239 A perception and monitoring array was implemented by deploying sensors across various structural regions of the support. Specifically, 9 sensors were installed on the canopy, 6 on the caving shield, and 6 on the side guard plates. Each individual pressure sensor had a measurement range of 0–20 kN. The digital twin system was used to monitor the inclination angle and load variations of the hydraulic supports in real-time. The motion behaviors of hydraulic supports include the lifting and lowering of columns, advancing, side protection, lateral adjustment, base lifting, among others (Fig.5). The twin behavior of the system primarily refers to the real-time digital twin mapping between the hydraulic supports and the platform. Specifically, the hydraulic support in the virtual space accurately and in real-time replicates the motion state of its physical counterpart in the steeply dipping mining face as it moves and changes. Figure 5 - Twin mapping of hydraulic support’s action 3.2 Attitude Evolution and Load Transfer Mechanism of Steeply Dipping Supports During the loading process of the supports in the steeply dipping working face, the average load measured by the support sensors gradually increased to 4.3 kN (2.19 MPa), with the peak total load reaching 38.7 kN (19.74 MPa). Subsequently, the load on the canopy decreased to 35.1 kN (17.90 MPa). The digital twin system indicated that the hydraulic support columns yielded with a height reduction of 3.7 cm. Upon further loading, when the total load reached 38 kN (19.39 MPa), the roof above the support fractured. High-definition monitoring showed that the roof mass slid into the down-dip support area, while the twin system displayed that the support tilted in the down-dip direction by approximately 4.25°. As the hydraulic support exhibited a continuous tilting tendency, its real-time tilting posture within the physical space was simultaneously rendered in the system interface. The digital twin system subsequently issued a hydraulic support tilt warning to alert operators for intervention. Attitude change of supports in steeply dipping working face is shown in Fig.6.
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