Backstepping Control of the Current Profile in the DIII-D Tokamak
M. D. Boyer, J. Barton, E. Schuster, M. L. Walker and D. A. Humphreys
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Salt Lake City, Utah, USA, November 14-18, 2011
Abstract
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Control of the spatial profile of the plasma current in tokamaks has
been demonstrated to be a key condition for advanced scenarios with
improved confinement and steady-state operation. Non-model-based
controllers tested at DIII-D have shown limitations, motivating the
design of model-based controllers that account for the dynamics of the
q profile. In this work, we utilize a control-oriented model of the
current profile evolution in DIII-D to design a backstepping boundary
control law for regulating the current profile around a desired
feed-forward trajectory. The control scheme makes use of the total
plasma current, total power, and line averaged density as actuators.
A simulation study is done to test the control law against
uncertainties in the model parameters and initial conditions, as well
as input disturbances. Finally, the implementation of the controller
in the DIII-D plasma control system is discussed and experimental
results are presented.