Antiwindup scheme for plasma shape control with rate and magnitude actuation constraints in the DIII-D tokamak

The advanced tokamak (AT) operating mode is the principal focus of the DIII-D tokamak. In order to be prepared for the higher control demands arising in AT scenarios, current efforts are focused on the development of an integrated multivariable controller to take into account the highly coupled influences of equilibrium shape, profile, and stability control. The first step of this project is the design of the shape and vertical controller which will be integrated in the future with control of plasma profiles. The time-scale properties of the system allow the separation of the vertical stabilization problem, approached by the authors in prior work, from the shape control problem, which is the focus of this paper. Ensured the vertical stability of the plasma, in this work we implement an anti-windup compensator that keeps the given nominal shape controller well-behaved in the presence of rate and magnitude constraints at the input of the nonlinear plant. The anti-windup synthesis problem is to find a nonlinear modification of the nominal linear controller that prevents undesirable oscillations but leaves the nominal closed loop unmodified when there is no input saturation.