Compensation for torque fluctuation caused by temperature change in fast and precise positioning of galvanometer scanners

This paper presents a compensation approach for torque fluctuation caused by temperature change of galvanometer scanners in laser-positioning servomechanisms. The galvanometer scanner is driven by a swaying motor which is used in laser drilling machines because of its precise positioning ability. However, since the motor temperature rises during the high speed motion, the reversible flux loss occurs. As a result, thermal demagnetization decreases a torque constant and the overshoot occurs at the settling waveform, resulting in deterioration of precision positioning performance. The proposed approach can estimate the temperature of a permanent magnet with a high degree of accuracy by detected current value using a pre-identified cooling coefficient. Specifically, the approach considers a rise in heat caused by eddy current loss. Then the approach compensates for torque fluctuation using the estimated temperature of the permanent magnet. The proposed approach has been verified by experiments using galvanometer scanners.