Kim, H. Hyun, M.O. Jang, H. Kim, M.S. Kim, Y. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-215-8 10.18429/JACoW-LINAC2022-THPOPA18 English 778-780 controls cavity LLRF EPICS cryomodule Contribution to a conference proceedings 2022 2022-09 https://doi.org/10.18429/JACoW-LINAC2022-THPOPA18 https://jacow.org/linac2022/papers/thpopa18.pdf We propose a tuner control system for low-energy superconducting linac at RAON. The frequency error of the superconducting cavities must be smaller than a few of Hz to operate in beam acceleration mode. To minimize the freuqency error as much as possible, the error is calculated in the low-level RF(LLRF), and the proposed tuner control system changes the superconducting cavity frequency by using a mechanical tuner and a motor attached to the cavity directly. This control system deals with not only the initial frequency error of the cavity but also the frequency drift of the cavity induced by external disturbance such as the slow fluctuation helium pressure automatically. In addition, an automatic proportional gain calibration technique is also proposed. In this paper, the detailed operation and techniques will be described.