Robust control of a SAG mill

It is now well accepted that process automation, closed-loop control and optimisation technologies enable higher feed rates, more consistent product qualities, lower utility usage and higher yields in a diverse range of process industries, In the minerals processing industry, as a general rule. it is advisable to consider the grinding circuit first, as good operation here is necessary for stable operation in the rest of the plant. Operating conditions in a grinding circuit are frequently such that production is significantly reduced due to the effects of process disturbances. most notably those associated with the feed ore. This paper demonstrates the design of a robust control scheme for a semi-autogenous grinding (SAG) mill. Feedback (1713), feedback plus feedforward (FF) and reduced order (i.e. less complex) robust controllers were all developed and tested-each providing tight control over the SAG mill power draw by adjusting the feed rate to the mill. This example clearly shows that using the available Matlab-based controller design package, it is possible to develop robust (i.e. in terms of strict guarantees on both controller performance and stability, despite model uncertainties) control systems for the minerals industry as readily as for other industries where advanced control is more routinely used. (C) 2002 Published by Elsevier Science B.V.