  This paper studies multi-agent systems with nonlinear consensus protocols,
i.e., only nonlinear measurements of the states are available to agents. The
solutions of these systems are understood in Filippov sense since the possible
discontinuity of the nonlinear controllers. Under the condition that the
nonlinear functions are monotonic increasing without any continuous
constraints, asymptotic stability is derived for systems defines on both
directed and undirected graphs. The results can be applied to quantized
consensus which extend some existing results from undirected graphs to directed
ones.
