Disturbance Observer-Based Robust Controller for a Multiple-Electromagnets Actuator

This article proposes a disturbance observer (DOB)-based robust controller to improve the control performance of an electromagnetic actuator (EMA) with multiple electromagnets by compensating for the uncertainties caused by magnetic fields’ nonlinearity and unmodeled magnetic properties. Conventional EMAs have been widely researched, but control strategies are limited to linearized magnetic field models based solely on intrinsic magnetic field strength. Thus, we designed a DOB-based double-loop feedback controller to extend the nominal feedback controller based on linearized magnetic field models. The DOB-based controller compensates for the unmodeled uncertainties and nonlinearities of multiple electromagnetic fields and improves performance in combination with the robustness of a conventional control scheme. The designed controller works as a force compensator for the target object and can widen the region of interest (ROI) of the given conventional EMA system without a scale-up design. Experimental results demonstrate that the proposed DOB-based controller improves the trajectory tracking error by 58.2% within the target ROI. Finally, the robustness of the proposed DOB-based controller for extended ROI is validated through a comparison with other control methods, which may increase the usefulness of the conventional EMA system.