Revisiting a fixed-point hierarchical control design for cryogenic refrigerators under constraints, nonlinearities and real-time considerations

This paper presents an extension of a recently proposed hierarchical control framework applied to linearization-based unconstrained control of a cryogenic refrigerator. The extension concerns the validation of the framework in the presence of both nonlinear models and constraints. It is also shown that real-time handling of these features requires a specific complexity reduction technique. This technique performs the distribution of the optimization process over cyclically changed decision variables aiming at limiting the number of iterations per updating period. Numerical simulations are proposed in order to show the impact of the parameters choices and to assess the real-time implementability of the proposed framework.