Integrators, Nonlinearities, and Anti-reset Windup for Different Control Structures

In most control schemes it is advantageous to introduce integrators to eliminate off-set due to load disturbances. It is, however, also important to introduce nonlinearities, for instance due to limitations in actuators. The interaction between the integrator and the nonlinearities will cause problems with reset windup. Ways to handle anti-reset windup for different controller configurations are discussed in the paper. Simple PID-controllers, cascade loops, state feedback controllers and pole-placement controllers are given a unified treatment. The discussion is supplemented with simulations.