Optimal Closed-Loop Control of the Azimuthal Velocity Profile in HELCAT by ExB Actuation
Z. Ilhan, D. Huxley-Cohen, J. Barry, E. Schuster, M. Gilmore and A. Ware
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Providence, Rhode Island, USA, October 29 - November 2, 2012
Abstract
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The cross-field turbulence-driven particle transport in magnetically
confined plasmas can be reduced by adequate shaping of the azimuthal
flow profile. An open-loop extremum-seeking controller has been
designed earlier to identify radial azimuthal flow profiles associated
with low RMS fluctuations in a magnetized laboratory device (HELCAT).
In this work we propose a model-based feedback controller that can
regulate the radial azimuthal velocity profile around a prescribed
low-fluctuation profile. The governing partial differential equation
for the azimuthal flow is reformulated into a reduced-order, control
oriented model by using truncated Taylor Series expansion. State-space
and linear quadratic control methods are then used to come up with an
optimal, feedback control law that can minimize both the tracking error
and the control energy. Computer simulations reflect the effectiveness
of the proposed controller as a tool to clarify the physics of
laboratory plasmas.