Abstract: The stability of the feedback interconnection of a linear stable system and a bounded perturbation is studied in time domain in this paper. It's shown how a complex system can be characterized by integral quadratic constraints(IQC's). And the IQC's theory in the time domain is given. For such model, A sufficient condition for the stability of the feedback interconnection is obtained, in some cases, this condition is also necessary. As the applications of the result in this paper, the problem of absolute stability is considered, then the time-varying circle criterion and other stability criteria are given.

Key words: integral quadratic constraint, time-varying system, stability

摘要： 在时域内研究了由一个稳定的线性系统和一个有界因果系统所构成的反馈内联系统的输入输出稳定性问题，给出了时域内的IQC的理论框架，得到了判定反馈内联系统稳定性的一些判据，同时也得出了一些必要条件。最后，作为前面结果的一个应用，将所得的结果应用到绝对稳定性问题中，得到了时变的圆判据和其他的一些稳定性判据。

关键词: 时变系统, 稳定性, 积分二次约束(IQC)