Sampled-data cooperative semi-global robust practical output regulation for nonlinear multi-agent systems with an uncertain leader

This article explores the problem of sampled-data cooperative robust practical output regulation for nonlinear multi-agent systems whose leader system is unknown. In this study, the nonlinearities of the follower systems are not constrained by the linear growth condition. Based on the robust control technology and the adaptive control technology, a distributed output-based sampled-data control protocol is developed to deal with the uncertainty of the exosystem which can belong to any large known compact set. We first perform the coordinate transformation of closed-loop system to obtain the so-called augmented system, and then perform the stability analysis for this system. As a result, it is proven that the steady-state tracking errors are in any small given neighborhood of the origin. Finally, the performance of the proposed controller is validated by a numerical example.