Naturally-switching velocity and admittance control (NSVAC) for bilateral teleoperation in CFETR remote handling

The bilateral control method serves as the primary means of interaction for remote handling (RH) in CFETR, effectively enhancing operations performance during interaction with the environment. However, traditional control methods excessively rely on the system's inherent performance and the operator skill, making it necessary to introduce the admittance control strategy to further enhance operational safety. This paper adopts the Naturally-Switching Velocity and Admittance Control (NSVAC) method, ensuring operational safety through a combination of velocity and admittance control. In this study, an analysis was conducted on the variations in interaction forces at different positions during the RH process. When the force is below a predetermined value, velocity control was applied; otherwise, admittance control was used. In order to naturally and smooth switching between the two modes, the control law and switch function were provided. Subsequently, the system behavior using NSVAC is analyzed and the stability analysis based on passivity control theory is conducted. Finally, the effectiveness of the NSVAC method is validated through simulation and experiments. The results strongly indicate that NSVAC not only meets practical operational requirements but also effectively guarantees the safety of operations throughout the process.