# A Digital Twin System for Adaptive Aligning of Large Cylindrical Components
## 2 Data integration  
The data collected during the interconnection process are managed in various data formats and methods to facilitate storage, query, and modification. Structured parameter data existing in the aligning system, such as geometric model data (geometric dimensions, assembly relationships, assembly positions, etc., used for virtual model visualization), physical model data (input data required for aligning error prediction mechanism models, relevant data of aligning platform raw errors), user management information, etc., have fixed formats and storage rules, and because they are fixed parameters of the aligning system, they will not be written or modified in batches, which are expressed and managed in a structured manner using tables, as shown in Figure 9.  
For the configuration parameter data used in the aligning system, such as the interfaces for transmitting data between subsystems (e.g., communication IP, communication ports), and the parameters required for functional models (e.g., aligning error mechanism model input data, aligning platform raw errors, control algorithm weight coefficients, etc. ), it is necessary to be easy to parse, read, write, and modify. Therefore, the XML (eXtensible Markup Language) data format is used for this data modeling, and a unified data format is constructed, achieving the integration and expression of heterogeneous system information. In addition, the relevant algorithm configuration parameter information during the aligning process is stored in an XML format file to achieve the rapid parsing, reading, and modification of key parameter data. For instance, Figure 10 shows some of the system parameter values required for the aligning error prediction and adaptive control algorithm, including assembly constraint information and force-position constraint information for the aligning system. This information is used as the configuration parameter inputs in the algorithm, outputting aligning error, and adaptive control adjustment parameter results for the aligning system of large cylindrical components. For real-time monitoring data of the aligning system, it refers to all dynamic process data that reflect the operating status, real-time performance, environmental parameters, sudden disturbances, etc. This type of data has the characteristics of large data volume and strong temporal correlation. Therefore, an unstructured data format is used for storage, and the data are defined and managed through timestamps and variable labels (Metrix) in \begin{table}
\begin{tabular}{l l l} \hline \hline
**Data Name** & **Data Type** & **Communication Interface** \\ \hline \multirow{3}{*}{Visual measurement data} & Measure the position coordinates of & The measurement software \\  & spatial points and solve the spatial pose & communicates with the device via \\  & of large components & Bluetooth \\ \hline \multirow{2}{*}{Strain gauge sensor data} & Monitoring the aligning stress changes at & RS485 Serial port for communication over \\  & the interface of large components & MODBUS \\ \hline \multirow{2}{*}{Beckhoff controller data} & Obtain information, such as relative & TwinCAT development platform to read \\  & displacement of the driver, motor & the PLC address, need to know the target \\  & movement, speed, etc. & amount of PLC address in advance \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Multi-source heterogeneous data of aligning system. Figure 9: Structured data representation. a time-series database for quick writing and querying. For example, Figure 11 shows the displacement of the large cylindrical component in the X direction at different times, i.e., the X-direction displacement values of the same Metrix at different timestamps recorded in a time database, where ab_camera_X represents the displacement of the large component in the X direction measured by the vision measurement system.