Evaluation of Platooning Efficiency for Heavy Duty Trucks using Cooperative Adaptive Cruise Control
Type of DegreeMaster's Thesis
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This thesis presents an evaluation of heavy duty truck platooning efficiency through fuel and coastdown testing. The trucking industry accounts for nearly 70% of the freight shipped in the United States. These heavy duty vehicles travel on average 5x more miles than passenger vehicles and consume billions of gallons of fuel. The trucking industry has a large potential for vehicle automation to achieve benefits such as reduced traffic congestion, increased safety, and reduced fuel consumption and greenhouse gas emissions. Cooperative Adaptive Cruise Control (CACC) is a vehicle automation system that allows two or more vehicles to act cooperatively by using Vehicle 2 Vehicle communication. This thesis describes a CACC system implemented on two heavy duty trucks to travel in close proximity to each other, or platoon. The main benefit of CACC truck platooning is fuel savings from aerodynamic drag reduction. The CACC system was evaluated through a series of test campaigns in order to study the benefits of truck platooning. An extensive fuel test was completed on a test track to study the fuel savings in a controlled environment. The nominal, aligned platoon was evaluated and the results were similar in magnitude and trends to prior work. Additionally, mixed traffic scenarios were tested with a forward pattern of passenger vehicles and a heavy duty truck to provide more realistic conditions like those experienced on-road. A novel aerodynamic evaluation, the controlled platoon coastdown, was then completed to quantify the drag area reduction of truck platooning. Previously, prior research described that coastdown testing could not be applied to platoons of vehicles because there is no method to maintain the gap distance between vehicles. In this thesis, the CACC system was modified to maintain the gap distance and complete a platoon coastdown in the lead and following vehicle positions. The drag area reductions for the following vehicle were distinct and significant in magnitude, 16.8 - 23.1% for the gap distances tested. The calculated drag reductions were also converted to an estimated fuel savings for comparison to the fuel test, and the results were within 2.3% of each other. In an effort to extend this work, a final test campaign was completed for on-road platooning. The highway fuel test is introduced, and the basic gravimetric results are presented. The fuel savings were lower than expected based on similar track-based tests, but the results are put into context with a study of the amount of traffic and platoon interactions. Future improvements to the CACC system and further evaluations of this truck platooning system are discussed.