The implementation of a generalised robust adaptive controller
Date
2015-01-08
Authors
Bergesen, Michel Ludvic
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
An adaptive controller is developed, comprising a robust parameter estimator
and an explicit pole assignment controller design. The controller
is reformulated to have a standard PID structure. A practical implementation
is facilitated on a digital microcomputer, connected to a physical
process. Test results are presented for this real process subject to
variable dead-time and an external disturbance. Simulation results are
also presented, for a nominally non minimum-phase process subject to variable
dead-time and large open-loop gain changes. Robust performance is
demonstrated under all of these circumstances. Recommendations are given
for the choices and considerations required in a robust practical implementation.
Much research has been done in the field of adaptive control over the past
few decades. However, a let needs to be learned about the robustness of
adaptive control algorithms. This research investigates the implementation
of a practical adaptive control algorithm, with numerous features
incorporated to improve the robust performance of such a controller. Parameter
estimation is performed using Recursive Least Squares (RLS), with
various signal conditioning filters to reduce estimator sensitivity to
noise and modelling errors. The control design is based on closed-loop
pole assignment, with adaptive feed forward compensation included. Further,
provision is made in both the estimation model and the feedback
control structure to eliminate deterministic immeasurable disturbances,
and to track deterministic set point variations. This is based on the
Internal Model Principle. Measured random disturbance signals are included
in the estimation model, for which "transfer function" polynomial
coefficients are estimated and then used in the feed forward control d e sign.
A new shift- operator, namely the 6-operator, is used in all controller
and estimator formulations. This has been shown to have better
numerical properties and to correspond more closely to continuous-time
control, than the traditional q operator of z-domain discrete control.
A practical implementation on a digital computer is investigated, applied
to a real plant typical of an industrial application. Simulation results
are also obtained for plant with non minimum-phase zeros and variable
dead-time.