Indirect robust model reference adaptive control for discrete-time system with output uncertainty

For a class of more general discrete-time systems with output uncertainty, the design and analysis of robust indirect model reference adaptive control (MRAC) with normalized adaptive law are investigated. The main work includes three parts. Firstly, it is shown that the constructed parameter estimation algorithm not only possesses the same properties as those of traditional estimation algorithms, but also it avoids the possibility of division by zero. Secondly, by establishing a relationship between the plant parameter estimate and controller parameter estimate, some similar properties of the latter are also established. Thirdly, by using the relationship between the normalizing signal and all the signals of the closed-loop system, and some important mathematical tools on discrete-time systems, a systematic stability and robustness analysis approach to the discrete indirect robust MRAC scheme is developed rigorously.