Lyapunov-based Adaptive Output-Feedback Control of MIMO Nonlinear Plants with Unknown, Time-varying State Delays

In this paper, we develop a model reference adaptive control (MRAC) scheme for a class of multi-input-multi-output (MIMO) non-linear dynamic systems with unknown time-varying state delay which is also robust with respect to an external disturbance with unknown bound. An output feedback adaptive control scheme uses feedback actions only, and thus does not require a direct measurement of the command or disturbance signals. A suitable Lyapunov-Krasovskii type functional is introduced to design the adaptation algorithms and to prove stability.