直線位相フィルタ型離散時間修正繰り返し制御とむだ時間補正型離散時間修正繰り返し制御の特性比較

Abstract

The modified repetitive control system is designed using a modified repetitive controller with a low-pass filter incorporated into the positive feedback loop for the time-delay element. The modified repetitive controller, however, functions only for the gain determined by the low-pass filter at the basic frequency as the desired value and the frequency obtained by multiplying it by integers. This problem can be solved by two methods: one is by using a modified repetitive controller with linear phase filter and the other by using a modified repetitive controller with corrected dead time.This paper describes the results of our study about the above two methods to identify the differences between them in their control characteristics and formulate the guidelines for their use as summarized below:(1) The modified repetitive controller with linear phase filter can basically function as well as the modified repetitive controller with corrected dead time only if its filter is of higher order. However, if the spectrum of the desired value is distributed over a wide frequency range, the use of a higher-order filter in the controller to increase its gain conversely results in narrowed frequency bandwidth, not providing so much improvement in its control performance as expected, and frequently presenting the practical problem of increasing the time required for the computation. Notwithstanding this, if the spectrum is locally distributed in a narrowed frequency range close to the basic frequency, an increase in the order of the filter used in the controller as allowed by the computation time enables its control performance to be improved.(2) The modified repetitive controller with corrected dead time, even if its filter is of first order, can perform its control function comparable to that of the modified repetitive controller with higher-order linear phase filter. This controller is a practical control method, particularly having the great advantage of increasing its gain to∞for direct current.