Use of Disturbance Measurement Feedforward in LQG
International Journal of Control,
vol 53, pp 579-596, March 1991.
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
scalar LQG control laws, which utilize feedforward.
An explicit adaptive regulator with disturbance measurement
feedforward is presented, based on a polynomial LQG design.
The addition of an optimized feedforward filter to a feedback
regulator involves the solution of only one additional linear
The regulator is designed to handle shape-deterministic
disturbances, such as steps, ramps and sinusoids,
as well as stochastic disturbances.
The properties of the off-line solution in the case of unstable
disturbance models are explained.
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:
Book Chapter which includes
the material of the paper, available in Postscript.
Conference paper in IFAC ACASP'89,
on the above theme.
Paper in Automatica 1988,
on the polynomial (non-adaptive) design of these regulators.
of an undergraduate course, where these adaptive
algorithms are utilized successfully.