Model based controller design approach for the TCV tokamak

In this paper a mixed PID/H∞ discrete-time controller is proposed for the control of the plasma shape and position in a tokamak. This controller is designed to be tested experimentally on the TCV tokamak, using high performance digital hardware. The challenge of the problem lies in the instability of the vertical position, the non-minimum phase characteristics and the non-linearity of the plant. The inner PID loop stabilises the plant, providing adequate stability margins, while the outer-loop H∞ controller provides the decoupling between the five controlled parameters. Simulations carried out using a validated linear model demonstrate a significant improvement of the performance compared with that obtained with an experimentally tuned MIMO controller.