Control system optimization techniques for real-time applications in fusion plasmas: the RFX-mod experience

A series of techniques are presented that have been developed to optimize the output magnetic field of the feedback control system on the RFX-mod reversed field pinch device. With the aim of minimizing the harmonic distortion and correcting localized error fields, these methods should be lightweight for real-time application and effective in improving the performance of a system that is routinely used for active control of magneto- hydro-dynamic plasma instabilities. The implementation of sim- ple, linear algebra based, real-time optimization methods will be described along with proof of the sought beneficial effects. Focus of the work is set on a spurious harmonics reduction technique based on the decoupling of sensors and actuators, a description of its derivation will be given together with the implementation in the control loop. A similar procedure for the compensation of faulted actuators will also be mentioned.