Recent Advances in the Modeling, Scheduling and Control of Flexible Automation

Abstract

This paper initially discusses the state-of-the-art and the current limitations in the modeling, scheduling and control of flexible automation. To model flexible automation, it is argued that the simulation tools must provide enhanced capabilities to consider both controller interactions and the flow of resources that support production. It is also demonstrated that scheduling and control must be considered concurrently in real-time to effectively manage flexible manufacturing systems (FMSs). The complexity of the modem FMS further requires that the integrated scheduling and control function must be distributed among several coordinators with the system. The second part of the paper presents several research developments pertaining to the modeling, scheduling and control of flexible automation including: a Recursive, Object-Oriented Control Hierarchy for the integrated distribution of scheduling and control; a Hierarchical Object-Oriented Programmable Logic Simulator €or the detailed modeling of FMSs; and a Hierarchical System Coordinator for implementing real-time scheduling and control. A physical emulator for an FMS which is being constructed is discussed as the example application in this presentation. Finally, the futureresearch plan and theeducational program based upon the developments is outlined.

Simulation-based real-time decision making for manufacturing automation systems: a review

“…In a typical hierarchical architecture, decision control commands are transferred in a top-down manner, and monitoring information is transferred in a bottom-up manner. For instance, Davis et al (1992Davis et al ( , 1993 applied the object-oriented concept to the hierarchical architecture for the control of FMS. However, the hierarchical architecture has some drawbacks such as fixed structure and communication bottleneck problems.…”

“…Implementation of optimisation function module can be found in Jones et al (1995), where artificial neural networks, real-time simulation, genetic algorithms and a trace-driven knowledge acquisition technique are integrated. Davis (1992) and Davis et al (1993) presented three fundamental concepts for modelling, scheduling and control of FMS. Firstly, they proposed a new control architecture, a Recursive Object-Oriented Control Hierarchy (ROOCH), for integrated distribution of scheduling and control.…”

A New Simulation Tool for the Modeling and Control of Distributed Systems

“…The simulation of distributed systems discussed here is based on the distributed modeling methodology-referred to as the Hierarchical Object-Oriented Programmable Logic Simulator (HOOPLS)-in Davis, Macro, and Setterdahl [26]; Davis et al [2]; and Davis [3]. This methodology is based on the belief that the interactions among the controllers must be considered by the simulation model to accurately model a system with a distributed control architecture.…”

“…In fact, the adopted modeling paradigm employed by most commercial simulation tools (i.e., entity flow through a stochastic queuing network) is totally inappropriate for modeling such systems. Davis et al [2] and Davis [3] discuss, in detail, the numerous restrictions that entity flow-based simulation languages impose on the modeling of an FMS. Mize et al [4] further discuss the inaccuracies that ensue from the use of current simulation languages to model an FMS.…”

Model Sharing in the Simulation and Control of Distributed Discrete-Event Systems

“…Over the past decade, the Manufacturing Systems Laboratory (MSL) at the University of Illinois has developed a new conceptual framework for the integrated modeling, scheduling and control of FMSs and other DESs, (see Davis et al [1993] and Davis et al [1997]). These developments can now be summarized into three fundamental concepts:…”