Nanoscale motion control using composite filter for disturbance observer

Nanoscale motion control is required for the miniaturization and performance improvement of mechatronic systems. In motion control at the nanometer scale, disturbances that do not affect the system at the macro scale might greatly influence the control performance. The torque ripple caused by current distortion is one of the most serious disturbance elements and should be eliminated. Compensation methods for current distortion have been researched, but the conventional method cannot be applied to control systems in the nanometer scale because a short sampling time is needed. To address this problem, a filter design method is proposed in this paper. The effect of the current distortion can be reduced by designing the filter in the disturbance observer to have a low-pass filter and a band-stop filter. By using high-precision acceleration control based on the proposed method, persistent oscillation can be suppressed, and control accuracy can be improved. The validity of the proposal is comfirmed by experiments.