Methods of Optimal Control for Fuel Efficient Class-8 Vehicle Platoons Over Uneven Terrain

Abstract

This thesis implements an NMPC control system to facilitate fuel-optimal platooning of class-8 vehicles over challenging terrain. Prior research has shown that Cooperative Adaptive Cruise Control (CACC), which allows multiple class 8 vehicles to follow in close proximity, can save between 3-8% in overall fuel consumption on flat terrain. However, on more challenging terrain, e.g. rolling hills, platooning vehicles can experience diminished fuel savings, and, in some cases, an increase in fuel consumption relative to individual vehicle operation. This research explores the use of Nonlinear Model Predictive Control (NMPC) with pre-defined route grade profiles to allow platooning vehicles to generate an optimal velocity trajectory with respect to fuel-consumption. In order to successfully implement the NMPC system, a model relating vehicle-velocity to fuel-consumption was generated and validated using experimental data. Additionally, the pre-defined route grade profiles were created by differencing a vehicles GPS-velocity over the desired terrain profile. The real-time NMPC system was then implemented on a two-truck platoon operating over challenging terrain, with a reference vehicle running individually. The results from NMPC platooning are compared against classical proportional-integral-derivative (PID) platooning methods to obtain comparative fuel-savings and energy efficiency. In the final analysis, significant fuel savings of greater than 14&20% were seen for the lead and following vehicles relative to their respective traditional cruise-control and platooning architectures.