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Description
In the process of isothermal demagnetization of the adiabatic demagnetization refrigerator, the proportional–integral–derivative controller (PID controller) is often used to control the temperature stability and achieve the optimal response by adjusting the control parameters (proportional term Kp, integral term Ki, derivative term Kd). However, the manual tuning of the PID control parameters in experiments is very time-consuming and the tuning efficiency is rather poor. A numerical simulation model is thus very useful to guide the selection of PID parameters. In this paper, the third stage CPA salt pill of a three-stage adiabatic demagnetization refrigerator is taken as an example, and the adiabatic demagnetization process and the ensuing isothermal demagnetization process at 100mK are simulated using COMSOL software. By integrating the PID control model, the simulation results show how the dynamic response varies with the control parameters Kp, Ki, and Kd, which provides a valuable reference for the selection of PID control parameters in the experiments. Some experimental results and their comparison with simulation results are also introduced.
