Abstract
This report is a review of the main neuro-control technologies. Two
main kinds of neuro-control approaches are distinguished. One entails
developing a single controller from a neural network and the other
one embeds a number of controllers inside a neural network. The single
neuro-control approaches are mainly system inverse: the inverse of
the system dynamics is used to control the system in an open loop
manner. The Multi-Layer Perceptron (MLP) is widely used for this
purpose although there is no guarantee that it can succeed in learning
to control the plant and that, more importantly, the unclear representation
it achieves prohibits the analysis of its learned control properties.
These problems and the fact that open loop control is not suitable
for many systems highly restricts the usefulness of the MLP for control
purposes. However, the non-linear modelling capability of the MLP
could be exploited to enhance model based predictive control approaches
since essentially, an accurate model of the plant is all that is
required to apply this method. The second neuro-control approach
can be seen as a modular approach since different controllers are
used for the control of different components of the systems. The
main modular neuro-controllers are listed. They are all characterised
by a ""gating system'' used to select the the modular units (i.e.
controllers or models) valid for the computing of a current input
pattern. These neural networks are referred to as the Gated Modular
Neural Networks (GMNNs). Two of these networks are particularly fitted
for modelling oriented control purposes. They are the Local Model
Network (LMN) and the Multiple Switched Models (MSM). Since the local
models of the plant are linear, it is fairly easy to transform them
into controllers. For the same reason, the analysis of the properties
of these networks can be easily performed and it is straightforward
to determine the parameter values of the controllers as linear regression
methods can be applied. These advantages among others related to
a modular architecture reveal the great potential of these GMNNs
for the modelling and control of non-linear systems.
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