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Download fileNon-linear PID predictive controller
journal contribution
posted on 2008-11-03, 16:21 authored by Wen-Hua ChenWen-Hua Chen, Donald J. Ballance, Peter J. Gawthrop, Jenny J. Gribble, John O'ReillyA new class of nonlinear PID controllers are derived for nonlinear systems using a Nonlinear
Generalised Predictive Control (NGPC) approach. First the disturbance decoupling ability of
the nonlinear generalised predictive controller is discussed. For a nonlinear system where the
disturbance cannot be decoupled, a nonlinear observer is designed to estimate the offset. By
selecting the nonlinear gain function in the observer, it is shown that the closed-loop system
under optimal generalised predictive control with the nonlinear observer is asymptotically stable.
It is pointed out that this composite controller is equivalent to a nonlinear controller with integral
action. As a special case, for a nonlinear system with a low relative degree, the proposed
nonlinear controller reduces to a nonlinear PI or PID predictive controller, which consists of a
nonlinear PI or PID controller and a prediction controller. The design method is illustrated by
an example nonlinear mechanical system.
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