The System Control Design Which Apply in Compensating Distortion of Laser Galvanometer

• Main Authors: Lin, Ju-Chen, 林如錚
• Other Authors: Chiou, Jin-Chern
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/6dwcc2

碩士 === 國立交通大學 === 電控工程研究所 === 100 === In a variety of laser processing method, the galvanometer scanning laser is one of the major processing systems. However, comprising non-linear components such as the rotating scanning galvanometers and the focusing lens in system result in many distortion problems. To decides the graphics of processing, galvanometer scanners control the laser travel direction which. And the focus lens is used to focus the laser power and adjust the spot size, which is an important component to affect the accuracy of laser processing. But these two parts will cause pillow distortion and barrel distortion when laser scanning. Furthermore, the positioning speed of the scanning motor is also a huge factor of distortion when operating high-speed scanning. In order to solve the aberration, the distortion theory, compensation and improvement are investigated in this thesis. We analysis the laser travel route of scanning mirror and focus lens to find the relation function between distortion and ideal graphics, then design appropriate controller to suppress generation of the barrel or pincushion distortion. On the other hand, distortion analysis will be achieved by investigate the system transfer function through system identification method. In order to determine the system, we construct a signal measuring system using the PSD component. The dynamic characteristic of laser galvanometer scanning system and the coefficient of transfer function can be obtained by calculating experimental data. Hence the laser galvanometer system model of laser scanning system has been identified. Then design the controller according to target speed, and reduce the oscillating time of scanning mirror. The results show that, after compensation, the distortion error of less than 8μm when scanning 20 × 20mm2 square. And the time reaching steady state is less than 200μs when the deflection angle is 3.5 degrees. The distortion situation is significantly improved.