Robustification of sample-and-hold stabilizers for control-affine time-delay systems

This paper deals with the stabilization in the sample-and-hold sense of nonlinear, control affine, retarded systems, affected by actuation disturbances and observation errors. Input-to-state stability redesign methods are used in order to design a new sampled-data controller. It is shown that stabilization in the sample-and-hold sense can be preserved by means of this new controller, regardless of the above disturbances and errors. It is assumed that both actuator disturbance and observation error are bounded, and the (arbitrary) bounds are known a-priori. It is moreover assumed that the observation errors do not affect or affect marginally the new control term obtained by input-to-state stability redesign. Simulations on a continuous stirred tank reactor with recycle validate the theoretical results.