Development ofautomatic control system for processing.

Hitoshi YoshitOllli, Yuichi Yanlaguchi and Yusuke Sawai

National Institute of Vegetable and Tea Science, 2769 Kanaya Kanaya-cho, Haibara-gun, Shizuoka 428-8501 Japan

Summary An automatic control systelll was developed in order to Inanufacture high quality without the operation by experts who are experienced in tea 111anufacture. The system gets the states oftea leaves and nlachinery through nlore than 40 sensors, and controls the machinery to keep the tea leaves in optimunl state during processing. The optinluln state of tea leaves during tea 111anufacturing process is that the tea leaf tenlperature is low and the surface oftea leaf is \vet. The sofnvare of the systelll consists of several progralns \vhich are executed as independent processes. SOllIe ofthese processes are executed on a \vorkstation which is the host COlllputer ofthe systelll, and the other progranls are executed on personal COlllputers which are connected to the host by the Intenlet. The operator can nlonitor and control the tea l11anufacturing process \vith a graphical user interface fronl an)'\vhere the Internet is available. The systenl \villlnake the operators free frolll the hard ,vorks in tea factories and give useful inforlllation such as the progress of tea processing to fanners \vho \vork in tea fields far fronl the tea factory.

Keywords Autonlatic Control, Tea Processing, Intenlet, Fuzzy Control, GUI

Introduction \vhich is the nlost popular type in Japanese green tea is Inade through six sub-processes shown in

Fig.l. Six different ll1echanisll1 machines are used O.6~1.0min respectively in these sub-processes because the physical properties of tea leaf change greatly ,vith the progress of tea processing. The physical properties of tea leaf also change in each sub-process. Therefore the tea process 15~20min lllachine 111USt be controlled according to the change of tea leaf. For exall1ple, the tell1perature and the quantity of hot air nlust be lower \vith the progress of drying of tea 30~40min leaves in the prinlary drying process ,vhich is the first drying process in the tea lllanufacturing process. The 30~40min adequate control is necessary for lllanufacturing high

quality tea. Ho,vever it is very difficult for the operator 20~30min ~vho is not skilled in tea Illanufacturing to control the lnachines adequately. The autolnatic control systelll Crude tea \vhich \volI1d be reported in this paper \vas developed in Fig.1 Manufacturing Process of Sencha order to Iuanufacture high quality tea \vithout the help of experts.

Session II -252- Structure of System The newly developed systel11 shown in Fig.2 is conlprised of six tea process nlachines and a C01l1puter network \vhich uses the Intenlet. The controller of the systellI controls the l11achines in the itel1lS sho\vn in Table 1 according to the tea states sho\vn in the sanle table. The controller is conlprised of at least two conlputers \vhich are connected each other by the Internet. Sonle nlodular progranls are assigned to the functions such as data acquisition, control and display, and operate cooperatively with the c0ll1111unication by the Intenlet.

\Vindows PC UNLX Workstation Windows PC 1------i Control terminal Network manager ...... __1 Shared memory 1 Browser 1- ..

Mail Software Windows PC Supervisor Data recorder

Control terminal Data deliverer Bulletin board manager

Data acquisition and control Data communicator rvlail manager I ~====~--- Cellar Phone

Fig.2 Structure of System Table 1 Measurement and Control Items of Tea Manufacturing Process Sub-process Measurement Items of Tea State Control Items to Machine Steaming Moisture content* Green leafquantity NUlnber ofrevolution ofsteaming druln Nunlber ofrevolution ofstirring shan Incline ofsteaming drum Primary drying Leaftemperature Hot air tenlperature Moisture content Air quantity Dampness Number ofrevolution ofInain shan Rolling Moisture content Rolling pressure Secondary drying Leaftemperature Hot air tenlperature Moisture content Air quantity Danlpness Number ofrevolution of11lain shaft Final drying Leaftenlperature Ftirnace telnperature Moisture content Rolling pressure Danlpness Ntllnber ofrevolution of11lain shan Drying Leaftemperature Hot air telnperature Initial Moisture content Air quantity Belt speed ofconveyor * by drying with an electronic oven

Measurement of Tea State The itel1lS oftea state which is necessary for control are sho\vn in Table I. Tea leaf telllperature is llleasured easily by a thelllister or radiation therlllolneter, while the l11easurenlent of the 1110isture content oftea leaf is very difficult because the physical properties oftea leaf do not differ luuch fronl water when the I1I0isture content of tea leaf is very high. Therefore a ne\v method for estiluation of the moisture content of tea leaf \vas used in hot air dryers such as a prilllary rolling dryer or a

-253- Session n l secondary rolling dryer ). The nloisture content of tea leaves is calculated by the following equation which is based on the \vater balance between drying air and tea leaves.

1+ n1- Jtp -.) - () 111 = nl l (x) - x. )qdt (1) W- l) (; .~ ()

where' m: Inoisture content (%db)., Inn: initiallnoisture content (%db), WI): initial tea quantity (kg)., tp: processing time (min),

Xe: absolute hWllidity ofexhaust air (kglkg'),

Xs: absolute hWllidity ofsupplied air (kglkg'\), q: dry air quantity (kg'/min), t: tinle (min). It is important for luanufacturing high quality tea to keep tea leaf tenlperature at low level. Tea leaf temperature rises under falling rate drying, therefore the surface of tea leaf nlust be kept wet to avoid superficial drying. Ifthe hot air telllperature and the air quantity are regulated adequately., the surface of tea leaf is kept \vet in the prilnary drying process or the early stage of the secondary 2 drying process ). We introduced danlpness \vhich is defined as the relative hUluidity equilibrating to the nloisture content of the surface of tea leaf in order to describing the state of the surface of tea leaf}). It is expressed b~/ the following equation.

\vhere cP t: tea leafdalnpness (-), pa: vapor pressure ofhot air (Pa), et: tea leaftenlperature (OC), ea: hot air temperature (OC), Ps( et): saturated vapor pressure at et (Pa). The danlpness indicates the highest value, 1.0 \vhen tea leaves are in constant rate drying.

Control ofTea Manufacturing Machine The systeln controls the tea manufacturing luachines in the items shown in Table 1. The supervisor, the controller of the system controls the Inachines according to the properties and states ofthe tea leaves on processing. The supervisor deternlines the control' values from the tea states on basis offuzzy logic sho\vn in Fig.3.

Fuzzifier n.ll1ction Defuzifier furx:tion low ralher ralher high 1.0 10 lower lower If leaf temperature is low tht>n raise hot air temperatme. 0.8 slightly 0.8 If leaftemperature IS radler low then raIse hot airtemperature slightly. ~ of Grade of membership If leaf temperature is rather high tht>n lower hot cur temperature shghtly. membership

o.~ --\-_..If leaf temperature is high then lower hl1t air temperature. ~ 0.2

37.5 -2.0 Leaf temperature Rise of hot air temperature

Fig.3 Fuzzy Logic

Operation of System We can nlo11itor and control a tea luallufacturillg process by this systell1 from anY\\lhere the Intenlet is available. We ll1uSt use a special progranl \vith GUI ShO\Vll in Fig.4 if \\,le \\Tant to not only nl011itor but also control the tea luanufacturillg process. In the case of the autoll1atic tea' nlanufacturing, we enter -the system only sonle properties of green leaf and a tea type before the starting of the 11lanufacturing. Only one ofthe operators who connect to the systenl can control the 11lanufacturing process. Ho\vever the operator \vho has the control po\ver can pass that to the other

Session II -254- operators. If we want only to know the progress of the tea manufacturing process, we can see that with the Internet browsers for general use shown in Fig. 5. We can also get the progress of the tea manufacturing by an e-mail or a cellar phone.

.'.":;u·Jt!,', *_ f~ •." n'- -...u.tt iii... ;.-.... 1 :'~, ..(. ·'::.i:r.·!r·::-;;:~ ~;ji:' '~:;'1'~ --r"'~-d"7' .~ ..,. ~ -: ..··c-~,~ ; -e'~'_i':!f ...i"::'~;.. :~":: .. _.~'~~"" :. J' ~.,::. : ;;F·~'6»~f\;· lot.{" t~...:;l~: ~ ,'J.• _. "'.=::":••j,.•:~:.; ..uu'-i-.'"i.-•..: ~':~;': ;'" ":':'::D=T;~;;'i~':;-~oi':r:'- '~liii~'~' ..'..,... ,. ~"~ ~.. ; .-J:;: .tt'".. ro';"_ ''':'C'~~

Fig.4 Graphical User Interface Fig.5 Information by the Internet Browser

Result and Conclusion Many experiments of tea manufacturing were 110.0 /~~ executed with this system under various conditions. ~~ 100.0 The system operated satisfactory, and the states of ~ tea leaves were kept good. Figure 6 shows an 90.0 example of the changes of the tea states and the e 80.0 ~ Hot air temperature control values in a primary drying process. The .3 .,~ 70.0 Co Tea leaf temperature supervisor, the controller of the system regulated E the hot air temperature and the air quantity to I-" 60.0 maintain the tea leaftemperature at a constant level 50.0 and to keep the surface of tea leaf wet during the 40.0 process. Therefore the quality of the tea which "- was processed by the system was rated highly. 30.0 0.0 10.0 20.0 30.0 40.0 This system made possible that high quality tea was processed automatically with only few 1.00 V,-\\. operations. Moreover, we can give the system the 0.90 II> I commands of the operation from anywhere the ~ 0.80 Co Internet is available. We can also get the ~ 0.70 o infonllation of tea manufacturing from anywhere 0.60 with a cellar phone. Therefore we will be able to 0.50 ,vork efficiently with the help of this system in 0.0 10.0 20.0 30.0 40.0 busy crop periods. 22.0 Reference '2 20.0 ~ 18.0 I I) Yoshitomi H., Nakano F., Tanaka S. and ~16.0 "- >- "'" \ Sumikawa 0.: Automatic Control of Tea " 14.0 ~ 12.0 Manufacturing Process (Part I), J. Soc. Agr. 10.0 Machin., VoI.62(4), 127-136 (2000). 0.0 10.0 20.0 30.0 40.0 2) Yoshitomi H.: Drying Characteristic of Tea Processing TIme (min)

Leaves (I ), J.Soc. Agr. Macin., Vol.48(2), Fig.6 Change of Tea States and Control 195-202 (1986). Values in a Primary Drying Process

-255- Session II