No description available.

No description available.

No description available.

While modern engineering systems have become increasingly integrated and complex over the years, interest in the application of control techniques which specifically attempt to formulate and solve the control problem in its inherently uncertain environment has been moderate, at best. More specifically, although many control schemes targeted at Heating, Ventilating and Air-Conditioning (HVAC) systems have been reported in the literature, most seem to rely on conventional techniques which assume that a detailed, precise model of the HVAC plant exists, and that the control objectives of the controller are clearly defined. Experience with HVAC systems shows that these assumptions are not always justifiable, and that, in practice, these systems are usually characterized by a lack of detailed design data and a lack of a robust understanding of the processes involved. Motivated by the need to more efficiently control complex, uncertain systems, this thesis focuses on the development and evaluation of a new neuro-fuzzy model-based predictive control scheme, where certain variables used in the optimization remain in the fuzzy domain. The method requires no training data from the actual plant under consideration, since detailed knowledge of the plant is unavailable. Results of the application of the control scheme to the control of thermal comfort in a simulated zone and to the control of the supply air temperature of an air-handling unit in the laboratory are presented. It is concluded that precious resources (as measured by actuator activity, for example) need not be wasted when controlling these systems. In addition, it is also shown that a very precise (and sometimes not necessarily accurate) control value computed at each sample is unnecessary. Rather, by defining the system and its environment in the fuzzy domain, the fuzzy decision algorithms developed here may be employed to get an "acceptable" control performance.

No description available.

Faults that develop in the heat exchanger subsystems in air-conditioning installations can lead to increased energy costs and jeopardise thermal comfort. The sensor and control signals associated with these systems contain potentially valuable information about the condition of the system, and energy management and control systems are able to monitor and store these signals. In practice, the only checks made are to verify set-points are being maintained and that certain critical variables remain within predetermined limits. This approach may allow the detection of certain abrupt or catastrophic faults, but degradation faults often remain undetected until their effects become quite severe. This thesis investigates the appropriateness of using mathematical models to track the development of degradation faults. An approach is developed, which is based on the use of analytical models in conjunction with a recursive parameter estimation algorithm. A subset of the parameters of the models, which are closely related to faults, is estimated recursively. Significant deviations in the values of the estimated parameters from nominal values, which represent `correct operation', are used as an indication that the system has developed a fault. The extent of the deviation from the nominal values is used as an estimate of the degree of fault. This thesis develops the theory and examines the robustness of the parameter estimator using simulation-based testing. Results are also presented from testing the fault detection and diagnosis scheme with data obtained from a simulated air-conditioning system and from a full size test installation.

Thesis (M. Eng. Sc.)--University of Adelaide, Dept. of Chemical Engineering, 1986. / Includes bibliographical references (leaves 276-279).

Thesis (M.Sc.)--Aberdeen University, 2009. / Title from web page (viewed on July 29, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Resumo: Neste estudo são apresentados os resultados de um trabalho realizado em uma bancada de testes, onde se constatou a diferença de potência elétrica de acionamento e do coeficiente de performance no funcionamento de dois diferentes tipos de compressores: um hermético a pistão e outro rotativo do tipo scroll, operando com inversor de frequência. No estudo variou-se a vazão do fluido refrigerante, e consequentemente o efeito frigorífico, por dois procedimentos distintos: restrição da passagem do refrigerante através de uma válvula de estrangulamento, mantendo-se a rotação do compressor a pistão constante, e por meio de variação de rotação do compressor scroll com aplicação de um inversor de frequência, mantendo-se a válvula de estrangulamento em uma posição fixa. Observou-se também a influência do inversor de frequência no controle da vazão de ar do sistema através de um conjunto motor-ventilador axial. Esse controle ora era realizado por uma válvula de controle "DAMPER", ora por meio da rotação do motor através do emprego do inversor de frequência, com o qual foi possível economizar até 87 % de potência elétrica requerida pelo ventilador. O estudo ainda demonstrou que existe uma faixa de trabalho na qual o inversor de frequência é capaz de economizar até 56 % da potência exigida pelo compressor para uma mesma carga térmica em relação ao compressor desprovido do inversor de frequência, no qual o controle da vazão de refrigerante ocorre através da válvula de estrangulamento. Conclui-se que a utilização do inversor de frequência, em sistemas onde a carga térmica requerida (efeito refrigerante) varia, pode resultar em uma significante economia de energia. / Abstract: This study presents the results of a work carried out on a test bench, where it was verified the difference of the electrical startup power and the performance coefficient of two different types of compressors, namely: a hermetic piston type compressor and a rotating scroll type compressor operating with a frequency inverter. In this study, the refrigerant flow rate was varied and, consequently, the cooling capacity obtained by two distinct procedures: one, by the restriction of the refrigerating flow while maintaining rotation of the piston compressor constant and the other, by varying the scroll compressor rotation through a frequency inverter while keeping the restrictive valve in a fixed position. Is showed also, the influence of frequency inverter in order to control the air flow rate system by employed with fan engine and afterwards compare with method which air flow rate is controlled by DAMPER valve, where until 87 % to fan actuation power was saved. Besides, the study demonstrated that there is a range where the frequency inverter is capable of savings up to 56% of the compressor demanding power for a defined cooling capacity in relation to a compressor without the frequency inverter, in which the refrigerating flow rate control occurs through the restrictive valve. Therefore, it is conclusive that the use of frequency inverters in systems where the required cooling capacity varies, it can result in an appreciated economy of energy. / Orientador: Pedro Magalhães Sobrinho / Coorientador: Teófilo Miguel de Souza / Banca: Agnelo Marotta Cassula / Banca: José Rui Camargo / Mestre