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Comp 452 Dissertation Thesis 2 Dissertation Thesis Proposal

“Cascade Control System Desing of HVAC System� Proposed by Necmeddin arkaci April 2009


Problem Statement

HVAC is an acronym that stands for �heating, ventilating, and air conditioning�. HVAC system uses control mechanism especially to maintain comfort conditions in the building environment, to keep the value of inside air quality possible with the goal, and to increase HVAC system efficiency. The main purpose of keeping control is that inspection of the region to be constantly kept at the desired conditions at interms of external environment and changing heat load. In HVAC system, control is usually in the form of temperature, humidity, plessure, and flow control. This control is designed with a different control system starategies Traditional control systems to supervise the operation of the system is based on the establishment of mathematical models like PID. A PID control algorithm (procedure) take action based on the coefficient, such as integral and differential identification and precise mathematical calculation. The main purpose of the project is to design a HVAC system based on cascade control system structure. The design technic is more optimal than traditional control system.


Literature Survey

Until the end of 19th century houses and buildings have been handed control of the temperature of the environment. When ambient temperature is increased, windows and door are opened and tempratures with the help of air movement were lower. Because this type of control stands people’s feelings, it is not posssible to keep constant value and continuity of the value in environment. The first applications of automatic control began with bimetal-based thermostat which is discovered in 1885. Until 1890 the first pneumatic control is implemented. HVAC system in the United States began firstly to be applied in large cinema and theater hall. The subject of automatic control has been discussed for first time in traditional meetings of American Society of Heating and Ventilating Engineers (ASHVE) in 1894. R.C. Carpenter defined time constant concept in an article in 1897. The concept defined the dynamic behavior of thermal systems in later years. This description briefly described as a time which is required to bring 63 of the desired room temperature. This description of the automatic control


is one of the first and important definitions. J. H. Kinely said his notion about what temperature settings should be for temprature control. Computers are used for trasferring data in HVAC system in 1966. Anolog to digital and digital to anolog converters has been developed in 1970.



In this project, we aim to design a control system for HVAC system based on cascade system strategies. An object of the project finds possible stabile structure for the design. Cascade control system architecture is selected suitable structure to provide this purpose. Cascade control system is applied with design of different configuration of PID control algorithm and its variatns PI,P. These configurations will be analyzed on the application process of matlab Simulink. And, the most appropriate and most stable structure can be selected from these configurations for HVAC system. Cascade Control Systems contain integrated sets of control loops;primary loops and secondary loops. Primary loop monitors the control variable and uses deviation from its setpoint to provide an output to the secondary loop. Secondary loop receives its setpoint from the primary loop and controls the reference variable accordingly. In this project, we choose Cascade control system as a design architecture for the system because cascade control system strategy has advantage. Some of these advantages are using of feedback at all levels, simple technology with PID algorithm, compatible with other control systems, such as feedback and feedforward architecture, large improvement in performance when the secondary is much faster than primary. Cascade system has some criteria for design. Cascade is desired when single loop performance unaccaptable and is a measured variable is available. Ans secondary variable must indicate the occurrence of an important disturbance, have a casual relationship from valve to secondary, and have a faster response than the primary. HVAC system is generally a suitable platform for the implementation of these cascade system design criterias. On the other hand, cascade control system has some disadvantages for HVAC control design. Some of these disadvantages are that additional controllers and sensors can be costly and multiple control loops make physical and computational architecture more complex.




In this proposal, HVAC system design issue is described as a problem statement. What is the purpose of HVAC systems are explained. To provide the purpose, which materials are needed that is explained. Traditional control systems and their structure described. In litrature servey part, the historical overwiev of HVAC system is given. And some important improvement in HVAC system explained. How is the first of applications in the area are explained. The important steps of the area are pointed out. Contribution of computer on HVAC design are described. In methodology,to improve stabile system for HVAC which materialn are needes is described. A notion of using cascade control system for the purpose are pointed out. Cascade control system defined and explained what advantages of cascade system strategies in HVAC design. A necessary criterias of implemetation of cascade system design are supported by HVAC system. And some disadvanteges of cascade control system in HVAC explained.

References 1) IEEE standard dictionary of Electrical and Electronics Terms, WileyInterscience, New York,1972. 2) 3) Sengirgen, Mesut, HVAC control system: past and present 4) HVAC system design handbook, 5) Rice, Robert,Cooper, Dougles, Arule base design methotology for the control of non-self regulating proces. 6) Skogestad,sigurd,controllability of feedback system,engelysge lysark 2001 7) system