Distributed controller design for a free-electron laser

In this paper, a distributed controller design is proposed for a linear accelerator such as the European XFEL. The linear accelerator is modeled as a chain of 25 subsystems, each representing one of the 25 radio frequency stations which form the XFEL plant. A distributed control scheme is presented that exploits the interaction between neighboring stations. A local controller is attached to each station; these local controllers exchange information with neighboring controllers, in order to reduce the error in beam energy at a given station by coordinated control action across neighboring stations. A recently developed framework for distributed control of spatially interconnected systems is employed to design the distributed controllers in a H-infinity mixed sensitivity approach. Simulation studies indicate a significant improvement in performance when the proposed control scheme is applied.