Delay-adaptive feedback for linear feedforward systems

Predictor techniques are an indispensable part of the control design toolbox for plants with input and state delays of significant size. Yet, they suffer from sensitivity to the design values. Explicit feedback laws were recently introduced by Jankovic for a class of feedforward linear systems with simultaneous state and input delays. For the case where the delays are of unknown length, using the certainty equivalence principle, we design a Lyapunov-based adaptive controller, which achieves global stability and regulation, for arbitrary initial estimates for the delays. We consider a two-block subclass of linear feedforward systems. A generalization to the n-block case involves a recursive application of the same techniques.