PI-Controller Applied to a Piezoelectric Nanopositioner Using Conditional Integrators and Optimal Tuning

For tracking control of nanopositioning stages using piezoelectric actuators, controllers with integral action can be employed to robustly track a reference in the presence of hysteresis, creep, and plant parametric uncertainties. In any practical configuration of instrumentation for this application, saturations will be present. Thus, a controller with integral action is prone to windup, which typically cause large transients and long settling times, and will in general degrade performance and potentially damage equipment. In this paper it is demonstrated that conditional integrators provides a very accessible and convenient framework for introducing anti-windup for any order integral controller, and the effectiveness is verified experimentally. Also, the influence reconstruction and anti-aliasing filters have on the stability limits for PI and PI controllers is investigated, and a novel tuning procedure is proposed in order to obtain the best performance for the overall system. It is demonstrated experimentally that optimal tuning can damp resonances and increase bandwidth.