Surrogate model-based cognitive digital twin for smart remote maintenance of fusion reactor: modeling and implementation

A remote maintenance robot system (RMRS) plays a critical role in safeguarding the fusion energy experimental device's security and stability. State-of-the-art intelligent technology such as cognitive digital twins (CDTs) is widely considered capable of improving complex equipment's performance and reducing management burden using a visualized system. However, the CDT virtual space cannot mirror the RMRS which is a kind of flexible multi-body system in real-time and with high fidelity. Therefore, we propose a CDT modeling method based on a surrogate model for the RMRS. Firstly, model-based system engineering is leveraged to build a structural modular architecture, which can decrease the modeling complexity of CDT and increase the modeling efficiency. Then, the surrogate models are self-learning within the CDT physical space, which reconstructs the RMRS's real-time dynamic performances and endows CDT with cognitive capabilities. Finally, after integrating the CDT system, a smart decision-making plan that compensates for the operation error is generated for RMRS's accurate control. We take a China Fusion Engineering Test Reactor (CFETR) multi-purpose overload robot (CMOR) as an example to demonstrate the implementation process. According to the results, CDT can achieve real-time (230 ms time delay) high-fidelity (5 mm control error) monitoring and accurate control, and CMOR conducts smart maintenance based on the simulation results. This method improves the efficiency of remote maintenance and provides solutions for high-duty cycle time of CFETR, it can also be applied to other tokamak fusion energy devices.