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Unreliable workstations or resources pose challenges in deadlock control for automated manufacturing system (AMS) since resources failures have negative impacts on system activities and make the situation more complex. There are two types of robust deadlock-free control policies, absorbing type and distributing type. Each of them has its advantage as well as its drawback. Based on two modified Banker's...
Deadlock avoidance policies (DAPs) are of vitally importance for system control in order that correct deadlock-free resource allocation decisions can be made and continuing system operations can be guaranteed. This paper aims to present a DAP for FASs with assembly processes as their most important operations. The DAP, which is based on a variant of the well-known Banker's approach in computer science...
Synthesizing maximally permissive controllers with fewest monitors has been a popular research topic. Current optimal controllers for large flexible manufacturing systems (FMS) require costly time consuming reachability analysis. Our previous work shows that among all n-dependent siphons, only one siphon (whose unmarked state follows specific token distribution) needs to be controlled. This greatly...
Ensuring nonblockingness remains challenging for automated manufacturing systems (AMS) owing to their discrete event dynamics. Both scalability and maximal permissiveness are essential for the synthesis and implementation of their centralized supervisors. Inspired by the divide and conquer philosophy, this work proposes a partition methodology and distributed control technique for large scale AMS...
Energy-efficient dispatching of rail-guided vehicles (RGVs) is demanded in an automated air cargo terminal. The problem aims to minimize total energy cost of operating RGVs for transporting the cargos subject to real time constraints. This work focuses on solving an optimal dispatching problem with a single RGV having multiple capacity. A mixed-integer linear programming (MILP) model is developed...
Petri nets have been recognized as one of the most powerful tools for modeling flexible manufacturing systems (FMSs). Deadlock prevention policies are used to solve the deadlock problems of FMSs. It is well known that theory of regions is the efficient method for obtaining maximally permissive controllers. All legal and live maximal behavior of Petri net models can be preserved by using marking/transition-separation...
Cluster tools, widely used for wafer fabrication processes, have complex scheduling problems because a tool consists of several single-wafer processing chambers and a robot, and has a number of scheduling constraints. Most scheduling studies on cluster tools have focused on steady cyclic cycles where identical work cycles are repeated. However, as the lot size tends to be smaller, a tool has longer...
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