Nonlinear dynamic modeling for control of fusion devices

In this paper the issue of modeling for control design with application to fusion devices is discussed. Given the difficulty to provide analytical solutions to the equations describing the system dynamics, the use of numerical tools for evaluating different control architectures is required. Although standard tools for computer aided control system design (CACSD) can be usefully employed for both analyzing the fusion device dynamics and designing control laws, dedicated tools are required to adequately describe the complex interactions among the different system components. In this paper the use of the nonlinear equilibrium code MAXFEA to support the control design task is described. MAXFEA is a finite element code able to produce quite good approximations of the plasma boundary location and shape, together with internal distributions of current and magnetic fields, and other plasma features. The code provides the simulation of the plasma dynamics, while all the other elements (diagnostics, controller, actuators) in the control loop system can be modeled independently and integrated in the code as external modules, thus making it a candidate tool for software-in-the-loop solutions.