To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster an...To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.展开更多
With an increasing number of vehicles with alternative powertrains, the choice of the most appropriate powertrain system for a vehicle class or a load cycle is challenging. This paper introduces a method to design an ...With an increasing number of vehicles with alternative powertrains, the choice of the most appropriate powertrain system for a vehicle class or a load cycle is challenging. This paper introduces a method to design an optimal alternative powertrain based on a longitudinal dynamic simulation. The objective function of the minimization problem describes the characteristic map of the traction system. The goal of the optimization is to minimize fuel consumption respectively energy demand. Different types of propulsion systems are investigated. The results show that the proposed method delivers useful alternative powertrains by applying an optimization with reasonable restrictions.展开更多
Roadways in Wyoming are characterized by challenging horizontal profiles,vertical profiles,a combination of the two and adverse weather conditions,all of which affect vehicle stability.In this study,we investigated th...Roadways in Wyoming are characterized by challenging horizontal profiles,vertical profiles,a combination of the two and adverse weather conditions,all of which affect vehicle stability.In this study,we investigated the impact of different operating speeds when negotiating combined horizontal and vertical curves under unfavorable environmental conditions on Wyoming’s interstates via vehicle dynamics simulation software.The simulation tools provided the acting forces on each tire of the vehicle and the side friction(skidding)margins.This allowed for examining the interaction between vehicle dynamics and road geometry in such alignments.Also,linear regression analysis was implemented to investigate the skidding margins based on the simulation results to demonstrate when a vehicle is more likely to deviate from its desired trajectory.Specifically,this examines the contributing factors that significantly influence the skidding margins.The results indicated that:1)the skidding margins are dramatically decreased by adverse weather conditions even with lower degree of curvature and gradient values of combined curves and more particularly at higher operating speeds conditions.Increasing the vehicle speed on the curve by 10%,the skidding margin dropped by 15%.2)Compared to heavy trucks and sports utility vehicles(SUVs),passenger cars require the highest side friction demand.3)The effect of applying brakes on vehicle stability depends on the road surface condition;applying the brakes on snowy road surfaces increases the potential of vehicle skidding especially for heavy trucks.This study assessed the curve speed limits and showed how important to assign safe and appropriate limits speed since the skidding likelihood is significantly sensitive to the vehicle speeds.This study is beneficial to Wyoming’s roadway agencies since hazardous sections having combined horizontal and vertical curves are identified.Also,critical situations that require additional attention from law enforcement agencies are pinpointed.Finally,recommendations that are valuable to roadway agencies are made based on this study’s findings.展开更多
The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of g...The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of great concern to transportation agencies. Therefore, high-fidelity vehicle dynamics simulation modeling was implemented to investigate the rollover propensity of trucks navigating curves. Scenarios included various road geometric designs, truck characteristics and wind conditions. A multiple linear regression model was also developed to investigate the impact of key parameters on truck rollover propensity. The modeling results indicated that wind speed and direction were influential factors in terms of truck roll stability. Trucks had a 76% higher chance of rolling over when subjected to 40 mph winds relative to being subjected to 20 mph winds assuming all else was unchanged. This study also demonstrated that the most unfavorable wind direction was not perpendicular (90 degrees) to the truck since the truck would continuously change its orientation when traversing combined horizontal and vertical curves. Its speed would also constantly fluctuate. On the contrary, this study’s results indicated that the 120-degree wind direction was the most critical one. Also, under blowing lateral wind conditions, the gross weight of the truck was found to be a contributing factor to rollover risk. Its impact varied depending on the radius of the horizontal curve the truck was navigating. This critical interaction was ignored in the road safety literature. This study offered new insights about the impacts of truck rollover precursors and, hence, this would lead to the proposition of effective truck safety countermeasures.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.50909025
文摘To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.
文摘With an increasing number of vehicles with alternative powertrains, the choice of the most appropriate powertrain system for a vehicle class or a load cycle is challenging. This paper introduces a method to design an optimal alternative powertrain based on a longitudinal dynamic simulation. The objective function of the minimization problem describes the characteristic map of the traction system. The goal of the optimization is to minimize fuel consumption respectively energy demand. Different types of propulsion systems are investigated. The results show that the proposed method delivers useful alternative powertrains by applying an optimization with reasonable restrictions.
基金the generous financial support of the Wyoming Department of Transportation (WYDOT)Mountain-Plains Consortium (MPC) (Grant number: 69A3551747108 (FAST Act)) for this study
文摘Roadways in Wyoming are characterized by challenging horizontal profiles,vertical profiles,a combination of the two and adverse weather conditions,all of which affect vehicle stability.In this study,we investigated the impact of different operating speeds when negotiating combined horizontal and vertical curves under unfavorable environmental conditions on Wyoming’s interstates via vehicle dynamics simulation software.The simulation tools provided the acting forces on each tire of the vehicle and the side friction(skidding)margins.This allowed for examining the interaction between vehicle dynamics and road geometry in such alignments.Also,linear regression analysis was implemented to investigate the skidding margins based on the simulation results to demonstrate when a vehicle is more likely to deviate from its desired trajectory.Specifically,this examines the contributing factors that significantly influence the skidding margins.The results indicated that:1)the skidding margins are dramatically decreased by adverse weather conditions even with lower degree of curvature and gradient values of combined curves and more particularly at higher operating speeds conditions.Increasing the vehicle speed on the curve by 10%,the skidding margin dropped by 15%.2)Compared to heavy trucks and sports utility vehicles(SUVs),passenger cars require the highest side friction demand.3)The effect of applying brakes on vehicle stability depends on the road surface condition;applying the brakes on snowy road surfaces increases the potential of vehicle skidding especially for heavy trucks.This study assessed the curve speed limits and showed how important to assign safe and appropriate limits speed since the skidding likelihood is significantly sensitive to the vehicle speeds.This study is beneficial to Wyoming’s roadway agencies since hazardous sections having combined horizontal and vertical curves are identified.Also,critical situations that require additional attention from law enforcement agencies are pinpointed.Finally,recommendations that are valuable to roadway agencies are made based on this study’s findings.
文摘The share of freight transportation is increasing on Wyoming’s roads. These roads are characterized by challenging mountainous terrain and severe crosswinds. The stability of freight trucks in such conditions is of great concern to transportation agencies. Therefore, high-fidelity vehicle dynamics simulation modeling was implemented to investigate the rollover propensity of trucks navigating curves. Scenarios included various road geometric designs, truck characteristics and wind conditions. A multiple linear regression model was also developed to investigate the impact of key parameters on truck rollover propensity. The modeling results indicated that wind speed and direction were influential factors in terms of truck roll stability. Trucks had a 76% higher chance of rolling over when subjected to 40 mph winds relative to being subjected to 20 mph winds assuming all else was unchanged. This study also demonstrated that the most unfavorable wind direction was not perpendicular (90 degrees) to the truck since the truck would continuously change its orientation when traversing combined horizontal and vertical curves. Its speed would also constantly fluctuate. On the contrary, this study’s results indicated that the 120-degree wind direction was the most critical one. Also, under blowing lateral wind conditions, the gross weight of the truck was found to be a contributing factor to rollover risk. Its impact varied depending on the radius of the horizontal curve the truck was navigating. This critical interaction was ignored in the road safety literature. This study offered new insights about the impacts of truck rollover precursors and, hence, this would lead to the proposition of effective truck safety countermeasures.
