
Accession Number : ADA317072
Title : Evolving Neural Networks for Nonlinear Control.
Descriptive Note : Final rept. 15 Mar 9331 Aug 96,
Corporate Author : GEORGE MASON UNIV FAIRFAX VA
Personal Author(s) : Hintz, Kenneth J. ; Zhang, Z. ; Duane, D.
PDF Url : ADA317072
Report Date : 30 SEP 1996
Pagination or Media Count : 66
Abstract : An approach to creating Amorphous Recurrent Neural Networks (ARNN) using Genetic Algorithms (GA) called 2pGA has been developed and shown to be effective in evolving neural networks for the control and stabilization of both linear and nonlinear plants, the optimal control for a nonlinear regulator problem, the XOR problem, and an amplitude modulation (AM) detector. This new approach consists of a twophase GA with the first phase using a set of Lindenmayer System (LSystem) production rules to evolve the NN architectures, and the second phase using genetic hillclimbing for connectivity weight tuning. The resulting amorphous (nonlayered) recurrent NNs are realvalued as opposed to the binaryvalued nets generated by the original GANNET program. Integral absolute error was the fitness function used in these experiments. A striking indirect result of this research is the few number of neurons which are required to effect the compensation and stabilization. Typical networks are from 415 neurons. The inclusion of a neural insertion/deletion operator in both the 2pGA and GANNET2 methods allows for the size of the NN to be evolved. This capability has been used to develop an empirical relationship between problem complexity and the required NN complexity. Problem complexity is measured by the number of symbols required to differentiate among binary patterns in a pattern recognition task. NN complexity is measured by number of neurons. while not yet definitive, empirical data from ARNNs evolved by GANNET2 show what appears to be a logarithmic relationship between the complexity of a regular expression and the size of a recurrent neural network which recognize it. Additional experiments are being performed to extend the region of evolved data to improve our confidence in this conclusion.
Descriptors : *NEURAL NETS, *EVOLUTION(DEVELOPMENT), ALGORITHMS, CONTROL, OPTIMIZATION, PRODUCTION, REGULATORS, NONLINEAR SYSTEMS, ERRORS, WEIGHT, TUNING, PATTERN RECOGNITION, LOGARITHM FUNCTIONS, GENETICS, AMPLITUDE MODULATION.
Subject Categories : Cybernetics
Distribution Statement : APPROVED FOR PUBLIC RELEASE