精密视觉印刷设备的自标定

为了提高全自动视觉印刷设备的精度,提出了一种简易、有效标定基于三自由度平面并联调整台的视觉丝网印刷设备的算法。首先,分析和标定了视觉测量系统,并通过激光干涉仪验证了结果的准确性。然后,分析了三自由度平面并联调整台的几何参数误差;基于印刷设备自身的视觉测量系统,分步标定了并联平台的动平台坐标系、传动比误差和仅需的部分几何误差源。提出了一种满足全姿态且适应不同制程的三角形面姿态插值方法和纠偏调整算法,从而避免了较为复杂的几何全参数辨识,降低了对调试人员的技术要求。实验结果表明：在并联调整台工作空间内,标定后的最大位置误差从标定前的161.6 μm下降为12.3 μm,最大姿态误差从标定前的2.232″下降为0.720″,基本满足印刷设备对精度的要求。

Self-alibration of precise vision-based printing equipment

To improve the precise of all automatic printing equipment, a simple and effective calibration method was proposed to calibrate the screen printing equipment based on a novel three-degree-of-freedom (3-DOF) planar parallel stage. Firstly, a vision-based measuring system was analyzed and calibrated, and its measurement accuracy was also evaluated by a laser interferometer. Then, the geometric errors of the 3-DOF planar parallel stage was analyzed and the frame of the parallel stage's movable platform, screw lead errors and some geometric errors were identified in steps based on a vision-based measuring system in the equipment. Furthermore, the orientation interpolation and alignment methods using a triangular area to position the alignment point were presented to satisfy the need for different product processes in the whole workspace. For the processing mentioned above, this calibration method can calibrate the equipment itself automatically without complicated identification for all geometric errors and the need for any background in parallel robot calibration. Experimental results after calibration show that the maximum position and orientation errors inside the workspace have been reduced from 161.6 μm and 2.232″ to 12.3 μm and 0.720″, respectively, which satisfies the equipment requirement for high accuracy.