Advanced Control Algorithm And Its Application In Tobacco Re-drying Production Line

Time delay processes exist extensively in process industry. The research on Time delay processes especially with large dead-time is always one of the most hotspots in control system. It is difficult to achieve the desired results by traditional control Algorithm.Combined integrating processes which exist extensively in process industry such as iron and steel, petrochemical, grain processing, tobacco, is one of the new integrating time delay processes. Combined integrating process is composed of two or more integrating time delay components. Essentially, it is open-loop stable process. It can be considered as the first-order process by first order pade approximation method. Currently, most combined integrating processes are controlled by conventional control strategies, such as PID controller, Smith predictor and internal model control, etc, which results in acceptable performance. However, with the rapid development of industry technology, energy conservation and emission reduction, traditional control strategies are no longer suitable. Thus, it is necessary and urgent to research control strategies exclusively for combined integrating processes.Tobacco re-drying production line through which tobacco leaf can attain required temperature and moisture level is used to re-dry tobacco leaf. The temperature of re-drying chamber is a class of process with Large dead-time and inertia, and the generalized moisture models of the cold chamber and outlet is a class of combined integrating processes. Controlled by conventional control strategies, the temperature of re-drying chamber will fluctuate frequently, and the generalized moisture of the cold chamber and outlet will be controlled by manual adjustment. What is worse, it will result in production quality problem and the tobacco leaf will be re-dried again. Therefore, it is necessary and urgent to research advanced control strategies on tobacco re-drying production line. Range from theory to practice, the main work is outlined as follows:(1) Based on dead-time process, a new predictive PI/PID control algorithm is proposed according to the desired closed-loop transfer function. The predictive PI/PID (PPI/PPID) controller is composed of two parts, which combined the function of prediction with PID controller perfectly. Advantages of these controllers are simple structure, few tuning parameters, and easy tuning procedures, the simulations show that the proposed controllers remain good dynamical performance and robust stability under disturbance and model mismatch, which show its value in industrial application.(2) Based on combined integrating processes, a new advanced anti-delay quasi-predictive PI algorithm is given according to the desired closed-loop transfer function. It also shown that the method by which the anti-delay quasi-predictive PI (ADQPI/ADQPID) controllers designed. The control algorithm is suitable for combined integrating processes as well as other processes because of the controllers are designed based the model of processes. The simulations show that the proposed controllers remain good dynamical performance and robust stability under disturbance and model mismatch.(3) The paper shows that the application of the advanced control algorithm which composed of PPI and ADQPI on the tobacco re-drying production line. Firstly, the models of re-drying chamber, cold chamber and outlet are proposed based on the special dynamical character of the tobacco re-drying system. Based on the temperature model of the re-drying chamber, four temperature controllers are designed by the predictive PI (PPI) algorithm. Because of the generalized moisture models of the cold chamber and outlet, two moisture controllers are given by quasi-predictive PI (ADQPI) algorithm. In addition, an advanced control scheme is designed aiming at the tobacco re-drying system. Practical application shows that the proposed advanced control algorithms can promote the control accuracy, lead to improvement in energy efficiency, and reduce the product cost.(4) A kind of advanced real-time control software is designed based on the OPTO22 PAC project. The control algorithm is proposed by the OPTO script of PAC Control, the HMI is designed by PAC Display. The processes are simulated by Matlab Simulink, the control strategies are operated by OPTO22 R-series controller. The simulations show that the software is valuable to be used in industrial production.