Modelling and Parameter Estimation of Dynamic Systems

Chapter 10: Parameter Estimation Using Artificial Neural Networks and Genetic Algorithms

10.1 Introduction

Research in the area of artificial neural networks has advanced at a rapid pace in recent times. The artificial neural network possesses a good ability to learn adaptively. The decision process in an artificial neural network is based on certain nonlinear operations. Such nonlinearities are useful: i) in improving the convergence speed (of the algorithm); ii) to provide more general nonlinear mapping between input-output signals; and iii) to reduce the effect of outliers in the measurements.

One of the most successful artificial neural networks is the so-called feed forward neural network. The feed forward neural network has found successful applications in pattern recognition, nonlinear curve fitting/mapping, flight data analysis, aircraft modelling, adaptive control and system identification [1 6]. An illustration and comparison of biological neuron and artificial neuron are given in Fig. 10.1 and Table 10.1 [7].

Table 10.1: Comparison of neural systems

Biological neuron (of human brain)

Artificial neuron

Signals received by dendrites and passed on to neuron receptive surfaces

Data enter through input layer

Inputs are fed to the neurons through specialised contacts called synapses

Weights provide the connection between the nodes in the input and output layers

All logical functions of neurons are accomplished in soma

Nonlinear activation function operates upon the summation of the product of weights and inputs f( ? W x i)

Output signal is delivered by the axon nerve fibre

The output layer produces the network's predicted response


Figure 10.1: Artificial neuron imitates biological neuron in certain ways

The artificial...

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