Title | Systematic design of a sawtooth period feedback controller using a Kadomtsev-Porcelli sawtooth model |
Publication Type | Journal Article |
Year of Publication | 2011 |
Authors | G. Witvoet, MR de Baar, E. Westerhof, M. Steinbuch, N.J Doelman |
Journal | Nuclear Fusion |
Volume | 51 |
Issue | 7 |
Pagination | 073024 |
Date Published | Jul |
Type of Article | Article |
ISBN Number | 0029-5515 |
Keywords | CONFINEMENT, CURRENT DRIVE, DISCHARGES, JET |
Abstract | A systematic methodology for structured design of feedback controllers for the sawtooth period is presented, based on dedicated identification of the sawtooth dynamics. Therefore, a combined Kadomtsev-Porcelli model of a sawtoothing plasma actuated by an electron cyclotron current drive system has been set-up. This is used to derive the linearized input-output relations (transfer functions) from the varying deposition location of the electron cyclotron waves (ECW) to the sawtooth period. These transfer functions are derived around a large collection of operating points. Assessment of these control-relevant transfer functions shows that a sawtooth period controller requires an integral (I) action to guarantee closed-loop stability with zero steady-state error. Additional proportional-integral (PI) action can be applied to further increase the closed-loop performance. The parameters of both the I and PII controllers have been optimized in terms of stability, performance and robustness. Moreover, the effect of the mechanical ECW launcher on the closed-loop performance is studied for realistic cases. It is shown that the launcher dynamics seriously affects the achievable closed-loop performance in present-day experiments. |
DOI | 10.1088/0029-5515/51/7/073024 |
Division | FP |
Department | TP |
PID | 4526a168564ccb214ff00f1e5d0f9326 |
Alternate Title | Nucl. Fusion |
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