The Use of Disturbance Measurement Feedforward in LQG Self-Tuners.

Mikael Sternad

IFAC Symposium ACASP'89: Adaptive Systems in Control and Signal Processing, Glasgow, UK, pp 353-358, April 1989.

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Outline:

Disturbances which act on a process can sometimes be measured and used by a controller. The use of such disturbance measurement feedforward can lead to large performance and robustness improvements, as compared to the use of feedback only. The paper discusses the design of indirect self-tuning scalar LQG control laws, which utilize feedforward.

Abstract:

An explicit adaptive regulator with disturbance measurement feedforward is presented. It is based on a polynomial LQG design. In feedback regulators, the addition and optimization of a feedforward filter involves the solution of only one additional linear polynomial equation.

The regulator is designed to handle shape-deterministic disturbances, such as steps, ramps and sinusoids, as well as stochastic disturbances.

Computational aspects, the computational complexity and the robustness against unmodelled dynamics are discussed. It is argued that the use of feedforward can improve not only the disturbance rejection, but also the stability robustness of an LQG feedback regulator.

Related publications:

Paper in IJC 1991, on the above theme.
Conference paper on indirect adaptive LQG, explicit criterion minimization and self-tuners for adaptive feedforward control.
Book Chapter which includes the material of the paper, available in Postscript.
Paper in Automatica 1988, on the polynomial (non-adaptive) design of these regulators.
Lecture notes of undergraduate course, where these adaptive algorithms are utilized successfully.