Page 14 - Adaptive Identification and Control of Uncertain Systems with Nonsmooth Dynamics

Introduction 3

fuzzy logic systems (FLSs) into adaptive control to handle unknown non-
linearities in the systems. However, it is noted that most non-linear adaptive
control techniques reported in the literature are for some specific non-linear
systems with smooth non-linearities, and thus they are not applicable di-
rectly for systems with non-smooth non-linearities. By combining the idea
of inverse model compensation and adaptive control, several adaptive con-
trol schemes have been recently reported to cope with actuator dead-zone,
backlash, hysteresis, and saturation, which show potential by further tailor-
ing adaptive control technique. Hence, it is appealing and of interests to
explore more intelligent approaches to increase the control performance.
This could be achieved by introducing more sophisticated piecewise linear
approximated model of such non-smooth non-linearities, which are more
suited for adaptive control design, and investigating model-free (e.g., data
driven) based control methods.
In this book, some recently proposed models of such non-smooth non-
linearities and the associated adaptive control methods based on the derived
models and the function approximation technique will be introduced.
These new model and control designs are derived to handle uncertain dy-
namic systems containing friction, hysteresis, dead-zone, or saturation in
the plants. We will show how non-smooth non-linear characteristics can be
adaptively compensated and how desired system performance is achieved.
Practical applications to several servo mechanisms are also included in this
book. Some of the results presented in this book have evolved from the
recent journal papers of the authors.

1.2 OBJECTIVE OF THE BOOK
The objective of this book is to provide necessary introduction of four dif-
ferent non-smooth dynamics widely encountered in the electro-mechanical
systems, such as friction, dead-zone, saturation, and hysteresis, and then
to present details of modeling, control design, and analysis, and techni-
cal guidance for the control implementation of systems with such non-
smooth behaviors and unknown non-linearities. The major focus is on
introducing new models of such non-smooth behaviors, which are more
suitable for control design and synthesis, and also on designing, analyzing,
and implementing adaptive control, which are able to accommodate such
non-smooth behaviors and other unknown dynamics (e.g., modeling un-
certainties and disturbance).