Abstract: A longitudinal control method was proposed to improve of robustness for an autopilot cooperative vehicle platooning longitudinal controller considering the time delay of vehicle actuator and the time delay of inter-vehicle communication. A platoon formation model was established with integrating the information including the vehicle position, the spacing deviation between vehicles, the vehicle speeds, and the vehicle accelerations between self-vehicle and the adjacent preceding-vehicle and between self-vehicle and the leadervehicle of the platoon. Boundary conditions of the time delays and the parameters of the PID (proportional, integral, differential) controller were derived based on the Lyapunov stability theory to keep the platoon stability. Simulation analyses were done for a platoon of ten vehicles. The results show that the maximum error is 0.8 m of the deviation of the spaces between vehicles when the controlled vehicle responds with the motion state changing of the adjacent front vehicle and the platoon leader vehicle. Therefore, the rear-end collisions can be avoided when happening a braking deceleration of 0.8 g at the emergency conditions of the platoon leader vehicle.

Key words: road traffic safety, autopilot, cooperative vehicle platooning, longitudinal control, time delays; platoon stability