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.

This paper discusses an object-oriented simulation project conducted for the United States Postal System (USPS) to test the reliability of an Ethernet LAN to support communication among various equipment contained at a General Mail Facility. The study was authorized by the National Institute of Standards and Technology to verify that the communication requirements derived from the implementation of their developed Postal Equipment Management System would not saturate the communication network. The simulated network handles over 400 transactions per second, and the USPS specified that eight hours of operation (one shift) must be simulated. The simulation was programmed in C++, and the completed study demonstrated that an Ethernet LAN can reliably support the communication requirements.