This Faculty Early Career Development (CAREER)research proposes to project leverages the development of a relative breakthrough in control-oriented modeling of vapor compression systems, which has been recently developed by the PI and his colleagues with close industrial collaboration. This novel modeling technique gives a low order dynamic model of a typical cycle that still retains physical system characteristics and enables the development of model-based controllers that are more universal, adaptable, and robust to changes in environmental conditions. This modeling paradigm will be applied to both subcritical and transcritical air conditioning systems, and utilized to develop model-based control strategies and diagnostic algorithms. A dual Youla parameter based interpolation framework is proposed for the formation of gain scheduled control and fault detection strategies. This approach permits interpolation between individually tuned controllers while ensuring stable transitions. Custom simulation tools will be used to provide a virtual environment for initial testing of control concepts, while experimental tests will complement the simulation studies in the evaluation of the proposed approaches.
This project proposes to apply a novel dynamic modeling paradigm to vapor compression cycle systems, while developing advanced model based control and diagnostic algorithms appropriate to the nonlinear, coupled dynamics of these systems. Particular attention will be given to transcritical CO2 based systems that are an attractive alternative to current air conditioning and refrigeration systems due to lower environmental impact. Nonlinear control strategies are proposed to maximize system efficiency while simultaneously satisfying changing demands for cooling capacity. Additionally, diagnostic algorithms will be employed to identify soft system faults that precede catastrophic system failure. The proposed work has broad application in automotive, aerospace, and residential energy industries, and the potential for dramatic economic and environmental improvements by significantly reducing energy usage, component failure, and the negative impacts of Hydrofluorocarbon (HFC) refrigerants in terms of global warming. Integrated with the research efforts is an educational initiative that seeks to increase minority participation in undergraduate research experiences (REUs). A combination of industry REUs, internships, and student-led short courses will accomplish dual duties of human capital development and technology transfer. Concurrently, the PI will work with local administration to improve minority participation in existing departmental REU programs.
This project resulted in the creation of essential tools for improving the operation and efficiency of air conditioning and refrigeration systems. These systems exhibit nonlinear, coupled dynamic behavior and require correspondingly advanced control strategies to achieve maximum efficiencies while not sacrificing human comfort. The first key outcome of this project is a set of simulation tools capable of predicting system behavior under changing conditions. Using these tools advanced control and optimization algorithms were created and tested. These algorithms were required to regulate critical system outputs and maximize system efficiency despite system nonlinearities and the coupled dynamics of different system components. Predictive control algorithms proved particularly effective. Beyond the control of basic operation, diagnostic algorithms were employed to identify soft system faults that precede catastrophic system failure. After testing in the virtual simulation environment, the control strategies were tested using a variety of actual air conditioning and refrigeration systems. Particular attention was given to transcritical CO2 based systems that are an attractive alternative to current air conditioning and refrigeration systems due to lower environmental impact. This work has broad application in automotive, aerospace, and residential energy industries, and the potential for dramatic economic and environmental improvements by reducing energy usage, component failure, and the negative impacts of Hydrofluorocarbon (HFC) refrigerants in terms of global warming. Integrated with the research efforts is an educational initiative that seeks to increase minority participation in undergraduate research experiences (REUs). A combination of industry-reviewed REUs and internships were used to directly train students and prepare them for careers in the energy industry. In summary, the project has resulted in a set of tools that comprise an integrated solution for vapor compression system operation, including modeling, simulation, actuator control, supervisory control, and fault detection. The technological innovations have a direct impact on society through more efficient operation of air conditioning and refrigeration systems. The reduction in energy, and corresponding reduction in energy production emissions directly affects individuals, though deliberately in ways that are noticed by the public, as they are intended to maintain, if not improve human comfort.
