ABSTRACT As nuclear fusion progresses from experimental research toward integrated power plant design, plasma control systems must operate within increasingly complex architectural, operational, and lifecycle constraints. This paper examines plasma vertical and radial position control from a model‐based systems engineering perspective, aiming to complement established control design practices by making system boundaries, interfaces, and dependencies explicit. Rather than proposing new control laws, the study focuses on how sensing, estimation, actuation, and constraint handling are organised and coordinated within the plasma position‐control function. Using SysML with the MagicGrid framework, we use model‐based systems engineering tools to make explicit the traceability from stakeholder value propositions and plant‐level operating objectives to tokamak subsystem functions and the plasma position‐control capability. This decomposition exposes dependencies across sensing, reconstruction, actuation, power delivery, and protection that can affect integration, extensibility, and fault tolerance. The analysis highlights how assumptions and interface couplings that are often implicit in conventional control workflows become increasingly important at system scale. The proposed framework is intended as a conceptual and organizational aid for fusion power‐plant programmes such as STEP Fusion (Spherical Tokamak for Energy Production), where physics assumptions, control requirements, subsystem interfaces, and plant architectures must be refined together under design uncertainty.
Mitra et al. (Mon,) studied this question.