Digital twin (DT) has been recognized as a promising technology for enhanced planning, monitoring and control of automatic assembly, with the capability of efficiency, adaptability and flexibility. While most of DT-based assembly focus on electronic products, limited attention has been paid to the assembling of heavy and large-size product with tight tolerance. This paper presents a DT model facilitating prediction and real-time adjustment for intelligent assembling of cylindrical parts. Vision guided feature fitting and coordinate frame construction are presented. Herein, assembly targets are defined considering eight sets of pin and hole, and the contacting planes. This approach improves the assembly success rate. To ensure efficient and robust robot assembly, we proposed a prediction model based on the DT system. Unknown errors and uncertainty of physical space are considered by small displacement torsor (SDT) theory and Monte Carlo simulation (MCS). Assembly planning and execution would efficiently adjust guided by the prediction result. A middle point is set in the robot planning that leaves pure translation in the docking phase. Real-time adjustment method is proposed to accurately assemble the cylindrical parts. Simulations and experiments are carried out to verify the effectiveness and feasibility of the proposed DT-based assembling method. The results show that the prediction results are the same as the actual assembly. Our assembly strategy achieves 97.31% success rate. By employing the assembly strategy and real-time adjustment, our method ensures that the majority of axes mismatch is below 0.1mm/0.05 deg, plane non-contacting below 0.05 mm.
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