Rear Of Vehicle Research Articles

Numerical Study on Aerodynamic Characteristics of Heavy-Duty Vehicles Platooning for Energy Savings and CO2 Reduction

This study aims to analyze the aerodynamic interaction between moving vehicles platooning with the change in the platooning conditions on a freeway. The effect of the vortex generated by the forward vehicle reduces the value of the stagnation pressure generated at the front of the rear vehicle, which effectively reduces drag on the driving vehicle. To elucidate this, a total of four vehicles were applied to platooning at a speed of 100 km/h by altering the gap distance of heavy-duty vehicles (HDVs) such as 0.5 Length (L), 1 L, 1.5 L, 2.0 L, and 2.5 L under the conditions of 1 L equal to 13.16 m. The stagnation pressure at the front of the following vehicle (FV) was reduced, and quantitative analysis of drag force generated at each leading vehicle (LV) and following vehicle that is platooning exhibited a reduction of about 51%, 56%, and 52%, respectively, when compared to the single moving HDV. This is considered as a reduction in engine power for the driving vehicle. Taken together, these results are effective in improving fuel efficiency and reducing CO2, a representative greenhouse gas, and predicting fuel and CO2 reduction based on HDV annual mileage according to the highway conditions and logistics.

Mamdani and Sugeno Fuzzy Logic Approach of PID Controller

Abstract: The design of a PID-type (Proportional-Integral-Derivative) controller based on a Fuzzy algorithm for deployment in a transportation cruising system is described in this work. To avoid collisions, a cruising system based on the Fuzzy rules has been developed. On the road, there are crashes between vehicles. Fuzzy Logic is a new type of logic which serves as a point of reference for driving the vehicle. It either increases or reduces the speed depending upon the speed of front, rear and ego vehicle. The speed of control is determined by the preceding vehicle's distance when it becomes too close and alerts the driver when required. There are two theories on fuzzy logic the first given by Mamdani and the other was given by Sugeno. Keywords: Proportional-Integral-Derivative (PID) , Fuzzy rules , Fuzzy Logic , Mamdani , Sugeno , Fuzzy Inference System

Eco-Co-Optimization strategy for connected and automated fuel cell hybrid vehicles in dynamic urban traffic settings

In urban traffic settings, the dynamic changes of the preceding and rear vehicles state, road gradient, road coefficient as well as the possible traffic congestion at signal intersections contribute to the difficulty of real-time optimal energy management for connected and automated fuel cell hybrid vehicles. To address this problem, an eco-co-optimization strategy is developed to achieve velocity planning and the promotion of energy management in this paper. First, gradient‑based model predictive control based on the fast projection gradient method is employed to obtain the real-time safe and optimal velocity according to the future information of driving conditions and signal lights state. Meanwhile, to achieve desirable velocity tracking and preferable power splitting, an energy management strategy based on model predictive control is designed, where a multi-objective performance function is leveraged to minimize the total cost, hydrogen consumption and extend battery service life. Additionally, an energy recovery strategy based on fuzzy logic control is executed to improve energy efficiency. The simulation results reveal that the developed strategy can obtain a real-time safe and optimal velocity sequence and enable the CAFCHV efficiently passes through the continuous signalized intersections. Simultaneously, compared with adaptive cruise control, the hydrogen consumption, SOC, global cost and battery degradation are reduced by 3.13%, 4.76%, 3.37%, and 14.48% in the planning state, respectively.

130-m Image sensor based Visible Light Communication (VLC) using under-sample modulation and spatial modulation

Visible light communication (VLC) allows low-cost, simple and flexible optical wireless communication (OWC) transmission. In this work, we put forward and demonstrate for the first time 100 m non-flickering image sensor based VLC using under-sampled phase shift on-off keying (UPSOOK) and 6-bit 4-light-emitting-diode (LED) spatial modulation. As each light emitting diode (LED) can provide three well distinguished intensity states, 6-bit data can be realized by using only 4 LEDs in the vehicle rear lamps. Bit-error-rate (BER) measurements at different camera ISO values are also studies. Experimental results show that 130 m long distance 120 bit/s image sensor based VLC system can be achieved using a single white-LED at ISO = 800. Results also show that 100 m long distance 720 bit/s image sensor based VLC system can be realized using 4 LEDs at ISO = 800. Both results satisfy the pre-forward error correction BER (pre-FEC, BER = 3.8 × 10−3).

Numerical Investigation of the Performance of Current Vehicle Rear Seats Using Finite Element Analysis

Numerical Investigation of the Performance of Current Vehicle Rear Seats Using Finite Element Analysis

Estimating the Workload of Driving Using Video Clips as Anchors

<div class="section abstract"><div class="htmlview paragraph">As new technology is added to vehicles and traffic congestion increases, there is a concern that drivers will be overloaded. As a result, there has been considerable interest in measuring driver workload. This can be achieved using many methods, with subjective assessments such as the NASA Task Loading Index (TLX) being most popular. Unfortunately, the TLX is unanchored, so there is no way to compare TLX values between studies, thus limiting the value of those evaluations. In response, a method was created to anchor overall workload ratings. To develop this method, 24 subjects rated the workload of clips of forward scenes collected while driving on rural, urban, and limited-access roads in relation to 2 looped anchor clips. Those clips corresponded to Level of Service (LOS) A and E (light and heavy traffic) and were assigned values of 2 and 6 respectively. Subjects said if they would perform any of 3 tasks—dialing a phone, manually tuning a radio, or entering a destination—while they were driving in each test scene. Finally, subjects provided other ratings for a wider range of situations (not shown in clips) to further examine the effects of road geometry, traffic, and other factors on workload. For each clip, vehicle dynamics data were available for the driven vehicle and the relationship of that vehicle to those in the scene. Using regression analysis, the rated workload (averaged across subjects) was estimated to be 8.87 - 3.01(LogMeanRange)+ 0.48(MeanTrafficCount)+ 2.05(MeanLongitudinalAcceleration), which accounted for 87% of the ratings, an extremely high value. In that expression, range is the distance from the subject’s front bumper to the lead vehicle rear bumper, mean traffic count is the mean number of vehicles visible in the road scene to radar, and the mean acceleration is that of the subject vehicle.</div></div>

The impact of different AR-HUD virtual warning interfaces on the takeover performance and visual characteristics of autonomous vehicles

Objective The objective of this study was to determine the different effects of the arrow-pointing augmented reality head-up display (AR-HUD) interface, virtual shadow AR-HUD interface, and non-AR-HUD interface on autonomous vehicle takeover efficiency and driver eye movement characteristics in different driving scenarios. Methods Thirty-six participants were selected to carry out a simulated driving experiment, and the eye movement index and takeover time were analyzed. Results The arrow pointing AR-HUD interface and the virtual shadow AR-HUD interface could effectively reduce the driver's visual distraction, improve the efficiency of obtaining visual information, reduce the number of times the driver's eyes leave the road, and improve the efficiency of the takeover compared with the non-AR-HUD interface, but there was no significant difference in eye movement indexes between the arrow pointing AR-HUD interface and the more eye-catching virtual shadow AR-HUD interface. When specific scenarios were considered, it was found that in the scenario of emergency braking of the vehicle in front, the arrow pointing AR-HUD interface and the virtual shadow AR-HUD interface had more advantages in takeover efficiency than the non-AR-HUD interface. However, in the scenarios of a rear vehicle overtaking the vehicle ahead and non-motor vehicles running red lights, there was no significant difference in takeover efficiency. For the non-motor vehicle invading the line, emergency U-turn of the vehicle in front, and pedestrian crossing scenarios, the virtual shadow AR-HUD interface had the highest takeover efficiency. Conclusions These research results can help improve the active safety of autonomous vehicle AR-HUD interfaces.

Two-lane mixed traffic flow model considering lane changing

Based on the analysis of the advantages and disadvantages of the existing car-following model and combined with the actual road conditions, an improvement scheme is proposed for the selected model. The improvement plan adds the consideration of the speed difference between the front and rear vehicles, and introduces the safe distance parameter of the most dangerous situation when the vehicle is braking. The comparison with the actual measurement results after simulation and conversion shows that the improved car following model is effective and the vehicle lane change rules are improved. The improvement of lane changing rules allows different lane changing rules to be obtained in different situations. The lane-changing rules are coupled with the improved car-following model to obtain a two-lane model based on different rules. The corresponding programming simulation is compared with the measured road results to verify the practicability of the model. The simulation result shows that the new model can still reproduce the road traffic flow under different lane changing rules. After the introduction of mixed traffic, the model can reproduce the maximum flow of the road within the error tolerance.

Co-optimization of speed planning and energy management for intelligent fuel cell hybrid vehicle considering complex traffic conditions

Fuel cell hybrid vehicles (FCHVs) offer great opportunities to reduce vehicle's operation cost and mitigate environmental impact. However, high-quality real-time energy management of FCHV is a difficult task due to different influences from complex traffic environments, such as dynamic changes of preceding and rear vehicle state, road slope and road coefficient. To address this problem, a cooperative control strategy is designed to achieve simultaneous speed planning and energy management promotion in this study. The upper control layer leverages a gradient-based model prediction control (GRAMPC) based on the fast projection gradient method to plan the speed sequence according to the information of future driving conditions as well as the real-time state of the preceding and rear vehicles. The bottom layer applies model prediction control (MPC) to achieve real-time preferable energy allocation, and a multi-objective control function is considered for the total cost minimization of energy management in terms of hydrogen consumption and battery life extension. The simulation results reveal that under the constraints of a dynamic environment, the proposed control strategy in planning state can reduce the traction power, hydrogen consumption, global cost, and battery degradation by 2.65%, 1.9%, 2.39%, and 8.14%, respectively.

Significance of tractor-trailer impacts to the rear of light vehicles

Objective This study determined the type of striking vehicle or object associated with serious injury to at least 1 occupant in the vehicle struck in the rear. Method The 1990–2015 NASS-CDS was analyzed for light vehicles involved in rear crashes. The type of vehicle struck in the rear resulting in serious injury to at least 1 occupant was determined. Rear impacts were identified with GAD1 = B without rollover (rollover ≤ 0). Vehicles with serious to maximum injury were identified as VAIS 3 to 6 (VAIS 3+). The type of striking vehicle or object was determined for the rear impacts causing serious injury. The risk and relative risk for serious injury were determined. Review of electronic cases was conducted for light vehicles with serious injury (VAIS 3+) in impacts by tractor-trailers or large trucks. Results The highest risk for serious injury to an occupant in the struck vehicle was from a tractor-trailer or large truck (2.71%), followed by a fixed object (1.49%) and van (1.00%). The average risk was 0.33%. The relative risk was 8.2 times for impact with a tractor-trailer or large truck and 4.5 times for impact with a fixed object. The highest risk impacts with a fixed object were rear impacts into a tree/bush (3.57%) and pole (2.90%). Tractor-trailers and large trucks accounted for 16.2% of serious injury in struck vehicles, followed by fixed objects at 12.9%; the 2 accounted for 29.1% of serious injury to occupants of struck vehicles. The case review identified 22 tractor-trailer and 1 large truck crashes involving 31 seriously injured occupants in the struck vehicle. There were 2 general crash scenarios associated with serious injury. One involved intrusion deforming the occupant compartment. The other involved vehicle accelerations sufficient to seriously injure an occupant in the struck vehicle without significant deformation to the occupant compartment. Conclusion This study provides insight into the striking vehicle or object associated with serious injury to light vehicle occupants in rear impacts. Tractor-trailer impacts into the rear of a vehicle involved a high risk for serious injury in the struck vehicle. The use of collision mitigation technologies, such as forward collision warning or automatic emergency braking, on the tractor-trailer may support better speed control and lead to lower closing velocities of rear impacts to light vehicles.

Study on the influence of seating orientation during frontal impacts by child occupant human body model response analysis

Objective Autonomous driving cars must be developed to ensure that children will have the highest level of protection in case of collision. Changes to the vehicle cabin design (different seat orientations, fully reclining seats, etc.) may significantly impact child occupant safety. Understanding child occupant responses under these new conditions is necessary to decrease risk and enhance child safety. In this study, child occupant response in different seating orientations exposed to frontal impacts with a focus on the head injuries and kinematics was analyzed. Methods Finite elements simulations were performed using the PIPER 6-year-old human body model (HBM). All simulations were carried out in a generic full vehicle environment. The child model was positioned in an adequate generic car restraint system (CRS) in the left rear vehicle seat in 4 seating orientations: 0° (forward-facing position), 30°, 60°, and 90° (living room position). Two scenarios were evaluated for all seating orientations according to the left front seat backrest position: reclined position nominal upright and rest position (55°). All seat configurations were subjected to the mobile progressive deformable barrier frontal impact (European New Car Assessment Programme [Euro NCAP] frontal impact testing protocol). A total of 8 scenarios were simulated in LS-DYNA. Results Based on the Euro NCAP injury risk rate, 90° seating orientation (living room position) was the safest among all selected scenarios independent of the left front seat backrest position. The worst case was found in 60° seat rotation. The highest values for Head Injury Criterion (HIC) and head acceleration (Acc 3 ms) were noted for this case. Higher Brain Injury Criterion (BrIC) values were observed at higher seat rotation angles. Hence, a 90° seating orientation showed the highest BrIC value. Attending to the skull stress, greater head injuries were caused principally by contact with the vehicle interior (seat headrest). Maximum stress values were reached at 30° and 60° seating orientations with the front seat in rest position. In 90° seating orientation, high stress values were also identified. Conclusions These results show that attending to these new seating orientations, current child safety standards are not sufficient to ensure children the highest level of protection. Other additional criteria such as BrIC or skull stress that offer a way to capture brain injuries should be used.

Study on a test bench of a vehicle rear axle fatigue behavior

This paper presents a study with finite elements of the rear axle of a car. The virtual model of the rear axle assembly of a vehicle is made. Based on this model we made a study of the state of stresses and strains that occur in the components of the rear suspension. When constructing the analysis model, we considered the bearing conditions, as well as the loads from the real operation of the assembly. The purpose of this finite element analysis is to determine the most requested areas of the rear axle assembly, as well as to compare the results obtained for specific deformations and stresses experimentally with those obtained by finite element analysis. Also, through the analysis with finite elements, we obtained and presented in the paper results regarding the fatigue behavior of the elements of the ensemble.

Multifidelity simulation of underhood thermal system for a bus engine

This study performs a combined 0-dimensional/3-dimensional modelling approach to investigate the fluid flow and heat transfer characteristics of bus thermal management systems. The 3-dimensional model is deployed to develop new correlations for the heat transfer coefficient (Colburn-j factor) and the friction factor (Fanning-f factor) at the air-side of the multi-louver radiator and charge-air cooler. The effect of the fan operation is also taken into account. The existing correlations in the literature developed for cars where the radiator and charge-air cooler are placed in the front section of the vehicle exposed to a uniform incoming air flow. While in buses, these components are placed at the vehicle rear section and in contact with a turbulent and non-uniform air flow, highlighting the need for development of new Colburn-j factor and Fanning-f factor for air flow within the louvered fins in these two components. The coefficients developed are incorporated into the 0-dimensional model to predict the thermal characteristics of the bus underhood for a range of operating conditions. The 0-dimensional model simulates the heat interaction of the multiple thermodynamic systems. Thus, a better understanding of the thermal management is achieved by investigating the energy distribution within the engine compartment and describing the performance of the thermal systems. The 0-dimensional/3-dimensional model is examined under the peak brake power condition. A coolant mass flow rate of 3.74 kg/s and fans speed of 4000 rpm are the most optimum results since the coolant’s temperature is decreased by 5 °C and the parasitic losses are kept at minimum.

Digital Triangular Road Signs for Improving Road Safety

Road accidents result in the loss of life and property, and statistics reveal that they are now the leading cause of death worldwide, surpassing diseases like HIV/AIDS, tuberculosis, and diarrhoea. One area contributing to road accidents is vehicle breakdowns parked on roads. Usually, drivers of broken vehicles use emergency triangular road signs (reflective triangles) to alert oncoming drivers. However, the effectiveness of reflective triangles is hindered by the inability of oncoming drivers to notice those reflective triangles at a reasonable distance due to bad weather and the topographical structure of the road. To solve this problem, the present paper develops a Digital Triangular Road Sign (DiTRoS) algorithm. The algorithm complements reflective triangles installed on the rear and front sides of the broken vehicle to warn oncoming drivers. Development of DiTRoS algorithm builds on navigation system enabled by global positioning system that works on portable devices –specifically the smartphones. The DiTRoS algorithm is tested in the natural environment. Results demonstrate that the DiTRoS algorithm is effective in notifying oncoming drivers in advance about the presence of the broken vehicle. The study ends by recommending minimum distance at which an oncoming driver may start receiving alerts.

Modeling AVs & RVs’ car-following behavior by considering impacts of multiple surrounding vehicles and driving characteristics

This paper proposes a mixed-vehicles car-following model based on FVAD (Full Velocity and Acceleration Difference) model to describe the microscopic car-following behavior of RVs (Regular Vehicles) and AVs (Autonomous Vehicles). The model involves the velocity of multiple front vehicles and a rear vehicle as well as the velocity difference, acceleration difference and headway between each front vehicle and the host vehicle. As for AV’s car-following model we introduced the molecular dynamic theory to quantitatively express the influence of multiple front vehicles on the host vehicle. The velocity of multiple front vehicles and headway between each of them and the host vehicle are used to express the influence. Besides, we consider drivers’ car-following styles in constructing the RV model. The stability analysis results indicate that the stability of traffic flow under the proposed model is not easily affected by the change in velocity, and is better than FVAD model. According to the data collected from the car-following field test mixed with AVs and RVs, we obtain the optimal value of the parameters in the model, and examine the fitting accuracy with a numerical simulation. The results indicate that compared with FVAD model, the MME (Mean Maximum Error) and ME (Mean Error) of RV model is reduced by 39.50% and 13.12%, respectively, and the accuracy is improved by 14.48%. The acceleration strategy controlled by the AV model is smoother than by the ACC (Adaptive Cruise Control) model. With effective car-following behavior control, it is helpful to improve the operation efficiency of AVs and enhance the stability of traffic flow. Additionally, the model can be utilized for platoon control in the case of RVs’ and AVs’ heterogeneous flow. This model can also serve as a tool to simulate car-following behavior, which is beneficial for road traffic management and infrastructure layout in AV and RV mixed traffic environment.

An Improved Lattice Hydrodynamic Model by considering the Effect of “Backward-Looking” and Anticipation Behavior

In order to prevent the occurrence of traffic accidents, drivers always focus on the running conditions of the preceding and rear vehicles to change their driving behavior. By taking into the “backward-looking” effect and the driver’s anticipation effect of flux difference consideration at the same time, a novel two-lane lattice hydrodynamic model is proposed to reveal driving characteristics. The corresponding stability conditions are derived through a linear stability analysis. Then, the nonlinear theory is also applied to derive the mKdV equation describing traffic congestion near the critical point. Linear and nonlinear analyses of the proposed model show that how the “backward-looking” effect and the driver’s anticipation behavior comprehensively affect the traffic flow stability. The results show that the positive constant γ , the driver’s anticipation time τ , and the sensitivity coefficient p play significant roles in the improvement of traffic flow stability and the alleviation of the traffic congestion. Furthermore, the effectiveness of linear stability analysis and nonlinear analysis results is demonstrated by numerical simulations.

Multi-body simulation with notch stress analysis of an axle assembly

The optimization of mining vehicle rear axle weld joints is a complex procedure. The designs for low-cycle fatigue with peak loads were analyzed using computational models and rig testing. On-road evaluation of high-cycle fatigue was performed with the entire vehicle. The iterative analysis is used in design optimization to minimize design cycle time. In sophisticated fatigue calculations with all affecting factors, FEM is utilized. In fatigue failures using road load data, the present deterministic method yields up to 80% correlations. Some critical failure spots were most likely missed owing to operational variations caused by the randomness and multiaxiality of load transfer in link mechanisms with non-linear elements. The fabricated rear axle housing joints are optimized by comparing damage state estimates using stochastic type and multiaxial equivalent loads obtained using Multibody Simulation. The damage state analysis as MBS input stimulus in FE weld models and bolted designs were compared.

Development of calculation method to study influence of end pieces and asphalt roadway impedance on total sound pressure measured at exhaust pipe mouth

The article contains a developed finite element model of the rear part of the vehicle with the mufflers made adjoining the sphere. Experimental research has been carried out in accordance with the rules of the ECE UN R51 amendment 03. Calculation procedure was made to study the influence of the reflecting surfaces on the total sound pressure by the example of the exhaust pipe mouth. The finite element model of the vehicle rear part has been developed. The results of calculations and experimental research of the sound pressures of the exhaust pipe mouth are given. The developed calculation procedure has been proved by the experiments.

Multi-anticipative bi-directional visual field traffic flow models in the connected vehicle environment

In the connected vehicle environment, a vehicle can obtain the information of multiple front and rear vehicles. This driving strategy of bi-directional visual field and multiple anticipation can be implemented to traffic flow modeling. In this paper, an extended car-following model with consideration of bi-directional visual field and multiple anticipation is proposed. A novel macroscopic traffic flow model is developed based on the relationship between the microscopic and macroscopic variables, and the validity of the model is confirmed through the theoretical and numerical studies. The stability analysis shows that the multiple anticipation can improve the stability of traffic flow, and the results of numerical simulation illustrates that the new model can reproduce the local clustering phenomenon of traffic flow.

Evaluation of static belt fit and belt torso contact for children on belt-positioning booster seats

Objective: Previous studies have indicated that gap between the seatbelt and torso (reduced belt torso contact) for children on belt-positioning booster seats (BPBs) may lead to less torso engagement and increased likelihood of shoulder belt slip-off during evasive vehicle maneuvers, potentially increasing injury risk during crashes. However, current BPB belt fit measures do not quantify belt gap and may not be able to fully discriminate between designs which provide good vs. poor dynamic outcomes. The goal of this study was to evaluate both novel (belt gap characteristics) and conventional measures of seatbelt fit for BPB-seated children. Methods: Ten BPBs and three seatbelt anchor locations were investigated. Fifty volunteers (4-14 years) were recruited and each evaluated on six unique combinations of BPB and seatbelt anchor location on a vehicle rear seat in a laboratory setting. A 3 D coordinate measurement system quantified positions of anatomic, seatbelt, BPB, and vehicle reference points. Novel belt gap (gap size, length, location, and percent torso contact) and conventional belt fit (position of belt on shoulder and pelvis) metrics were calculated using anatomic and seatbelt landmarks. Variation in belt fit and belt gap outcomes due to BPB, seatbelt anchor location, and anthropometry were investigated. Results: BPBs produced significantly different outcomes, while seatbelt anchor location did not. BPBs with features that directly routed the lower portion of the shoulder belt more forward on the buckle side produced the largest (29.3 ± 12.6 mm) and longest (106.9 ± 68.2 mm) belt gap on average, while BPBs that pulled the belt less forward or did not directly route the belt produced the smallest (13.9 ± 6.7 mm) and shortest (16.9 ± 33.9 mm) gap on average. Belt gap outcomes were not strongly correlated with conventional belt fit metrics, indicating that evaluation of belt gap may provide additional insight when attempting to discriminate between BPBs which provide good vs. poor seatbelt engagement during vehicle maneuvers and crashes. Conclusions: This is the first study to evaluate belt gap characteristics for BPB-seated children. Results suggest that belt fit and belt gap are influenced by BPB design, particularly lower shoulder belt routings, and may have implications for belt engagement during dynamic events.