Advanced RWM Feedback with Truncated Balanced Realization

Stabilizing the resistive wall mode (RWM) requires advanced control techniques. State-space methods such as truncated balanced realization have shown promise in VALEN simulations [1]. Advanced control theory is particularly relevant to large tokamaks such as ITER. In this presentation, we make use of a balanced realization, which highlights the plasma modes that are simultaneously controllable and observable, and optimizes the efficiency of the controller. Furthermore, the {\it truncated} balanced realization approximates the system with a reduced model in order to minimize the computational load, a critical factor in real-time control of large systems. Since finding the optimal truncation remains an open problem [2], it is essential to compare the effectiveness of different truncation models with the full balanced realization, as well as other control schemes. We present theoretical and simulation-based predictions of the different feedback models, soon to be implemented in real-time using a GPU computer at HBT-EP. \\[4pt] [1] {\sc Katsuro-Hopkins, O., et al.} 2007 {\em Nucl. Fusion \/} {\bf 47}, 1157. \newline [2] {\sc Dullerud, G.E. \& Paganini, F.} {\em A Course in Robust Control Theory \/}. Springer: 2000.