Integrated structure selection and parameter optimisation for eng-genes neural models

  • Authors:
  • Patrick Connally;Kang Li;George W. Irwin

  • Affiliations:
  • School of Electronics, Electrical Engineering and Computer Science, Queen's University Belfast, Belfast BT9 5AH, Northern Ireland, UK;School of Electronics, Electrical Engineering and Computer Science, Queen's University Belfast, Belfast BT9 5AH, Northern Ireland, UK;School of Electronics, Electrical Engineering and Computer Science, Queen's University Belfast, Belfast BT9 5AH, Northern Ireland, UK

  • Venue:
  • Neurocomputing
  • Year:
  • 2008

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Abstract

The eng-genes concept involves the use of fundamental known system functions as activation functions in a neural model to create a 'grey-box' neural network. One of the main issues in eng-genes modelling is to produce a parsimonious model given a model construction criterion. The challenges are that (1) the eng-genes model in most cases is a heterogenous network consisting of more than one type of nonlinear basis functions, and each basis function may have different set of parameters to be optimised; (2) the number of hidden nodes has to be chosen based on a model selection criterion. This is a mixed integer hard problem and this paper investigates the use of a forward selection algorithm to optimise both the network structure and the parameters of the system-derived activation functions. Results are included from case studies performed on a simulated continuously stirred tank reactor process, and using actual data from a pH neutralisation plant. The resulting eng-genes networks demonstrate superior simulation performance and transparency over a range of network sizes when compared to conventional neural models.