A. Mele

A MIMO architecture for integrated control of plasma shape and flux expansion for the EAST tokamak

This paper deals with the magnetic control system of the EAST tokamak, i.e. with the system in charge of controlling the position and the shape of the plasma column into the vacuum vessel, as well as the current that flows into it. A multi-input multi-output architecture is proposed in order to achieve integrated control of both plasma boundary and flux expansion in the scrape-off layer. The proposed architecture is based on an XSC-like control approach [1]. In order to show the effectiveness of the proposed approach, a set of Matlab/Simulink® tools that allow to reproduce in simulation the EAST experiments is used. This simulation environment is validated against the experiments, and is then exploited to design and validate the proposed MIMO controller.

New conditions for annular finite-time stability of linear systems

In this paper we investigate the annular finite-time stability (AFTS) problem for linear systems. A system is said to be annular finite-time stable if the norm of the system state remains within an upper and lower treshold for a given finite interval of time. Two necessary and sufficient conditions are provided for AFTS, the former requiring the solution of a differential Lyapunov equation (DLE), the latter involving an optimization feasibility problem constrained by differential linear matrix inequalities (DLMIs). We show that the DLE-based condition is more efficient from the computational point of view; however the DLMI-based condition is the starting point to investigate the design problem. To this regard a necessary and sufficient condition for the existence of a state feedback controller which renders the closed loop annular finite-time stable is provided. A numerical example illustrates the improvement of the proposed approach with respect to those existing literature.

On plasma vertical stabilization at EAST tokamak

In this paper we discuss the problem of plasma vertical stabilization at the EAST tokamak. By exploiting a plasma/circuit linearized model, we show that the plant cannot be strongly stabilized by using the in-vessel coils and a singleinput-single-output controller that feeds back only the plasma vertical speed żp (i.e. without integral action on żp). Moreover, a stable multi-input-single-output controller that stabilizes the plant without the need of feeding back the plasma vertical position is presented. The proposed solution permits to achieve stabilization of the EAST plant without coupling the vertical stabilization system with the plasma shape controller. Such decoupling is a key requirement to enable advanced design approaches for plasma shape controller.