SIMULATION OF A HELICON PLASMA SOURCE USING A MULTIVARIABLE FUZZY MODEL

This paper reports work on the development of an automatic control sys tem for a Helicon plasma processing source, The lack of a definitive p hysical model for the plasma physics of the source and the power coupl ing mechanism to the plasma precludes the use of traditional control a lgorithms. This paper develops a fuzzy model that simulates the behavi or of the plasma source using the process of genetic algorithms to ide ntify and optimize the parameters of the fuzzy model, This type of mod el will eventually be used to test a fuzzy control system for the plas ma source, In this work, an extensive set of experimental data was acq uired,where the magnetic field and input power to the plasma source a ere varied over a aide range while the electron number density was mea sured, From this learning dataset, the genetic algorithm derived the v alues of the parameters for the difference equation that describes the system, The fuzzy model so constructed was used to predict the behavi or of the source from known input parameters, Comparing the prediction s with experimental observations showed that the fuzzy model was gener ally able to predict the behavior of the plasma as its input parameter s were varied with a precision of better than 10%.