An anti-windup framework for systems with non-standard actuator characteristics

We examine anti-windup architectures for linear systems containing what might be broadly called non-standard actuators - actuators which may not be easily approximated by simply a saturation or rate-limit, but which are a more complex interconnection between linear elements and sector-bounded nonlinearities. An LFT type approach is taken to modelling such actuators and a fairly generic anti- windup approach is developed, allowing for a wide class of nonlinear actuators, including, but not limited to, actuator models with rate, amplitude or deadzone limitations. We also consider the synthesis for this class of actuators using the coprime factor approach, and it is shown that, in some circumstances, the IMC approach to anti-windup compensation yields desirable closed-loop robust stability properties.