Availability Principle Applied to a Fuzzy Supervisory Control of a Pilot Flotation Column

Abstract

This work presents a study of fuzzy expert control system, based on the availability principle, of a pilot flotation column at the Hybrid Process Control Laboratory in Santa Maria University. Sensors and actuators are communicated to a programmable Logic Controller (PLC) where calibrations and local control are implemented, and the data is sent to a PC network, where a Distributed Control System (DCS) is running. Process model predictions are obtained by running a simulator fed with actual operating variables and virtual variables associated to feed characteristics. All data is displayed at PC stations and historical data files are also built for further analysis. Operating variables (real and virtual) can also be analyzed off-line by advanced software tools. Supervisory control running on PC network writes DCS set points on PLC.The supervisory control performance was experimentally evaluated by keeping the mineralogical objectives of concentrate grade and recovery in narrow bands. The operation of the supervisor was compared to a base case where there is no supervisory control, and each experiment was subjected to stochastic auto-correlated disturbances in the feed conditions. The fuzzy supervisory control, unlike conventional control, is more capable of maintaining the metallurgical results within control limits during almost 90% of the operating time. An availability principle for manipulated variables was successfully tested acting on top of the fuzzy logic decision system.