Reconfiguration and verification of modular discrete event control systems

The economy of today is being shaped by globalization. To cope with fierce market conditions Reconfigurable Manufacturing Systems (RMS) are being developed with a production capacity and functionality that can accommodate market fluctuations.;A central component of a manufacturing system is the logic control. One fundamental problem that arises in RMS is that because the system must frequently change, the logic control must be itself reconfigurable. A second problem is that in order for the reconfiguration time to be short, the logic must be verifiable. Errors must be detected before the logic is implemented in order to avoid costly downtime. This dissertation describes methods to design logic control for RMS together with logic verification procedures. There are three main contributions.;The first contribution is a method to automatically generate the control logic for a manufacturing cell of RMS. By using formal methods, the approach allows for very large, verifiably correct controllers to be automatically created. The method was applied to a RMS cell of the Reconfigurable Factory Testbed (RFT) at the Engineering Research Center for RMS.;The second contribution is an architecture for logic control that uses Event-Condition-Action (ECA) rules, which have evolved from the Artificial Intelligence field where they are recognized as a highly reconfigurable tool to design reactive behavior. The resulting logic control designs have been evaluated by measures of reconfigurability and modularity from the manufacturing and computer science literature respectively. The approach was used to design cell and system level controllers for the RFT.;The third contribution is a pair of logic verification methods. The first method introduces condition sets for deadlock detection, and the second includes modular verification techniques using event languages. The methods allow logic control to be verified as correct in a modular fashion, that is, without exhaustively enumerating and checking all possible states.;All contributions aim at improving system reconfigurability. The effectiveness of the methods has been demonstrated by their application to the RFT. The importance of these improvements are the economical benefits taken from saving system design time and effort, which assume even greater proportions for larger scale manufacturing systems.