| This thesis takes the central air conditioning evaporator as the research object. The present research situation of evaporator modeling and control methods is summarized.Working principle of the evaporator are analyzed, it is presented that the object is with the characteristics of high order, nonlinear, strong coupling.Firstly, based on the conservation of mass and energy in N-S equations, moving boundary method, concentration of modeling method are adopted to establish the mechanism model of evaporator in this thesis. The state matrix by the first order Taylor expansion is linearized at the working point. By reducing the order to appropriately simplify the model, three variables which can represent the characteristics of evaporator accurately are reserved, then a space model with three order state is transformed into standard one.Secondly, a direct fuzzy adaptive controller and adaptive laws are design and structure respectively. According to the established model of evaporator, select control law making tracking error converge to zero gradually. The controller is constituted by a fuzzy logic system,the control law is estimated by the fuzzy logic system, and the fuzzy logic system is structured by product inference engine, single-valued fuzzy generator and center average fuzzy canceller.The adjustable parameter of fuzzy logic system is linear. By making the negative derivative of Lyapunov function the adaptation law is obtained.Finally, the control performance of directly fuzzy adaptive controller is proved theoretically. Afterward, Simulink is used to build the modules of the control system. S function is used to present the controlled object and the controller respectively. Under different working points, the simulation results of direct fuzzy adaptive controller, PID controller and fuzzy PID controller are compared. The results show that the fuzzy adaptive control method under different working points has the ideal control effect with no more than3% overshoot. |
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