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Nonlinear controllers such as globally linearizing controller (GLC) (Isidori,
1989; and Jana et al., 2005a), generic model controller (GMC) (Lee and Sullivan,
1988; and Signal and Lee, 1992) and internal model controller (IMC) are a class
of advanced controllers which were developed in the late 1980s to get a
better performance than the conventional proportional-integral (PI) or
proportional-integral-derivative (PID) controllers. These control schemes require the
feedback of state variables to implement the efficient control laws. Although
open-loop observer, i.e., direct integration of the process model, is employed to estimate
the required state feedback, which performs satisfactorily for several applications,
a closed-loop observer with feedback correction is still desirable, when the
system consists of modelling error(s) or pure integrator(s).
In the present study GMC scheme is chosen as it is extensively used to
control the nonlinearities and interactions in the nonlinear industrial processes. As
the performance of the GMC scheme also depends on the accurate feedback of
the state information to the controller, the combination of GMC law and an
efficient state estimator is required to improve the closed-loop performance. |
