Dual-Rate Adaptive Control for Mixed Separation Thickening Process Using Compensation Signal Based Approach

The mixed separation thickening process (MSTP) of hematite beneficiation is a strong nonlinear cascade process with frequency of slurry pump as input, underflow slurry flow-rate (USF) as inner-loop output, and underflow slurry density (USD) as outer-loop output. The model parameters such as settling velocity of slurry particles and slurry height are unknown and nonlinear. Moreover, these model parameters vary from flotation middling, sewage, and magnetic separation slurry. In this paper, the unknown change of the above dynamic characteristics are described by the previous sample unmodeled dynamics and its change rate. A novel adaptive controller using compensation signal based approach is developed. Inner-loop closed-loop control system equation and lifting technology are adopted to develop dual rate adaptive control method. Two compensation signals are constructed and added onto the linear proportional-integral (PI) controller. Such two compensation signals aim at eliminating the effects of the previous sample unmodeled dynamics and tracking error, respectively. The stability and convergence analysis is given and a simulation experiment on hardware-in-the-loop simulation system of MSTP based on industrial data is carried out, where it shows that the USD, USF, and its changing rate can be controlled well inside their targeted ranges when the system is subjected to unknown variations of its parameters.