Stability analysis and model-based control in EXTRAP-T2R with time-delay compensation

Erik Olofsson (1) , Emmanuel Witrant (2) , Corentin Briat (2) , Silviu-Iulian Niculescu (3) , Per Brunsell (1)

1 Alvfèn lab
2 GIPSA-SLR - GIPSA - Systèmes linéaires et robustesse
3 L2S - Laboratoire des signaux et systèmes

In this paper, we investigate the stability problems and control issues that occur in a reversed-field pinch (RFP) device, EXTRAP-T2R (T2R), used for research in fusion plasma physics and general plasma (ionized gas) dynamics. The plant exhibits, among other things, magnetohydrodynamic instabilities known as resistive-wall modes (RWMs), growing on a time-scale set by a surrounding non-perfectly conducting shell.We propose a novel model that takes into account experimental constraints, such as the actuators dynamics and control latencies, which lead to a multivariable time-delay model of the system. The openloop field-error characteristics are estimated and a stability analysis of the resulting closed-loop delay differential equation (DDE) emphasizes the importance of the delay effects. We then design a structurally constrained optimal PID controller by direct eigenvalue optimization (DEO) of this DDE. The presented results are substantially based on and compared with experimental data.

Domaines: Physique des plasmas [physics.plasm-ph]; Automatique / Robotique

Erik Olofsson, Emmanuel Witrant, Corentin Briat, Silviu-Iulian Niculescu, Per Brunsell. Stability analysis and model-based control in EXTRAP-T2R with time-delay compensation. CDC 2008 - 47th IEEE Conference on Decision and Control, Dec 2008, Cancun, Mexico. ⟨hal-00329874⟩