Nonlinear observability of grinding mill conditions

A nonlinear observer model of a grinding mill is developed. The model distinguishes between the volumetric hold-up of water, solids, rocks and balls in the mill where solids are all ore small enough to discharge through the end-discharge grate, and rocks are all ore too large to discharge. The model includes the discharge rate, abrasion rate of rocks and the abrasion rate of balls as parameters. It is shown that with mill discharge flow-rate, discharge density, and volumetric hold-up measurements the model states and parameters are locally (weakly) nonlinearly observable, but riot linearly observable. Although instrumentation at the mill discharge is not, yet included in industrial circuits because of space restrictions, this study motivates the benefits to be gained from including instrumentation at the mill discharge. If mills are fitted with adequate measurement instrumentation at the discharge, important mill states and parameters can be estimated. (C) 2016, IFAC (International Federation of Automatic. Control) Hosting by Elsevier Ltd. All rights reserved.