Search Results

Abstract Since the steady-state computational fluid dynamics (CFD) Reynolds-averaged Navier–Stokes (RANS) turbulence models offer low-cost and sensible accuracy, they are frequently utilized for bluff bodies’ external aerodynamics investigations (e.g., upwind, crosswind, and shape optimization). However, no firm certainty is made regarding the best model in terms of accuracy and cost. Based on cost and accuracy aspects, four RANS turbulence models were studied, which are Spalart–Allmaras, realizable k-ε, RNG k-ε, and SST k-ω. Ahmed body with a 25° slant angle benchmark case was introduced for this investigation. Two grids were generated to satisfy the near-wall treatment of each turbulence model. All grid settings were proposed and discussed in detail. Fluid-structure analysis was performed on five different planes.

Abstract Parking an articulated vehicle is a challenging task that requires skill, experience, and visibility from the driver. An automatic parking system for articulated vehicles can make this task easier and more efficient. This article proposes a novel method that finds an optimal path and controls the vehicle with an innovative method while considering its kinematics and environmental constraints and attempts to mathematically explain the behavior of a driver who can perform a complex scenario, called the articulated vehicle park maneuver, without falling into the jackknifing phenomena. In other words, the proposed method models how drivers park articulated vehicles in difficult situations, using different sub-scenarios and mathematical models.

Abstract The lightweight structure of a semitrailer composite leaf spring is designed and manufactured using glass fiber composite to replace the conventional steel leaf spring. The sliding composite mono leaf spring was designed based on the conventional parabolic spring design theory. The composites product design (CPD) module of CATIA software is used to create the lamination of the composite leaf spring. Using finite element analysis of the position and proportion of ±45° biaxial layer by OptiStruct software, it is found that a certain proportion (nearly 5%) of a ±45° biaxial layer can effectively reduce the shear stress under the condition of keeping the total number of layers fixed. Then, the natural frequency, stiffness, and strength of the composite leaf spring are simulated by the finite element method. Finally, the stiffness, fatigue, and matching of the designed spring are tested by experiments.

Abstract A rear underrun protection device (RUPD) plays a fundamental role in reducing the risk of running a small car beneath the rear or the side of a heavy truck because of the difference in structure heights in the event of a vehicle collision. Even in cars with five-star safety ratings, crashing into a truck with poorly designed RUPD results in a passenger compartment intrusion (PCI) more than the maximum allowable limit as per the United States (US) American National Highway Traffic Safety Administration (NHTSA) standards Federal Motor Vehicle Safety Standard (FMVSS). In this article, mild steel was used to fabricate the new designs of RUPD. The design was analyzed using finite element (FE) analysis LS-DYNA software. Simulations of a Toyota Yaris 2010 and Ford Taurus 2001 were performed at a constant speed of 63 km/h at the time of impact. The ability to prevent severe injuries in a collision with the rear side of the truck was estimated to optimize the underrun design.

Abstract Articulated vehicles form an important part of our society for the transport of goods. Compared to rigid trucks, tractor-trailer combinations can transport huge quantities of load without increasing the axle load. The fifth wheel (FW) acts as a bridge between the tractor and trailer, which can be moved within the range to achieve rated front and rear axle loads. When the FW is moved front, it adversely affects the cab dynamics and cab suspension forces. Compared to the cab pitch and roll, yaw motion increases drastically. The current study tries to address this issue by providing reaction rod links in the rear cab suspension. In this study, a 4×2 tractor with a three-axle semitrailer is considered by keeping the FW at its frontmost position, which is the worst-case scenario for a cab. Three different cases of reaction rod arrangement and its influence on cab dynamics are studied in comparison with a model without reaction rods.

Abstract Heavy-duty (HD) engines for sale in the United States must be demonstrated to emit below allowable criteria and particulate emission limits over the operational load and speed cycle specified by the Federal Test Procedure (FTP) Heavy-Duty certification test. The inherently nonlinear load response of internal combustion engines tends to increase torque variability during the most dynamic portions of the test cycle. This clouds assessment of engine developments intended to improve transient performance and leads to frequent invalidation of certification tests. This work sought to develop and evaluate test torque control strategies that reduce this variability. Several load-control algorithms were evaluated for this purpose using a Cummins ISX15 HD diesel engine loaded with a transient alternating current (AC) dynamometer.

Abstract This article provides a dimensionless analysis of the rearward amplification (RA), that is, the ratio of peak lateral acceleration between tractor and rearmost trailer, of commercial trucks with single and double trailers. Through the nondimensionalization, a series of dimensionless parameters that are critical to the lateral and yaw dynamics of the vehicle are determined, which primarily includes vehicle mass ratio, momentum ratio, wheelbase ratio, and longitudinal center of gravity (CG) position ratio. A series of simulations are performed with sinusoidal steering maneuvers with various frequencies ranging from 0.01 Hz to 0.6 Hz. A frequency analysis of the effect of the dimensionless parameters on the RA for the single- and double-trailer trucks is provided. The simulation results suggest that increasing the trailer load causes a larger RA at the steering frequencies below 0.5 Hz.

Abstract The development of a long-term sustainable hydrogen energy economy for commercial vehicle transportation will need to overcome key critical technical and logistics considerations in the near term. As compared to zero-emission powertrains, fossil-fuel-based powertrains provide mission flexibility and high uptime at a comparatively low total cost of ownership (TCO). While the incumbent carbon-intensive powertrains suffer from poor efficiency and are not sustainable to support global climate change initiatives in transportation decarbonization, techno-economic challenges continue to create complex barriers to the large-scale displacement of these with highly electrified powertrains architectures. This article specifically addresses opportunities that well-targeted subsidies would afford in achieving fuel cell electric powertrain financial parity with diesel powertrains in heavy-duty trucks (HDTs).

Abstract Unstable articulated vehicles pose a serious threat to the occupants driving them as well as the occupants of the vehicles around them. Articulated vehicles typically experience three types of instability: snaking, jack-knifing, and rollover. An articulated vehicle subjected to any of these instabilities can result in major accidents. In this study a Nonlinear Model Predictive Control (NMPC) that applies brake-based torque vectoring on the trailer is developed to improve the articulated vehicle stability. The NMPC formulation includes tire saturation and applies constraints to prevent rollover. The controller output is a left and right brake force allowing the longitudinal velocity change to be incorporated into the model. Simulations were conducted to instigate snaking and jack-knifing and show the NMPC controller result compared to a simple proportional controller.

Abstract The future of heavy trucking will require greater aerodynamic improvements and will involve active and automated systems that tailor varied parameters to optimize energy efficiency over a broad operational range. Continuous advancement of accuracy and precision is needed to realize these ever-smaller aerodynamic gains and to generate more detailed aerodynamic characterizations to feed these system-wide optimizations. To accomplish this, a comprehensive aerodynamic development approach is needed and should include computational fluid dynamics, operational testing, and wind tunnel testing. In 2016, a high-fidelity 1/3 scale wind tunnel model of a tractor-trailer heavy truck was developed for Reynolds equivalent wind tunnel testing with full coverage rolling road ground simulation. The model and support system were designed and built for use in the Windshear rolling road wind tunnel.

Abstract The increased scope of active and passive safety in motor vehicles and the enforcement of approval requirements for individual parts and assemblies affect the design and parameters of a car’s motion. The tire, which transmits forces and torques onto the road’s surface is a particularly crucial element in the vehicle. Its structure, type of mixture, and operating conditions determine the safety of vehicle motion. The three-axial force system loads the tires of the car and affects both the tread and sidewall, as well as the suspension and steering system. Taking into account the controllability and stability of movement, the tire is subjected to dynamic and thermal loads, as well as to wear and random damage. This negatively impacts on the joints of composite layers. The sudden loss of pressure in the tire can lead to serious accidents, especially when moving at high speeds, due to changes in the rolling radius.

Abstract In this article, safe driving methods for large articulated vehicles passing roundabouts are presented using the design of experiment (DOE) method. First, the roundabout driving safety evaluation based on the rollover propensity index calculated with the tire loads was performed through various PC-Crash simulation analysis. And, using the Taguchi method, which is a representative DOE method, major factors affecting the rollover index were set by type and the sensitivity analysis results were quantitatively obtained. Finally, safe driving methods at roundabouts for large articulated vehicles through systematic reduction of rollover propensity were presented, demonstrating that they can be directly applied to advanced driver assist systems.

Abstract Excessive brake heating of trucks on downgrades is a cause of continuing concern for the Wyoming Department of Transportation (WYDOT). Brake failure on downgrades characteristically takes a catastrophic toll on lives and property. The Grade Severity Rating System (GSRS) developed by the Federal Highway Administration (FHWA) recommends a maximum safe speed limit that has been identified as a feasible remedy for reducing the incidence of downgrade truck crashes. However, truck characteristics and roadway geometrics have changed over the years following the development of the GSRS. To deal with this development, a research project was initiated by the WYDOT in 2016 to update the GSRS model. The test truck used for the field tests in the prior research project was fitted with disc brakes on the front axle and drum brakes on the rear axle. However, disc brakes represent only about 20% of the brake market.

Abstract SAE guidelines for computational fluid dynamics (CFD) and wind-tunnel tests on semi-trailer trucks were complied with to investigate the influence of adding a lateral skirts device—in the lower trailer part—on the improvement of the total drag force and the airflow structure around the truck. A reduced-scale (1:28) semi-trailer truck moving at three various speeds (i.e., 50 km/h, 75 km/h, and 100 km/h) is considered in this study. A reasonable agreement between experimental and numerical results was achieved in terms of the drag force parameter with a highest relative error of about 13% obtained in the case of the lowest speed (i.e., 50 km/h) of a truck without skirts. The numerical results yielded an average drag coefficient value of 0.48, which is reduced to 0.45 when the skirt device is added to the vehicle model.

Abstract Articulated vehicles contribute to the major portions of cargo transport through roads. Fifth wheel (FW) is an important component in these vehicles, which acts as the bridge between tractor and trailer and is often used as a parameter to adjust the axle loads. Ride and comfort studies linked to FW position exist. However, its influence on durability is often not considered seriously. In this article, three different FW positions placed at 200 mm, 400 mm, and 600 mm in front of the rear axle are studied virtually on a 4×2 tractor with three-axle semitrailer combination. To assess the risk associated with FW movement, acceleration-based pseudo-relative damage, power spectral density (PSD), and level crossing plots are analyzed for each FW position. Further, fatigue analysis is done on the cab structural components to understand the durability. Outcome shows that the FW position has an influence in determining the cab dynamics and durability of the components to a great extent.

Abstract This article presents a multistage, coupled thermal management simulation approach, informed by physical testing where available, to aid design decisions for PACCAR’s SuperTruck II hybrid truck cabin concept. Focus areas include cabin insulation, battery sizing, and sleeper curtain position, as well as heating, ventilating, and air-conditioning (HVAC) component and accessory configurations, to maintain or improve thermal comfort while saving energy. The authors analyzed weather data and determined the national vehicle miles traveled weighted temperature and solar conditions for long-haul trucks. Example weather day profiles were selected to approximate the 5th and 95th percentile weighted conditions. A daylong drive cycle was developed to impose appropriate external wind conditions during rest and driving periods.

Abstract A detailed model for pneumatic S-cam drum brake systems is developed and integrated into a multibody dynamic model for a 33-ft A-double long combination vehicle (LCV). The model, developed in TruckSim®, is used to study the dynamics of LCVs during straight-line braking at various speeds. It includes the response delay in braking that occurs from the time of application to when the brakes are applied at the drum for all axles. Additionally, the model incorporates an accurate characterization of brake torque versus chamber pressure at different speeds, along with the anti-lock brake system (ABS) dynamics, to yield an accurate prediction of the vehicle’s deceleration during braking. The modeling results are compared with test results at speeds ranging from 20 mph to 65 mph on dry pavement. A close match between the model’s prediction and test results is observed.

Abstract The present study assesses the use of a two-equation eddy-viscosity turbulence model, which is a shear-stress transport (SST) k-ω turbulence model, in two-way coupled aerodynamics and vehicle dynamics simulation of a heavy ground vehicle subjected to crosswind. The obtained results are compared with the corresponding results of the improved delayed detached-eddy simulation (IDDES) conducted at similar conditions from the previous literature. The aim is to evaluate the effects of different turbulence models used in aerodynamics simulations to resolve the vehicle dynamics results in two-way coupled simulations. The results present that the absolute relative percent differences between the lateral displacement, yaw angle and roll angle results of the SST k-ω and the IDDES simulations are less than 1%, 3%, and 10%, respectively.

Abstract A combination of machine learning (ML) and optimal fuzzy control (OFC) is proposed for the semi-active air suspensions of heavy trucks to further improve ride comfort and road friendliness. To obtain the study aim, a vehicle dynamics model with 10 degrees-of-freedom (10-DOF) is established in the MATLAB/Simulink environment to simulate and calculate the objective functions of the root-mean-square (RMS) acceleration responses of the vertical driver’s seat and pitching cab angle and the dynamic load coefficient (DLC) on the wheel axles under various working conditions. Based on the OFC with its control rules optimized by the genetic algorithm (GA) and the data map of the random road surfaces, an ML method of the Adaptive Network-based Fuzzy Inference System (ANFIS) in MATLAB is developed and applied to control the semi-active air suspensions.

Abstract This study provides a simulation-based comparative analysis of the distance and time needed for long combination vehicles (LCVs) - namely, A-doubles with 28-, 33-, and 48-ft trailers - to safely exercise an emergency, evasive steering maneuver such as required for obstacle avoidance. The results are also compared with conventional tractor-semitrailers with a single 53-ft trailer. A multi-body dynamic model for each vehicle combination is developed in TruckSim® with an attempt to assess the last point to steer (LPTS) and evasive time (ET) at various highway speeds under both dry and wet road conditions. The results indicate that the minimum avoidance distance and time required for the 28-ft doubles vary from 206 ft (60 mph) to 312 ft (80 mph) and 2.3 s to 2.6 s, respectively. The required LPTS represents a 6% to 31% increase when compared with 53-ft semitrucks.