# Vertical Machining Center Feed Axis Thermal Error Compensation Strategy Research
## 2 Research Object and Methodology
### Embedded Thermal Error Compensation Control System Design  
#### 2.2.1 Embedded Thermal Error Compensation Controller Requirement Analysis  
The thermal error compensation process is performed through the acquisition of the surface temperature of the CNC machine as input parameters of the thermal error prediction model. The thermal error compensation value calculated at the current time is transmitted to the CNC system. The CNC system dynamically adjusts the feed dis  
Figure 1: Vertical machining center VMC655H. Figure 2: Schematic sketch of the feed shaft drive method. placement according to the thermal error prediction value to achieve real-time thermal error compensation. Considering that the actual use of thermal error presents time lag, time variation, comprehensive nonlinearity, and other characteristics, it is difficult to use a single thermal error prediction model for characterization. The introduction of the thermal error compensation scheme under variable motion parameters makes the thermal error compensator meet the characteristics of fast loading and high applicability. The embedded compensator system must meet both the temperature data acquisition and real-time communication data-processing tasks of CNC machine tools, as well as the application requirements as dynamic identification of motion parameters. The functional requirements of the control system are shown in Table 1.  
For the above design requirements, the functional division of the thermal error compensator under dynamic identification of motion parameters is shown in Table 1. To integrate into the embedded control system, the OPC UA client is implemented, and this solution attempts to connect to Siemens machine tools through the OPC UA protocol. To realize the universal applicability of the embedded thermal error compensator, the establishment of the thermal error model and the implementation of the compensation are packaged into two modules of the application framework to cope with the construction and performance of the thermal error model in different environments. The flow of the data signal is shown in Figure 3. \begin{table}
\begin{tabular}{c c} \hline
**System Content** & **Functional Requirements** \\ \hline \multirow{4}{*}{CNC machine tools} & (1) Provides information on parameters such as machine motion position \\  & (2) Provides home position offset implementation and other means \\  & (3) Accepts and processes the parameters of the embedded thermal error compensator \\ \hline \multirow{4}{*}{The thermal error modeling platform} & (1) Processes (sensitive point screening) the collected data \\  & (2) Builds different thermal error models according to requirements \\  & (3) Selects the compensation implementation interface \\  & (4) Compiles and links to executable files \\  & (5) Imports thermal error compensation models to the thermal error compensator \\  & (6) Provides essential UI interaction \\ \hline \multirow{4}{*}{Embedded compensation controller} & (1) Collects filtered temperature data and records them \\  & (2) Accepts the machine position and its related information \\ \cline{1-1}  & (3) Dynamically selects the applicable thermal error compensation implementation model \\ \cline{1-1}  & (4) Loads the model and executes the thermal error compensation scheme \\ \cline{1-1}  & (5) Provides essential UI interaction \\ \hline \end{tabular}
\end{table} 
Table 1: System functional requirements for dynamic motion parameter recognition. Figure 3: Thermal error compensator signal transmission flow diagram. Considering the limited computing power of resources in the embedded environment, the compilation and modeling process are made more flexible and convenient by creating an easy-to-load thermal error compensation model on the PC side and compiling it into an executable file. In the embedded thermal error compensator, the ELF loader differs from the traditional IAP upgrade model by separating the application and the operating system underlay so that the application can still be loaded while the system is running.