Prevention of windup in output constrained minimum-phase systems

This contribution presents a new method for the prevention of problems caused by saturating sensors in an otherwise linear loop. Different from the known anti-windup schemes for input constraints the compensator is not stabilized during saturation, as this can lead to a deadlock situation in case of persistent disturbances. The new approach also does not use the modification of the linear part of the loop with the aid of a saturation indicator. The main feature of the new solution is an appropriate design of the controller which guarantees that sensor saturation does not destabilize the nonlinear loop. As the signal model for the persistent disturbances is active during saturation a robust rejection of persistent disturbances is achieved. Using a two-degrees-of-freedom control structure one also obtains a robust reference behaviour.