Safety Factor Profile Control in Tokamaks via Feedback Linearization
55th IEEE Conference on Decision and Control
Las Vegas, Nevada, USA, December 12-14, 2016
| Abstract |
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The tokamak is a torus-shaped machine in which a reactant plasma is confined using magnetic fields for the purpose of generating energy from nuclear fusion reactions. In order to be commercially competitive, a tokamak needs to operate for long periods of time at high-performance operating points. Those high-performance scenarios are characterized by a steady-state, stable plasma operation, which is closely related to a property of the plasma that is known as the safety factor, q. Therefore, control of the q profile is one of the crucial aspects to the success of tokamaks. Significant research has been carried out to find control algorithms for the q profile in tokamaks. Most of that previous work makes use of approximate lineariza- tion and linear control techniques. In the present work, we propose a nonlinear model-based controller for the regulation of the q profile using feedback linearization. This nonlinear control approach may be applicable to a greater range of operating conditions, and may be able to reject larger perturbations than previous linear controllers. Moreover, this control design combines the advantages of both nonlinear and linear control techniques, because the nonlinear model is exactly linearized by making use of an appropriate input transformation. The effectiveness of the controller is demonstrated via a simulation study in which the controller is tested in a DIII-D scenario.