Research On Feedback Control Of Superconducting Accelerometer

Superconducting gravity instruments prevail over traditional instruments in many aspects,for example,extremely low noise level,small drift,good stability etc.The key to the superconducting gravimeter and the superconducting gravity gradiometer is the superconducting accelerometer(SA).The core of the SA is a magnetic spring vibrator constructed by a proof mass,a suspension plane coil,a detection plane coil,and parietal curved coils which maintain the motion attitude of the proof mass.Firstly,as for the sidewall coil,it currently has a limited ability to maintain the stability of the proof mass in the open-loop control state,leading to a serious problem of cross-coupling of the system.Secondly,as for sensitive axial direction of the proof mass,the non-linear effect is relatively large because of the open-loop detection state.And from the perspective of weak signal detection,it can improve system’s SNR to apply closed-loop control.In summary,the study of closed-loop control of SA is of great significance.In view of the fact that closed-loop control in the horizontal direction involving multiple pairs of control loops is more difficult to achieve,the closed-loop control starts from the sensitive axial of the mass.The realization process is to output SQUID voltage through the feedback network and to drive the final controlling element of the suspension plane coil in order to achieve the proof mass’ s closed-loop control.For one thing,in the closed-loop control research,the mathematical model of the related physical system is carried out.In the next place,the feasibility of the proportional control is explored by the relevant simulation analysis and experiment with the starting points of the simple structure and convenient adjust.According to the problem in the proportional control experiment,the further research is carried out with the PID,and accordingly the circuit board including the first-order active high-pass filter,the PID controller and the voltage converter is built and tested.Based on the SA,the proportional control experiment and PD and PID control experiment were completed.Above on,experiment shows that proportional feedback control can not achieve significant closed-loop control effect.Moreover,the open-loop transfer function of the system is measured by the external excitation method,which provides some suggestions for the further study.And,the further experiment shows the control of PD has the control effect.While the PID control effect is limited by the system failure and has not been confirmed.