Requirements Analysis of Using Object-Orientation in Filling Machine Systems
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Requirements Analysis of Using Object-Orientation in Filling Machine Systems Peter Wodzynski MASTER THESIS in Automatic Control 2013 Supervisor: Peter Lindberg, Tetra Pak Department of Automatic Control Lund University Box 118 SE-221 00 LUND Sweden ISSN 0280-5316 ISRN LUTFD2/TFRT--5924--SE © 2013 by Peter Wodzynski. All rights reserved. Printed in Sweden by Media-Tryck. Lund 2013 Acknowledgements Firstly I would like to thank Anders Olsson, for introducing me to Niklas Svanberg, the core automation manager of Tetra Pak Carton Bottle. Niklas gave me the opportunity to write my master thesis at Tetra Pak and for this I am a very grateful. I would also like to thank all the people I was able to interview at Tetra Pak, for they were all very friendly and supportive. Last but not least I would like to thank my supervisor Peter Lindberg, who has been an inspiration and an excellent mentor to me. Thank you so much for the countless hours of help and all the laughter. Abstract The use of an object-oriented approach in software engineering has proven to be successful for many years, but in the fields of mechanics and automation it has been ignored for long. The Tetra Pak Carton Bottle automation team believes that a switch from a function- oriented architecture to an object-oriented one would be of benefit not only to them but also any department which is involved with development, production, and maintenance of filling machines. Many product projects of today make the mistake of having its participants jumping straight into the implementation part of the project while skipping the work of first defining requirements of what the product shall accomplish. People in general like to start by doing the how of the project without first focusing on the what. But if the needs of other product concerned are overlooked then there is a risk of an important part being left out, perhaps leading to a weaker product. This master thesis focuses on the what part of a development project where an object-oriented architecture shall be deployed for Tetra Pak’s development, production, and maintenance of machine systems. During the master thesis requirements from various stakeholders were defined based on interviews and discussions held with various Tetra Pak departments. The result, the requirements, show that Tetra Pak has several areas which would be benefited by an object-oriented architecture by making Tetra Pak’s machines more modular and the maintenance of them simpler. Contents 1. Intro ............................................................................................................................................ 1 1.1. Aim .......................................................................................................................................... 1 1.2. Methods .................................................................................................................................. 1 1.3. Report Structure ...................................................................................................................... 1 2. Tetra Pak’s Automation History ................................................................................................... 2 2.1. Machines before the PLC .......................................................................................................... 2 2.2. The PLC .................................................................................................................................... 2 2.3. Tetra Top - Moulding a top ....................................................................................................... 3 2.4. A unique product ..................................................................................................................... 3 2.5. Cost focus ................................................................................................................................ 4 2.6. The new servo technology ........................................................................................................ 4 2.7. Importance of the automation system ..................................................................................... 4 3. Filling machines........................................................................................................................... 5 3.1. Selling package material ........................................................................................................... 5 3.2. Aseptic package ....................................................................................................................... 5 3.3. A6 ............................................................................................................................................ 6 Carton bottle............................................................................................................................... 6 The machine ............................................................................................................................... 6 Machine flow .............................................................................................................................. 7 4. Tetra Pak Development Plan and Stakeholders............................................................................ 8 4.1. V-model ................................................................................................................................... 8 5. Object-oriented Principles ......................................................................................................... 10 5.1. Classes ................................................................................................................................... 10 5.2. Object .................................................................................................................................... 10 5.3. Encapsulation ......................................................................................................................... 11 5.4. Inheritance ............................................................................................................................. 11 5.5. Polymorphism ........................................................................................................................ 12 6. Requirement elicitation process ................................................................................................ 12 7. Automation ............................................................................................................................... 13 7.1. Conclusions and requirements ............................................................................................... 13 7.2. Stakeholder input ................................................................................................................... 14 7.2.1. PLC Programming ............................................................................................................ 14 7.2.2. System Manufacturer Rockwell ....................................................................................... 15 7.2.3. Program Structure ........................................................................................................... 15 7.2.4. Variables ......................................................................................................................... 16 7.2.5. Add-on Instruction blocks ................................................................................................ 16 7.2.6. Similar Add-on Instructions .............................................................................................. 17 7.2.7. Manual intervention in programs .................................................................................... 17 7.2.8. HMI ................................................................................................................................. 18 7.3. Object-oriented architecture analysis ..................................................................................... 18 7.3.1. Class Library .................................................................................................................... 18 7.3.2. Programming guidelines and encapsulations ................................................................... 18 7.3.3. Hierarchy ......................................................................................................................... 18 7.3.4. Reusability ....................................................................................................................... 19 7.3.5. Reusability, inheritance and local adaptions .................................................................... 19 7.3.6. HMI ................................................................................................................................. 20 8. Automation Machine Variants ................................................................................................... 21 8.1. Conclusions and requirements ............................................................................................... 21 8.2. Stakeholder input ................................................................................................................... 22 8.2.1. Machine Variants............................................................................................................. 22 8.2.2. Testing functions ............................................................................................................