转塔式贴装头吸嘴三维位姿误差分析与标定

Three Dimensional Position Error Analysis and Calibration of Nozzles in Turret Mounter

针对转塔式贴装头因机械加工及装配误差导致吸嘴部件不垂直于贴装平面的问题,提出了一种吸嘴三维位姿误差的自动标定方法.对吸嘴进行理论建模与误差分析,通过机器视觉采集图像计算及坐标变换得出吸嘴在不同高度下的各个自转角度下的基坐标,利用最小二乘法拟合出吸嘴的自转圆心基坐标、半径大小以及吸嘴与竖直方向的偏角.通过实验分析吸嘴实际运动轨迹,一方面对理论计算吸嘴下降任意高度下自转圆心基坐标与实际自转圆心基坐标进行比较,另一方面对吸嘴自转到目标角度下计算基坐标与旋转之后实际位置坐标进行比较,结果表明总误差小于±50μm,满足元件贴装位置精度要求.

The nozzle of precision SMT cannot be perpendicular to the mounting plane due to manufacturing and assembly errors. This paper presented an auto calibration method of nozzle position error. First, a theoretical model of the pose of the nozzle was made to analyze the position error of the nozzle, and the machine vision was used to acquire images and calculate the image coordinates of the nozzle. Then the physical coordinates of the nozzle was obtained by coordinate transformation during the process of nozzle calibration. The center position and radius of the self rotation circle of the nozzle was fit when the nozzle was in different height, and different angles of the nozzle in the vertical direction were obtained. Experiments on the above theory were performed, focusing on predicting the center position of the self rotation circle of the nozzle in different height and predicting the real physical coordinates of the nozzle after self rotating a certain angle. The experiment result show that the error is less than ±50 μm, which satisfies the majority of the requirements of component placement.