Thermal Demagnetization Compensation for Fast and Precise Positioning in Galvanometer Scanners

To improve the positioning accuracy of galvanometer scanners, we have developed a thermal demagnetization compensation (TDC) approach. In recent years, increase in power consumption of the galvanometer scanner results from high-speed motion; therefore, a magnet's temperature rise increases. Generated torque of the galvanometer scanner decreases with a rise in temperature because of demagnetization so that positioning ability of the galvanometer scanner declines. The proposed TDC approach estimates magnet temperature with a high degree of accuracy from the detected current using preidentified thermal characteristics. On the basis of estimated temperature, the TDC approach is able to compensate for generated torque fluctuation caused by the magnet's temperature rise without additional thermal sensors. Furthermore, the TDC performs efficiently even so the settling waveform has transient response error caused by continuous movement. In addition, the TDC approach performs for various operating frequencies. When we applied the TDC approach to galvanometer scanners installed on laser-drilling machine, the TDC approach reduced the maximum positioning error by 32%, and all shots were less than an accuracy tolerance.