Design And Analysis Of High Performance Feedback Controller Of ADS's Superconducting Cavity

In accelerator driven sub-critical system's(ADS)superconducting linac,superconducting half-wavelength resonator is a kind of cavity used to accelerate protons.The function of LLRF control system is to provide a modulated RF signal for the cavity.By improving the control accuracy and anti-interference ability of the LLRF system,the superconducting cavity can meet the frequency,amplitude and phase requirements of superconducting linac in complex electromagnetic environment,so as to achieve the goal of accelerating the high-quality proton beams.Firstly,this paper analyzed the correlation LLRF technology and given the linear transfer function's model of superconducting cavity.Based on this model,we designed and analyzed a simple PI controller and a lead-lag compensation controller with better control performance.This paper designs a parameter tuning method for the PI controller of ADS' superconducting cavity,this method is successfully applied in LLRF system of ADS' superconducting linear accelerator to improve the performance of existing PI controller.In view of the superconducting cavity need higher frequency stability,this paper analyzed the control logic and stability of the minimum orthogonal component tuning method,and tested the stability and actual performance of the new tuning algorithm's controller.The experimental results and theoretical analysis prove that the stability of the tuning system is better than that of the previous generation system.Through the analysis of I loop and Q loop under the condition of mistuning,it is concluded that the single input single output(SISO)controller can not meet the control performance requirements under the condition of mistuning because the superconducting cavity bandwidth is very narrow.A multiple input multiple output(MIMO)controller which is more suitable for superconducting cavity is designed by using state-space,which improves the controller performance under detuning conditions.The research work in this paper provides theoretical guidance for the research and development of ADS' digital LLRF controller,carry out preliminary research for the improvement of the existing low-level system,and explore a feasible technical route.