A SIMPLIFIED FUZZY MODEL TO MIMIC A NONLINEAR-SYSTEM, APPLIED TO A PLASMA SOURCE

This paper develops a fuzzy model to simulate the behavior of a nonlin ear system, in particular a plasma source, with a view to developing a control system for processing plasmas employing a helicon source, Gen etic algorithms are employed to optimize fuzzy rules related to the pa rameters of the fuzzy model which contain a set of variable zeros and poles of the nonlinear system as well as its time delay, A practical a pplication of the fuzzy model is to estimate the electron number densi ty of a low-temperature plasma. Based on the membership functions of t he input and output, a set of fuzzy rules by which the variable zeros and poles are identified is derived and optimized using a genetic algo rithm, The principal reason for investigating the proposed fuzzy model is the subsequent computer-aided design of a fuzzy controller to cont rol the nonlinear system. Two experimental results are presented to va lidate the fuzzy model method, One shows a computer simulation and the other predicts the real-time behavior of the plasma source as its inp ut parameters are varied.