napredni mehatronski postopek na~rtovanja odprtega krmilja

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Hace A., Poli~ A., Jezernik K.: Napredni mehatronski - An Advanced Mechatronic

Prispevek posega na podroèje proizvodne avtomatizacije v okviru prilagodljivih proizvodnihsistemov. Predstavljen je nov mehatronski postopek snovanja krmilja strojev, ki uvaja interdisciplinarninaèin celovitega naèrtovanja strojev, pri katerih so mehanski, elektronski in informacijski vidiki proizvodnegasistema obravnavani sinergijsko. V prispevku je opisan krmilnik rezalnega stroja, ki je zasnovan naporazdeljeni zgradbi krmilja in z novimi postopki snovanja krmilnih funkcij. Zgrajen je na arhitekturi osebnegaraèunalnika z odprtim operacijskim sistemom realnega èasa QNX. �iroko raz�irjeno grafièno okolje MicrosoftWindows rabi kot vmesnik èlovek - stroj. Krmilnik in uporabni�ki vmesnik sta povezana s protokolom EthernetTCP/IP in se tako lahko povezujeta tudi na pisarni�ko raven omre�ja avtomatizirane proizvodnje. Za opislogiènih krmilnih funkcij je predstavljena nova metoda, ki temelji na matriènem opisu Petrijevih mre�. Omogoèasimulacijo in analizo sistema s èimer se lahko bistveno skraj�a razvojni cikel izdelave krmilja stroja, obenempa je zdru�ljiva s obièajnimi naèini za programiranje logiènih krmilnikov. Krmilje je tako bolj zanesljivo inuèinkovito ter prijazno do uporabnika.© 2004 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: avtomatizacija proizvodnje, RNK-PLK, sistemi operacijski èasovno realni, sistemi vodenja,mre�e Petrijeve)

This paper addresses the field of factory automation within the scope of flexible production systems.It presents a new mechatronic approach to machine control, which introduces an integrated andinterdisciplinary method to holistic machine design. The mechanical, electronic and informatics aspects of aproduction system are involved synergistically. The paper describes a distributed control architecture for acutting machine. In addition, it applies a new approach to the development of control functions. The controllerwas built on the open QNX real-time operating system for the PC architecture. The commonly acceptedgraphical-user-interface environment of Microsoft Windows serves as the front-end of the HMI. The controllerand the HMI are interconnected by an Ethernet TCP/IP link that is extended to the office-level of factoryautomation. A new method for describing logic control functions introduces a modular logic controller thatis specified and formalized using a matrix representation of Petri nets. It allows a system simulation and anoff-line analysis that can significantly shorten a machine control development cycle. The new method iscompatible with standard programming languages for logic controllers. Furthermore, it represents a basisfor the design of more efficient, reliable, and user-friendly machine control.© 2004 Journal of Mechanical Engineering. All rights reserved.(Keywords: factory automation, CNC-PLC, real-time operating systems, embedded systems, Petri nets)

An Advanced Mechatronic Approach to Open Machine-ControlDesign

Ale{ Hace - Ale{ Poli~ - Karel Jezernik

© Strojni{ki vestnik 50(2004)10,469-486ISSN 0039-2480UDK 658.52.011.56:681.51 004.42Kratki znanstveni prispevek (1.03)

© Journal of Mechanical Engineering 50(2004)10,469-486 ISSN 0039-2480

UDC 658.52.011.56:681.51 004.42Short scientific paper (1.03)

Napredni mehatronski postopek na~rtovanjaodprtega krmilja strojev

0 UVOD

Sodobni stroji so tehnolo�ko zelo zahtevni,avtomatizirani, v prihodnosti pa se bodo morali boljeprilagoditi proizvodnji na zahtevo. Zato se v zadnjemèasu raziskave in razvoj na podroèju proizvodnihsistemov usmerjajo k tak�nim re�itvam, ki bodo izbolj�aleprestrojlivost (rekonfigurabilnost), prilagodljivost,hitrost in toènost, z namenom skraj�anja razvojnih ciklovizdelkov in odzivnih èasov na nove zahteve trga. Zauresnièitev teh ciljev je treba razviti:

0 INTRODUCTION

Modern machines are technologically verydemanding and highly automated. However, in the nearfuture they will improve in terms of production-on-demandperformance. Therefore, the research and developmentgoals in the field of production systems involve solutionsthat will allow for the creation of production systems witha higher degree of reconfigurability, flexibility, speed, andprecision, in order to improve the response to new marketdemands and to cut the time-to-market. In order to achieve

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- inteligentne proizvodne postroje z novimimehatronskimi moduli, ki se bodo zmo�niprilagoditi na procesno usmerjene proizvodnezahteve,

- prestrojlive inteligentne krmilne zgradbe in sistemeza krmiljenje takih postrojev,

- metode in vtiène enote za komunikacijo medpostroji,

- inteligentne vmesnike èlovek - stroj za enostavnej�eupravljanje postrojev,

- mre�na orodja za porazdeljeno proizvodnoavtomatizacijo,

- in�enirska orodja za oblikovanje krmilnih sistemov,simulacijska orodja in okolja, komunikacijskealgoritme, protokole in jezike.

Na�tete komponente lahko razdelimo nakomunikacijske module, module za vodenje procesovin krmilne module ter module z dodatnimi procesnimifunkcijami. Dodatne procesne funkcije lahkovkljuèujejo tako strojne kakor programske re�itve zaizvedbo veèfunkcijskih strojev, ki se bodo znaliprilagoditi zahtevani nalogi. Krmilni moduli vsebujejoodloèitveno logiko, usmerjanje prenosa materiala,polizdelkov in izdelkov, nadzor in zanèno krmiljenjeprocesov, proizvodne informacije ter dodatno �ekomunikacijske funkcije. Tako se lahko stroj prilagajaspremembam proizvodnih parametrov, pri èemerproizvodno strategijo lahko izbiramo tudi v skladu zdrugimi stroji. Odprta porazdeljena zgradba vodenjamora torej podpirati funkcije krmiljenja strojev,komunikacije med stroji in optimizacije proizvodnje.Uporabni�ki vmesnik pa mora operaterju omogoèatisimulacije proizvodnih postopkov, nadzor inmorebitne intervencije med izvajanjem, logistiènopodporo ter e-podporo in e-vzdr�evanje. Nova shemaproizvodne avtomatizacije mora biti izoblikovana,izvedena in testirana v industrijskih uporabah.

Mehatronika uvaja nov, integriran ininterdisciplinarni naèin celovitega naèrtovanjaizdelkov, kjer so mehanski, elektronski in informacijskividiki proizvodnega sistema obravnavani sinergijsko.Pomeni osnovo za nove inteligentno krmiljenenaprave z napredno funkcionalnostjo, veèjozanesljivostjo in bolj�o uèinkovitostjo. Prispevek jemetodolo�ko osredinjen na praktièni in�enirski temeljza naèrtovanje, oblikovanje, izvedbo in delovanjeinteligentnih proizvodnih sistemov. Je uporabnonaravnan in uvaja mehatronski naèin naèrtovanjafunkcij raèunalni�kega numeriènega krmilnika [5] inlogiènih krmilnih funkcij [12]. Naèrtovanje krmiljastroja poteka takole: najprej so predstavljenitehnologija tipiènega sodobnega rezalnega strojain naèelo delovanja ter glavne strojne funkcije. Sledizasnova grafiènega uporabni�kega vmesnika zauèinkoviti nadzor in krmiljenje stroja, doloèena jezgradba strojne opreme za krmilje stroja, na koncupa so razviti algoritmi krmiljenja stroja inpredstavljeni nekateri rezultati.

this improved performance, the following technicalitems need to be delivered first:- intelligent production machinery with smart

mechatronic modules capable of adapting toprocess-oriented manufacturing requirements

- re-configurable intelligent-control architecturesand systems

- methods and plug-in units for intermachinecommunication

- human-machine interfaces for collaborativeproduction automation

- networking tools for distributed production automation- engineering tools like control-system configurator,

simulation environment, communicationalgorithms, protocols and languages

The components can be classified ascommunication/control modules and modules withadditional process functions. These additionalfunctions can consist of both hardware prototypesand software solutions to realize multifunctionalmachines, self-adapting to the required task. Thecontrol modules contain decision making, routingcontrol, process control, and production information.Further extensions can make possible machines thatcommunicate with each other, with the product, andwith resources. The machine can smoothly adapt tochanging manufacturing parameters by negotiatingthe best manufacturing strategies with other machinesand/or other products. An open, distributed controlarchitecture must be developed to manage control &communication and optimization. However, human�machine interaction will involve process monitoring,e-assistance, logistics, coaching of external experts,e-maintenance, simulation presentation and processintervention. The new production automation schememust be configured, implemented, and tested inindustrial applications.

Mechatronics introduces a new, integratedand interdisciplinary approach to the overall designof products in which mechanical, electronic, andinformatics aspects are treated synergetically.Mechatronics presents a basis for a new, intelligentcontrolled product with advanced functionality,higher reliability and better efficiency. This paperfocuses methodologically on the engineeringplatform for the design, configuration, implementionand operation of intelligent production systems anddescribes an application of CNC control [5] with amatrix logic controller [12]. It enters the mechatronicdesign of the machine-control as follows: a typicalmodern cutting machine and its purpose arepresented as well as outlining the technology, themain machine functions and the operation principle.Further more, a graphical user interface for efficientmachine management is designed. An appropriatehardware platform is determined and finally, controlalgorithms are developed and some resultspresented.

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VT èrpalka

HP pump

Prenosni sistem

Transport system

XY sistem XY system

X

Y Rezalna �oba Cutting head

Vhodna sekcija

Input section

Izhodna sekcija

Output section

Rezalna sekcija

Cutting section

Material za razrez

Cutting material

Prenosni trak

Transport belt

Podajalni valji

Feeding rollers

1 REZALNI STROJ

Nova tehnologija rezanja z vodnim curkomje v primerjavi s sedanjimi tehnologijami veliko boljpro�na in zato bolj prilagodljiva sodobnim tr�nimrazmeram, omogoèa pa tudi hitro izdelavo prototipovin razvoj popolnoma novih izdelkov. Obravnavanirezalni stroj je namenjen razrezu usnja, tekstila insintetiènih materialov, uporaba te tehnologije jemogoèa tudi na drugih podroèjih, npr.: kamnose�tvo,steklarstvo, lesarstvo, papirni�tvo, gumarskaindustrija, obdelava ploèevine, �ivilska industrija itn.

1 THE CUTTING MACHINE

New waterjet-cutting technology is, incomparison with existing technologies, more flexibleand therefore more favorable to market demands. Itenables high-speed prototyping, just-in-timeproduction and the development of new products.The presented cutting-machine paradigm can be usedfor cutting leather, textiles and synthetic materials;however, the technology potential extends to thecutting of stone, glass, sheet metal, paper, rubber, itis also applicable in the food industry, etc.

Stroj sestavljajo trije poglavitni deli:prenosni sistem, sistem XY in visokotlaèni rezalnisistem. Shematsko je stroj prikazan na sliki 1.Prenosni sistem podaja material v rezalno sekcijo inga dr�i v èasu rezanja. Sestavljata ga prenosni trakin podajalni valji. Podajalni valji dozirajo material zarazrez na prenosni trak. Prenosni trak prepeljematerial v rezalno sekcijo, odrezke pa iz rezalne vizhodno sekcijo, kjer jih operater pobere in odlo�i napaleto. Taka zasnova prenosnega sistema omogoèazvezno podajanje materiala v rezalno sekcijo.Omogoèeno je tudi rezanje delov, ki so dalj�i odrezalne sekcije stroja.

Sistem XY predstavljata medsebojnopravokotno name�èeni osi, ki ju poganjata zmogljivaservomotorja. Os X sestavljata dve vzporedno le�eèivreteni, ki ju poganjata loèena servomotorja. Vretenoosi y le�i na obeh vretenih osi x. Rezalna �oba jename�èena na osi y, z visokotlaèno hidravliènoèrpalko pa je povezana prek pro�ne cevi. Tak�narazporeditev koordinatnih osi omogoèa optimalendostop do rezanega materiala ne glede na polo�ajrezalne �obe.

Osnovni re�im obratovanja stroja jeavtomatski cikel. Funkciji prenosa materiala in rezanja

Sl. 1. Rezalni strojFig. 1. Cutting machine

The machine consists of three main parts:the transport system, the XY system and the high-pressure cutting system. Figure 1 presents the machineschematically. The transport system passes the cuttingmaterial into the cutting section and holds it duringthe cutting period. It consists of a belt conveyer andfeeding rollers. The feeding rollers pass the cuttingmaterial on the belt conveyer. The belt conveyertransports the cutting material into the cutting section,while the cut pieces are transported to the outputsection simultaneously. The cut pieces are then pickedup by the operator and put onto a pallet. Such atransport-system construction makes possible thecontinuous cutting-material feed, which is importantfor cutting pieces longer than the cutting section itself.

The XY system is a two-axis coordinate table.The axes are perpendicular to each other and poweredby high-performance servo drives. The x-axis consistsof two parallel ballscrews, driven by separate drives,while the y-axis lies over the x-axis ballscrews. Thecutting nozzle of the high-pressure cutting system isplaced on the y-axis and connected to a high-pressurehydraulic pump with a highly flexible pipe.

The basic operation mode of the machine iswithin an automatic cycle. The functions of material

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se izvedeta zaporedno znotraj posameznega cikla.Med rezanjem stoji operater pri izhodni sekciji inpobira odrezke predhodnega rezanja. Po koncu rezanjain po spraznitvi izhodne sekcije se izvede nova fazaprenosa materiala.

2 KRMILNIK

transport and cutting are performed sequentiallywithin a single cycle. The operator is standing at theoutput section and taking out the cut pieces. In themeantime, the cutting procedure is continuing. Assoon as the cutting is finished and the output sectionis empty, a new transport phase is executed.

2 CONTROLLER

Sl. 2. Splo�na krmilna shema Fig. 2. General machine-control scheme

Krmilnik stroja skupaj s konstrukcijskozasnovo stroja mora zagotavljati �elenofunkcionalnost, hkrati pa mora omogoèiti varno inuèinkovito upravljanje stroja (sl. 2). Krmilje takovsebuje veè funkcij, ki jih lahko v grobem razdelimona tehnolo�ke funkcije, funkcije upravljanja inpomo�ne funkcije. Med tehnolo�ke funkcije �tejemotiste, ki so povezane z osnovnim namenom stroja,npr.: vrtanje, rezanje, varjenje ali zgolj pozicioniranje.Med pomo�ne funkcije uvr�èamo tiste splo�neganamena kakr�en je nadzor delovanja stroja, varnostljudi in opreme, razpoznavanje napak in odpravljanjemotenj v delovanju. Funkcije upravljanja sousmerjene k operaterju, da dose�emo uèinkovitouporabo in upravljanje stroja. Namenjene sokomunikaciji èlovek - stroj in so navadno izvedenena tekstovnih ali grafiènih opravilnih panelih zdodanimi krmilnimi gumbi. Opravilni panel je prikljuèenna programljivi logièni krmilnik (PLK) ali raèunalni�kinumerièni krmilnik (RNK), ki izvajata algoritmekrmiljenja stroja. Ti se lahko razdelijo na vrednostnoin dogodkovno naravnane algoritme. Vrednostnonaravnani algoritmi (numerièno krmilje) kakr�no jepozicioniranje, so navadno izvedeni na RNK.Dogodkovno naravnani algoritmi (logièno krmilje), kivkljuèujejo funkcije, kakor so zagon in zaustavitev,so navadno vgrajeni na PLK. Izvedba tako obse�nein zahtevne strukture krmilnih funkcij je mogoèe le zzahtevno krmilni�ko zgradbo. Pri gradnji zanesljivihin zmogljivih strojev z zahtevno tehnologijo, visokostopnjo samostojnosti ter prijaznim upravljanjem, jetreba uporabiti integriran postopek naèrtovanjakrmilja. V svetu �e vedno prevladujejo sicer zelozmo�ni, a zaprti RNK/PLK sistemi, vendar pa se vzadnjih letih v praksi vse bolj uveljavljajo tudi krmilja,ki uporabljajo tehnologijo osebnih raèunalnikov (OR).

The machine and controller must bedesigned so as to ensure the desired functionality,as well as safe and efficient machine management(Figure 2). Such machine control is composed offunctions divided into machine technology functions,machine management functions and machine auxiliaryfunctions. The machine technology functions coverthe machine�s elementary purpose, such as drilling,cutting, welding or positioning. The machine�sauxiliary functions are general purpose functions,such as monitoring operating conditions, machineand operator safety, fault diagnosis and faultrecovery. The machine management functions areoperator-oriented functions for efficient machineusage and managing. They are intended for the userto communicate with the machine and are usuallyimplemented on textual or graphical operating panelssupplemented with pushbuttons. The operating panelis connected to the programmable logic device andnumeric control, which implement control algorithms.The control algorithms can be divided into value-handling algorithms and event-handling algorithms.The value-handling algorithms, such as positioning,are usually implemented on computer-numerical-control (CNC) devices. The event-handlingalgorithms, such as start/stop, are usuallyimplemented on programmable logic controllers(PLCs). In order to implement such a complex andextensive set of machine-control functions, a complexcontrol architecture is necessary. This demands anintegrated design approach that considerscomplicated technology, a high machine performance,high level of autonomy, short recovery times anduser-friendly management. Capable hardware-basedproprietary CNC/PLC systems still dominate the worldof machine control; however, a PC-based control

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Programska oprema za nadzorni vmesnik èlovek - stroj(VÈS), za upravljanje stroja, logiène krmilne postopkein krmilne algoritme je zgrajena modularno ter na voljoza sprejemljivo ceno. Sistemski integratorji lahkopreprosto kombinirajo strojne in programskekomponente za gradnjo uèinkovitih, standardnih inodprtih re�itev krmilnih sistemov, s tem pa se izognejouporabi dragih zaprtih sistemov z omejenofunkcionalnostjo. Pri naèrtovanju odprtih sistemov, kiuporabljajo standardne strojne in programske re�itve,so manj�i stro�ki, tak�en sistem je mogoèe raz�iriti indograditi ter omogoèa izbolj�ave v prihodnosti. Koristivkljuèujejo ne le ni�je stro�ke, paè pa tudi bolj�ofunkcionalnost sistema in komunikacijsko povezavo spodjetjem. Poleg tega je mogoèe skraj�ati razvojni cikel,z uporabo simulacijskih orodij in orodij zarazpoznavanje napak pa se skraj�a tudi èas zastojev vproizvodnji, s èimer se poveèa produktivnost inzmanj�ajo vzdr�evalni stro�ki.

2.1. Vmesnik èlovek - stroj

Grafièni uporabni�ki vmesnik (GUV), ki jepredstavljen na sliki 3, je glavni del VÈS na rezalnemstroju. GUV je izveden na zaslonu osebnegaraèunalnika krmilnega sistema in zdru�uje vse prikazeter funkcije, ki so potrebne za upravljanje stroja.

Namen GUV je, da zagotovi uporabnikuprijazen nadzor nad delovanjem stroja. Uporabnikusporoèa vse koristne strojne informacije na zaslonunadzorne plo�èe, to so:- splo�ne informacije, ki vkljuèujejo re�im in naèin

obratovanja stroja (avtomatsko/roèno, izvajanje/ustavitev), ime in stanje trenutnih tehnolo�kih

technology has become a widely used industrypractice in recent years. Software for a human�machine interface (HMI), machine-control, sequencecontrol, logic control and motion control has beenmodularized and is now available at a reasonablecost. System integrators can now easily packagehardware and software components when buildingeffective open-standard control systems andeliminate the dependence on costly, low-functionproprietary systems. An open-system design thatuses standard hardware and software minimizes cost,permits system scalability, and ensures futureperformance enhancement. Benefits include, notonly cost reduction, but also improvement in thefunctions and communication to the enterprise.Moreover, it allows for faster design cycles, lowerdowntime using diagnostics and simulation tools,increased productivity and decreased maintenancecosts.

2.1 Human�Machine Interface

The main module of the cutting machineHMI is the graphical user interface (GUI), which ispresented in Figure 3. The GUI brings together all ofthe displays and functions for the management ofthe cutting machine.

It provides user-friendly machine-operationcontrol and has all the relevant machine informationon the monitor screen, this includes:- general system information, which comprises the

machine operation mode (auto/manual), theexecution mode (running/stopped), the name of theprocedure that is actually performed, and other

Sl. 3. Grafièni uporabni�ki vmesnikFig. 3. The graphical user interface

okno procedureprocedure window

kronologija sporoèilmessage history

napakefaults

kontura rezanjacutting contour

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postopkov, ter druge informacije o stanju stroja,- informacije o hitrosti rezalne glave, ki vkljuèuje

�eleno in dejansko vrednost,- podatki o posameznih oseh, to so polo�aj in druge

informacije stanja,- podatki o delovnem programu (ime, trenutni blok,

stanje),- podatki o orodju (curek odprt / zaprt),- podatki o stanju postopkov na PLK (avtomatsko

obratovanje stroja zagnano / v teku / ustavljeno),- podatki o dodatnih oz. pomo�nih napravah na

stroju (visokotlaèna èrpalka, napajanje stroja,varnostni krog),

- razne druge informacije (izklop v sili, stanje na mre�i,bri�i napako),

- razlièna sporoèila, ki vkljuèujejo veè stopenjopozoril in druga sporoèila operaterju, ki seprika�ejo sproti kakor nastajajo ustrezni dogodkina stroju; za ponovni zagon po napaki na strojumora operater opozorila zbrisati roèno.

GUV omogoèa nadzor, programiranje inoblikovanje stroja, podpira pa tudi veèfunkcijskeprogramske krmilne gumbe. V osrednjem podroèjuzaslona nadzorne plo�èe vkljuèuje polje, v kateremizri�e geometrijsko obliko obrisov rezanja. Ko sedelovni program nalo�i, se naèrtovani obris rezanjaprika�e v celoti. Posamezni segmenti, ki se re�ejo, intisti, ki so �e bili odrezani, so oznaèeni z razlièno barvo.Hkrati se na naèrtovanem obrisu s kri�cem oznaèujedejanski polo�aj rezalne glave. Informacija o polo�ajurezalne glave se osve�uje v relativno kratkih èasovnihintervalih.

Okna uporabni�kega vmesnika so krmiljenainteraktivno glede na trenutno stanje stroja oziromapostopka. V primeru spremembe re�ima obratovanjaGUV samodejno ustrezno zamenja okna. GUV vsebujerazlièna okna, nekatera med njimi se pojavljajo navmesniku dinamièno. Okno postopka se pojavi nazaslonu samodejno, ko se postopek na stroju za�ene.Okno poka�e vse korake postopka med izvajanjem.Operater je tako ves èas natanèno voden skozipostopek, prika�ejo pa se tudi navodila za morebitneroène posege operaterja. Tak�en naèin naredidelovanje stroja pregledno, omogoèa pa tudi hitroodkrivanje napak in ponoven zagon stroja v primeruzastoja.

Uporabni�ko prijazno upravljanje olaj�adoloèanje napak na stroju, s tem pa je tudivzdr�evanje la�je. Prepoznava napak je mogoèa ssporoèili, ki jih GUV sporoèa operaterju. Sporoèila onapakah so prikazana na lahko razumljiv in primerennaèin. Medtem GUV nadaljuje spremljanje inzapisovanje vseh novih opozoril. Informacije ostanju stroja se zbirajo ciklièno, z relativno dalj�operiodo osve�evanja, reda ene sekunde, karomogoèa sprotno poroèanje sporoèil in primernohiter odziv na stroju.

general machine-state information- feedrate information, which includes commanded,

actual and override values- axis details, which comprise position and other

related status information- program information (program name, program

block, program status)- tool information (jet start/stop)- PLC information (automatic operation stopped,

started, running)- auxiliary devices information (HP pump state, mains

state, safety-circuit state)- miscellaneous information (emergency-stop

pressed, network alive, reset fault)- message information, which includes various levels

of alarm and operator messages that appear as theyoccur; however, to recover from a failure the alarmsmust be cleared manually by the operator.

The GUI provides monitoring, programming,configuring, and multifunction software-buttonssupport. Furthermore, it contains the contour-geometryfield that occupies the central area of the screen. Itshows up a whole program with a planned cuttingcontour when loaded, however, during the programexecution the cutting head path is redrawn in real-timewhile traveling. The contour segments that are cuttingand those that have already been cut are markeddifferently. The actual position of the cutting head onthe planned cutting contour is marked with a cross.

The GUI has a window structure, which isdriven on the basis of the machine�s and/or theprocedure�s actual state, e.g., when the machinechanges the operation mode the GUI simultaneouslyswaps the pre-defined windows accordingly. Some GUIwindows perform their operation dynamically, i.e., aprocedure window appears on the operator screenwhen a certain machine-control procedure is started.It displays all the procedure steps that are to beexecuted to accomplish the procedure. The operator iscarefully guided through the procedure; instructionsare displayed for manual interventions, if necessary.This approach makes the machine�s operationtransparent. Consequently, the potential fault can beclearly identified and the operation can be recoveredquickly.

The user-friendly approach isolates faults andso incorporates easy maintenance diagnostics. Thefaults are identified by messages displayed on the GUI.Error messages are displayed in an easilyunderstandable and correct manner. Furthermore, theoperator is able to display a message-history list toaddress an alarm condition. Meanwhile, the GUIcontinues to monitor and record all the new alarm events.The machine state information is acquired cyclicallywith a relatively slow refresh period with respect to fastposition measurement; however, the cycle rate is lessthan a second in order to ensure a prompt machineresponse and to serve messages as they occur.

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2.2. Strojna oprema krmilnika

Èe �elimo vgraditi funkcionalnost RNK/PLKv osebni raèunalnik (OR), mora ta delovati v realnemèasu. �e veè, za izvedbo krmilnih algoritmovservomotorjev se mora OR odzivati v strogem realnemèasu. Odziv OR mora biti tako logièno in povrhu tega �eèasovno pravilen � odzivati se mora sproti, pravoèasnoin napovedljivo, èasovni odziv mora biti vnaprejdoloèljiv za najslab�i primer. Operacijski sistem za OR, kiomogoèa delovanje v realnem èasu, je QNX [14].Operacijski sistem QNX je primeren tudi za uporabo vrobotiki in avtomatizaciji [4], o èemer so �e poroèali�tevilni avtorji ([1], [2], [7] in [15]), saj ima prilagodljivozgradbo, ki zagotavlja robustno in zanesljivo delovanjevgrajenih sistemov. Zelo natanèni programski èasovnikiomogoèajo delovanje v strogem realnem èasu na poceniin raz�irjeni strojni opremi. Tako je lahko z uporabosodobnih enoprocesorskih osebnih raèunalnikov, ki sedobijo na tr�i�èu, mogoè razvoj tak�nih sistemov, ki imajov istem raèunalniku vgrajene krmilne algoritme, mre�nopodporo in grafièni uporabni�ki vmesnik. S tak�nozgradbo krmilnika je mogoèe zamenjati obièajnoveèprocesorsko zgradbo �gostitelj/DSP�, ki se pogostouporablja v sistemih vodenja. Tak�en sistem je drag inni tako prilagodljiv, programska oprema pa je zelozahtevna. Prednosti enoprocesorskega sistema takovkljuèujejo ni�je stro�ke in manj�o zahtevnost sistema,veèjo prilagodljivost in dogradljivost. V predstavljeniuporabi upo�tevamo �e zdru�ljivost s sedanjoprogramsko opremo RPN/RPI, razvito v okolju MicrosoftWindows, zato je krmilni raèunalni�ki sistem zasnovan zdvema osebnima raèunalnikoma (sl. 4):- VÈS raèunalnik z okoljem Microsoft Windows na

katerem teèe grafièni uporabni�ki vmesnik inkomunikacijska podpora za povezavo s sedanjotovarni�ko programsko opremo RPN/RPI.

2.2 Hardware

In order to implement CNC/PLCfunctionality on a PC platform it must operate in realtime. Moreover, a hard real-time feature is aprerequisite for motion control. The QNX real-timeoperating system [14] can be a good candidate foruse in the field of robotic and automationapplications [4]. Many authors have reported onPC-based control applications with QNX ([1], [2],[7] and [15]). It is attractive, particularly forembedded systems, since it provides flexiblesoftware architecture, as well as a robust and reliableimplementation. Such embedded systems with high-accuracy timers enable hard real-time performanceimplemented on a cost-effective and widelysupported hardware platform. Therefore, modernhigh-speed consumer-grade PCs are capable ofimplementing the motion-control algorithms as wellas the networking and the user interface on a singleCPU. This architecture replaces the traditionalmultiprocessor �host/DSP� board architecture oftenused in control applications, which suffers from thehigh cost of the hardware, the limited flexibility ofthe system, and the complexity of the software. Theadvantages of a single-processor system includereduced cost and lower complexity, as well asincreased flexibility and upgradeability. However,in order to achieve interoperability of the alreadyexisting CAD/CAM software that has beendeveloped in the Microsoft Windows environment,we suggest a computer-control architecture with twoPCs (Figure 4):- The HMI computer with the Microsoft Windows

environment implements the user interface packageand network support for existing CAD/CAMsoftware.

Sl. 4. Krmilni sistemFig. 4. The control-system block diagram

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- Krmilnik RNK je osebni raèunalnik z operacijskimsistemom QNX za izvajanje funkcij RNK/PLK vstrogem realnem èasu.

Programski paket RNK/PLK je name�èen naosebnem raèunalniku in obsega krmilne algoritme zasistem XY, osnovne nadzorne rutine za vodni curek,krmilne postopke in komunikacijske module. Konènaoblika sistema je naèrtovana brez uporabni�kegavmesnika (tipkovnice, mi�ke in zaslona), torej kotvgrajen sistem. Raèunalnik z name�èenim okoljemMicrosoft Windows ima name�èen programski paketz grafiènim uporabni�kim vmesnikom, gosti pa tudiprogramsko opremo RPN/RPI z zunanjo povezavoEthernet na tovarni�ko lokalno omre�je. Nauporabni�ki vmesnik so prikljuèene �e obièajnevhodno/izhodne enote. Raèunalnika sta med sebojpovezana z standardnimi vmesni�kimi karticami FastEthernet. Raèunalnik RNK je opremljen z vhodno/izhodno vmesni�ko kartico, ki predstavlja krmilnivmesnik. Krmilni vmesnik povezuje krmilni raèunalniks strojem. Prikljuèen je na servomotorja in na zunanjiPLK, ki je dodan za raz�iritev sistema z loèenointeligentno I/O okolico. Glavne naloge PLK sokrmiljenje prenosnega sistema in visokotlaène èrpalke.Povezava RS-232 omogoèa prenos veèje mno�icepodatkov med krmilnikom RNK in zunanjim PLK.Moènostni in varnostni algoritmi krmilja so izvedeniz relejsko logiko.

2.3 Programska oprema

2.3.1 Raèunalni�ki numerièni krmilnik

RNK izvaja razliène naloge, potrebne zavodenje stroja: osnovne krmilne logiène postopke,èasovno kritiène algoritme polo�ajne krmilne zanke,pospe�evanje/zaviranje in generiranje poti,interpretiranje delovnih programov, vmesnik zaprogramiranje stroja, upravljanje s programi z datoteènimsistemom, obdelava drugih strojnih podatkov in mre�napodpora. Z zunanjim PLK skrbi za usklajeno delovanjesistema XY, prenosnega sistema in visokotlaène èrpalke.Vse uporabni�ko pomembne informacije, ki so povezanes strojem, morajo biti prenesene do uporabnika. TakoRNK sporoèa uporabni�kemu vmesniku informacije opolo�aju in hitrosti rezalne glave, o izvajanju delovnegaprograma za rezanje, razlièna sporoèila in opozorila.Nadalje krmilnik vzdr�uje informacijski most, ki povezujezunanji PLK z uporabni�kim vmesnikom, s èimer jeomogoèen prenos podatkov o delovanju prenosnegasistema in visokotlaène èrpalke. Da je mogoèe izvajativse te naloge, mora programska oprema krmilnika RNKdelovati v realnem èasu, pri èemer so pogoji strogegarealnega èasa povezani s krmilnimi algoritmiservomotorjev, medtem ko se informacijska podporauporabni�kega vmesnika lahko izvaja v mehkem realnemèasu. V veèprocesnem konkurenènem enoprocesorskemraèunalni�kem okolju programski model odjemalec -

- The QNX computer responds deterministically inhard real-time to serve for the CNC/PLCfunctionality.

The CNC/PLC package is hosted by thePC platform. The package comprises the XY controlalgorithms, the basic water-jet control routines, theoperator level control procedures, and thecommunication modules. The end-user installationof the CNC controller is designed as an embeddedsystem without a keyboard, a mouse and a displaydevice connection. The Windows computerimplements the GUI as well as hosting the CAD/CAM software with a link via an additional Ethernetconnection to the factory LAN. The GUI connectsthe user input/output devices. Both PCs areinterconnected by standard Fast Ethernet interfacecards. The control interface, which utilizes the high-performance multifunction I/O board for the PCmotion-control applications, connects the CNCcontroller with the XY system. The control boardis linked with XY servo drivers as well as with theexternal PLC, which is added for dislocatedintelligent I/O expansion. The PLC�s main tasksare to control the transport system and the HPpump. The RS-232 line allows for information flowbetween the CNC controller and the external PLC.The power and safety circuits are implemented byrelay logic.

2.3 Software

2.3.1 Computer Numerical Controller

The CNC performs the various tasksnecessary for the machine-control: basic logiccontrol procedures, time-critical position-controlloops, acceleration/deceleration, NC pathgeneration, program loading and interpreting,machine programming interface, graphical userinterface, file management, data processing, andnetworking. Additionally, it provides forinteroperability with the external PLC in order tosynchronize the operation of the XY system, thetransport system, and the HP pump. All user-important information related to the machine mustbe passed to the operator. Thus, the CNC controllersupplies the GUI with the position/speed of thecutting head, the cutting program executioninformation, the messages and the alarm conditions.Furthermore, the controller forms an information linkthat connects the external PLC with the GUI. Thelink enables the transfer of the transport systemand the HP pump operation data. In order toaccomplish all the tasks cited above, the CNCsoftware-package architecture must allow for real-time operation: hard real-time requirements areassociated with motion-control algorithms, while theGUI overall messaging scheme needs soft real-time

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stre�nik omogoèa izvedbo tak�ne arhitekture procesov,ki ustreza na�tetim zahtevam. Ta model je v QNX mogoèezelo preprosto izvesti z uporabo tak�ne medprocesnekomunikacijske sheme, pri kateri je stre�ni procesblokiran, medtem ko èaka na sporoèilo od odjemalca.

Predlagana arhitektura procesov krmilnikaje strukturirana kakor ka�e slika 5. Procesi sonaèrtovani tako, da izvajajo naslednje naloge:- Stre�nik krmilnega vmesnika izvaja naloge na

nizkem novoju: dostopa do vmesni�ke kartice I/Oin tako omogoèa zajemanje in izdajanje digitalnihter analognih signalov.

- Interpolator, vmesni pomnilnik referenènih toèk, XYkrmilnik, krmilna logika skrbijo za izvedbouporabni�kih nalog: interpolator na osnovi delovnegaprograma generira �eleno vrednost, ki se shrani vpodatkovnem vmesniku; ta zagotavlja nemotensprotni pretok podatkov do krmilnega modula, ki izvajakrmilne algoritme servomotorjev v strogem realnemèasu. Ti moduli skrbijo tudi za zaèetno inicializacijoservosistema, èe je ta opremljen z prirastkovnimipolo�ajnimi merilniki. Krmilni modul vkljuèujealgoritme za varno in zanesljivo ustavitev ob pojavunapak na servosistemu, kakor so: prevelik sledilnipogre�ek, nalet na programske oziroma strojnepolo�ajne omejitve, napaka na motorjih ipd. Modulkrmilne logike izvaja logiène krmilne funkcije ciklièno.

- Podatkovni stre�nik omogoèa drugim procesomuporabo skupnih podatkov, ki so shranjeni v

execution. The architecture scheme that complieswith such requirements implements the client/serversend-driven model. It can be easily applied by theQNX synchronous messaging scheme. The send-driven model assumes that the server is blockedwhile it is waiting for a message from the client, i.e.,the server process is in a receive-blocked state.

The proposed control-application processarchitecture is structured as shown in Figure 5. Theprocesses are designed to perform the followingtasks:- the hardware server performs access to the low-

level I/O board facilities and thus provides a digitaland an analog signal interface.

- the interpolator, the setpoint buffer, the XYcontroller, and the logic control execute user-leveltasks: the interpolator generates setpoints on thebasis of user path requests, passes them to thebuffer, which ensures continuous data flow to theXY controller that implements the position-controlalgorithms in hard real time, thus performingmotion-control tasks involving incrementalmeasurement system initialization, safe and reliableemergency stop at fatal errors such as: followingerror, software and hardware limits, servo fault, etc.The logic control module cyclical runs logic controlprocedures.

- the data server allows other processes to use thecommon data that are stored in the shared memory

Sl. 5. Programska zgradba RNK/PLKFig. 5. The CNC/PLC software architecture

upravitelj vtiènic

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skupnem deljenem pomnilniku.- Uporabni�ki vmesnik izvaja funkcije, kot so

sporoèanje informacij operaterju, roèni vnoskrmilnih ukazov, vnos in interpretacija delovnegaprograma, na podlagi katerega se krmilijointerpolator, XY krmilnik in krmilna logika, ter nadzorsistema; podpira vhodno/izhodne naprave, to sotipkovnica, mi�ka in monitor, nadalje pa tudi mre�niprotokol uporabni�ke ravni, ki je zgrajena na skladuTCP/IP.

- TCP/IP odjemalec/stre�nik skrbita za mre�noEthernet povezavo z raèunalnikom VÈS. ProtokolTCP/IP omogoèa povezavo veè oddaljenihraèunalnikov in hkrati relativen varen prenospodatkov. Protokol uporabni�ke ravni, ki doloèapomen komunikacijskega sporoèila, je v osnoviukazni interpreter. Podatki se izmenjujejo na zahtevostre�nika na raèunalniku VÈS ciklièno. Tako sezagotovi zvezno osve�evanje podatkov nauporabni�kem vmesniku. Za primerno kratko periodoin dovolj hitro odzivnost sistema na posredovanjeoperaterja pa mora biti informacijski paket èim manj�iglede na pasovno �irino komunikacijskega kanala.Zato je k periodiènemu informacijskemu paketu, kivsebuje osnovne informacije o stanju stroja, dodana�e dogodkovno krmiljena informacijska shema. Tazbira kraj�a sporoèila, ki imajo pogosto prednost invsebujejo informacijo o drugih dogodkih na stroju(npr.: napake, opozorila) ter morajo biti samodejnoobdelana ali sporoèena operaterju.

- Po�iljatelj in sprejemnik serijskegakomunikacijskega kanala komunicirata z zunanjimPLK prek serijske povezave RS232. PLK odgovarjana zahteve po�iljatelja in se odziva z ustreznimisporoèili, ki jih po�ilja sprejemniku. Sporoèila sosestavljena iz spremenljivk s preddoloèenimpomenom, da so lahko èim kraj�a, saj je hitrostprenosa po serijskem kanalu razmeroma majhna.

Eksperimentalni rezultati

Krmilni raèunalnik RNK je bil izveden naosebnem raèunalniku z AMD ATHLON 800MHzThunderbird procesorjem na GA-7IXE4 matièni plo�èiz 64MB RAM. Na raèunalnik VÈS je bil prikljuèen spovezavo Fast Ethernet (100Mbps), s serijskopovezavo RS232 pa na zunanji PLK. Na tem sistemuso se lahko krmilni algoritmi polo�ajne zanke izvajali skratko periodo 200µs, tipièna nastavitev je bila 1ms,kar je omogoèalo veliko natanènost polo�ajnegavodenja pri velikih rezalnih hitrostih do 1m/s. Postopkikrmilne logike so se izvajali s periodo 4ms, kar je dovoljhitro za razmeroma poèasne procese, ki jih nadzirajologiène krmilne funkcije. Podatki na uporabni�kemvmesniku so se osve�evali s periodo 0,5s. Na to jevplivala razmeroma poèasna serijska povezava zzunanjim PLK, ki je s 19200 Baudov prenosne hitrostipodatkov omejila komunikacijsko periodo na 200ms.

area.- the user interface implements the user input/output

module and the G-code program interpreter thatissues path requests and logic control commands,and system monitoring; it supports input andoutput devices such as a keyboard, a mouse and amonitor as well as the application-layer protocolthat is stacked on the TCP/IP.

- the TCP/IP client/server deals with the Ethernetnetwork communication link to the HMI computer.The TCP/IP protocol makes possible theconnection to remote computers and a reliablecommunication link. A dedicated application-layerprotocol essentially presents the commandinterface. The data transfer is performed cyclicallyon the basis of the HMI computer requests, thushaving contiuous data displayed on the GUI.However, the information scheme has to be astiny as possible to achieve a high refresh rate anda rapid response to operator interventions.Therefore, only the main machine-statusinformation is included in the communicationpacket, and a so-called eventdriven messagingscheme with small packets is added to supportsporadic events (such as faults and alarms) onthe machine that must be or automaticallyprocessed either passed to the operator promptlyin order to provide user-friendly machinemanagement.

- the serial comm. sender/receiver provide dataexchange between the external PLC and the CNCcontroller via a serial RS232 communication link.The PLC responds to sender requests. It sendsdata to the receiver and thus supplies the requesteddata that consists of variables with a predefinedmeaning in order to have short messages and sopreserve a relatively high update rate due to thelow communication bandwidth.

Experimental results

The CNC controller was implemented ona PC with AMD ATHLON 800MHz Thunderbirdprocessor on a GA-7IXE4 motherboard with 64MBof RAM, connected via a Fast Ethernet (100Mbps)link to the HMI computer and the RS232connection with the external PLC. Thepositioncontrol period achieved by the proposedsystem ranges from 200µs, but is typically 1ms,which allowed highly accurate position controlat a high speed of 1m/s. The control logic processwas executed during a 4ms period, which was fastenough for the relatively slow processescontrolled by the logic control functions. The GUIdata was cyclically refreshed during a 0.5s perioddue to the slow PLC communication bandwidthof 19200 Baud transfer rate; this gave acommunication period of 200ms.

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Na sliki 6 so prikazani rezultati polo�ajnegakrmiljenja rezalnega sistema.Krmilni signal na izhoduRNK je predstavljal referenèno hitrost servomotorjem.Krmilni algoritem je bil v tem primeru raèunan s periodo250µs. Na diagramu levo je prikazan testni obris vravnini XY, desna diagrama pa trajektorije posameznihosi z referenèno hitrostjo zgoraj, sledilnim polo�ajnimpogre�kom v sredini in krmilnim izhodnim signalomspodaj.

2.3.2 Naèrtovanje programljive krmilne logike

Osnovni namen PLK je izvajanjedogodkovno naravnanih logiènih funkcij, kakor sovklop/izklop stroja, izbira avtomatskega ciklaoziroma roènega upravljanja, zagon/zaustavitevcikla, nadzor aktuatorjev, zaznavanje napak inspremljanje obratovalnih razmer. Klasièno seprogramiranja krmilnih funkcij lotimo na podlagièasovnega diagrama izvajanja tehnolo�kih funkcijstroja in na podlagi krmilne sheme elektroo�ièenja[9]. S tem so podane tehnolo�ke funkcije stroja inzgradba njegovega krmilja. Izvedba funkcij zaupravljanje, nadzor in varovanje stroja ter funkcijza samodejno zaustavljanje, razpoznavo in odpravonapak, pa je prepu�èena presoji in izku�njamprogramerja. Zaganjanje tak�nih strojev se ponavadi lahko priène �ele po konèanju vseh strojnihin elektromonta�nih del. Krmilna logika se v oblikiprograma nalo�i na PLK, nakar se priène s

Figure 6 shows the control results. Theoutput of the CNC position controller was the speed-command signal transmitted to the servomotors. Theposition-control algorithm was executed at 250µsintervals. The left diagram presents the test contour inthe XY plane, the right diagrams present the responseof the X and Y axes, respectively, showing the referencespeed signal, the following error and the control signal.The results show high-performance position tracking.

2.3.2 Programmable logic control design

The basic task of the PLC is to run event-handling logic functions, such as operation modeselection, machine start/stop/pause, manual operation,supervision of actuators, error detection, operatingcondition monitoring, etc. In practice, the programmingof logic control functions is based on a timed bar-chart oftechnological functions and on the control wiring diagram[9]. This specifies the technological functions of themachine and the control architecture. The implementationof the functions for the management, control andprotection of the machine and the functions for automatic-stop, diagnosis and error recovery are dependent on thelogic control designer�s experiences, and the dependencybetween the different control functions cannot be verifieduntil the target system is built and tested. The testing ofsuch a machine starts after the assembly is finished andis based on a try-and-fix approach. The control programis loaded into the controller and the start-up procedure

Sl. 6. Krmilni rezultatiFig. 6. Control results

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testiranjem osnovnih funkcij v roènem re�imuobratovanja, sledi testiranje avtomatskih funkcijin na koncu �e optimizacija delovanja stroja.

Za skraj�anje razvojnega cikla naèrtovanjakrmilnih funkcij je bil razvit nov naèin obravnavedogodkovnih sistemov ([11] do [13]), ki omogoèanaèrtovanje in analizo pravilnosti zasnovanihkrmilnih funkcij ter simulacijo zmogljivosti ciljnegasistema �e pred izvedbo, vkljuèujoè mehanske,elektronske in informacijske komponente. Na tanaèin je mogoèe preveriti konstrukcijske infunkcionalne re�itve ciljnega sistema �e v zgodnjifazi razvojnega cikla, kar bistveno skraj�a trajanjein zmanj�a stro�ke projekta v primerjavi zugotavljanjem funkcionalnih pomanjkljivosti �ezgrajenega ciljnega sistema. Metoda temelji napredpostavki, da logiène krmilne funkcijepredstavimo kot dogodkovne sisteme, za katere soznaèilna specifièna stanja. Sistem v vsakemtrenutku zavzame le eno diskretno stanje, prehodv novo stanje pa se zgodi ob pojavu dogodka priizpolnjenih pogojih. Stanja krmilnih funkcij sopogosto povezana s stanji aktuatorjev, ki jihfunkcija krmili, ali pa s stanji delovnega postopka.Prehod krmilne funkcije med stanji se zgodi obpojavu dogodka, npr. pritisk na gumb, aktiviranjezaznavala ali doseganje mejne vrednosti. Novostanje, ki ga bo funkcija zavzela po pojavudogodka, je odvisno od trenutnega stanja funkcijein dogodka ter od trenutnega stanja preostalihfunkcij na stroju in od vhodnih krmilnih signalov.

Petrijeve mre�e (PM) ([5] in [10]) so medpogosteje uporabljanimi orodji za obravnavodogodkovnih sistemov ([16] in [17]). Ena od njihovihprednosti je, da jih je mogoèe hitro spremeniti v enegaod standardiziranih naèinov za programiranje PLK-jev [3]. Petrijeve mre�e so v osnovi dvodelni graf, kipremore dve vrsti vozli�è, po navadi predstavljenimis krogi in pravokotniki. Stanja funkcij prikazujejo krogi,trenutno delujoèe stanje oznaèuje kro�ec. Pravokotnikisimbolizirajo dogodke, ki povzroèijo prehode medstanji. Dopustne prehode med stanji funkcije

begins by checking the manual control functions first,the automatic functions next, and then finally theperformance optimization.

To shorten the development cycle of the logiccontrol design, a new matrix-based approach for thehandling of the event-driven systems was introduced([11] to [13]). It enables the design and analysis of theproposed logic control functions and a performanceanalysis of the target system, even before it is actuallybuilt, including machine construction, electronics andinformation technology. This enables the verification ofthe construction and the functionality of the target systemin the early development phase. Possible modificationsof the solutions involve relatively small costs comparedto late-development-phase modifications on the actuallybuilt system, which is of great importance for the project�stiming and costs. The method is based on the assumptionthat the logic control functions are considered as discreteevent-driven systems that are characterized by specificdiscrete states. In every instance the system occupiesonly a single discrete state. The state transition is triggeredby a specific event and under predefined conditions.Each control function�s discrete state is related to thestate of the controlled actuators or with the state of thecontrolled process. The transition of the control functionbetween the states happens if an event such as a buttonbeing pressed, a sensor being activated, a threshold valuebeing reached, etc., occurs. The new state of the controlfunction depends on the current state of the controlfunction, the occurred event, the state of the other controlfunctions in the system and the control input signals.

Petri nets (PNs) ([5] and [10]) are a widelyused tool for the treatment of event-driven systems([16] and [17]). They can be easily converted intostandardized PLC programming languages [3]. A PNnet is a bipartite graph with two types of nodes,usually represented by circles and rectangles. Thecircles stand for function states; a currently activestate is indicated by a token. Rectangles symbolizeevents that cause state transitions. The allowedtransitions between function states are determinedby directed arcs. An additional arc, which is

Sl. 7. Petrijeve mre�e krmilnih funkcij postopka prenosa materialaFig. 7. Petri Nets of the control functions for the transport-of-material procedure

T1 Di screte-event sys tem

Ready to Cut

Korak1

Korak2

Korak3

T2 Dis crete-events ystem

T4


Podajanje materiala (1)

Pomik miz (2)

Stop

CW

T3

Di screte- eventsystem

T1

Di screte- eventsystem

T4

Discrete-event sys tem

T2 Dis crete-event sys tem

Pogon potiskalca (3)

CCW Stop

T2 Di screte-event system

T1 Di s crete-eventsystem

Start/Stop uporabnika (4)

OK

T2 Di screte-eventsystem

T1 Di screte-eventsystem

Start Detekcija napak (5)

Napaka

Nazaj

T3 Di s crete-eventsystem


u(1,1)

u(1,2)

u(1,3)

u(1,4)

u(3,1)

u(3,3)

u(3,2)

u(3,4) u(4,2)

u(4,1)

u(4,3)

u(4,4)

u(5,2)

u(5,1)

Stop

T2 Di screte-events ystem

T1 Di s crete-events ystem

Nazaj

T3 Di s crete- eventsystem

T4 Discrete-event sys tem

u(2,2) u(2,1)

u(2,3)

u(2,4)

Naprej

Pomik traka (2) Belt conveyer (2)

Korak1 Step1

Korak2 Step2

Korak3 Step3

Naprej Forward

Nazaj Backward Nazaj

Reverse

Napaka Error/Fault

Prenos materiala (1) Transport material (1)

Pripravljen za rezanje RdyToCut

Upravljanje (4) User start/stop (4)

Zaznavanje napak (5) Error-handling (5)

V redu OK

Pogon potiskalca (3) Pusher (3)

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ponazarjajo usmerjene èrte. Dodatna pu�èica,povezana v pravokotnik, pomeni zunanje pogoje, kivplivajo na prehod med stanji ob pojavu dogodka[9]. Nekaj primerov PM, ki pomenijo krmilne funkcijerezalnega stroja s slike 1, prikazuje slika 7.

Strukturo grafa PM lahko predstavimo zvpadnostno (incidenèno) matriko M [10]. Stolpcimatrike M pomenijo stanja krmilne funkcije, medtemko vrstice pomenijo dogodke. Komponente matrikeM(i,j) lahko zavzamejo vrednosti:

(1).

Vpadnostne matrike PM s slike 7 predstavlja (2):

Stanje sistema po k dogodkih predstavljavektor m(k). Njegove komponente so razpolo�ljivastanja funkcije, pri èemer velja:

(3).

Vektorje stanja PM s slike 7 predstavlja (4).Imena komponent ustrezajo imenom prostorom PM sslike 7.

(4).

Podobno kakor trenutno stanje krmilnefunkcije m(k) so z uporabo vektorjev zapisani tudidogodki in zunanji pogoji, ki vplivajo na sistem.Komponente vektorja x(k) predstavljajo dogodke zakrmilno funkcijo, komponente vektorja u(k) papredstavljajo zunanje pogoje za pojav dogodkov.

(5).

Vektorje dogodkov za PM s slike 7predstavlja (6), zunanje pogoje zanje pa opisuje (7).

connected to a rectangle, adds an external conditionthat has an affect on a state transition when an eventoccurs [9]. Some examples of PNs representing thelogic control functions of the cutting machine fromFigure 1 are presented in Figure 7.

A pure PN-graph structure can be presentedby the incidence matrix M [10]. The columns of thematrix M represent the states of the function, whereasthe rows represent the events of the function. Thecomponent M(i,j) can have the values:

(1).

Equation (2) represents the incidence matrices:

(2).

The state of the function after the k-thoccurrence of events is denoted by the vector m(k). Itscomponents represent the states of the function where:

(3).

The state vectors of the PN from Figure 7are represented by (4). The name of the componentcorresponds to the PN place.

(4).

Similar to the control function�s current statem(k), the control function�s events and externalconditions are described using vectors. Thecomponents of the vector x(k) represent the eventsfor the control function, while the components of thevector u(k) represent the external conditions for theoccurrence of the events.

(5).

The event vectors for the PN from Figure 7are described by (6). Equation (7) represents theexternal conditions for the appearance of these events.

(6).

delujoèe

delujoèe

1 2 3 4 5

1 , , , ,

2

3

Pripravljenna rezanje Stop Stop Stop

V reduKorakm m Naprej m CW m Start mNapakaKorak Nazaj CWW Nazaj

Korak

é ùê ú é ù é ù é ùê ú é ùê ú ê ú ê ú= = = = =ê ú ê úê ú ê ú ê ú ë ûê ú ê ú ê ú ê úë û ë û ë ûê úë û

04-10stran 482


(7).

Predstavljen naèin omogoèa formalen opisprehajanja stanj logiènih krmilnih funkcij. Formalizemje sestavljen iz dveh delov: najprej so glede natrenutno stanje krmilne funkcije m(k) doloèeni vsidogodki xe(k), ki jih trenutno stanje omogoèa [8],[16]. Iz nabora omogoèenih dogodkov je nato spomoèjo pogojev u(k) izbran en dogodek x(k), kakorka�e enaèba (8), ki bo spremenil stanje krmilne funkcije[12]:

Matrika F je del vpadnostne matrike M, kipredstavlja pogoje za prehajanje v novo stanje. Novostanje krmilne funkcije m(k+1) je nato izraèunano zenaèbo (9) glede na trenutno stanje m(k) in dogodek,doloèen z vektorjem x(k):

Znak Å pomeni Boole-ov skalarnizmno�ek. Raèuna se kot navadni skalarni zmno�ek,le da sta mno�enje in se�tevanje zamenjana zlogiènima ALI in IN. Shematièno je formalizemprikazan na sliki 8.

Modularni logièni krmilnik [12] omogoèaalgebrski naèin doloèanja prehajanja stanjdogodkovno vodenega sistema glede nastrukturo sistema M, trenutno stanje m(k) ,trenutne dogodke x(k) in trenutne zunanjepogoje u(k).

Rezultati

Zamisel matriènega modularnega logiènegakrmilnika je prikazana na primeru postopka prenosamateriala, ki obsega naslednje krmilne funkcije:

(7).

The presented approach enables a formaldescription of the logic control functions�s stateevaluation. The formalism consists of two parts:firstly, all the enabled events xe(k) according to thecurrent state m(k) of the control function aredetermined [8], [16]. From the set of enabled eventsxe(k), a single event is selected according to thecurrent conditions vector u(k) using (8) assuggested by [12]:

(8).

The matrix F is part of the incidence matrixM and represents the conditions for a transfer into anew state. The selected event x(k) occurs andchanges the current state of the control function m(k)into new state m(k+1) using (9):

(9).

The Å symbol denotes an inner productconjunction, which is calculated like an inner product,but logical OR and AND are used instead ofmultiplication and addition, respectively. Figure 8shows the formalism schematically.

The modular logic controller was introducedby [12]. It enables an algebraic description of thestate evaluation of the event-driven systemaccording to the structure of the system M, thecurrent state of the system m(k), the current eventsx(k), and the current external conditions u(k).

Results

To illustrate the idea of the matrix-basedmodular logical controller, the functions for thematerial transport procedure are presented:

Sl. 8. Modularni logièni krmilnikFig. 8. Modular logic controller

P1 Discrete-event system

Dogodkovno voden sistem Event-driven system

Discrete-event controller Omogoèeni dogodki Enabled events

( ) ( )e k k= Äx F m

m x

T1 Discrete-event system

T2 Di scr e te-e ve nt system


P2 P3

( 1) ( ) ( )

T

k k k

= -

+ T

M S F

m = m + M x


u

&

Dogodkovno voden sistem Event driven system

3,2 1,3 4,2 5,1

3,3 1,3 4,31 2 3 4 5

3,1 4,34,1 1,3 5,2

3,1

1 3 & & 10

3,8 5,53 & & 10 6 6,5, , , ,

5 & & 5

7 7 7

mèas m m pos m

m èasèas m m pos èasu u u u u

m mpos m m pos m

mèas èas èas

< < <é ùé ù é ù é ùê úê ú ê ú ê ú < <> > < < é ùê úê ú ê ú ê ú= = = = = êê úê ú ê ú ê ú> > ëê úê ú ê ú ê ú> > >ê úë û ë û ë ûë û

úû

04-10stran 483


RdyToCut

Step1

Step2

Step3

STOP

CW

CCW

Pos

HOLD

FWD

BWD

Pos

Stop

Start

Reverse

OK

Err

Prenos materiala Transport material

Potiskalo Pusher

Pomik traka Belt conveyer

Upravljanje User start/stop

Zaznavanje napak Error-handling

Èas (s) Time (s)

1

2

3

4

5

6

7

8

9

10

- The transport material represents the maintechnological function. It consists of the initial state�Ready to Cut� and three sequentially executedSteps 1 to 3.

- The pusher is used for moving the belt conveyer.It is implemented as an electrical motor with threestates: (i) rotating clockwise (belt forward), (ii)rotating counter clockwise (belt return) or (iii) itcan be stopped.

- The belt conveyer represents the function ofmoving the belt conveyer. Three states areavailable: moving forward, backward or it is stopped.

- User start/stop is a user-oriented function forprocess management.

- Error-handling is a supervision function for userand machine safety.

By using the incidence matrices M1 to M5from (2), the equation (8), and the PN next stateequation (9), the transport system of the machinefrom Figure 1 can be simulated with Matlab.

The aim of the simulation is an analysis ofthe designed logic control and its response to criticalevents. Figure 9 presents the states� evaluationdiagram of the control functions after a failure duringthe transport of material. The diagram involves thefollowing control functions: Transport material,Pusher, Belt conveyer, User Start/Stop, and ErrorHandling. The Pos variables from the Pusher andthe Belt conveyer control functions are continuousand denote the current position of the pusher andbelt conveyor, respectively. The allowed transitionsof the states can be interpreted from Figure 7.

- Prenos materiala predstavlja osnovno tehnolo�kofunkcijo. Sestoji se iz izhodi�ènega stanja in trehzaporedno izvr�enih korakov.

- Potiskalo je uporabljeno za pomikanje prenosnegatraka. Vpeljan je kot elektromotor s tremispecifiènimi stanji: (i) vrtenje v smeri urnega kazalca(pomik naprej), (ii) vrtenje v nasprotni smeri urnegakazalca (pomik nazaj) in (iii) mirovanje.

- Pomik traka predstavlja funkcijo pomikanjaprenosnega traka. Funkcija lahko zavzame tristanja: prenosni trak se pomika naprej, nazaj alipa miruje.

- Upravljanje je uporabni�ko usmerjena funkcija zaupravljanje postopka.

- Zaznavanje napak je nadzorna funkcija zazagotavljanje varnosti uporabnika in stroja.

Z uporabo vpadnostnih matrik M1 do M5 izenaèbe (2), enaèbe izbora dogodkov (8) in enaèbeprehajanja stanj (9), je obravnavan sistem mogoèesimulirati s programskim paketom Matlab.

Namen simulacije je analiza delovanjazasnovanega logiènega krmilja in odziva logiènegakrmilja na kritiène dogodke. Slika 9 prikazuje diagramprehajanja stanj posameznih krmilnih funkcij medpostopkom prenosa materiala v stroj. Diagramopisuje potek naslednjih krmilnih funkcij: prenosmateriala, potiskalo, pomik traka, upravljanje inzaznavanje napak. Spremenljivki pos iz krmilnihfunkcij potiskalo in pomik traka sta zvezni inoznaèujeta trenutni polo�aj potiskala in prenosnegatraka. Dovoljeni prehodi med posameznimi stanji sorazvidni s slike 7.

Sl. 9. Èasovni diagram stanj krmilnih funkcijFig. 9. States� evaluation diagram

Korak1

Pripravljenna rezanje

Korak2

Korak3

V redu

Napaka

Nazaj

04-10stran 484


Nazaj Backward

Stop Stop

Naprej Forward

Petrijeva mre�a Petri net

Sekvenèni funkcijski diagram (IEC 1131) Sequential function chart (IEC 1131)

Naprej Forward

Nazaj Backward

Stop Stop

T1

T2

T3

T4 u(2,4)

u(2,1)

u(2,3)

u(2,2)

The procedure in Figure 9 is as follows:After Step2 is started (1), the pusher starts rotatingclockwise (2) and the belt conveyer starts movingforward (3). When a failure is detected (4), the pusheris immediately stopped (5) to prevent further damage.The belt conveyer is stopped as a result (6). Torecover from the failure, the operator chooses thereverse command (7) and the pusher is returned (8)until the initial position is reached (9). The process iscontinued when the operator executes the startcommand (10).

For the programming of logical controllers,standardized programming languages conforming toIEC 1131 can be used, especially the ladder diagramand the sequential function chart (SFC). The logiccontrol functions presented in Figure 9 can be simplyconverted to the SFC ([3] and [9]). The PN placescorrespond to the SFC steps and the PN transitionscorrespond to the SFC transitions. The PN-to-SFCconversion is illustrated in Figure 10. The SFC stepsare represented by the rectangles, the doublerectangle denotes the initial step.

3 CONCLUSIONS

This paper presents a mechatronic-orientedapproach to open machine-control design that coversmechanic, electronic and informatic aspects of aproduction system. Firstly, the machine technologyand operation concept was determined. Then a proper,user-friendly HMI design was described, whichenables efficient machine technology handling anduser-friendly machine control. The control hardwareis based on consumer-grade PC technology,supplemented with an efficient real-time operatingsystem and Ethernet network technology. Thesuggested concept allows the implementation ofdiverse control, a user interface, and networkingtasks on a single processor platform. Value-handlingalgorithms for servo tasks are implemented using aclassic approach from program interpreting,interpolating that generates motion trajectories andfinally position control. For event-handlingalgorithms, a new matrix-based approach was

Potek, prikazan na sliki 9 je naslednji: v koraku2 (1) se priène potiskalo vrteti v smeri urnega kazalca(2), kar pomakne prenosni trak naprej (3). Ob pojavunapake (4) se mora potiskalo takoj ustaviti (5), s èimerse zmanj�a mo�nost po�kodbe stroja. Zaradi tega seustavi tudi prenosni trak (6). Napako odpravi operaters sprostitvijo potiskanja (7). Pri tem se potiskalo (8) inprenosni trak pomakneta nazaj v izhodi�èe (9). Ko jenapaka odpravljena, lahko operater ponovno po�eneavtomatsko izvajanje prenosa materiala (10).

Za programiranje logiènih krmilnikov souporabljeni jeziki v skladu s standardom IEC 1131,predvsem stikalni naèrt in sekvenèni funkcijskidiagram (SFD). Predstavljena metoda je skladna zuporabo standardiziranih programskih jezikov. PM sslike 7 je mogoèe preprosto spremeniti v SFD ([3] in[9]). Prostori Petrijeve mre�e v tem primeru kar ustrezajokorakom SFD-ja, prehodi Petrijeve mre�e pa ustrezajoprehodom SFD-ja. Primer spremembe Petrijeve mre�ev sekvenèni funkcijski diagram prikazuje slika 10.Koraki v SFD-ju so prikazani z okvirèki, izhodi�ènikorak pa je oznaèen z dvojnim okvirèkom.

3 SKLEP

V tem èlanku je predstavljen mehatronskousmerjen naèin naèrtovanja odprtega krmilja stroja, kisinergijsko obravnava mehanske, elektronske ininformacijske vidike proizvodnega sistema. Na zaèetkusta doloèena tehnologija stroja in naèelo delovanja.Nadalje je predstavljen primerni uporabni�ki vmesnik,ki omogoèa uèinkovito obvladovanje tehnologije strojain uporabniku prijazno upravljanje stroja. Strojna opremakrmilja temelji na standardni tehnologiji OR, dopolnjeniz uèinkovitim operacijskim sistemom za delo v realnemèasu in Ethernetni komunikacijski tehnologiji. Tak�nazasnova omogoèa izvedbo razliènih krmilnih algoritmov,uporabni�kega vmesnika in mre�nih opravil na enemsamem procesorju. Vrednostno naravnani algoritmi zapozicioniranje so vpeljani na klasièni naèin:interpretiranje delovnega programa, interpolacija, kigenerira trajektorije gibanja, in konèno polo�ajnokrmiljenje. Za dogodkovno naravnane algoritme jeuveden nov matrièni naèin. Modularni logièni krmilnik

Sl. 10. Pretvorba Petrijeve mre�e v SFDFig. 10. PN-to-SFC conversion

04-10stran 485


omogoèa loèeno naèrtovanje in analizo logiènih krmilnihfunkcij, njihovo modularno povezljivost in ponovnouporabnost v drugih sistemih. Tak naèin omogoèaanalizo vrednostno in dogodkovno naravnanihalgoritmov �e preden je ciljni sistem dejansko zgrajen.To je �e posebej pomembno pri naèrtovanju dragih innamenskih sistemov ter strojev, pri katerih podrobnihtestiranj ni mogoèe izvesti na ciljnem sistemu. Napodroèju obièajne gradnje strojev prina�a predlaganinaèin koristi za naèrtovalca stroja in za konènegauporabnika: omogoèa skraj�anje razvojnega cikla terintegrirano naèrtovanje tehnologije stroja in njegovegakrmilja, ki pa je bolj zanesljivo, uèinkovito in prijazno douporabnika.

examined. The modular logic controller enables thedesign of separated control functions, their separatedanalysis, modularly linkage and the reusability inother systems. Such an approach allows for systemanalysis, including both value- and event-handlingalgorithms, even before a target system is actuallybuilt. This is of great value in designing expensivededicated systems and machines, where the targetsystem is not available for the performance of detailedtests. In the field of regular machinery building, aproposed approach enables shortened developmentcycles, the integrated design of machine technologyand machine control, which is more reliable, efficientand user-friendly.

4 LITERATURA4 REFERENCES

[1] Arutunian, E.B., D.R. Meldrun, N.A. Friedman, & S.E. Moody (1998) Flexible software architecture foruser-interface and machine control in laboratory automation. BioTechniques 25-4, 698-705.

[2] Bezi, I., & G. Tevesz, (1994) PC based robot controller for advanced control algorithms. Proc. of the JointHungarian - British International Mechatronics Conference, Budapest, Hungary, 1994.

[3] Frey G., M. Minas, K.H. John, (2001). Integration von Petrinetzen in den Steuerungsentwurf nach IEC61131,Proc. of the SPS/IPC/Drives, Nürnberg, Germany, 197-205

[4] GM Powertrain Group, Manufacturing Engineering Controls Council (1996). Open, modular architecturecontrols at GM Powertrain. Whitepaper available at http://www.arcweb.com/omac/Techdocs/Open_at_GMPTG.pdf

[5] Hace, A., K. Jezernik (2003) The open CNC controller for a cutting machine. Proc. of IEEE ICIT 2003,Maribor, Slovenia, 1231-1236

[6] Jensen, K. (1997) Coloured Petri nets. Basic concepts, analysis methods and practical use. Volume 1. Basicconcepts. Monographs in theoretical computer science, 2nd corrected printing. Springer-Verlag.

[7] Loffler, M.S., V.K. Chitrakaran, & D.M. Dawson (2002). QMotor 3.0 and the QMotor robotic toolkit: A PC-based control platform. IEEE Control Systems Magazine 22-3, 12-26.

[8] Mireless J. Jr. & F.L. Lewis (2001) Intelligent material handling: Development and implementation of amatrix-based discrete-event controller. IEEE Trans. on Industrial Electronics. 48-6, 1087-1097.

[9] Park, E., D.M. Tilbury, & P.P. Khargonekar (1998) A formal implementation of logic controllers for machiningsystems using Petri nets and sequental function chart. Proc. of the 1998 Japan-USA Symposium onFlexible Automation, Otsu, Japan.

[10] Peterson J.L. (1981) Petri net theory and the modeling of systems, Prentice-Hall, New Jersey.[11] Poliè, A (2003). Matrièni opis diskretnega dogodkovnega sistema. Zbornik tretje konference AIG�03,

Maribor, Slovenija, 179-184[12] Poliè, A., A. Hace, K. Jezernik (2003) Matrix based logic controller. Proc. of IEEE ICIT 2003, Maribor,

Slovenia, 370-374[13] Poliè, A., A. Hace, K. Jezernik (2003) System specification, performance analysis and control implementation

using matrix-based approach. Proc. of 12th International Workshop on Robotics in Alpe-Adria-DanubeRegion, Cassino, Italy.

[14] QSSL, Kanata, Ontario K2M 1W8 Canada [On-line]. Available at: http://www.qnx.com[15] Sukhatme, G.S., J.E. Montgomery, & M.J. Matariæ (1999) Design and implementation of a mechanically

heterogeneous robot group. Proc. of the SPIE conference, Boston, Massachusetts.[16] Tacconi D.A. & F.L. Lewis (1997) A new matrix model for discrete event systems: Application to simulation,

IEEE Trans. on Control Systems, 17-Oct., 6271.[17] Zhou, M., F. DiCesare & A. A. Desroches (1992) A hybrid methodology for synthesis of Petri net models

for manufacturing systems. IEEE Trans. on Robotics and Automation, 8-3, 350-361.

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Naslov avtorjev: Ale� HaceAle� Polièprof.dr. Karel JezernikFakulteta za elektrotehniko,raèunalni�tvo in informatikoUniverza v MariboruSmetanova ulica 172000 [email protected]

Athors� Address: Ale� HaceAle� PolièKarel JezernikFaculty of Electrical Engineeringand Computer ScienceUniversity of MariborSmetanova ulica 17SI-2000 Maribor, [email protected]

Prejeto: 22.7.2003

Sprejeto: 30.9.2004

Odprto za diskusijo: 1 letoReceived: Accepted: Open for discussion: 1 year

napredni mehatronski postopek na~rtovanja odprtega krmilja

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