Dynamic Matrix Control Of The Cane Sugar Crystallization Process

The Model Predictive Control (MPC) strategy has been developing quickly both in the theory research and practice application, for its three characteristics of predictive model, receding horizon control construction and feedback correction. It meets the industrial process control's needs. The process of boiling in a sugar refinery is a productive process of cane sugar's crystallization. In this complicated chemical and physical process, both heat transfer and mass transfer occur. Since the boiling crystallization process itself has many factors suffering disturbance and has great nonlinear, so it is hard to control the boiling crystallization process with ordinary method. It is pointed out in the paper that the model used for MPC of a complex system should be build based on mechanism and analytical relations of mass, energy and momentum and other physical property (for example growth rate dispersion and so on) in the sugar boiling process, and DMC is applied and take the model as predictive model in the sugar boiling process. A simulation test has been taken to the OS (oversaturation) control of boiling sugar process by means of Dynamic Matrix Control using complex mechanism model in MATLAB. The test shows that the control strategy of using Dynamic Matrix Control for the sugar boiling process is correct. This paper also concentrates on the study of nonlinear DMC approaches from the view -point of predictive model and optimal model.After simply analyzing the basic theory and prepotency of model predictive control algorithm, a kind of model predictive control algorithm proper for industrial cane sugar crystallization process control is discussed, which has rapid responsive-speed and good robust capability-Dynamic Matrix control(DMC).The main contents of this paper are as follows:1.A survey of the development and status of MPC is given. An introduction of related control strategies is also given;2.Systems analysis of the boiling crystallization process is made;3. Based on the detailed description of the principles and algorithm of the DMC has the following advantages: simple algorithm, less on line calculation, high controlprecision and disturbance attenuation by the theory analysis and simulation;4. During the study of boiling sugar crystallization process, two ways of PID and DMC are applied in order to compare their results. DMC control is proved to be much better than PID control with the advantages of rapid response, robust and anti-jamming through simulation in the boiling sugar process.5. A multi-model predictive control scheme is proposed for nonlinear systems. Of course, there are some defects in DMC control, such as the fluctuation of OS.Main reasons are abnormal complexity and strong coupling in the boiling sugar crystallization process. By taking single variable control in the study of simulation, so the results can' t conform to the practical boiling sugar process because it is a system of multivariable control.In order to solve the problem, the best way is to apply multivariable DMC strategy.