Robust vertical control of ITER plasmas via static output feedback

It is now well known that in order to reach plasma burning conditions it is needed to operate with high elongated unstable plasmas. These plasmas can be hardly stabilized using Poloidal Field coils placed outside the tokamak vessel, due to the shielding effects of the conducting structures. Therefore for the ITER tokamak it has been proposed to install in-vessel coils for the plasma vertical stabilization. In this paper we design a plasma vertical controller which makes use of both in-vessel and ex-vessel coils for the stabilization of ITER plasmas in various operating conditions. Besides guaranteeing robust stabilization of ITER plasmas, the controller also takes into account constraints on the current flowing in the in-vessel coils; such constraints are required to operate these coils safely. Furthermore the proposed controller is designed as a static-output feedback, where only three gains have to be specified. A sufficient condition is provided to design the controller by solving a Bilinear Matrix Inequalities feasibility problem. The effectiveness of the proposed approach is shown in simulation on a number of ITER plasma configurations.