Simulation Design Of Wood Drying Contraction Stress Control System Based On PLC

The drying contraction stress produced in the drying process of wood(a kind of external force and internal stress produced by the reduction of the size of water loss in the drying process)is the main factor causing wood cracking,and the drying contraction stress is accurate.The design of intelligent control system has become an important problem in the study of wood drying process.In this paper,PLC technology,fuzzy PID technology and automatic detection technology are applied to the wood drying process,and a set of accurate wood drying contraction stress control system is developed,which can monitor and control the drying contraction stress produced in the wood drying process in real time.The specific tasks of this article are as follows:1.A reasonable and accurate wood drying contraction control system is developed.The main components of this system are wood drying equipment,wood drying contraction control system,wood dry shrinkage measurement system and wood weight loss measurement system.The main components of this system are wood drying equipment,wood drying force control system,wood dry shrinkage measurement system and wood weight loss measurement system.The main components of wood drying device are condenser motor,refrigeration solenoid valve,dehumidifying solenoid valve,compressor cooling solenoid valve,electrical control cabinet,circulating fan,plate heat exchange and air-cooled condenser.Among them,the core of this paper is the wood dry shrinkage control system,it mainly includes the following aspects:(1)data management systemThe main function of the data management system is the collection,transmission and processing of data.It is mainly accomplished by sensors,PLC and analog modules.The first step is the drying contraction stress and quality that the sensor will collect.The analog signal,such as dry shrinkage,is transmitted to the analog input module;The second step is to convert the digital signal into the corresponding engineering value and store it by PLC after conversion,and the third step is to process the converted value through the CPU of PLC.(2)Monitoring systemThe monitoring system is upper computer as management level,and the touch screen of MCGS configuration software is used as man-machine exchange interface of real-time recording and processing of field data,including data real-time display,data storage,drying control,etc.Alarm information query and display functions.(3)Control systemThe main functions of the control system are monitoring and automatic control.PLC,as the field control level,uses STEP7 programming software to program the user progra-m to complete the data processing of the PLC control system,loop control and fuzzy PID switching control algorithm execution and so on.The communication between the host computer and PLC is established by using PPI protocol.The server will acquire the data through communication and display it in real-time on the man-machine exchange interface of the host computer.The remote control software VNC is selected to control the system.The system can be set by touch screen,the system can be started,the data backup,fault detection and protection,and the system can be set.Stop and shut down the working process.2.Based on the fact that wood drying process environment is a nonlinear,large inertia and time-varying system,it is difficult to achieve satisfactory results by using conventional control methods.A fuzzy PID switching controller is designed,which does not depend on the precise mathematical model of the controlled object.Taking the deviation and variation rate of drying contraction stress as input parameters,the fuzzy PID switching algorithm is used to reason,the fuzzy PID switching control algorithm is used,and the fuzzy control algorithm is used to give full play to its fast response in the case of large error.When the error is small,the fuzzy self-tuning PID control algorithm is adopted to give full play to its good static performance,and this switching control algorithm is not only fast.It also has high steady-state precision,and realizes the accurate control of wood drying process.3.Select Pinus sylvestris var.mongolica as drying specimen to test the accuracy and stability of the control system.The experimental results show that the wood drying device is in normal operation,the dry shrinkage force is controlled accurately and stably,and the drying contraction stress can reach the stability when the setting value is reached.