Adaptive disturbance estimation applied to harmonic disturbance rejection

The work presented was motivated by a control problem dealing with regulation of molten steel level during continuous casting. The process is such that influx is controlled based on feedback (liquid-) level measurements and feedforward (solidified-) efflux settings. Regulation of the liquid level to set-point is crucial to the quality of the solidified product, and must be achieved in the face of unmeasured oscillatory disturbances. Therefore, a control design methodology was sought that could provide oscillatory disturbance rejection. The author presents a viable solution to an important design equation relative to system disturbance response. The solution is perfectly general, and can be easily extended to non-square system matrices by use of the Moore-Penrose generalized inverse. Furthermore, it is demonstrated through simulation that it is possible to effect harmonic disturbance rejection using proven linear control methodologies enhanced with adaptation. An ad-hoc parameter estimator is used, and it is found that the overall system response is sensitive to some inherent characteristics of the adaptation technique employed. Alternatively, use of more sophisticated parameter estimation algorithms or nonparametric estimation adaptation may lead to better overall response than is demonstrated herein