This paper investigates consensus problems for continuous-time multiagent systems with time-varying communication graphs subject to input noise. Based on input-to-state stability and integral input-to-state stability, robust consensus and integral robust consensus are defined with respect to L∞ and L 1 norms of the noise function, respectively. Sufficient and/or necessary connectivity conditions are obtained for the system to reach robust consensus or integral robust consensus under mild assumptions. The results answer the question on how much interaction is required for a multiagent network to converge despite a certain amount of input disturbance. The -convergence time is obtained for the consensus computation on directed and K-bidirectional graphs.
Introduction.Coordination of multiagent networks has attracted a significant amount of attention in the past few years, due to its broad applications in various fields of science including physics, engineering, biology, ecology, and social science [42,15,25,21,9]. Distributed control using neighboring information flow has been shown to ensure collective tasks such as formation, flocking, rendezvous, and aggregation [24,17,18,19,30].Central to multiagent coordination is the study of consensus, or state agreement, which requires that all agents achieve a common state. The idea of distributed consensus arose as early as 1980s in the classical work [41] for the study of distributed optimization methods. Since then consensus seeking has been extensively studied in the literature for both continuous-time and discrete-time models [15,21,38,39,3,4,28,18,45,46,49,48], where node interactions are carried out over an underlying communication graph. The connectivity of this communication graph plays a key role in consensus analysis. The "joint connectivity," i.e., connectivity defined on the union graph over a time interval, and similar concepts are important in the analysis of consensus stability with time-dependent topology. Uniformly joint connectivity, which requests that the union graph be connected for all intervals longer than some positive constant, has been employed for consensus problems for discrete-time and continuous-time agent dynamics, as well as directed and undirected interconnection topologies [41,15,18,13,6]. In [15], the authors proved the consensus of a simplified Vicsek model under uniformly joint connectivity, followed by some more precise analysis in [3,4,28]. In [13] and [6], the jointly connected coordination was investigated for second-order agent dynamics. A nonlinear continuous-time *