Application of SysML to design of ATCA based LLRF control system

The paper presents the methodology of design of ATCA based LLRF system for XFEL linear accelerators. The LLRF system is used to control RF field in superconducting accelerating cavities regulating amplitude up to 0.03% and phase up to 0.03 deg. It is complex mixed analogue-digital control with latency of order of few tens of nanoseconds. The ATCA architecture was chosen due to high availability and reliability. The system design process is based on systematic and formal approach using SysML language and tools. This modern methodology changes the way of system description from “document centric” to “model centric”. It allows easy communication inside the designers team that is very important in wide international collaboration. In the design process the Use Case description of system functionality was applied. The hierarchical structure and requirements for subsystems was derived from the top level requirements and defined functionality of the system. The functions of various SysML diagrams are presented together with discussion which parts of the system are best described by which diagram type. Both structural and functional views of the system are presented. Since the discussed LLRF system will have distributed architecture the particular effort was put on interfaces description. The SysML tool used in the project was used not only to build SysML model but also allows to estimate project cost using Use Case Points method. This feature is very beneficial in preparation of the project budget.