# A Method for Building a Mixed-Reality Digital Twin of a Roadheader Monitoring System
## 5 Conclusions  
This paper aims at solving the problems that cannot be completely solved by traditional monitoring technologies such as the complex operating environment, high incidence of accidents, and out-of-sight tunneling information during the underground operation of roadheaders. By combining the advantages of digital twin and mixed-reality technologies, a digital twin monitoring system for roadheaders is established. The digital twin includes five basic parts: the multi-dimensional attribute physical entity, digital twin virtual entity, data processing system, user interaction system, and transmission network connection system by analyzing the working operation process and characteristics of the boom-type roadheader. Combined with the TCP/IP protocol and C/S network architecture, the efficient, accurate, and rapid transmission of the roadheader cutting information is realized for the digital twin monitoring system, achieving the behavior synchronization and bidirectional control of the virtual and real roadheaders. Through an MR human-computer interaction platform, the virtual roadheader is driven and displayed by the motion data of the roadheader model, which was collected and transmitted to the UIS, where the physical entity and the digital object coexist collaboratively. The data exchange program is designed using the Winform framework and socket communication method, and the digital twin data exchange system of the roadheader is established to provide an information transfer platform for the bidirectional transmission and format conversion of data within the system and combined with the MySQL (v8.0) database for data storage. Some of our conclusions are as follows:  
* The roadheader digital twin monitoring system enables users to fully display the operating status and environmental changes of the roadheader, assists users in completing information identification beyond the line of sight, and improves the efficiency of users' information acquisition, achieving the bidirectional mapping and bidirectional interaction between the digital model and physical entity.
* The operating information of the roadheader experimental prototype can be quickly transmitted to the digital model to achieve the action synchronization of both. After measurement and calculation, the average delay is 60 ms, and the timeliness is good.
* The motion angle values of the roadheader prototype and the digital model are highly consistent. The maximum angle transmission errors of the cutting arm and the slewing platform are 3.756% and 5.000%, respectively, and the average transmission errors are 0.288% and 0.757%, respectively, and the accuracy is good.  
Figure 23: Scatter plot of delay time difference.  
* The measurement errors generated during the action execution process of the road-header prototype model are relatively large, with the maximum values being 15.028% and 19.725%, respectively, and the average values being 3.695% and 1.306%, respectively. Although the maximum values are large, the average values are both lower than 3.7%, so they basically meet the accuracy requirements.