Purpose

The purpose of this study was to solve the problem of pose measurement of various parts for a precision assembly system.

Design/methodology/approach

A novel alignment method which can achieve high-precision pose measurement of microparts based on monocular microvision system was developed. To obtain the precise pose of parts, an area-based contour point set extraction algorithm and a point set registration algorithm were developed. First, the part positioning problem was transformed into a probability-based two-dimensional point set rigid registration problem. Then, a Gaussian mixture model was fitted to the template point set, and the contour point set is represented by hierarchical data. The maximum likelihood estimate and expectation-maximization algorithm were used to estimate the transformation parameters of the two point sets.

Findings

The method has been validated for accelerometer assembly on a customized assembly platform through experiments. The results reveal that the proposed method can complete letter-pedestal assembly and the swing piece-basal part assembly with a minimum gap of 10 µm. In addition, the experiments reveal that the proposed method has better robustness to noise and disturbance.

Originality/value

Owing to its good accuracy and robustness for the pose measurement of complex parts, this method can be easily deployed to assembly system.

中文翻译：

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一种用于精密装配的基于高斯混合模型的轮廓引导姿态对齐方法

目的

本研究的目的是解决精密装配系统各个零件的位姿测量问题。

设计/方法/方法

提出了一种新的基于单目显微系统的可实现微型零件高精度姿态测量的对准方法。为了获得零件的精确位姿，开发了基于区域的轮廓点集提取算法和点集配准算法。首先，将零件定位问题转化为基于概率的二维点集刚性配准问题。然后，将高斯混合模型拟合到模板点集，轮廓点集用分层数据表示。采用最大似然估计和期望最大化算法对两个点集的变换参数进行估计。

发现

该方法已通过实验在定制装配平台上的加速度计装配中得到验证。结果表明，所提出的方法可以以10 µm的最小间隙完成字母-基座组装和摆动件-基部组装。此外，实验表明所提出的方法对噪声和干扰具有更好的鲁棒性。

原创性/价值

由于其对复杂零件的姿态测量具有良好的准确性和鲁棒性，因此该方法可以很容易地部署到装配系统中。