Adaptive Control of Time-Varying Parameter Systems with Asymptotic Tracking

A continuous adaptive control design is developed for nonlinear dynamical systems with linearly parameterizable uncertainty involving time-varying uncertain parameters. The key feature of this design is a robust integral of the sign of the error (RISE)-like term in the adaptation law which compensates for potentially destabilizing terms in the closed-loop error system arising from the time-varying nature of uncertain parameters. A Lyapunov-based stability analysis ensures asymptotic tracking, and boundedness of the closed-loop signals.