  This brief addresses the distributed consensus problem of nonlinear
multi-agent systems under a general directed communication topology. Each agent
is governed by higher-order dynamics with mismatched uncertainties, multiple
completely unknown high-frequency gains, and external disturbances. The main
contribution of this brief is to present a new distributed consensus algorithm,
enabling the control input of each agent to require minimal information from
its neighboring agents, that is, only their output information. To this end, a
dynamic system is explicitly constructed for each agent to generate a reference
output. Theoretical and simulation verifications of the proposed algorithm are
rigorously studied to ensure that asymptotic consensus can be achieved and that
all closed-loop signals remain bounded.
