Plugging is well known to be a major cause of instability in industrial cement mills. A simple nonlinear model able to simulate the plugging phenomenon is presented. It is shown how a nonlinear robust controller can be designed in order to fully prevent the mill from plugging.
Grognard, F., Jadot, F., Magni, L., Bastin, G., Sepulchre, R., & Wertz, V. (2001). Robust stabilization of a nonlinear cement mill model. IEEE Transactions on Automatic Control, 46(4), 618-623. https://doi.org/10.1109/9.917663 (Original work published 2001)