Design and evaluation of cooperative adaptive cruise control (CAAC) for the improvement of highway traffic flow

The subject of intelligent transportation systems (ITS) began to take worldwide attention in the last decade. One main purpose of deploying ITS is the improvement of traffic flow capacity on highways while ensuring safety. Cooperative Adaptive Cruise Control (CACC) is a method used to support the flow of road vehicles at a safe distance in the form of vehicle strings. In order to enable small inter-vehicle spacing, CACC is implemented on each vehicle by the use of vehicle distance measurements as well as information from other vehicles via vehicle-to-vehicle communication. An important goal of CACC is the achievement of string stability in order to attenuate fluctuations in the vehicle motion along vehicle strings. Hereby, CACC designs in the literature are lmited to the case of homogeneous vehicle strings, where all vehicles have identical dynamic properties. In the first part of this thesis, an original CACC H∞ controller design method is developed for the practical case of heterogeneous vehicle strings while achieving v string stability. The second part of this thesis considers the issue of delay in the CACC control design for platoons of vehicles. Several H∞ control design methods for time-delay systems are applied to address both communication and vehicle plant delay. For each method, a longitudinal controller for a platoon of vehicles is obtained which results in the achievement of string stability. In addition, a comparison of the different methods regarding the supported delay and inter-vehicle spacings is performed. The findings of the thesis are supported by representative simulation experiments. We note that, to the best of our knowledge, no research has considered the CACC design for heterogeneous vehicles and CACC design with delay.