Redesign and Stability Analysis of Input/Output Variable Structure Model-Reference Adaptive Control (I/O VS-MRAC) Systems

Redesign and stability analysis of I/O VS-MRAC systems are presented. The key novel idea is to consider the effect of the uncertainty on the plant "high-frequency gain" (HFG) as an input disturbance acting on a plant with known (nominal) HFG. This leads to redesign and substantial simplification of the stability analysis, under less restrictive assumptions. Detailed discussion is presented for the case of relative degree n*= 2. The paper briefly indicates how the analysis is (more easely) extendable to the general case n*¿2.