Model-based feed-forward control for time-varying systems with an example for SRF cavities

Abstract

To derive feed-forward signals the impulse response matrix has to be inverted. While for time-invariant systems this matrix has a Toeplitz structure, this is not the case for time-variant systems. Thus, the derivation of the inverse scales cubically with the length of the signal horizon. This paper presents an efficient way to calculate the inverse impulse response matrix based on the description as linear fractional transformation. With this the calculation effort scales only linearly with the horizon. The feed-forward signal generation is applied in this paper for superconducting accelerating structures. The superconducting accelerating cavities are operated in pulsed mode. Each cavity is fed by a 1.3GHz radio frequency signal with high power. Model-based feed-forward control is essential here to relief the feedback controller and with this to minimize the power consumption and therefore heating of different components. To derive a model-based feed-forward signal, first, a reasonable reference signal is to be chosen, which is done here based on physical properties of the cavities, then the efficient inversion of the impulse response matrix is applied. Experimentally results from the European X-ray free-electron laser are presented.

Sven Pfeiffer et al., Model-based feed-forward control for time-varying systems with an example for SRF cavities, IFAC-PapersOnLine