A high-precision digital twin modeling approach for the serial-parallel hybrid drilling robot in aircraft assembly

Abstract

Digital twin (DT) models with high-fidelity could map physical entity states precisely, raise the credibility of simulation, enhance the accuracy of processing decisions and improve feedback control precision in intelligent manufacturing, while the modeling process is frequently constrained by the complexity of the physical entity structure. This paper aims to propose a high-precision DT modeling method for aircraft assembly equipment and a drilling robot system with complex structures is taken as the research object. A physical model detailing the structure of the hybrid drilling robot is developed via the combination of Denavit-Hartenberg (D-H) and the virtual mechanism methods. A logical model is established based on the kinematic model of the hybrid drilling robot to express its behavior for drilling. The Levenberg-Marquardt (L-M) least-squares method is applied for calibration of DT model, which reduces the influence of geometric errors by identifying structural parameters in the physical model. The average position and normal errors have decreased to 1/10 and 1/8 respectively compared to before calibration, leading to enhanced accuracy in DT modeling. DT control software is developed to integrate physical model and logical model and is combined with hybrid drilling robot to construct DT system. The drilling quality experiment of DT system for flat and single curvature plates is designed and the results showed that the average positioning errors after the DT model calibrated are reduced by 39.29 % and 49.25 %, respectively. In addition, these drilling quality meets the drilling requirements of large aircraft body fastener assemblies.