tlw stop nosition cOrltrol syster to cove ti le crane to ll,e tar:',ct n0sitian is real ized 1,y ~e('dh<1ck ShC''.T,l

~\y

t' le

(l)

. 11 =-x: max (x. set - x) min

(5 '

\l 1 ex

x

\\ ~ r

n xset 11

xset xset j(

Rn J

,;

two equations

Xx~ ma;.; min

x =

n

foll. 0~ving

set - x) 11

Limit rrane Crane Crane Crane Crane

operator position set value speed set value accelera~ion set value position feedhack Ra in speed feedback ~ain

ilowever, the crane speed and the acceleration of the actu'll crane clepend on tLe C:1ilrilcteristics o~ tl-:e motor us ed to d rive t ' ,c: cr!1ne, so t:,C' tlnper and lower limits o f the sn~e~ set value and the acceleration set val\le are estahlished, takin~ the motor characteristics into consideration.

Automatic Control of an Overhead Crane \uiustin~ S\,'Her.. Tt is "ecessary to control both the stop - pos iti or and anti-s\"inf w it ~1

on e 'lanup] atc ll.

v~

r i a1; le, the c r ane :lc c elera-

ti " n . The r (>fore , the: '('s t iMportant problE'm is to [!(';ust t; ' ese t'"I(, c0nt r ol "ys t er,s in on'er ~o cont r ol t~H' crane . T!,is proh lem is sohed as ,i(>seri:" etl I' clm,·. ':',en tile c ra ne is in uniform dece l e ration MOtion, the swing anp.le ie i.n ">ala nce \... it!; t ',e acceleration. ;!it h t;1£' assuMPtion t' ,at El = ='1 in the P'1uation (1) , t :lis rel"ti0tlship ca n be expresser! ',y t l,e e'lua t ion «(,)

e

e

= :

Ui)

-.;

~

The crane i ., "love,1 un<'er t he foll o"il1g cOI1,litions : (1) The crane is accelerated an '~ dp celerated wit h approxiMately uniforM acceler~tion o r dece leration Motion. (:2) "'hen t J..,e c r ane is accC'lC!rated 0r ·i ec eler ated , tl,e s\"ing ?n?lC! in ba lanc e ·.... itll acceleration and ~pcpleration is 1110wed and the ,nti-s\. . inr control is na-1e to s upp r-ess devia tion fro M t~,is s"'in~ angle. Tn t h is case , t he equation ~ ) enn he introduced as a rational r elationsh ip e'1'lation showing t he relatio ns h ip het\yeen the crane acceleration and t he swin g angle. Therefore, the swing a np, le set value set ca n he calculated from the crane acceleration set value Xset which is determi.ned by t'le stop-position control system usin~ the f ~ l: o­ 'i..

in~

eClu ation :

8 set =

2. Vs e t

( 7)

~

1887

t ion start positi0n
~ :lle r

t he

(r(l !1'~

;1 .:'lC 1);1r: :i C"?1

'~ ' E'11

.:'; P("c>, '

hr'l ;~ (;

r<:;lc I ICc.;

is .'lrrd

:":eru, r

1

:f·

i(~( : .

S(!leClil:;'. " 0 , ( . and ,t.x so that the ti'1le

fro:p. ch . .)

, ~ec. ~ 1 0 r ,1tio71

''':L'' c(~le r .'ltion

cn l' o0i n t

" t<1 r t i n ~ ~

po i n t t o L'll' eCOf:es alld i ntef~ r a '

nult i n l e of t'lE' s 'lillf, f'e;rioc\. the cr;me ston s a t t "e tar get n0siti o" ",it ), out s,,·ins: .

Single evrle;

~~t~na tic

~ p e r B ti o~ .

Vhen specifly1ng the coil attributes such as coil width, holding and rc'casinf positi on , a coi 1 : s t r:l1'~s"C"rte , l f ro, t l (' specifiec: ;00 sition to t'IP t.:lr~'~ t Jlos iti on autoMaticall y only hy r;iv in:>; the start i ns tructio ns . ,1 1 is 0peration is perforrled by t he ,::e'luen ti a l c oml' inRt lon 0f f U'1ctio l1S such as traversi n" , ~lOis tin :'" l0werin~ and to n1' clo sinr. "ioure t, S!lOh'S a sc!:cMatic flowchart o f t hc si n3 le cycle auto~atic operation. Tl;e ahove me·· tione d functf0ns will be Jcscri!w d Lelo\" . TravellinG c0ntr01.. In ad
{'sing this control system, the crane can hp. smoothly accelerated or decelerated, since the swing an~le corresponding to the acceleration is allowed. Further , excessive prolon~ation of the transfer time by the anti-swing control can be solved.

Stop -po sition cont rol of hoisting. This is a program control system according to, the hoisting stop position, acceleration and deceleration position determined from th e coil outside oiameter, and a previously specified speed rattern.

Stooping control svstem. The anti-swin~ and stop-position control system rlescribed above can effect the re'luire~ contr0l accurRcy. "owe ver, \.]'len applyinp this system to the ac tual crane , t'lere ~re the Fo l lo"ing n-oblems to he solved when stonpin~ the cr~ne. (1) It t~ k es a Ion!; tire t ,~ stop t'le crane . ecall se of t hp increase in interaction ~e tween t he anti-swing control ~ystem and the ston-positi0n control svste~. (2) The control ner forMance at 10" speed CAnno t he gua ra n tee d hecause of the characteristic of t he crane run Motor. (J) Si nce th.· c ra ne i s stopper. Fballv usi!1 ~ il Mechanical b rake , swin~in~ may brc cause~ hy th e b rak in g when the crane sneed is not zero . To solve these problems, t he program control system is a~orted only " hen stoppi ng t'le crane. The total operation senuence is nerformed by a combination of this pro~rR~ control system ~nc' the ~ ove nentionc~ feedhack control systel11. The cont rol syst . m is as f0::0WS : (1) The crane is "'~ l~ at t he speen of Vo, at a ~clocity unifor~ with the swin e angle zero using the feEn ba c~ control . (2) The crane is ,'eceJerated at llniFor"l ,",eceleration velocity from the decelera-

Stop-position control of tones. This is a sequence control used to stop the tones openine/closinp, operation by the operation of limit switches selected according to the coil \.]i<1. th.

P

Safety measure. (1) Installation of a sensor for coil holding (2) Installation of a sensor to prevent collision aeainst other cranes (3) Installation of a sensor to prevent collision of the tong claws ap,ainst the coil (/') '1onitoring of the auomatic operation time of each sequcnce (5) ~onitorinp, of control accuracy of each sequence (lUTL nr

()"" r CUIPHnTT

Automated Hotlel t::rane One of the existing cranes now in use was selectec and remodelle d to conduct the accuracy t e sts for the ahove mentioned control systems. That is, a cranp in TIN-ePL (tinning coil preparation line) yard was selected, takinr. the required functions of the crane in a cold strip mill and the above mentioned conditions

E. Ohnishi et al.

1888

ri~ure

for ::!utorn.;=ttion into consif'eration. 5 shC)l's thl? layou '.: in the v;"r(~.

n\ltline

0"

''t)(!el l. rRCP rnst..'Illation.

(4) ,\ chnnf'e if' th e coil outsidc diameter caus e',1 a chal1(p in the center of gravi ~ y. n::lr.plv, a ehiH);e fe, t h!: S'•.;iIF:, peric(l. 1 11(' stonnil' " e,) ntrol '''as nfferte ,\ 1.)' t1 :is l~'1 ;"t!i~e.

TRhle 1 shows the prin r ipRl functions of the model crane and the sensors develooe (l. "'i~u­ re f S'lO"-'S the structure of t he control equipment. T1H~ spt'cificiltions of t',e princ LPR] piec e~

of

t-~(pli ' ·· ~ent

ilre .~C'

fol:!.oy"rs :

'.\ltr>matic operation controller. The Rutomatic operation of th e crane is hasically a seqllence control. ,\ r.·iero-processor Ions adollted, tald" , i n t o consi ; ~er:ltion t~l(' ('e '!elopr.1C:lt of

t Ile :lnti-s\.::inr

extens ion for

ltov, ~

""0ntrol, (~ t(".

Tt is .'t f f i cli 1, t to J; \:!tect t 1l(' s u 1.n O ()f :t coil d irpc:t. l·;, so ,\ r ' ct~,od c1ctectill? t1 ',(' s~.Jin~ of t ll (- $\.! j!l~ of the to"l!"S ~'ire \\~as aU0~tP(~ . .\ ~ntf!!ltio-rnet.­ er was IlSP I; ,'1S " ~~etpct\ l r to detpr:t t'10. 5't,,in~

of th e tongs wire in t 1,e tr~~~V0rS0 nn~ t'-Clvcl ,'in'C'tlon hv ('i 'Ji ,' in n t l,e total s"'in~ O\'er t"" C'nti r(" circu;rf c rcne., into t"'0 c1 irec nr:!!:.e~v.

v

:J.nt~ ':'.

~i. ~, urc

const rll ct in n o f thr swir n

~p. r..:; nr

cor

'1('l1 f~i. n ;-

.... Pc.

7 Ca)

n~ ~ l e

r ::- ;: .:1si.n0'.

~hOHS

5en~~r.

\

stron~

a l\" hi»h1v r ~ lia h le s pn sor '''
The

ffi() · \"~

to t.h(· cnil

t:r: erf'l is ;-10 prohle!1

s· vi ,-.£, peri0 t ~

~~0 rrc"s ';J(":n ( : i : I ("

si ~e .

(.') -;-'1(' 1nti-std:'p. contro l ?ccura cy al"! t',e stop-nos ition control accuracy were not affecte d by a chan ~e in the tran sfe r d i s iance. Ch) h'hen cont '-olli n?, the traverse notion and the travel motion simultaneously, n~ it h ­ er control nerformance was affect ed aJv ' rsely.

:1.!1d t ~ 1e

synchro- ~ i1it.1.l syste~ was adopted for position detectin~ and cor re ct ions at the [i~­ ed position was adopte~ to prpvent errors due to "heel slip.

tions,

FOh'f'v~ r,

us.in::. ~.1

I- up .

~

t~e

\.! l "! ('p

cr'1nc ,,,'a s

oreratp.i~

r e T'p.i1t~dly

to

a,:j u.; t all " con fi rm ea c:, cor,l rc-I c', ar,1c teristic of t~ ''" siHg le cycle il'! to!'Oatic operation syste,., d e s~ rL l;ed In the precerlin<>: n'1ra ~ raph. Tahle ~ s~IO'... S t he test results of anti-swinp accuracy 1nJ th e stop-position accuracy. "i~ure 2 shows a tynic.?l examnle of t',e si:nultaneous control of t 1le 'lnti-s,.linrc
CO'lCr.t:SIO' j ,\s ,11'scribe c\ above. the autl ·ors have achievE' ·1

cnti-s,dn r, control, stop-position control an .l coil holding and rel ea sin g control as the bRsic fRctors of the automation of overhead cranes in the existing cold strip mill and have estab1ishe~ a sinple cycle automatic operation technoloo,y. To actually establish rks.

Tsukui, T. (19~O). Automated Y
Automatic Control of an Overhead Crane

1889

.. ...

... , '

'.....

01

An

•• omole of OYI' !'\eo d

f,P L

~O'"

D

Irove ll, r>o

-0' 0 "'0 ond r" e os ,ng

a t co-

40T /I OT I

Fig.l. Schematic diagram of the crane and tongs c.on'rol pOOlrn ror o nl ,- , ,", ono

Co l

control

'S'Q,lofu." tOt'"

. .! .

·~.~ro'OOO'I

11 I 1 1I1 .• I . I • , • I OullW'ot . ."'OOft9Ie_

: . :: .1 ;"

~ -n:,~.~ ),I I1 t r

..

)--

1

.

;.~

A -..J-.".~

.

T ·

I

An '"OfJ\Ollot

Iro.,..'

1"

:- :- :

"'OllOf'l

(:.,1 ."G""

T'OII""OI''''''''' c~

tOMd 1l1l'i"_' 0

.eo

V onOI

OO.5a ,,_ ,

Fig.4. Flow of single cycle automatic operation

Fig.2. Pattern of anti-swing and stop-position control

Ant i - SWInQ control system SW1no onOle

preset

Crone

1-

ill B- : , f

commord

,

I I ' I

'-

-

5"'1''''l O"'lle_

L-____~

~

I (

I ~ffi -J 5100 POSition control system

1---- ---

Cro ne POSItion

Crone

s~ed

I SWlI'lQ alQIe preset

Crone

Crone soeed commend

I

I

I

J

Swu'O ono'.

Fig.3. Feedback control system

. ~

1890

E. Ohnishi

et aZ.

TABLE 1 Specifications of the Hodel Crane Spit , .f ,eOI ,on, A ... ,I,g.y

tOT

A ... ,I .or'l

r, '"

Spon

,p"d

No ,,,

8 ... , 1'1'1 , 1'1

T,o". . "

A"., I,O',

4Qm/""n

TrO .... 1

100 ... ,,,,,"

Fig.S. Layout of the model yard

1829 "''''

100'",,,,

_

2340'",,,,

':JOB'mm -

6 10'"","

w"Gh!

.--

!

Polo,"

!

M't.o

no ."

32 T

• S

CO":::' -- -~."

......

TrO .. . 1

AutOll'lot,t

c.ontf'Ol

M'mory

l/a

C or. 01

16 ~ ~"'"

ROM

( IG -

! .

...

8<>.00'<0. AID

16

tit'" 6G

po.nlt,)

PO"' ,on

~old,nQ.

I

For

A.lea,'ng

'0"''1

Load , ,,g , Co. I u"*' tond, Coo l 1dQ', Tong. GCIIt" ....

O'h,r eron,

oprOOtl'l.";

TABLE 2 Control Accuracy of Each Function

--l

~-:: "m~- T,,~::~'" =~:-- :,-:::~;- ~,o,,"

t !

-

Fig.6. Structure of control equipment

- --t I

lr~'" "ap

--- ~

!

!

i

"Omm

. ,'" ." "O mm

!

",,", .,., !

~o .......... In" ~ 3O", m

1)0""0 1'

frove.,.

I i

S_nu o " " o'~"

l (J,., ,,,

o

O ~·

!~ " "n

""'n,,., !JO ......

o

O ~·

!.40mm

.."",,,! ' O ,,,,"

! IQ m,"

.,.,, "' !

~ O "',.,

Otll ' -,,,, ,";

:

HO,,,

"op POI , "O"

"""031 "top

-;Ci, -- ,

-

----Ac

hiJ

et

:I!

_

.

...

~•..!..:....:.:.l_--.:_~,!.....:_~~• .• l.

.~.;. '"i --

3

"09.'

of oP." '''Q

.. """,'oOu'oI> I, .,

,_ ,

-= ~~~~ :,~

~......

""" < l,.'......'_ .......... _ _.....

'n' ,

':

PC""O~

S' ''' ' O · ' .H>' •• '

L.nL

,.,

-....

................

Fig.7. Schematic dia3ram of sensors

___ _

Discussion to Paper 66.3 Y. Morita (Japan): The crane yard is twodimensional. Is the load carried along one line at a time? Or, is there a simultaneous movement in the both directions? If the latter is the case, do you see any problem? T. Egusa (Japan): Our control system is a two-dimensional system.