Deadlock detection, prevention, and avoidance for automated tool sharing systems

Automated tool sharing systems provide a technological response to the high cost of tools in flexible manufacturing systems. These systems allow different machines to use the same tools by automatically transferring them from machine to machine as tooling needs evolve. With these systems, tool allocation is a real-time issue that requires sophisticated control techniques to make the right allocation decisions. An essential property that tool sharing policies must guarantee is deadlock-free operation. Although manufacturing researchers have investigated the performance aspects of tool sharing through simulation, no work has yet addressed deadlock handling strategies for these real-time systems. In this paper, we characterize the structural and computational properties of the tooling deadlock problem. We develop polynomial algorithms that detect and avoid deadlock, and we investigate the safety implications of special structures appearing in tool sequences.