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    Research Project
    Dwight David Eisenhower Transportation Fellowship Program (DDETFP) Graduate Fellowship
    Mechanical Engineering; TAMU; https://hdl.handle.net/20.500.14641/542; Department of Transportation-Federal Highway Administration
    There has been a renewed interest in connected and autonomous vehicles with commercial deployment expected in the near future. Connected vehicles have the potential to improve mobility on roadways by increasing throughput as they allow vehicle following with short inter-vehicular gaps that would otherwise be unsafe for a human driver to maintain. Such platoons have the added benefit of reducing net fuel consumption due to aerodynamic drafting. Naturally, the study of vehicle platoons and vehicle following strategies is important for the future of mobility. Some modern passenger vehicles come equipped with Adaptive Cruise Control (ACC), though the implementation varies from manufacturer to manufacturer. Typically, ACC systems allow the user to choose among a few preset time headway options and rely on on-board sensors such as radars/cameras to estimate the relative distance and relative velocity to the vehicle in front. To prevent collisions in a platoon of such vehicles, local uctuations in spacing errors need to be damped out as it propagates down the string of vehicles. It is known [1] that to guarantee string stability for a homogeneous ACC platoon, the time headway employed has to be at least twice the parasitic lags in the vehicles. For a typical passenger car, the actuation lags are in the range of 0:2s to 0:5s , which yields a minimum time headway of 0:4s to 1s. This translates to an inter-vehicle spacing of about 12 to 30 metres at highway speeds. Heavy freight trucks may have larger actuation lags, necessitating spacing greater than 30m. This may not be lucrative especially if the goal is to reduce net fuel consumption, which requires such vehicles to follow closely in order to take advantage of slip-streaming We can further reduce the time headway by equipping the vehicles with wireless transceivers to communicate with each other. Cars can use Vehicle to Vehicle (V2V) communication to obtain additional information about the preceding vehicle's acceleration; this is referred to as Cooperative Adaptive Cruise Control (CACC). A more advanced communication topology can also be utilized which involves using information from two preceding vehicles; we refer to this as CACC+. Analytical results on CACC and CACC+ platoons in the past were built on the assumption that the communication link between the vehicles is ideal. But, in reality, wireless links often experience packet drops and other imperfections due to interference or bandwidth restrictions. Over the course of this project, we built on previous results to incorporate packet drop phenomenon and determine the minimum string stable time headway for both CACC and CACC+ platoon. A copy of the relevant published papers are provided as an attachment.