# Digital Simulation and Analysis of Assembly-Deviation Prediction Based on Measurement Data
## 1 Introduction
[PERSON] [12] proposed a core engine rotor assembly accuracy-prediction model utilizing the concept of elastic contact of the assembly surface. By adjusting and optimizing the installation phase of the rotor based on the model predictions, the assembly accuracy was significantly improved. [PERSON] et al. [13] developed an assembly-prediction method by leveraging high-precision big data collection and \"assembly deformation compensation and correction\" technology. This method allowed for the prediction of the optimal assembly angle and position of each stage of the rotor disk, thereby improving assembly accuracy and reducing the potential for errors. [PERSON] [14] first proposed the use of computers to define the geometric shape, dimensions and tolerances of parts. With the progress in computer-aided tolerance analysis, there have been more and more studies conducted on digital assembly via 3D tolerance-analysis software. [PERSON] [15] conducted a study on dimensional deviations in engine compartments using 3 DCS software and performed a root cause analysis of the resulting assembly deviations. [PERSON] et al. [16] adopted the VSA software to investigate the cause of significant concentricity of pivot point for a type of core machine test part. [PERSON] et al. [17] used 3 DCS software to analyze and optimize the tolerance of spacing in the landing gear intersection for the nacelle of the turbopro engine, which solved the problem with intersection spacing of the landing gear. The aforementioned studies present practical instances and methodologies for the analysis and optimization of assembly utilizing deviation-analysis software. However, these studies solely focus on the analysis and optimization of assembly deviations in design models, without further integrating real-world components with the design models. In addition, there is no guidance provided for actual assembly processes through the utilization of digitized assembly based on real-world components. The assembly is realized in a 3D space, where a small amount of discrete 1D and 2D measurement data cannot reflect the 3D shape, the distribution of high and low points, and the exact location of the component. Therefore, for the assembly-deviation analysis of the machined parts, it is necessary to combine 1D, 2D and 3D measurement methods and to integrate the obtained data to better indicate the size, shape, deformation and contour error of the machined parts. To perform 1D and 2D measurement of parts with high precision, various high-precision measurement equipment items such as coordinate-measuring machines, laser trackers and articulated arm coordinate-measuring machines can be used. Moreover, for the assembly of ultra-large equipment, high-precision digital photogrammetry can be used as well. In terms of 3D measurement, the high-precision 3D laser scanning equipment based on line laser, structured light and phase shift method is advantageous. Currently, many researchers are investigating and applying 3D measurement methods. For instance, [PERSON] [18] employed binocular grating 3D measurement technology to measure an impeller, achieving a low-cost and high-accuracy 3D graphic visualization of the impeller. [PERSON] et al. [19] utilized structural light to measure the surface differences of a body-in-white in 3D and addressed the issues of poor accuracy and low efficiency of manual measurement by fitting the reference line using the RANSAC algorithm. [PERSON] et al. [20] utilized various 3D measurement instruments and proposed a 3D measurement process model-construction method for aircraft assembly. In this paper, micro gas turbine is taken as the research object to establish a digital assembly-deviation-prediction and -analysis model based on design tolerance and actual measurement data. This not only improves the rationality of design and the reliability of assembly but also accelerates the process of equipment development and reduces production costs, which demonstrates its applicability in practice.