Simulation Research On Fuzzy Adaptive PID Control In Wood Drying Kiln

With the development of the society and increasing demands for wood drying, effective utilization of wood has become an advanced subject concerned by science researchers. Wood drying is an important measure of improving wood's physical mechanics performance, fair use of wood, reducing loss of wood's downgrade, increasing utilization efficiency of wood. It is also one of the key techniques of guaranteeing woodwork's quality. Wood drying usually performs PID control, which control accuracy is not very good because of lacking adequate flexibility. The PID controller has disadvantages of inconvenient coefficient modification, incapacity of self-adjusting, etc. Therefore, modern high quality control systems are crucial problems need to be solved in the innovation of wood drying equipments.The control process of wood drying is the same as the process of controlling medium's temperature and humidity in a kiln in order to reduce water ratio of wood to some expected value. According to actual characteristics of wood drying, this thesis proposes a new intelligent PID coefficient adjusting method based on existing neural network model. The method combines fuzzy control with PID control to construct a fuzzy adaptive PID controller, which realizes optimum control of system. It performs fundamental theories and methods of fuzzy mathematics to modeling performers' knowledge, using control rules. At the same time, it considers these rules and related information (for example, original PID coefficients) as knowledge and stores them in computers. Then according to real response of control system, computers apply fuzzy reasoning to realize automatic optimum setting of PID coefficients.The thesis simulates by fuzzy logic toolbox and Simulink of MATLAB. Through simulation, analysis and comparison between PID control and fuzzy adaptive PID of wood drying kiln, the results show that steps response curve of the fuzzy adaptive PID controller has the advantages of rising quickly, high adjusting precision and good stabilization, short transition time and small overshoot. This is difficult for PID control to realize. For these reasons the fuzzy adaptive PID controller is feasible and effective. The controller's coefficient self-adjusting can be realized, and its performance is better than traditional PID controllers. To effective guarantee the quality of wood drying, reduce energy use and lessen costs, these advantages have important guiding significance of theoretical and practical research.