On Appointed-time Reduced-order Observer-based Consensus Protocol Design for Lipschitz Nonlinear Multi-agent Systems

This paper addresses the consensus of Lipschitz nonlinear multi-agent systems under directed graphs. To release the communication burden and avoid potential network attack, it is set that only the relative output information measured by the local sensors can be used to generate the observer and the protocol; while no observer information exchange via communication channel is allowed. Such protocol design structure is known as the distributed attack-free protocols. By viewing the relative input as well as the Lipschitz nonlinearity as the unknown input, the unknown input observer is introduced to formulate the observer. Following this method, a minimal-order appointed-time observer is designed to estimate the consensus error, based on which the fully distributed adaptive protocol is proposed to achieve consensus of the Lipschitz nonlinear multi-agent systems under strongly connected graphs.