Urban platooning using a flatbed tow truck model

Abstract

Finding solutions to traffic congestion is an active area of research. Many ideas have been proposed to reduce this problem, among of this ideas is moving in platoon. The constant time headway policy (CTH) is a very important platoon control policy, but it is too conservative and induces large inter-vehicle distances. Recently, we have proposed a modification of CTH [1], [2]. This modification reduces inter-vehicle distances and makes CTH very practical. This paper focuses on the control of platoons in urban areas. To control the vehicles, we assume that the longitudinal and the lateral dynamics are decoupled. We take into account a simplified engine model. We linearize the two dynamics using exact linearisation technique. Then, we use the modified CTH control law, adapted to urban platoons, for the longitudinal control and the robust sliding mode control for lateral control. The stability and the safety of the platoon are also studied. The conditions of stability of homogeneous and nonhomogeneous platoons are established. The conditions to verify the safety of the platoon for the longitudinal control (assuming stable and accurate lateral control) are exhibited. The weaknesses (large inter-vehicle distance, weak stability near low frequencies) of the CTH are solved. The improved performance and the safety of the platoon are verified by simulation using TORCS (The Open Racing Car Simulator). A platoon consisting of ten vehicles is created and tested on a curved track, keeping a small desired intervehicle distance. The stability and safety of the longitudinal and lateral controls are tested in many scenarios. These scenarios include platoon creation, changing the speed and emergency stop on straight and curved tracks. The results demonstrate the effectiveness of the proposed approach.