  We study the platoon control of vehicles with third-order nonlinear dynamics
under the constant spacing policy. We consider a vehicle model with parameter
uncertainties and external disturbances and propose a distributed control law
based on an event-triggered extended state observer (ESO). First, an
event-triggered ESO is designed to estimate the unmodeled dynamics in the
vehicle model. Then based on the estimate of the unmodeled dynamics, a
distributed control law is designed by using a modified dynamic surface control
method. The control law of each follower vehicle only uses the information
obtained by on-board sensors, including its own velocity, acceleration, the
velocity of the preceding vehicle and the inter-vehicle distance. Finally, we
give the range of the control parameters to ensure the stability of the vehicle
platoon system. It is shown that the control parameters can be properly
designed to make the observation errors of the ESOs bounded and ensure the
string stability and closed-loop stability. We prove that the Zeno behavior is
avoided under the designed event-triggered mechanism. The joint simulations of
CarSim and MATLAB are given to demonstrate the effectiveness of the proposed
control law.
