A mixed decoupling/decentralized controller for coil current control in tokamaks

In this paper we propose a control scheme which consists in a trade-off between a decoupling controller and a decentralized control action. The motivation for this design technique arises from experimental applications wherein input-output decoupling is a soft requirement (namely, it is sufficient that it is almost guaranteed) and wherein it is highly desirable that the control action is predominantly decentralized. A relevant example lies in the coil current control in tokamaks, where several coils are jointly employed to regulate certain plasma parameters (such as shape control). A possible solution for these situations is to use the combined control schemes proposed here. We illustrate this fact on the coil current control of the Joint European Torus (JET) located in Culham, UK