Enhancing SIRIUS fast orbit feedback actuators using IIR filters

Studies with the SIRIUS Fast Orbit Feedback (FOFB) system revealed that its power supplies were operating near saturation, which limited the achievable FOFB controller gain. Further analysis identified avoidable noise sources in Beam Position Monitors (BPMs) and adjacent magnet power supplies as the main causes of this behavior. This paper presents a model-based approach employing Infinite Impulse Response (IIR) filters to attenuate the effects of such noise sources on the control effort as well as equalization of actuators' dynamic responses without any hardware modifications. The proposed method effectively reduces actuator effort and provides response equalization adding negligible phase shift in the band of interest, resulting in higher FOFB loop gain and improved rejection of orbit disturbances up to 1 kHz.