  Control problems of mixed-autonomy traffic system consisting of both
Human-driven Vehicles (HV) and Autonomous Vehicles (AV) have gained increasing
attention. This paper is focused on suppressing traffic oscillations of the
mixed-autonomy traffic system using boundary control design. The mixed traffic
dynamics are described by a 4 x 4 hyperbolic partial differential equations
(PDE) which governs propagation of four properties in traffic including density
of HV, density of AV, friction between two classes of vehicles from driving
interactions, and averaged velocity. We propose event-triggered boundary
control design since control signal of traffic light on ramp or varying speed
limit cannot be updated in a continuous time fashion. We apply event-triggered
mechanism for a PDE backstepping controller and obtain dynamic triggering
condition. Lyapunov analysis is conducted to prove the exponential stability of
the closed loop system with the event-triggered controller. Numerical
simulation demonstrates how car-following spacing of AV affects
event-triggering mechanism of control input in mixed-autonomy traffic.
