Agent-based control of a lithoshop : a simulation study

Most control systems used in manufacturing have a hierarchical structure. Hierarchical control systems become very complicated and dificult to maintain and modify when the underlying production systems grow in size and complexity. Moreover, they are characterized by a relatively high sensitivity to failures. As opposed to hierarchical systems, heterarchical control systems are exible, modular, easy to modify, and to some extent fault-tolerant. In this paper, a simulation study is presented of the application of heterarchical control concepts in the production of integrated circuits. For specification, the CSP-based language x is used which is well suited for the description of autonomous components cooperating with each other by exchanging information. Simulation experiments show that the heterarchical control system described enables the lithoshop to perform equally well as the hierarchical control system does. The heterarchical control system can be modified or extended very easily, offers transparency and is very well capable of handling machine and even control component failures.