Research And Application Of Complex Control Strategies In Hot Air Leaf Moistening System

Leaf moisturizing,as the first process after the pre-treatment of leaf re-baking,the efficiency of the subsequent stem leaf separation process is directly affected by the effect of the conditioning cylinder on the heating and humidification of the tobacco leaves.For a long time,research on the control system of the leaf moisturizer and even the entire re-baking industry has been mainly focused on the optimization of the moisture of the tobacco moisture.However,there is a serious coupling between moisture and temperature,and the moisture absorption capacity of tobacco leaves is extremely sensitive to temperature changes.So,how to improve the accuracy of temperature control and maintain the stability of key process parameters has gradually been paid attention.The temperature process of the conditioning cylinder is a large delay time process.In addition,there are various strong disturbances in the working environment of conditioning cylinder.In order to improve the stability of the outlet temperature of the conditioning cylinder and the rapid response capability of the temperature control system.The works and innovations in this article are as follows:1.By analyzing the internal mechanism of the conditioning cylinder and supplementing it with actual sampling data,mathematical models of the outlet temperature of the leaf wetter,and the circulating hot air temperature before and after heat exchange were established.2.According to the relationship between hot air temperature and outlet temperature,a cascade control scheme composed of three closed loops is designed.In this scheme,the inner and outer loop subcontrollers and the main controller both adopt the predictive PI（Proportion Integration）controller.3.It is predicted that the PI algorithm has relatively high requirements for hardware.In order to improve the practicality of the algorithm,the predictive PI algorithm is simplified into a special PID control form.So that,the PID algorithm has a good predictive function and easy parameter tuning when dealing with low-order objects with large time delays.In addition,the stability of this PID controller is analyzed.4.The combined integral link is often used in the moisture object model.In order to further simplify the design of the entire conditioning cylinder system,the characteristics of the combined integral are briefly analyzed.On the premise of small model uncertainty,a typical combined integral link is used to apply the pseudo-predictive PI controller to temperature objects with large time delay.5.Integrated Time and Absolute Error An improved Integrated Time and Absolute Error（ITAE） performance evaluation index is proposed with fully considering the practicability of the controller output.The evaluation index is combined with the simulated annealing algorithm to realize the self-tuning of the controller parameters.6.Relying on the Opto22 platform and taking the multi-loop cascade control strategy as the core,engineering design works such as algorithm programming,environment configuration and monitoring interface development for the temperature control system of the conditioning cylinder have been completed.The results show: Compared with the traditional double closed-loop cascade control,the multi-loop cascade control can further improve the speed of the system to eliminate disturbance through the added sub-loop.This scheme can provide support for accurately,stably and quickly controlling the outlet temperature of the conditioning cylinder.In the face of low-order large time delay controlled objects,the predictive PI algorithm can be simplified into a special PID controller.The PID controller has similar performance to the predictive PI controller.The pseudo-predictive PI controller with the combined integral as the core has good dynamic performance and no steady-state error when facing the controlled object with small model uncertainty.In summary,the model-based complex control strategies have certain advantages in terms of system stability,robustness,and anti-disturbance.These controllers have practical significance.