Abstract
For a conventional modified repetitive control system, designing of its pre-compensator so as to maximize the lowpass filter band width has been considered to contribute to the improvement of its control performance such as its tracking performance for reference input and its insensitivity to disturbance. The control performance of the control system, however, basically depends on its sensitivity function in the main frequency bands possessed by the reference input and disturbance. This fact suggests that the control performance of the control system should be evaluated using its sensitivity function. Therefore, the sensitivity functions of the conventional modified repetitive control system and the modified repetitive control system with corrected dead time already proposed by the authors were first calculated. The results of the calculation showed that the expansion of the lowpass filter band width did not necessarily result in improved sensitivity function of the control system in the intended frequency band.
The results of the investigation, however, indicated that some sensitivity functions of both systems to be compared intersect with each other in the intended frequency bands, suggesting that it is difficult to judge precisely whether the control performance of the system are good or not by its sensitivity function. Therefore, a new design method applicable both for the conventional modified repetitive control system and our proposed modified repetitive control system with corrected dead time was proposed. This newly proposed design method is based on simulation of such a modified repetitive control system to calculate its performance index IAE (integral of absolute value of error) and design the system so as to minimize its IAE.
The overall results of the investigations thus conducted by the authors revealed that a modified repetitive control system with corrected dead time, if so designed using the newly proposed method as to minimize its IAE, can achieve further improvement in its control performance.
