A Distributed Reference Governor Approach to Ecological Cooperative Adaptive Cruise Control

To achieve a safe vehicle platooning system, it is essential to guarantee the string stability of the vehicle platoon while handling the safety, comfort, and performance constraints. This paper presents a distributed reference governor (RG) approach to the constraint handling of vehicle platoons equipped with cooperative adaptive cruise control. First, a string stable platoon is designed based on a frequency-domain approach. Second, an RG is designed that sits behind the controlled system and keeps the output inside the defined constraints. RG does not change the behavior of the controlled system; therefore, the platoon remains string stable based on the frequency-domain design. Only when there is a possibility of violating the defined constraints, the RG would intervene to push the system back into the constraints. Third, to improve the platoon's energy economy, a controller is presented for the leader's control using nonlinear model predictive control method, assuming it is a plug-in hybrid electric vehicle. Evaluations performed with a platoon model constructed using high-fidelity models of the baseline vehicle show that the proposed method is able to simultaneously maintain the string stability and platooning constraints, while improving the total energy economy of the entire platoon. Moreover, the results of the hardware-in-the-loop testing demonstrate the performance of the proposed controller in real-time application.