  This paper addresses the output synchronization problem for heterogeneous
nonlinear multi-agent systems with distributed event-based controllers.
Employing the two-step synchronization process, we first outline the
distributed event-triggered consensus controllers for linear reference models
under a directed communication topology. It is further shown that the
subsequent triggering instants are based on intermittent communication.
Secondly, by using certain input-to-state stability (ISS) property, we design
an event-triggered perturbed output regulation controller for each nonlinear
multi-agent. The ISS technique used in this paper is based on the milder
condition that each agent has a certain ISS property from input (actuator)
disturbance to state rather than measurement (sensor) disturbance to state.
With the two-step design, the objective of output synchronization is
successfully achieved with Zeno behavior avoided.
