本論文探討一單輸入單輸出系統步階輸入訊號的強健追蹤控制問題。不同於許多相關文獻直接從△-G-K架構進行分析(其中G並非原始的受控體),我們將依常態控制對象有無極點或零點在原點處來分別進行討論。我們推導出各類型受控體,在不同的不確定因素干擾下,仍然保有追蹤能力的充要條件並且提供相關控制器設計方法。而對閉迴路系統所能容許的不確定因素大小也提供了簡單的上界估測。 This paper investigates the robust control problem of tracking a stepinput to a single-input-single-output system. In contrast to severalrelevant papers starting analyses directly from the △-G-K framework(where G is not the original plant), our discussion proceeds fordifferent cases in which assumptions for the nominal plants are madebased on whether they have a zero or pole at the origin. We derivenecessary and sufficient conditions for keeping robust tracking up inthe presence of different kinds of uncertainty for the cases andprovide the relevant controller design method. Simple upper boundestimates for the size of admissible uncertainty are given.