Optimal Decentralized Platoon Management and Control of Autonomous Cars

Kurzfassung

To deal with current high level of congestion, especially in urban areas, as bottleneck of mobility, connected vehicle system in the form of platoon or Connected Cruise Control (CCC) might be the solution as it decreases stop-and-go significantly as well as fuel economy. A system of vehicular platoon is a string of two or more closely vehicles traveling with desired cruising velocity and distance. Compared with human drivers, an automatic platoon control system has the advantages of decreasing intervehicle distance (i.e., tight formation), and is thus considered a promising solution for reducing traffic congestion, aerodynamic drag, and fuel consumption. In last decades highway platooning, by focus on truck platooning, has been investigated but urban platooning has come to attention only recently, [1] , [2]. Urban platooning, unlike the highway platooning in which the vehicles drives several kilometrages together, has very dynamic nature. Therefore, a decentralized management module is needed to define when and how a vehicle can join another vehicle and form a platoon or leave its current platoon. At the same time, this module must react to non-cooperative road users and make interaction between platoon members and other road-users possible. In the European project MAVEN (Managing Automated Vehicles Enhances Network), [3], a platoon management module has been designed, developed and tested by using an extended version of the standard message CAM (cooperative awareness message), [4]. In order to make the platoon management generic and usable out of MAVEN scope, standard messages must be used instead of extended one. In the European project TransAID, [5], a Maneuver Coordination Message (MCM) is proposed that can be used in cooperative maneuvers with or without infrastructure support, [5]. The MCM, which is in standardization process, can replace the extended messages used in MAVEN. Managing a platoon is not the only challenge, keeping the platoon stable is also crucial. The tight formation control of a platoon has a particular difficulty known as “string instability”, i.e., disturbances of system states are amplified along the string of vehicles. The string instability of tight formation platoons can cause the emergence of a jam (e.g., stop and go) without bottleneck in both circuits and highways, which seriously compromises the benefits of platoon control. A platoon is said to be string stable if it has the property, i.e., the disturbances are not amplified when propagating along the vehicle string, [7]. That’s why a string-stable controller is needed to be designed overcome the above mentioned issues.