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Technical Paper

Yaw Stability Control and Emergency Roll Control for Vehicle Rollover Mitigation

2010-10-05
2010-01-1901
In this paper a yaw stability control algorithm along with an emergency roll control strategy have been developed. The yaw stability controller and emergency roll controller were both developed using linear two degree-of-freedom vehicle models. The yaw stability controller is based on Lyapunov stability criteria and uses vehicle lateral acceleration and yaw rate measurements to calculate the corrective yaw moment required to stabilize the vehicle yaw motion. The corrective yaw moment is then applied by means of a differential braking strategy in which one wheel is selected to be braked with appropriate brake torque applied. The emergency roll control strategy is based on a rollover coefficient related to vehicle static stability factor. The emergency roll control strategy utilizes vehicle lateral acceleration measurements to calculate the roll coefficient. If the roll coefficient exceeds some predetermined threshold value the emergency roll control strategy will deploy.
Technical Paper

Verification, Validation and Uncertainty Quantification (VV&UQ) Framework Applicable to Power Electronics Systems

2014-09-16
2014-01-2176
The development of the concepts, terminology and methodology of verification and validation is based on practical issues, not the philosophy of science. Different communities have tried to improve the existing terminology to one which is more comprehensible in their own field of study. All definitions follow the same concept, but they have been defined in a way to be most applicable to a specific field of study. This paper proposes the Verification, Validation, and Uncertainty Quantification (VV&UQ) framework applicable to power electronic systems. Although the steps are similar to the VV&UQ frameworks' steps from other societies, this framework is more efficient as a result of the new arrangement of the steps which makes this procedure more comprehensible. This new arrangement gives this procedure the capability of improving the model in the most efficient way.
Journal Article

Vehicle System Simulator: Development and Validation

2011-09-13
2011-01-2166
A graphical user interface (GUI) toolbox called Vehicle System Simulator (VSS) is developed in MATLAB to ease the use of this vehicle model and hopefully encourage its widespread application in the future. This toolbox uses the inherent MATLAB discrete-time solvers and is mainly based on Level-2 s-function design. This paper describes its built-in vehicle dynamics model based on multibody dynamics approach and nonlinear tire models, and traction/braking control systems including Cruise Control and Differential Braking systems. The built-in dynamics model is validated against CarSim 8 and the simulation results prove its accuracy. This paper illustrates the application of this new MATLAB toolbox called Vehicle System Simulator and discusses its development process, limitations, and future improvements.
Technical Paper

Vehicle Refinement and Testing of a Series-Parallel Plug-in Hybrid Electric Vehicle

2014-10-13
2014-01-2904
The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech is ready to compete in the Year 3 Final Competition for EcoCAR 2: Plugging into the Future. The team is confident in the reliability of their vehicle, and expects to finish among the top schools at Final Competition. During Year 3, the team refined the vehicle while following the EcoCAR 2 Vehicle Development Process (VDP). Many refinements came about in Year 3 such as the implementation of a new rear subframe, the safety analysis of the high voltage (HV) bus, and the integration of Charge Sustaining (CS) control code. HEVT's vehicle architecture is an E85 Series-Parallel Plug-In Hybrid Electric Vehicle (PHEV), which has many strengths and weaknesses. The primary strength is the pure EV mode and Series mode, which extend the range of the vehicle and reduce Petroleum Energy Usage (PEU) and Greenhouse Gas (GHG) emissions.
Technical Paper

Vehicle Inertia Impact on Fuel Consumption of Conventional and Hybrid Electric Vehicles Using Acceleration and Coast Driving Strategy

2009-04-20
2009-01-1322
In the past few years, the price of petroleum based fuels, especially vehicle fuels such as gasoline and diesel, have been increasing at a significant rate. Consequently, there is much more consumer interest related to reducing fuel consumption of conventional and hybrid electric vehicles (HEVs). The “pulse and glide” (PnG) driving strategy is first applied to a conventional vehicle to quantify the fuel consumption benefits when compared to steady state speed (cruising) conditions over the same time and distance. Then an HEV is modeled and tested to investigate if a hybrid system can further reduce fuel consumption with the proposed strategy. Note that the HEV used in this study has the advantage that the engine can be automatically shut off below a certain speed (∼40 mph, 64 kph) at low loads, however a driver must shut off the engine manually in a conventional vehicle to apply this driving strategy.
Technical Paper

Vehicle Design and Implementation of a Series-Parallel Plug-in Hybrid Electric Vehicle

2013-10-14
2013-01-2492
The Hybrid Electric Vehicle Team (HEVT) of Virginia Tech has achieved the Year 2 goal of producing a 65% functional mule vehicle suitable for testing and refinement, while maintaining the series-parallel plug-in hybrid architecture developed during Year 1. Even so, further design and expert consultations necessitated an extensive redesign of the rear powertrain and front auxiliary systems packaging. The revised rear powertrain consists of the planned Rear Traction Motor (RTM), coupled to a single-speed transmission. New information, such as the dimensions of the high voltage (HV) air conditioning compressor and the P2 motor inverter, required the repackaging of the hybrid components in the engine bay. The P2 motor/generator was incorporated into the vehicle after spreading the engine and transmission to allow for the required space.
Technical Paper

Vehicle Design Analysis and Validation for the Equinox REVLSE E85 Hybrid Electric Vehicle

2007-04-16
2007-01-1066
The Hybrid Electric Vehicle Team of Virginia Tech (HEVT) is participating in the 2005 - 2007 Challenge X advanced technology vehicle competition series, sponsored by General Motors Corporation, the U.S. Department of Energy, and Argonne National Lab. This report documents the Equinox REVLSE (Renewable Energy Vehicle, the Larsen Special Edition) design and specifies how it meets the Vehicle Technical Specifications (VTS) set by Challenge X and HEVT through simulation and test results. The report also documents the vehicle control development process, specifies the control code generation, demonstrates an analysis of hybrid powertrain losses, and presents the REVLSE vehicle balance in its intended market.
Technical Paper

Validation of a Driver Recovery Model Using Real-World Road Departure Cases

2013-04-08
2013-01-0723
Predicting driver response to road departure and attempted recovery is a challenging but essential need for estimating the benefits of active safety systems. One promising approach has been to mathematically model the driver steering and braking inputs during departure and recovery. The objective of this paper is to compare a model developed by Volvo, Ford, and UMRTI (VFU) through the Advanced Crash Avoidance Technologies (ACAT) Program against a set of real-world departure events. These departure events, collected by Hutchinson and Kennedy, include the vehicle's off road trajectory in 256 road departure events involving passenger vehicles. The VFU-ACAT model was exercised for left side road departures onto the median of a divided highway with a speed limit of 113 kph (70 mph). At low departure angles, the VFU-ACAT model underpredicted the maximum lateral and longitudinal distances when compared to the departure events measured by Hutchinson and Kennedy.
Journal Article

Validation of Event Data Recorders in Side-Impact Crash Tests

2014-04-01
2014-01-0503
This study evaluated the accuracy of 75 Event Data Recorders (EDRs) extracted from model year 2010-2012 Chrysler, Ford, General Motors, Honda, Mazda, and Toyota vehicles subjected to side-impact moving deformable barrier crash tests. The test report and vehicle-mounted accelerometers provided reference values to assess the EDR reported change in lateral velocity (delta-v), seatbelt buckle status, and airbag deployment status. Our results show that EDRs underreported the reference lateral delta-v in the vast majority of cases, mimicking the errors and conclusions found in some longitudinal EDR accuracy studies. For maximum lateral delta-v, the average arithmetic error was −3.59 kph (−13.8%) and the average absolute error was 4.05 kph (15.9%). All EDR reports that recorded a seatbelt buckle status data element correctly recorded the buckle status at both the driver and right front passenger locations.
Journal Article

Validation of Event Data Recorders in High Severity Full‑Frontal Crash Tests

2013-04-08
2013-01-1265
This study evaluates the accuracy of 41 Event Data Recorders (EDR) extracted from model year 2012 General Motors, Chrysler, Ford, Honda, Mazda, Toyota, and Volvo vehicles subjected to New Car Assessment Program 56 kph full-frontal barrier crash tests. The approach was to evaluate (1) the vehicle longitudinal change in velocity or delta-V (ΔV) as measured by EDRs in comparison with the high-precision accelerometers mounted onboard test vehicles and (2) the accuracy of pre-crash speed, seatbelt buckle status, and frontal airbag deployment status. On average the absolute error for pre-crash speed between the EDR and reference instrumentation was only 0.58 kph, or 1.0% of the nominal impact speed. In all cases in which the EDRs recorded the seatbelt buckle status of the driver or right front passenger, the modules correctly reported that the occupants were buckled. EDRs reported airbag deployment correctly in all of the tests.
Technical Paper

VTool: A Method for Predicting and Understanding the Energy Flow and Losses in Advanced Vehicle Powertrains

2013-04-08
2013-01-0543
A crucial step to designing and building more efficient vehicles is modeling powertrain energy consumption. While accurate modeling is indeed key to effective and efficient design, a fundamental understanding of the powertrain and auxiliary systems that contribute to the energy consumption of a vehicle is equally as important. This paper presents a methodology that has been packaged into a tool, called VTool (short for Vehicle Tool), which can be used to estimate the energy consumption of a vehicle powertrain. The method is intrinsically designed to foster understanding of the vehicle powertrain as it relates to energy consumption and losses while still providing reasonably accurate results. This paper briefly explains the methodology of VTool and demonstrates the capability of VTool as a design tool by presenting 4 example exercises.
Technical Paper

Utilization of Finite Element Analysis to Develop Automotive Components

2010-10-06
2010-36-0004
The finite element method (FEM) is used daily in the automotive industry for such purposes as reducing the time of product development and improving the design based on analysis results, followed by later validation by tests in the laboratory and on the proving ground. This paper will present some of the methodology used to develop automotive components by finite element analysis, including procedures to specialize FEM models to obtain quantitative and qualitative results for systems such as body, chassis, and suspension components, as well as validation of the models by experimental data.
Technical Paper

Using Surface Texture Parameters to Relate Flat Belt Laboratory Traction Data to the Road

2015-04-14
2015-01-1513
Indoor laboratory tire testing on flat belt machines and tire testing on the actual road yield different results. Testing on the machine offers the advantage of repeatability of test conditions, control of the environmental condition, and performance evaluation at extreme conditions. However, certain aspects of the road cannot be reproduced in the laboratory. It is thus essential to understand the connection between the machine and the road, as tires spend all their life on the road. This research, investigates the reasons for differences in tire performance on the test machine and the road. The first part of the paper presents a review on the differences between tire testing in the lab and on the road, and existing methods to account for differences in test surfaces.
Journal Article

Using Performance Margin and Dynamic Simulation for Location Aware Adaptation of Vehicle Dynamics

2013-04-08
2013-01-0703
One seminal question that faces a vehicle's driver (either human or computer) is predicting the capability of the vehicle as it encounters upcoming terrain. A Performance Margin (PM) is defined in this work as the ratio of the required tractive effort to the available tractive effort for the front and rear respectively. This simple definition stems from and incorporates many traditional handling metrics and is robust in its scope of applicability. The PM is implemented in an Intervention Strategy demonstrating its use to avoid situations in which the vehicle exceeds its handling capabilities. Results from a design case study are presented to show the potential efficacy of developing a PM-based control system.
Journal Article

Using Objective Vehicle-Handling Metrics for Tire Performance Evaluation and Selection

2013-04-08
2013-01-0743
This paper outlines the development of a simulation-based process for assessing the handling performance of a given set of tires on a specific vehicle. Based on force and moment data, a Pacejka tire model was developed for each of the five sets of tires used in this study. To begin with, simple handling metrics including under-steer gradient were calculated using cornering stiffness derived from the Pacejka model. This Pacejka tire model was subsequently combined with a 3DOF non-linear vehicle model to create a simulation model in MATLAB/Simulink®. Other handling metrics were calculated based on simulation results to step and sinusoidal (General Motors Company) steering inputs. Calculated performance metrics include yaw velocity overshoot, yaw velocity response time, lateral acceleration response time and steering sensitivity. In addition to this, the phase lag in lateral acceleration and yaw rate of the vehicle to a sinusoidal steering input were also calculated.
Technical Paper

Upper Extremity Interaction With a Helicopter Side Airbag: Injury Criteria for Dynamic Hyperextension of the Female Elbow Joint

2004-11-01
2004-22-0007
This paper describes a three part analysis to characterize the interaction between the female upper extremity and a helicopter cockpit side airbag system and to develop dynamic hyperextension injury criteria for the female elbow joint. Part I involved a series of 10 experiments with an original Army Black Hawk helicopter side airbag. A 5th percentile female Hybrid III instrumented upper extremity was used to demonstrate side airbag upper extremity loading. Two out of the 10 tests resulted in high elbow bending moments of 128 Nm and 144 Nm. Part II included dynamic hyperextension tests on 24 female cadaver elbow joints. The energy source was a drop tower utilizing a three-point bending configuration to apply elbow bending moments matching the previously conducted side airbag tests. Post-test necropsy showed that 16 of the 24 elbow joint tests resulted in injuries.
Technical Paper

Unconventional Truck Chassis Design with Multi-Functional Cross Members

2019-04-02
2019-01-0839
An unconventional conceptual design of truck chassis with multi-functional cross-members is proposed, and an optimization framework is developed to optimize its structure to minimize mass while satisfying stiffness and modal frequency constraints. The side rails are C-sectional channels of variable height and were divided into six sections, each with different thickness distribution for the flanges and the web. The gearbox cross-member and the intermediate cross-members are compressed-air cylinders, and hence they act as multi-functional components. The dimensions and thickness of the side rails and the air-tank cross members are defined by a set of parameters which are considered as design variables in the optimization problem. The structure consists of three additional fixed cross-members which are modeled using beam elements. The limits of the design variables are decided while considering manufacturing limits.
Journal Article

Tire Traction of Commercial Vehicles on Icy Roads

2014-09-30
2014-01-2292
Safety and minimal transit time are vital during transportation of essential commodities and passengers, especially in winter conditions. Icy roads are the worst driving conditions with the least available friction, leaving valuable cargo and precious human lives at stake. The study investigates the available friction at the tire-ice interface due to changes in key operational parameters. Experimental analysis of tractive performance of tires on ice was carried out indoor, using the terramechanics rig located at the Advanced Vehicle Dynamics Laboratory (AVDL) at Virginia Tech. The friction-slip ratio curves obtained from indoor testing were inputted into TruckSIM, defining tire behavior for various ice scenarios and then simulating performance of trucks on ice. The shortcomings of simulations in considering the effects of all the operational parameters result in differences between findings of indoor testing and truck performance simulations.
Technical Paper

Thermo-Mechanical Reliability of Nano-Silver Sintered Joints versus Lead-Free Solder Joints for Attaching Large-Area Silicon Devices

2010-11-02
2010-01-1728
Nano-silver sintered bonding was carried out at 275°C and under 3MPa pressures, and soldering in a vacuum reflowing oven to reduce voiding. Both joints are subject to large shear stresses due to the mismatch in coefficients of thermal expansion (CTE) between the chip and the substrate. In this study, residual stresses in the chip-on-substrate assemblies were determined by measuring the bending curvatures of the bonded structures. An in-house optical setup measured the bending curvatures using a thin-film stress measurement technique. From the measured bending curvatures and the mechanical properties of the constituent materials, residual stresses were calculated. The thermo-mechanical reliabilities of both joining techniques were tested by thermal cycling. The chip assemblies were cycled between -40°C and 125°C (100 minutes of cycle time, 10 minutes of dwell time) and the changes in their bending curvatures were measured.
Journal Article

The Development of Terrain Pre-filtering Technique Based on Constraint Mode Tire Model

2015-09-01
2015-01-9113
The vertical force generated from terrain-tire interaction has long been of interest for vehicle dynamic simulations and chassis development. To improve simulation efficiency while still providing reliable load prediction, a terrain pre-filtering technique using a constraint mode tire model is developed. The wheel is assumed to convey one quarter of the vehicle load constantly. At each location along the tire's path, the wheel center height is adjusted until the spindle load reaches the pre-designated load. The resultant vertical trajectory of the wheel center can be used as an equivalent terrain profile input to a simplified tire model. During iterative simulations, the filtered terrain profile, coupled with a simple point follower tire model is used to predict the spindle force. The same vehicle dynamic simulation system coupled with constraint mode tire model is built to generate reference forces.
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