Flux-Controlled Hybrid Reluctance Actuator for High-Precision Scanning Motion

To achieve highly precise and linear scanning motion by a hybrid reluctance actuator (HRA), this article proposes a flux-controlled mode that uses regulated magnetic flux as the control input for the actuator operation and evaluates its performance in comparison with the conventional current-controlled mode. In the conventional case, HRAs exhibit magnetic nonlinearities (e.g., hysteresis) and position-dependent force that can make the system unstable. A model-based analysis reveals that they are included in the variable magnetic flux of an HRA. Thus, they are captured by flux estimation and rejected by flux feedback control for high-quality scanning motion. For the estimation, sensor fusion with a current monitor and a search coil is used. Proportional integral (PI) controllers are used for the flux feedback control, as well as for current feedback control of the benchmarking current-controlled mode. During scanning, feedforward control is used to compensate linear dynamics. When sine motions are experimentally tested at 60–300 Hz, the current-controlled mode exhibits a nonlinearity between 6% and 23%, which is decreased to less than 5% by the flux-controlled mode. For a <inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>75 <inline-formula><tex-math notation="LaTeX">$\mathrm{\mu }$</tex-math></inline-formula>m triangular motion at 100 Hz, the flux-controlled mode decreases the tracking error by a factor of 19 to 3.2 <inline-formula><tex-math notation="LaTeX">$\mathrm{\mu }$</tex-math></inline-formula>m, successfully demonstrating its high-quality linear scanning motion.