The authors treat the control of a chip refiner to produce wood pulp, where the incremental gain between the motor load and the plate gap is subject to sudden changes due to pad collapse. Passive adaptive control with fault detection, active suboptimal dual control, and dual-control solutions are discussed. For dual control, the choice of the control criterion is crucial, as it must reflect the peculiarities of the process. Two nonquadratic performance indices are proposed, and the myopic solutions are computed. Simulations show the superior performance offered by these indices. >