Control of an Overactuated Nanopositioning System with Hysteresis by Means of Control Allocation

This paper is devoted to the analysis, modeling and controller design of the overactuated nanopositioning lifting and actuating unit (LAU) applying dynamic control allocation. A detailed model is provided and its parameters are identified from experimental data. Since the LAU system is subject to magnetic hysteresis, we apply Preisach's operator to handle this phenomenon. The control objective is the vertical displacement in the millimeter range with nanometer precision under a control effort distribution. For this, a dynamic control allocation is proposed in which a frequency distribution of the control effort is considered. Low frequency components are assigned to the slow pneumatic actuator while higher frequencies are handled by the voice coil drive. A Kalman filter is used to compensate the significant actuator dynamics. The position controller is based on a feedback linearization framework with a disturbance observer for enhanced robustness. Finally, the validity and feasibility of the proposed method is demonstrated by simulation and experiment.