# A Digital Twin System for Adaptive Aligning of Large Cylindrical Components
## 4 Adaptive Control of the Aligning Process for Large Cylindrical Components  
The aligning process of large components needs to take into account the positioning accuracy and aligning quality, so it is necessary to combine the measured information and prediction information to carry out the force/position cooperative adaptive control of the aligning system. First, based on the multi-source state information obtained during the aligning process, identify the current assembly status of large components. Then, a mapping model between the aligning state and aligning stress is constructed, based on which the aligning stress of large components under different aligning states can be obtained. Furthermore, by comparing it with the expected position of large components, model reference adaptive control information for large components driven by actual measurement information is obtained. Afterwards, the control information is calculated as the displacement information of the dynamic aligning platform system in the aligning system, and the positioning adjustment of each motion axis in the dynamic platform system is allocated to achieve coordinated control. * **Aligning status recognition**: as shown in Figure 5, the aligning features have multiple holes and pins. To achieve the aligning assembly of large components with multiple pins and holes, it is necessary to first consider the assembly interference problem caused by manufacturing, positioning, and other errors between pins and holes. The geometric analysis of various aligning states is required to obtain the geometric errors of large components in different coordinate directions under different aligning states. Based on the set assembly accuracy constraints in each coordinate direction, the current aligning assembly state of large components can be accurately identified, unassembled, aligning the assembly in progress, aligning the assembly completed, etc. For the aligning assembly in progress, the aligning assembly state is divided and identified based on the translation displacement error or rotation angle error of the coordinate axis, and the discrete aligning assembly states of large components are obtained, such as aligning states with poor translation error along the X-axis, \begin{table}
\begin{tabular}{l l l} \hline \hline
**Data Storage Type** & **Characteristic** & **Optional Storage Form** \\ \hline \multirow{2}{*}{Relational data} & Structured, business data & \multirow{2}{*}{SQL Server} \\  & storage & \\ \hline \multirow{2}{*}{Time serial data} & Large-scale data storage, & \multirow{2}{*}{OpenTSDB} \\  & efficient query & \\ \hline \multirow{2}{*}{Configuration data} & Easy to parse and fast & \multirow{2}{*}{XML} \\  & read/write & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of different types of databases for the aligning system. poor rotation angle around the Y-axis together with poor translation error along the Z-axis, etc. * **Mapping relationship between aligning stress and pose of large component:** due to the rather complex force-bearing conditions of the multi-pin-hole assembly, based on the classified types of discrete aligning assembly states, finite element simulations of the aligning stress in various assembly states are necessary. To analyze the displacement, stress, strain, etc., in all assembly states, each unit simulation result needs to be combined to obtain the overall assembly mechanical information. Since the magnitude of the error directly influences the force degree on the contact between the pin and the hole, the independent variable of each simulation is set as a set of discrete pose deviations, and the relationship between the pose deviations and the aligning stress is obtained through parametric scanning. Therefore, based on the discrete pose states of large components, the aligning stress simulations are conducted respectively, and the data are processed by fitting to obtain the mapping relationship between the aligning stress and the pose deviation for the large component.