CONTROL OF FLEXIBLE MANUFACTURING SYSTEMS
L. Mic, Raluca Fat, Tiberiu Stefan Letia · ACTA TECHNICA NAPOCENSIS - Series: APPLIED MATHEMATICS, MECHANICS, and ENGINEERING · 2015
Many applications are of hybrid type, which means that they consist of two parts: a discrete events and a discrete time (continuous) part. The control synthesis for these kinds of systems is difficult because they involve interactions of different types of models belonging to different approaches. The control components have to react to internal or external asynchronous discrete events as consequences of the changes of the environment. The control of these systems must be constructed such that the system fulfills its specifications: reach or avoid some stated, avoid the deadlocks execute cyclically or parallel sequences of events with the shortest periods of time. The discrete events part is modeled using Timed Petri Nets (TPN) and the continuous part using Discrete Time Systems (DTS) and Fuzzy Logic Control (FLC). New methods are presented that are able to link the TPN and FLC models in order to describe the hybrid control system, resulting Enhanced TPN (ETPN) models of systems. The search means to automatically find a controller modeled by ETPN that fulfills some specified requirements. The control synthesis is made employing the techniques of Genetic Programming (GP) which uses the tree representations (LISP expressions) of the ETPNL descriptions of the hybrid system. The parameters of the controller are synthesized using the techniques of Genetic Algorithms (GA). The individuals of the populations taking part to the evolutionary process of GP are organized into species based on some parameters like the isomorphic distance between them.