Fixed-point Based Hierarchical MPC Control Design For a Cryogenic Refrigerator
In this paper, a simple, general and scalable hierarchical control framework is proposed and validated through the interconnection of the Joule-Thomson 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. In this paper, a simple, general and scalable hierarchical control framework is proposed and validated through the interconnection of the Joule-Thomson 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.
Reference
M. Alamir, P. Bonnay, F. Bonne and V. V. Trinh. Fixed-point based hierarchical MPC control design for a cryogenic refrigerator. Journal of Process Control, To appear 2017-2018
Experimental investgation of control updating period monitoring in industrial PLC-Based fast MPC: Application to the constrained control of a cryogenic refrigerator
In this paper, a complete industrial validation of a recently published scheme for on-line adaptation of the control updating period in Model Predictive Control is proposed. The industrial process that serves in the validation is a cryogenic refrigerator that is used to cool the supra-conductors involved in particle accelerators or experimental nuclear reactors. Two recently predicted features are validated: the first states that it is sometimes better to use less efficient (per iteration) optimizer if the lack of efficiency is over-compensated by an increase in the updating control frequency. The second is that for a given solver, it is worth monitoring the control updating period based on the on-line measured behavior of the cost function.
Reference
F. Bonne, M. Alamir and P. Bonnay. Experimental investigation of control updating period monitoring in industrial PLC-based fast MPC: Application to the constrained control of a cryogenic refrigerator. Journal of control theory and technology, Vol. 15, Number 2, pages 92-108, 2017.
Distributed cooperative control framework of a cryogenic system
In this paper a recently proposed distributed control framework is applied to the model of a real-life cryogenic plant. The main advantage of the distributed control architecture is to allow for a modular design of the control algorithms. The paper shows that the cooperative nature of the solution enables an initial decentralized design to be improved by properly choosing the relative priority assignment between subsystems.
Reference
H. Ding, M. Alamir, F. Bonne, A. Hably and P. Bonnay. Distributed cooperative control framework of a cryogenic system. Proceedings of IEEE International Conference on Industrial Technology, Sevilla, Spain, 2015. [download]
Nonlinear observer of the thermal loads applied to the helium bath of a cryogenic Joule–Thompson cycle
In this paper, a nonlinear observer of the thermal loads applied to the helium bath of a cryogenic refrigerator is proposed. The thermal loads represent a time-varying thermal disturbance expected to take place in future tokamaks refrigerators such as those used in the cooling systems for the International Thermonuclear Experimental Reactor (ITER) or the Japan Torus-60 Super Advanced (JT-60SA). The proposed observer can serve as a monitoring tool for cryogenic operators and/or in observer-based advanced control strategies. The observer is based on a part of the nonlinear model of the refrigerator. The paper details how the physical model of the Joule–Thompson cycle is obtained and the structure of the observer and validates its performance using experimental data.
Reference
F. Bonne, M. Alamir and P. Bonnay. Nonlinear observers of the thermal loads applied to the helium bath of a cryogenic Joule-Thompson Cycle. Journal of Process Control (Elsevier), Vol 24, Issue 3, pages 73-80, (2014). [download]
Multivariable control architecture for a cryogenic test facility under high pulsed loads: Model derivation, control design and experimental validation
In this paper, a complete framework including modeling, identification and control design for an exper- imental Helium refrigerator facility submitted to high pulsed loads is proposed. Such high pulsed loads are expected to take place in future Tokamaks such as the International Thermonuclear Experimental Reactor (ITER) or the Japan Torus-60 Super Advanced (JT60SA). The control architecture is split into two loops: The first concerns the warm compression system while the second manages the remaining part of the refrigerator (often called the cold box) in which the set-points of the first loop are viewed as manipulated variables. The efficiency of the proposed solution is experimentally assessed under several scenarios including those involving realistic high pulsed loads.
Reference
F. Clavel, M. Alamir, P. Bonnay, A. Barraud, G. Bornard and C. Deschildre. Multivariable Control Architecture For a Cryogenic Test Facility Under High Pulsed Loads: Model Derivation, Control Design and Experimental Validation. Journal of Process Control. Vol 21. Issue 7, pp. 1030-1039 (2011). [download]
Other publications on cryogenic refrigerators
F. Bonne, M. Alamir, P. Bonnay. Physical Control Oriented Modeling of Large Scale Refrigerators to Synthetize Advanced Control Schemes: Model Design and Validation Against Experimental Data and First Control Results. Cryogenic Engineering Conference and International Cryogenic Materials Conference. CEC/ICMC, Anchorage Alaska, USA, 2013.
F. Bonne, M. Alamir, P. Bonnay and B. Bradu. Model-Based Multivariable Controller For Large Scale Compression Stations: Controller Design and Experimental Validation On the LHC 18KW Cryogenic Helium Refrigerator. Cryogenic Engineering Conference and International Cryogenic Materials Conference. CEC/ICMC, Anchorage Alaska, USA, 2013.
F. Clavel, P. Bonnay, G. Bornard, M. Alamir, A. Barraud and C. Deschildre. An innovative control of a warm compression system for a Helium Refregirator subject to high pulsed loads. Proceedings of the Interenational Cryogenic Engineering Conference (ICEC 23), Wroclaw, Poland, 2010.
