High-accuracy Fuzzy Controllers for Vacuum Cooling of Phosphoric Slurry Using Variable Universes of Discourse

Maintaining phosphoric slurry within the optimal temperature range is of great significance in improving the quality of the phosphoric acid product. Due to the lack of integral parts and the limited number of expert rules, general fuzzy controllers are commonly incapable of achieving accurate output. This paper proposed a novel fuzzy controller based on variable universes of discourse (VUD) to improve the accuracy of the temperature of phosphoric slurry. By tuning the motorized motor in the vacuum pump, the controller can obtain an appropriate vacuum degree in flash evaporators. With the online operation of contraction-expansion factors, fuzzy rules can be reproduced online, which is equivalent to the densification of fuzzy sets on universes of discourse. Thus, the output accuracy of VUD fuzzy controllers can be enhanced significantly. The experimental results show that VUD fuzzy controllers can tune the temperature of phosphoric slurry to within the optimal range and have a much better effect than general fuzzy controllers.