High Energy Accelerator Research Organization;
1-1 Oho;
Tsukuba;
Ibaraki 305-0801;
Japan;
The Graduate University for Advanced Studies;
Hayama;
Kanagawa 240-0193;
Japan;
Institute of Modern Physics;
Chinese Academy of Sciences;
Lanzhou 730000;
China;
Low-level radio frequency; Disturbance observer; Iterative learning control;