Constrained self-tuning control of raw material blending process in cement industry

The main goal of raw meal blending control in cement industry is to maintain near the reference moduli values and to decrease the variation of the chemical composition, rejecting disturbances. For this purpose, some commercial control systems are available today. However, the control structure in these systems usually consists of quality control. In this paper, the proposed constrained self-tuning controller deals with not only quality control but quantity control as well. This is accomplished by inserting an energy term into the quadratic performance index. The self-tuning controller designed according to this performance index is based on a time-series model, characterizing the relationship between the feedrates and the moduli values. Because of technological constraints, an optimization problem is formed to compute the control signal. The optimization problem is solved to obtain the least expensive and, if possible, the least sensitive mix of raw materials that satisfies the quality requirements of the raw meal under incomplete and stochastic information of the different raw material component concentrations.