Adaptive Systems with Closed-loop Reference Models: Stability,   Robustness and Transient Performance
  This paper explores the properties of adaptive systems with closed-loop reference models. Using additional design freedom available in closed-loop reference models, we design new adaptive controllers that are (a) stable, and (b) have improved transient properties. Numerical studies that complement theoretical derivations are also reported. 
Travis E. Gibson, Anuradha M. Annaswamy and Eugene Lavretsky
math.OC cs.SY nlin.AO