Systematic Anti-Windup Compensator Design for
Swedish Control Meeting ``Reglermöte'',
Luleå, Sweden, June 6-7, 1996.
The aim of anti-windup compensation is to modify the dynamics of a
control loop when control signals saturate, so that a good transient
behaviour is attained after desaturation, while avoiding nonlinear
oscillations and repeated saturations.
Model-based anti-windup compensation is here considered for
multiple-input multiple-output (MIMO) systems.
We assume a model of a multivariable plant and a nominal
controller structure to be given as rational fractional representations.
A modified controller structure is proposed, which leaves the nominal
closed-loop dynamics unchanged, as long as none of the control
By diagonalizing the loop gain around the saturation
nonlinearity, the problem of modifying the behaviour during and after
saturation is reduced to separate scalar design
problems, one for each control signal.
The multivariable control problem can then be solved by
utilizing two concepts widely taught in basic control education:
scalar loop gains and describing functions.
The design aim of obtaining a fast desaturation transient is sometimes
contradictory to the aim of avoiding repeated resaturations, due to
A H-2 optimization criterion is proposed as a tool for developing
The proposed approach is applicable to continuous-time as
well as discrete-time systems. Although it is developed for systems in
input-output form, it can be used for systems and controllers
described in state-space form
- Related publications:
(ECC 1997), which presents the methodology.
with details and examples.
described in a report by Rönnbäck and Sternad 1993.
- Postscript (uncompressed)
Postscript (compressed, .gz) 94K ;