Current profile and normalized beta control via feedback linearization and Lyapunov techniques
Andres Pajares and Eugenio Schuster
Nuclear Fusion 61 (2021) 036006 (20pp)
Abstract
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Simultaneous control of the current profile and normalized plasma beta
is an essential control problem in the development of advanced tokamak
scenarios. However, this control problem is especially challenging due
to the nonlinear nature of the current, heat, and particle transport
dynamics, as well as the difficulty to understand and accurately model
such processes. In this work, a nonlinear, robust, model-based controller
for the simultaneous regulation of the current profile and normalized
beta has been designed using feedback linearization and Lyapunov redesign
techniques. Feedback linearization avoids approximate linearization of
the plasma dynamics, retaining the original physics content of the model.
Moreover, the use of Lyapunov redesign techniques makes the controller
robust against the uncertainties arising during the modeling process.
The controller’s performance in the presence of unknown dynamics is
tested in nonlinear, one-dimensional simulations using the Control
Oriented Transport SIMulator (COTSIM) code, which employs plasma models
that are significantly more complex than those employed for control
synthesis.