Robust level control of a dry-surge ore pile

This paper presents a new method for controlling the height of a mineral processing dry-surge ore pile between specified upper and lower levels by manipulating the outlet ore flow. The upper level should not be exceeded for safety, while the height should always be higher than the lowest allowable level to maintain a reserve for continuous operation downstream of the ore pile. However, this is a non-trivial control problem because the disturbance of the unpredictable discontinuous ore input must be attenuated in the continuous outlet ore flow. In addition, ore is mined from multiple sites and causes the physical properties of the ore to be uncertain. To deal with these issues, a control problem is formulated to attenuate the disturbance from the discontinuous feed and guarantee stability given the inaccurate process model. To solve the formulated control problem, a robust height controller is developed using the linear matrix inequality technique. It is shown that the robust controller attenuates four times more variability in outlet ore flow than a gain-scheduled PI controller and guarantees robust closed loop stability.