Design And Research Of Wood Drying Kiln Distributed Control System

It has been widely focused on how to improve the utilization of wood by various countries’ government, wood processing enterprises and wood scientists along with the reducing forest resources in the worldwide. Wood drying is one of the most significant parts of wood processing. Comparing with the dried wood, un-dried wood usually maintains the characters of low mechanical properties and suppleness. Therefore, the quality of dried wood could affect the quality of wood products directly.Although wood drying industry holds highly development speed in China, as the result of starting the drying industry late and getting lower attention, it may exist obvious disparity with the developed countries no matter in theoretical study area, drying equipment or wood drying control system. Nowadays, several problems appear in China’s wood drying industry, which includes low degree of automation, human factors easily affect wood drying process and low accuracy of the controller.Based on"iow carbon, high efficient wood drying and key technology functional improvements study"project supporting and the problems in China’s wood drying industry, this paper accomplished the following studies and designs:(1)Combined with the structure and idea of distributed control system, which is "centralized management, decentralized control", this paper designed wood drying kiln distributed control system that included field control station, engineer station and system network. The field control station was including the main control module, digital and analog input/output module, communication module, sensors, actuators and display module to accomplish the functions of collecting field signal, processing data, sending control signal and connecting with PC. Engineer station was built up by industry grade PC to accomplish the functions of configuration, monitoring the operation of other stations, alarming and print reports. Industry communication network was composed by industry grade Ethernet, which had the merits of long distance communication and low packet loss rate, to exchange the data from PC to consoles computer. Beyond that, Web publishing capabilities the system designed allowed the engineers could monitor and control the wood drying process through the Internet from long distance.(2)A Mamdani type fuzzy neural network controller that based on BP network was designed in this paper. It could maintain both merits of fuzzy control and neural network, which were rely on lower accuracy of control object and self-learning capability. This controller could generate fuzzy rules and adjust membership functions to improve the self-learning ability and express ability of the system. Therefore, the control system might hit higher intelligence level.The field experiments reveled that wood drying distributed control system could improve the degree of automation, production efficiency and management efficiency of wood drying process. The expected results was achieved; The simulation experiments revealed that comparing with the traditional fuzzy controller, wood drying kiln fuzzy neural network controller might have lower overshoot, smaller adjust time and have better robustness. It might have a better temperature and humidity control effect to wood drying kiln.