First-principles-driven control of the rotational transform profile in high performance discharges in the DIII-D tokamak

In this work, a first-principles-driven, control-oriented, nonlinear, partial-differential-equation model of the poloidal flux profile evolution is utilized to design a feedback control algorithm to regulate the rotational transform profile in the DIII-D tokamak. The control goal is to regulate the rotational transform profile, which is related to the poloidal flux profile, around a particular target profile. A singular value decomposition of the nominal plasma model at steady state is carried out to decouple the system and identify the most relevant control channels. A mixed sensitivity H_∞ control design problem is formulated to synthesize a stabilizing feedback controller to minimize the reference tracking error with minimal control energy. Simulations based on the first-principles-driven model show that the H_∞ controller is capable of regulating the system around the target i profile in the presence of disturbances. When compared to a previously designed data-driven model-based controller, the proposed first-principles-driven model-based controller shows potential for improving the control performance.