Fixed-point Based Hierarchical MPC Control Design For a Cryogenic Refrigerator
For industrial control of cryogenic refrigerators, this framework addresses the need for flexible, modular control architectures that can handle destabilizing interconnections and enable operator handover.
The paper proposes a hierarchical MPC framework for cryogenic refrigerators that handles destabilizing interconnections and allows changing overall system behavior by adjusting only coordinator parameters, without modifying local controllers. The framework is validated on a cryogenic refrigerator combining Joule-Thompson and Brayton cycles.
In this paper, a simple and general hierarchical control framework is proposed and validated through the interconnection of the Joule-Thompson and the Brayton cycle stages of a cryogenic refrigerator. The proposed framework enables to handle the case of destabilizing interconnections through state and/or control signals (which is the case of the cryogenic refrigerator example). Moreover, it offers the possibility to simply change the behavior of the overall system (depending on the context) by only changing the coordinator problem's parameters without changing the set of local controllers used by subsystems which is a common industrial requirement regarding industrial control architectures. Finally, the proposed scheme enables a smooth operator handover on a specific subsystem and/or actuator.