Cautious adaptive control of an industrial flotation circuit

Abstract

A minimum variance adaptive control system has been applied to the control of an industrial lead rougher flotation circuit. The adaptive control algorithm is developed without the use of complex mathematics, with particular attention given to the practical aspects of implementation. Although this adaptive control algorithm is used extensively at Mount Isa Mines Limited, a single control loop is discussed in detail to demonstrate the application of this technique to flotation control. Several modifications have been applied to the standard algorithm to improve its robustness. The most important modification is the inclusion of a cautious controller in parallel with the adaptive controller. A proportional-integral-derivative (PID) controller, tuned conservatively to operate over a wide spectrum of conditions, has been used for the cautious controller in this application study. The final control action is a weighted combination of the cautious and adaptive control actions. A simplified method has been developed for determining the proportioning parameter H(t), which determines the mix of cautious and adaptive control. The inclusion of this modification to the standard algorithm has been found in practice to improve the stability of the control system, particularly when the adaptive controller is in the initial tuning phase. The recorded utilisation of this control system is 75%, which in a flotation control application is indicative of success.