Raimo Ylinen

Model predictive control for grinding systems

Abstract Grinding systems are often modelled by multivariable impulse response or weighting function matrices. These kind of models are very suitable for design of model predictive controllers. Two predictive control algorithms have been developed and tested with two simulated models of grinding systems. Their design is based on decoupling of the steady state interactions. The dynamic interactions cannot be eliminated but their strengths are reduced by dynamic compensation.

On characterization of pulp and froth in cells of flotation plant

Abstract Dynamic models of pulps in industrial flotation cells are presented with emphasis on the modelling of their chemical conditioning. They are reduced to steady state models that can be combined to describe banks and networks of cells. Kinetic characterization of minerals in the plant is outlined on the basis of samples from appropriate points, their analysis and simulation between such points, in order to model the solids transfer from pulp to froth in the cells. Models of the froth layers and studies of their surface views are reviewed. Images of froths have been recorded in two plants and results of their analysis are presented. Scene analysis is considered a valuable means in acquisition of new information of processes in flotation cells.

Modeling of visual flotation froth data

Abstract In this paper, the principles of sensor fusion are presented. A new sparse coding method based on a generalization of the generalized Hebbian algorithm (GGHA) is presented. The algorithm is realized using a modification of the Kohonen network. The method is tested on an image analysis of flotation froth, in order to find features corresponding to the poisoning phenomenon in a flotation cell. The features found are capable of predicting the poisoning earlier than the ordinary process instrumentation.

Vision- and model-based control of flotation

Abstract A new vision system for monitoring and control of flotation processes has been developed The system produces information of the flotation froth structure and colour. This can be used for estimation and prediction of the state of the process. Due to the complexity and nonlinearity of the flotation process the classification methods have been applied to classify the operation conditions Process models containing image variables have been constructed and applied to simulation. The equipment has been installed on an industrial flotation plant. New control strategies based on image information have been developed and tested.

APPLICATION OF POLYNOMIAL SYSTEMS THEORY TO NONLINEAR SYSTEMS

Abstract A global linearization of nonlinear input-output descriptions by relaxing the appropriate appearances of inputs, outputs and their derivatives is applied. The resulting time-varying linear systems are described by skew polynomial systems accepting most of the methods of ordinary polynomial systems. The properties like stability and controllability of nonlinear systems can be analyzed using the linear theory. The feedback designs can also be carried out by linear methods. The methodology is illustrated by examples.

POLES AND ZEROS OF MULTIVARIABLE LINEAR TIME-VARYING SYSTEMS

Abstract In the paper it is shown that the pole set of a linear system can be calculated by suitable polynomial factorizations. The theoretical issues related to poles and zeros of time-varying systems are discussed. Further, it is shown how the poles and zeros can be defined starting from a state-space realization of the input-output system.

Robust Control of Variable Flow Processes

Abstract Models of continuous flow processes with variable parameters are studied and methods developed for their robust control. Such processes have proven invariant under variable flow and volume, if they are presented as functions of composite variables which have been introduced recently. Their finite impulse response (FIR) models are obtained e.g. by physical testing or identification, and expressed in terms of discrete, equidistant values of the appropriate variable. In the present study, such a model of a time-variable process with a long time delay is considered a high-order model; this is subsequently reduced to a low-order state-space model by means of the optimal Hankel-norm approximation. The robust feedback control is developed in terms of the same variable on the basis of the low-order model. The application of the control algorithm to the simulated process proves the approach superior to such conventional and robust control methods which have the regular time as their independent variable under unsteady conditions.

Soft Computing at a Flotation Plant

Flotation is used in mineral processing industries for separation of grains of valuable minerals from those of side minerals (Laskowski and Woodburn 1998). In the continuous flow flotation cell (Fig. 1), air is pumped into a suspension of ore and water. The desired mineral tends to adhere to air bubbles and rises to the froth layer where the concentrate floats over the edge of the cell; the main part of other minerals remains in the slurry. The separation of minerals requires that the desired mineral is water-repellent: in zinc flotation, this can be reached by conditioning chemicals as copper sulphate CuSO4; xanthate is needed to reach lower surface tension, etc.

A Separation Theorem for Polynomial Feedback Systems

Abstract A separation principle for the pole placement design of polynomial systems is presented. The design of an output feedback controller can be divided into two independent design tasks: a generalized state observer design and a generalized state feedback design.

Modeling of Visual Flotation Froth Data

Abstract In this paper, the principles of sensor fusion are presented. A new sparse coding method based on a generalization of the generalized Hebbian algorithm (GGHA) is presented. The algorithm is realized using a modification of the Kohonen network. The method is tested on an image analysis of flotation froth, in order to find features corresponding to the poisoning phenomenon in a flotation cell. The features found are capable of predicting the poisoning earlier than the ordinary process instrumentation.