Research On The Control Of Wood Drying Contraction Stress Based On ARMA Neural Network And Fuzzy-PID Algorithm

Drying contraction stress is an external force and internal stress produced by the reduction of the size of the wood due to the water dispersion during drying.The occurrence and development of drying contraction stress is complex,which is related to drying conditions,shrinkage rate,the difficulty of water movement and the ability of materials to resist deformation,and its size directly affects the drying speed and drying quality of wood.But because the drying process of wood involves many uncertain links such as lag,nonlinearity and time-varying,it is helpful to establish a proper mathematical model and accurate control system of wood shrinkage force,which is conducive to the analysis of the relationship between wood moisture content,drying contraction stress,medium temperature and relative humidity,and is helpful to understand and master the change of shrinkage force in drying process,and to be the basis of dry shrinkage drying.The establishment of the system and the precise control of the drying contraction stress provide theoretical basis,which is of great theoretical and practical value to improve the drying speed and ensure the quality of wood drying.The main contents and results of this thesis are as follows:1.the mathematical model of wood drying process was established by combining ARMA model and BP neural network.Firstly,the model of temperature humidity moisture content change process is established by ARMA model,then the mathematical model of water content and dry shrinkage force is established by BP neural network based on ARMA model.Finally,the relationship model between temperature and humidity and drying contraction stress is established by connecting them in series.2.combining the characteristics of classical PID control and fuzzy logic control,the fuzzy adaptive PID control scheme is designed,which realizes the self-tuning and adaptive adjustment of three parameters of PID.The parameters are automatically adjusted under the condition of model parameter perturbation,uncertainty generation and external interference,so that the control process meets the requirements of performance index.Finally,the simulation drying contraction stress control system of Simulink is built by using the fuzzy controller design toolbox in MATLAB.3.the comparison of the drying contraction stress control of the classical PID and the fuzzy adaptive PID is carried out.The results show that the classical PID control has a large overshoot in drying contraction stress due to the inaccuracy of the controlled object,and the dynamic adjustment time is long,the system fluctuates greatly,but there is no steady-state error.The fuzzy adaptive PID control has the advantages of fast response,high precision,good steady-state performance and small fluctuation of the system,which can meet the basic requirements of wood shrinkage process control.