A methodology for analysis and control of discrete event dynamic systems

The rapid developments in computer technology have resulted in a widespread use of discrete event dynamic systems (DEDSs). This type of system is complex because it exhibits properties such as concurrency, conflict and non-determinism. It is therefore important to model and analyse such systems before implementation to ensure safe, deadlock free and optimal operation. This thesis investigates current modelling techniques and describes Petri net theory in more detail. It reviews top down, bottom up and hybrid Petri net synthesis techniques that are used to model large systems and introduces on object oriented methodology to enable modelling of larger and more complex systems. Designs obtained by this methodology are modular, easy to understand and allow re-use of designs. Control is the next logical step in the design process. This thesis reviews recent developments in control DEDSs and investigates the use of Petri nets in the design of supervisory controllers. The scheduling of exclusive use of resources is investigated and an efficient Petri net based scheduling algorithm is designed and a re-configurable controller is proposed. To enable the analysis and control of large and complex DEDSs, an object oriented C++ software tool kit was developed and used to implement a Petri net analysis tool, Petri net scheduling and control algorithms. Finally, the methodology was applied to two industrial DEDSs: a prototype can sorting machine developed by Eurotherm Controls Ltd., and a semiconductor testing plant belonging to SGS Thomson Microelectronics Ltd.

Technical change and work organisation

This thesis is an exploration of the social and political processes involved in the introduction of new technology to the shopfloor. Through a series of case studies of applications of microelectronics to batch manufacture, it attempts to uncover the ways in which the values and interests of managers, engineers, workers and others profoundly influence the choice and use of technology, and thus the work organisation which emerges. Previous analyses have tended to treat new technology as if it had "impacts" on work organisation - especially skills - which are inevitable in particular technical and economic circumstances. It is in opposition to this view that technical change is here treated as a matter for social choice and political negotiation, the various interested parties to the change being shown to attempt to incorporate their own interests into the technical and social organisation of work. Section one provides the relevant background to the case studies by summarising and criticising previous theoretical and empirical work in the area. The inadequacies of this work for our concerns are drawn out, and the need for detailed studies of the political aspects of technical change is justified. The case studies are presented in section two as a set of "episodes" of innovation, and section three analyses the empirical findings. The innovations are compared and contrasted in order to illustrate the social and political dynamics involved in the various stages of the innovation process. Finally some comments are made on policy issues for which the research has important implications.

Attitudes towards advanced manufacturing technology (AMT):the role of AMT experience, skill level and job involvement

Studied the attitudes of shopfloor employees toward AMT as a function of experience with working with AMT, skill level, and job involvement. Survey data were collected from 115 employees of a large microelectronics company in England. Four job types were identified, which differed in terms of mode of work (manual/AMT) and skill level (low/high). Results show that those who worked with computers had more favorable attitudes toward AMT than those who did not. Results support A. Rafaeli's (see record 1986-20891-001) finding that the most favorable attitudes toward AMT were held by those who worked with computers and had high job involvement. Skill level had no significant effects on Ss' attitudes.