ROBUSTNESS OF DISCRETE-TIME ADAPTIVE CONTROLLERS - AN INPUT-OUTPUT APPROACH

In this note, we present a general input-output approach that can be u sed for the design and analysis of robust discrete-time adaptive contr ol schemes. In particular, we consider a model reference adaptive cont roller. The design approach involves the use of the Certainty Equivale nce Principle to combine a robust control structure with a robust adap tive law. Using exponentially weighted l2 norms and exploiting the pro perties of the adaptive law and the control structure, robust stabilit y is established for the closed loop adaptive control scheme. For clar ity of presentation, the analysis is kept qualitative, though necessar y modifications are indicated for obtaining a quantitative result.