FUZZY CONTROL IN GREEN ANODE PLANT MIXERS

摘要

This paper presents the results obtained by using "Fuzzy Logic" to improve the control system of continuous green paste mixers at the ALBRAS anode plants. Fuzzy Logic is used to convert heuristic control rules stated by a human operator into an automatic control strategy. Through Fuzzy Logic the system is able to track the mixer current set point. A control strategy base was elaborated intuitively, observing how the operators commanded the mixer's damper. When the continuous mixer is being controlled adequately it produces a homogeneous green paste with the required qualities of mechanical rigidity, as well as a minimum standard deviation of the anode density. These paste characteristics depend directly on the damper control, and the previous system was unable to control this appropriately, causing variations in the mixture of the paste and consequently the amount of green scrap produced. Sometimes the operators needed to adjust the damper manually. The controller program was developed with ladder language and runs on programmable logical controller (PLC). The new system has been running since 2002 in the anode plants. The current used as the control varies around an established target. The results demonstrate the effectiveness and viability of the system that subsequently will be being implanted on other anode plant equipment.