Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and

Transcription

1 Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author.

2 Design and Development of a Hybrid Control System for Flexible Manufacturing A Thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Manufacturing and Industrial Technology at Massey University Michael David Butler 1994

3 ABSTRACT Flexible Manufacturing Systems (FMS) appeared upon the manufacturing scene in the early 1970s, installations presently number in the thousands. However, many current installations in fact lack flexibility, do not operate in real-time and are prohibitively expensive. Therefore there are obvious benefits to be gained from making improvements to existing flexible manufacturing systems. Research conducted for this thesis focused on two major areas. The implementation of the FMS control system on a SCADA package and the development of an auction based scheduling system. This entailed the development of a hybrid control model composed of three distinct layers; factory, cell and intelligent entity. Key portions of both the factory and cell controllers were then implemented so as to create a minimal system. This has been completed to the point where the auction algorithm has been implemented and tested in an appropriate framework. In achieving the goals mentioned above a number of novel design concepts have been utilised. There are two which are most important, these are the use of low cost modules for the construction of a flexible co-operative manufacturing system, and the ability of this system to operate in a physically distributed area via a Local Area Network. Meaning it is inherently adaptable and resistant to failure. These novel design concepts were ingrained throughout the entire three layered control model. It is felt that this research has succeeded in demonstrating the possibility of implementing a FMS control system on a low cost SCADA package using low cost software and computing elements. The ability of the distributed, auction-based approach to operate successfully within this system, has also been demonstrated through simulation. I

4 ACKNOWLEDGMENTS I would like to acknowledge a number of members of the staff within the Production Technology Department whose assistance has proved invaluable; Prof Don Barnes, Len Chisholm, Dr Simon Hurley and Nola Babbage. I would also like to thank my fellow postgraduate students, especially Heather, Ian, Nigel, Mike and Kev all who have given me friendship and encouragement My supervisor Dr Saeid Nahavandi has over the last two years provided me with help and direction. Without his drive and dedication this research would never have been possible. I would finally like to thank my friends and family both past and present who have supported, encouraged and provided me the wisdom to continue. III

5 TABLE OF CONTENTS Chapter Topic of Research Scope of Research The Importance of Flexible Manufacturing Chapter Introduction Review of Current Control Models for Flexible Manufacturing Systems Cellular Technology Hierarchical Control Structures Heterarchical Control Structures Comparisons between Heterarchical and Hierarchical Control Structures The Hybrid Control System and Real Time Scheduling Virtual Manufacturing Devices Chapter Introduction Development of the Hybrid Control Model Scope of Proposed Hybrid Control of a flexible Manufacturing System The Hybrid Control Methodology Proposed Physical Model of a Hybrid FMS Controller Basic Definitions and Assumptions for Formulation of the Model Factory Controller Factory Control Entities Factory Controller as an Integration Tool V

6 3.4. Cell Controller Cell Controller Entities Intelligent Entity Intelligent Entity Control Model Virtual Manufacturing Device Auctioning Defmitions of Terms The Principal Behind the Auction System The Multi/ Single Agent Approach The Proposed Auction System Auction Co-ordination Bid Formulation Conclusion Chapter Introduction Implementation Requirements of the FMS Control Model FIX DMACS Introduction to the FIX DMACS Software Evaluation of FIX DMACS Conclusion of FIX DMACS Evaluation Programming Language Implementation Requirements of the Programming Language Introduction to Visual Basic Evaluation of Visual Basic Conclusion of Evaluation of Visual Basic Low Level Device Controller Implementation Requirements for the Low Level Device Controller Introduction to Fisher & Pyke! PSC Evaluation of Fisher & Pykel PSC Conclusion of PS C Evaluation Conclusion VI

7 Chapter Introduction The Implementation of the Three Layered Flexible Manufacturing Systems Model Flexible Manufacturing System Control Model Assumptions Implementation of the Cell Control Layer Implementation of Low Level control, Intelligent Entity Layer Implementation of Factory Control Layer Communications FMS Communication The Flexible Manufacturing Systems Control Data Model Scope of the Flexible Manufacturing Systems Control Data Model The Data Model Limitations to Implementation Conclusion Chapter Introduction The Implementation of the Flexible Manufacturing System Control using SCAD A Software Experimental Method Distributed Database Cost of Implementing the FMS Control System FIX DMACS as a Framework for the Implementation of the Control Aspects of the FMS FIX DMACS as a Tool for the Integration of Humans into a Manufacturing EnvironmenL Flexibility of the Distributed Architecture Implemented within FIX DMACS Design and Implementation Problems Discussion of the Auction Based Scheduling Method Conclusions VII

8 Chapter Introduction Completion of Current lmplementation Improvements in the Hybrid FMS Model and Implementation Improvements in the Bidding Algorithm References Dedication Appendix VIII

9 LIST OF FIGURES AND TABLES List of Figures 2.1 Typical factory hierarchy Factory operational model in a hybrid methodology Three layer functional control model Factory controller functional model Layout of factory controller application software Cell controller functional model Device/machine control algorithm Model of IE structure Decomposition of cell directions Communications VMD or data objects Bid messaging process Bid token passing around factory Bid calculation model Diagram of FIX DMACS applications Example of a FIX DMACS database block Distributed layout of FIX DMACS system Screen dump of VB with a test application Example of state logic program flow Flow of jobs in a cell controller Virtual and physical models of VMD operations Four steps of device control algorithm IX

10 5.4 Master control algorithm Device set up process Bid formulation algorithm Auction message passing bree initial phases of communication in the auction process Specification of a FIX DMACS analog output database block Tirree levels of information representation A typical FIX DMACS view screen of a cell controller Interaction between generic decision rules and the VMD Structure of applications within the factory controller Factory configuration main menu window Factory definition menu window Machine list definition window Job batch size window Model of IE communications FMS Data Model Queue loading over five devices Job flow diagram of experiment 2, simulation Job flow diagram of experiment 2, simulation Legend of jobs for figure Definition of jobs used in experiment 2, simulation 1 & Layout of computer hardware for simulation of the EFf auction algorithm Job flow diagram from experiment 4, simulation 2 showing effect of machine failure X

11 6.8 Scan Rate vs Database Size Graph showing database scan time vs bid calculation rime for the auction algorithm Job flow diagram from experimental factory Job flow diagram from experiment 4, simulation 3 of experimental factory XI

12 List of Tables 2.1 Comparison of heterarchical and hieratical control structures Controller cost and performance comparison Example of database blocks which make up the VMD Evaluation of scheduling methods XII

13 XIII