High-Precision Automated 3-D Assembly With Attitude Adjustment Performed by LMTI and Vision-Based Control

In this paper, a fully automated microassembly methodology is proposed to assemble a slice micropart into a groupware in three-dimensional (3-D) space with the requirement of attitude adjustment. To accurately acquire the attitude of the slice micropart, we proposed an automated measurement method based on a laser triangulation measurement instrument (LTMI) guided by microscopic vision as well as an accurate calibration method for the telecentric vision system based on nonlinear damping least square method. To achieve automatic assembly, a three-stage microassembly strategy is presented: 1) attitude adjustment of the groupware based on multimicroscopic vision regarding the slice micropart's attitude as the target; 2) coarse-to-fine alignment of the slice micropart to the groupware in 3-D space on the basis of LTMI and microscopic vision; 3) remove microgripper of slice micropart until itis completely glued. Fully automated microassembly experiments are conducted, and the results demonstrate the reasonability of proposed approaches. The task has been performed with the following accuracy: 3 μm for the center position error, 2 μm for the depth error and 0.3° for the attitude error.