Plasma Position and Elongation Regulation at FTU Using Dynamic Input Allocation

In this paper we employ and extend the dynamic allocation theory first presented in a recent work by the last author, L. Zuccarian, to guarantee asymptotic tracking of a prescribed elongation of the plasma cross section in the Frascati Tokamak Upgrade (FTU). This task is hard to accomplish because it can only be achieved using the so-called poloidal coil, a high bandwidth actuator needed to perform high performance horizontal plasma position regulation. Another actuator, the poloidal coil, could be used for this positioning task, but its bandwidth is insufficient. Using dynamic input allocation it is possible to hierarchically achieve the two goals above by way of a nonlinear scheme suitably exploiting the two actuators: the high priority (fast) goal is the horizontal position regulation task, while the low priority (slow) goal is the elongation regulation. We present theoretical results supporting the proposed scheme, as well as simulations and experiments showing the effectiveness of the proposed solution.