Abstract
To contribute to the development of sustainable transport that is safe, eco-friendly, and efficient, this research proposed a safe and ecological speed control system for heavy-duty vehicles on long–steep downhill and sharp-curved roads under a partially connected vehicles environment consisting of connected heavy-duty vehicles (CHDVs) and conventional human-driven vehicles. This system prioritizes braking and lateral motion safety before improving fuel efficiency and ensuring traffic mobility at optimal status, and optimizes the speed trajectories of CHDVs to control the entire traffic. Speed optimization is modelled as an optimal control problem and solved by the iterative Pontryagin’s maximum principle algorithm. The simulation-based evaluation shows that the proposed system effectively reduces the peak temperature of the brake drums, the lateral slip angle of the vehicle wheels, and the lateral load transfer rate of the vehicle body; all these measurements of effectiveness are limited to safe ranges. A detailed investigation reveals that the proposed system reduces fuel consumption by up to 15.49% and inhibits the adverse effects on throughput. All benefits increase with the market penetration rate (MPR) of CHDVs and the traffic congestion level and reach significant levels under low MPRs of CHDVs. This indicates that the proposed system has good robustness for the impedance from conventional vehicles and could be implemented in the near future.
Highlights
Due to the limitations of topography and geological structures, there are often some road sections with poor alignments on mountain highways, such as long–steep downhill and sharp-curved roads [1]
Due to the remarkable performance of this model, it was introduced into the Vehicle Dynamics Analysis Non-Linear (VDANL) module of the Interactive Highway Safety Design Model developed by Federal Highway Administration (FHWA) [13]
To fully use the gravity force to accelerate the connected heavy-duty vehicles (CHDVs) before it reaches the exit point, and optimize the speed profile of the CHDV in the acceleration process, the expected terminal speed is set to be equal to the initial speed that is close to its desired speed before entering the control area
Summary
Due to the limitations of topography and geological structures, there are often some road sections with poor alignments on mountain highways, such as long–steep downhill and sharp-curved roads [1]. These controllers macroscopically optimize the movement of entire traffic consisting of connected vehicles and human-driven vehicles, allowing them to be readily implemented in the real world [52] Most of these traditional controllers prefer to adopt low speed limits to ensure driving safety, and leads to significant adverse effects on the throughput on the roads [53]. The control objective is enhancing safety and improving fuel efficiency for heavy-duty vehicles, while ensuring that the adverse effects on the traffic mobility on these high-risk roads remain minimal This control system contains a brake drum temperature rise model with the consideration of engine braking, and a lateral stability model based on vehicle dynamics model, which can provide accurate time-varying information on braking system and vehicle for enhancing the control effect.
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