  This paper investigates a new method for consensus in a group of nonlinear
complex multi-agent systems using fixed-order non-fragile dynamic output
feedback controller, via an LMI approach. The proposed scheme is decentralized
in the sense that each agent relies on the relative output information among
the adjacent agents. The consensus based controllers are designed to minimize
the effects of nonlinear terms of the agents as well as external disturbances.
Converting consensus problem to stabilization of an equivalent augmented system
using proper transformations, Lyapunov stability theorem is applied to obtain
unknown controller parameters in order to guarantee consensus and
simultaneously acquire considered control objectives. Finally, to demonstrate
the effectiveness of the proposed algorithm and compare with similar earlier
researches, a numerical example on a multi-agent system consisting of single
link flexible manipulators is carried out.
