Christoph Thomas

Defuzzification in Fuzzy Controllers

An important subject in fuzzy control theory is tuning of a fuzzy controller. If one wants to tune a fuzzy controller, one can focus on the choice of rules, membership functions, number of input and output fuzzy sets and their degree of overlapping, implication, and connection operations, and defuzzification method. All these choices are closely related and in no way independent of each other. We describe six important defuzzification methods and their respective merits and shortcomings, dependent on the rules, domains, etc. Further, we give an alternative approach for the case in which the output fuzzy sets have different shapes or are asymmetrical. We illustrate this by several examples.

Verkehrslastregelung in ATM-Netzwerken mit Fuzzy-Methoden

Zusammenfassung.Wir beschreiben zwei Anwendungen der Fuzzy-Logik im Bereich der Breitbandkommunikationsnetzwerke und benutzten dabei Fuzzy-Methoden für Verkehrsmanagement in ATM-Netzwerken (Asynchroner Übertragungsmodus). Zwei wesentliche Funktionen für die Verkehrsregelung im ATM-Konzept sind die Zugangskontrolle (Call Admission Control, CAC) und die Verbindungskontrolle (Usage Parameter Control, UPC). Wir präsentieren eine ‘fuzzy Lösung’ für beide Regelungsprobleme und zeigen den Erfolg dieser Regelungsmodule an Hand von Simulationsergebnissen und heuristischen Betrachtungen.Abstract.We describe two applications of fuzzy logic in the area of broadband communication networks where we use fuzzy methods for traffic management in ATM (Asynchronous Transfer Mode) networks. The ATM concept requires two main functions concerning traffic control: Call Admission Control and Usage Parameter Control. We present a fuzzy logic solution for both control tasks and show the success by presenting simulation results and heuristic valuations.