Managing the complexity of plasma physics in control systems engineering

The magnetized nuclear fusion plasma is a non-linear dynamic system with limits and constraints. It requires a sophisticated plasma control system with a wide variety of functions and components to ensure optimal and safe performance. A graph-based modelling framework is proposed for the integrated development of physics models, plasma scenarios and control systems. The framework contains actuators and sensors, continuous plasma processes and variables, discrete plasma states and events, and requirements. Most importantly, it defines the couplings between these elements. A Dependency Structure Matrix (DSM), a technique to represent and organize complex graphs, analyses these couplings to reveal a potential global system layout. The framework is demonstrated for ITER, resulting in a fully traceable graph model. The DSM suggests that the system can be organized into five distinct groups: Heating and current drive, magnetic configuration, burn dynamics, transport and exhaust, and plasma–wall interaction. Each group consists of actuators, sensors and physics. All couplings between groups are made apparent in the DSM. Although ITER features specific actuators and sensors, these groups appear common for magnetically confined fusion devices.