Track-Based Aerodynamic Testing of a Two-Truck Platoon

Abstract

<div class="section abstract"><div class="htmlview paragraph">Fuel savings from truck platooning are generally attributed to an aerodynamic drag-reduction phenomena associated with close-proximity driving. The current paper is the third in a series of papers documenting track testing of a two-truck platoon with a Cooperative Adaptive Cruise Control (CACC) system where fuel savings and aerodynamics measurements were performed simultaneously. Constant-speed road-load measurements from instrumented driveshafts and on-board wind anemometry were combined with vehicle measurements to calculate the aerodynamic drag-area of the vehicles.</div><div class="htmlview paragraph">The drag-area results are presented for each vehicle in the two-truck platoon, and the corresponding drag-area reductions are shown for a variety of conditions: gap separation distances (9 m to 87 m), lateral offsets (up to 1.3 m), dry-van and flatbed trailers, and in the presence of surrounding traffic. For the standard aligned platoon, the results demonstrate up to 8% drag reduction for the lead vehicle, with drag reductions exceeding 20% for the trailing vehicle at some yaw angles. Wind-velocity measurements on the following truck suggest that the drag-area reductions are due to a combined effect of reduced apparent wind speed and reduced effective yaw angle in the wake of the lead truck. In the presence of a three-vehicle traffic pattern forward of a single truck, drag-area reductions on the order of 10% were observed relative to the same truck travelling in isolation. When platooning with this surrounding-traffic pattern, the trends and magnitudes of aerodynamic drag reduction are shown to be retained, relative to the platoon in the absence of other traffic, corroborating observed trends in of fuel-savings performed simultaneously.</div><div class="htmlview paragraph">As a supplement to the current study, a first-of-its-kind coast-down test was undertaken with the two-truck platoon where the CACC system was used to maintain a constant distance between the vehicles during each coast. The CACC system was used on the following vehicle when the lead vehicle was coasting and on the lead vehicle when the follower was coasting. Despite some scatter in the data from this proof-of-concept study, the results are consistent with those of the principal constant-speed measurement technique of this paper. This preliminary study demonstrates that the coast-down test method, which previously was only applied for single vehicles, is also applicable to vehicle platoons.</div></div>

Structured learning of safety guarantees for the control of uncertain dynamical systems

“…The trailing vehicle can measure its own speed v 2 , the distance d between the two vehicles, and the road grade α. The aerodynamic drag on the trailing vehicle reduces when d reduces [26], as shown on Figure 5b. Therefore, the control objective is to minimize the distance between the two vehicles, without ever risking a collision.…”

Advances in Vehicle and Powertrain Efficiency of Long-Haul Commercial Vehicles: A Review

“…Platooning has a lower impact on reducing the drag coefficient of the lead truck, resulting in a comparatively smaller FE improvement compared to the following trucks, typically ranging between zero and 5% [100][101][102][103]. The drag coefficient of the following truck decreases with shorter separation from the lead truck, but road safety and braking are limiting factors for the inter-vehicle distance [104][105][106][107]. Speed of platooning trucks, trajectory, spacing, and lane changing also affect fuel consumption [100,101,108].…”

An evaluation framework of automated electric transportation system

“…The "drafting effect" (i.e., a technique where two vehicles or more align in a closing manner in order to reduce the overall effect of drag caused by the front vehicle's slipstream) created would also reduce aerodynamic drag for follower vehicles, thus reducing the amount of energy required to power a vehicle along its path (Browand et al, 1996). It has been shown by field experiments that the average reduction of fuel consumption per vehicle can reach up to 10% when the intervehicle distance is around 10 meters (McAuliffe et al, 2017). Furthermore, recent technological advancements in wireless power transfer (WPT) enable an alternative way to power the in-motion vehicles.…”