Optimal Platooning of Heavy-Duty Vehicles

Abstract: The vehicle and transport industry have a constant strive towards reduced fuelconsumption  and  for  HDVs  are  there  numerous  of  different  approaches.   Twoapproaches that have been proven to reduce fuel consumption in previous workare look-ahead control (LAC) and platooning. LAC uses knowledge about the fu-ture road topography to optimize the vehicles velocity. Platooning is when HDVsdrive relatively close to each other in order to reduce air drag.  Platooning vehi-cles can also optimize their velocity based on the preceding vehicles trajectory,known as adaptive look-ahead control (ALAC).Utilizing LAC/ALAC can enable a pulse-and-glide (PnG) strategy, where thevehicle engages neutral gear and freewheels e.g. in a downhill. Thereby reducesthe fuel consumption.  So, the main purpose of this thesis was to study how pla-tooning vehicles and the control strategy known as pulse-and-glide (PnG) inter-act when pursuing lower fuel consumption.  Therefore, a vehicle model, a pla-toon model and optimization-based controllers (LAC/ALAC) were designed anddeveloped.   For the optimization-based controllers was dynamic programming(DP) chosen as optimization solver.The results shows that the combination of these approaches has a great poten-tial to enable substantial fuel reduction, both for individual vehicles and for theentire platoon.  The most suitable strategy, in terms of fuel consumption, for theplatoon as a whole is closely related to the one for individual vehicles. The strate-gies resulting in the largest fuel reduction for a single vehicle does also give thelargest total fuel reduction for the platoon as a whole.  According to the results,a lead vehicle should utilize both LAC and PnG. The other platooning vehiclesshould  employ  ALAC  in  order  to  also  utilize  PnG  meanwhile  keeping  a  shortintermediate distance.According to the results the greatest potential fuel reduction is achieved forthe downhill segment. For the last vehicle in the platoon it is as high as 42 %, com-pared to the nominal case (a single vehicle using conventional cruise control andnot shifting gears). The potential fuel reduction for the flat and uphill segmentsare similar to each other, 22 % and 20 % respectively. For all three segments PnGaccounts for roughly 1-3 percentage points of the entire platoons fuel reduction.In reality the road topography is constantly varying, so it is also promising thatthe fuel efficiency is improved for all types of road segments