A comparative experimental study of five multivariable control strategies applied to a grinding plant

This paper deals with the implementation of five multivariable adaptive, as well as classical, control strategies in an industrial grinding plant. The extended horizon, pole-placement, model reference, direct Nyquist Array an d sequential loop closing algorithms were studied and implemented at CODELC O-Andina's copper grinding plant, with each of them delivering good perform ance. The 2 x 2 system chosen to be controlled has the percentage of solids (percentage of +65 mesh) fed to the hydrocyclones and the level of the sum p as output variables, and the water flow added to the sump and the pump sp eed as input variables. The adaptive extended horizon algorithm performs th e best, although all five strategies considerably improve the actual operat ion of the plant which consists of only one control loop. After a compariso n amongst the control strategies, a brief economic impact analysis is perfo rmed to support the claim that multivariable control algorithms substantial ly improve the operation of the grinding plant, maintaining the percentage of solids (percentage over mesh 65) around a pre-specified value (optimal f or practical purposes); thus obtaining interesting economic benefits. (C) 1 999 Elsevier Science S.A. All rights reserved.