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A Maneuver-Based Threat Assessment Strategy for Collision Avoidance

SAE International Journal of Passenger Cars - Electronic and Electrical Systems

Beihang University, China-Weiwen Deng
General Motors LLC, USA-Jinsong Wang
  • Journal Article
  • 07-12-01-0003
Published 2019-08-22 by SAE International in United States
Advanced driver-assistance systems (ADAS) are being developed for more and more complicated application scenarios, which often require more predictive strategies with better understanding of the driving environment. Taking traffic vehicles’ maneuvers into account can greatly expand the beforehand time span for danger awareness. This article presents a maneuver-based strategy to vehicle collision threat assessment. First, a maneuver-based trajectory prediction model (MTPM) is built, in which near-future trajectories of ego vehicle and traffic vehicles are estimated with the combination of vehicle’s maneuvers and kinematic models that correspond to every maneuver. The most probable maneuvers of ego vehicle and each traffic vehicles are modelled and inferred via Hidden Markov Models with mixture of Gaussians outputs (GMHMM). Based on the inferred maneuvers, trajectory sets consisting of vehicles’ position and motion states are predicted by kinematic models. Subsequently, time to collision (TTC) is calculated in a strategy of employing collision detection at every predicted trajectory instance. For this purpose, safe areas via bounding boxes are applied on every vehicle, and Separating Axis Theorem (SAT) is applied for collision prediction…
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Simulation Study on the Airflow and Heat Transfer Characteristic in a Nacelle

Beihang University, China-Yongqi Xie, Jianzu Yu, Hongxia Gao
Published 2008-06-23 by SAE International in United States
Five design schemes of helicopter nacelle ventilation cooling system were proposed to provide efficiently cooling for the nacelle. In order to evaluate the cooling effect of these design schemes, the characteristic of airflow and heat transfer in the nacelle was numerically calculated by a general CFD software. Unstructured mesh and finite volume method (FVM) were applied for calculation regions and governing equations discreteness, and standard k - ε model was adopted to solve turbulent governing equation. For five schemes of nacelle cooling system, the influence of cooling air inlet size, position, mass flow rate and ambient temperature under hover condition on the flow and temperature field distributions was discussed. Also transient calculations were carried out when the engine was shut down. The results provided a theoretical basis for design and optimization of nacelle ventilation cooling system.
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Influence of the Length of Valve Slots on ECHPS Performance

Beihang University, China-Liu Yahui, Gao Feng
Tshighua University, China-Ji Xuewu
Published 2007-08-05 by SAE International in United States
The flow-control type electronically controlled hydraulic power steering system (hereinafter ECHPS) is the simplest form of ECHPS. To get better performance, the power steering gear should be modified. One of the modification methods is cutting short the slot of the valve. One common formula could compute the orifice size of the control valve was given and several valves with different length of slots were analyzed based on the formula. The assistance characteristics of ECHPS with these valves were calculated. At last, two steering gears with different slot length were made for experiment. The results show the assistance characteristics of the short slot valve is better than the long slot one.
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