Development of iterative learning and disturbance observer-based LLRF control system for international linear collider

This paper shows the development of a iterative learning control (ILC) combined with a disturbance observer (DOB)-based control for the digital low-level radio-frequency (LLRF) system of international linear collider (ILC) project. The motivation of this study is to compensate for the repetitive (or predictable) and unpredictable disturbances in the radio-frequency (RF) system such as beam loading, Lorentz force detuning (LFD) and microphonics. Results in a cavity simulator-based test bench demonstrate the possibility of the presented control approach. We have a plan to further generalize this approach to LLRF systems at superconducting test facility (STF) and future ILC project. (author)