Robust-based control design for the beam injector facility

This paper develops a robust control design for the electron beam injector facility in the Swiss Free Electron Laser (SwissFEL) machine. The relationship between radio frequency parameters and the electron beam quantities are commonly modeled as a static response matrix. Typically, the response matrix has a high condition number which makes inverse-based control approaches very sensitive to gain uncertainties. This problem is usually addressed by singular value decomposition to invert the response matrix, followed by filtering the singular values, so that the inverse-based control performs better in regards to uncertainties in the model. In this paper, we study a more structured robust MIMO control design that can be applied to all systems that have static response matrix (such as “orbit correction” system). To the best knowledge of the authors, it is the first time that such a robust control scheme is implemented on an accelerator machine. The designed controller has been successfully tested at the SwissFEL injector test facility and the results are compared to the inverse-based control design.