Study On Signal Acquisition And Control Model Of PLC Control System For Tobacco Vacuum Conditioning

Vacuum conditioning is the key process of cigarette production in tobacco factories and it can increase tobacco leaves moisture and temperature,remove impurity gas and improve the quality of tobacco leaves.At present,domestic tobacco factories rely on experience to control vacuum conditioning without precise control based on thermodynamic model,which leads to the problems of insufficient moisture regain,unsatisfactory moisture content and large steam loss in traditional vacuum pre-conditioner.It is not conducive to the follow-up process,but also affects the production quality of cigarettes.To improve the moisture regain efficiency of the vacuum conditioning and reduce steam loss has always been the focus of tobacco manufacturers' attention.Therefore,a thermodynamic parameter model is proposed to control the vacuum moisture regain process.In this paper,we design the experimental vacuum pre-conditioner,and then we analysis vacuum pre-conditoner's overall structure,box and control cabinet,the core component of the machine,in detail.Signal acquisition and processing is the basis for the control of experimental machine.According to sensors time constant,sampling frequency in signal digital engineering application,and the steam cycle,we determined the acquisition frequency and action period of actuator in the machine.Because the model-based precise control proposed in this paper requires higher signal accuracy,we further study the data processing of temperature,pressure and flow meters,including precision correction and filtering processing.In addition,according to the relationship between heat absorption and exothermic of water and superheated steam,we establish the internal and external heat balance model of vacuum preconditioner by RGSA-RBFNN and least square method to quantitatively control the vacuum conditioning processWe carry out the controlling experiment of tobacco vacuum conditioning on the experimental machine.The results show that the tobacco moisture content can be effectively improved by controlling the moisture regain process based on thermodynamic parameter model proposed in this paper.