Smith Predictor Compensating for Vehicle Actuator Delays in Cooperative ACC Systems

Cooperative adaptive cruise control (CACC) employs intervehicle wireless communications to realize short intervehicle distances and, hence, to improve road throughput. However, the vehicle actuator delay and communication delay have a significant effect on the (string) stability properties. Therefore, a Smith predictor has been applied to compensate for the vehicle actuator delay, while utilizing a proportional-derivative controller and a constant time gap spacing policy. The control actuation is conducted on a delay-free vehicle model to follow a preceding vehicle with a desired distance, such that the resulting scheme leads to individual vehicle stability independent of the vehicle actuator delay. Moreover, this approach allows for a smaller minimum string-stable time gap compared to without the compensator, thus taking full advantage of CACC. In addition, the Smith predictor has been adapted to take acceleration disturbances into account. The results are experimentally validated using a platoon of two passenger vehicles, illustrating the practical feasibility of this approach.