  Two types of general nonlinear consensus protocols are considered in this
paper, namely the systems with nonlinear measurement and communication of the
agents' states, respectively. The solutions of the systems are understood in
the sense of Filippov to handle the possible discontinuity of the nonlinear
functions. For each case, we prove the asymptotic stability of the systems
defined on both directed and undirected graphs. Then we reinterpret the results
about the general models for a specific type of systems, i.e., the quantized
consensus protocols, which extend some existing results (e.g., [1,2]) from
undirected graphs to directed ones.
