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Technical Paper

Validation of a Roll Simulator for Recreational Off-Highway Vehicles

2012-04-16
2012-01-0241
A two-degree-of-freedom Roll Simulator has been developed to study the occupant kinematics of Recreational Off-Highway Vehicles (ROVs). To validate the roll simulator, test data was collected on a population of ROVs on the market today. J-turn maneuvers were performed to find the minimum energy limits required to tip up the vehicles. Two sets of tests were performed: for the first set, 10 vehicles were tested, where the motion was limited by safety outriggers to 10-15 degrees of roll; and for the second set, three of these vehicles were re-tested with outriggers removed and the vehicle motion allowed to reach 90 degrees of roll. These quarter-turn rollover tests were performed autonomously using an Automatic Steering Controller (ASC) and a Brake and Throttle Robot (BTR). Lateral and longitudinal accelerations as well as roll rate and roll angle were recorded for all tests.
Technical Paper

Validation and Enhancement of a Heavy Truck Simulation Model with an Electronic Stability Control Model

2010-04-12
2010-01-0104
Validation was performed on an existing heavy truck vehicle dynamics computer model with roll stability control (RSC). The first stage in this validation was to compare the response of the simulated tractor to that of the experimental tractor. By looking at the steady-state gains of the tractor, adjustments were made to the model to more closely match the experimental results. These adjustments included suspension and steering compliances, as well as auxiliary roll moment modifications. Once the validation of the truck tractor was completed for the current configuration, the existing 53-foot box trailer model was added to the vehicle model. The next stage in experimental validation for the current tractor-trailer model was to incorporate suspension compliances and modify the auxiliary roll stiffness to more closely model the experimental response of the vehicle. The final validation stage was to implement some minor modifications to the existing RSC model.
Technical Paper

Validation Results from Using NADSdyna Vehicle Dynamics Simulation

1997-02-24
970565
This paper presents an evaluation of a vehicle dynamics model intended to be used for the National Advanced Driving Simulator (NADS). Dynamic validation for high performance simulation is not merely a comparison between experimental and simulation plots. It involves strong insight of vehicle's subsystems mechanics, limitations of the mathematical formulations, and experimental predictions. Lateral, longitudinal, and ride dynamics are evaluated using field test data, and analytical diagnostics. The evaluation includes linear and non-linear range of vehicle dynamics response.
Technical Paper

Tractor-Semitrailer Stability Following a Steer Axle Tire Blowout at Speed and Comparison to Computer Simulation Models

2013-04-08
2013-01-0795
This paper documents the vehicle response of a tractor-semitrailer following a sudden air loss (Blowout) in a steer axle tire while traveling at highway speeds. The study seeks to compare full-scale test data to predicted response from detailed heavy truck computer vehicle dynamics simulation models. Full-scale testing of a tractor-semitrailer experiencing a sudden failure of a steer axle tire was conducted. Vehicle handling parameters were recorded by on-board computers leading up to and immediately following the sudden air loss. Inertial parameters (roll, yaw, pitch, and accelerations) were measured and recorded for the tractor and semitrailer, along with lateral and longitudinal speeds. Steering wheel angle was also recorded. These data are presented and also compared to the results of computer simulation models. The first simulation model, SImulation MOdel Non-linear (SIMON), is a vehicle dynamic simulation model within the Human Vehicle Environment (HVE) software environment.
Technical Paper

Springback Prediction Using Combined Hardening Model

2000-10-03
2000-01-2659
The main objective of this paper is to simulate the springback using combined kinematic/isotropic hardening model. Material parameters in the hardening model are identified by an inverse method. Three-point bending test is conducted on 6022-T4 aluminum sheet. Punch stroke, punch load, bending strain and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Material parameters are identified by minimizing the normalized error between two bending moments. Micro genetic algorithm is used in the optimization procedure. Stress-strain curves is generated with the material parameters found in this way, which can be used with other plastic models. ABAQUS/Standard 5.8, which has the combined isotropic/kinematic hardening model, is used to simulate draw-bend of 6022-T4 series aluminum sheet. Absolute springback angles are predicted very accurately.
Technical Paper

Simulation Results from a Model of a Tractor Trailer Vehicle Equipped with Roll Stability Control

2010-04-12
2010-01-0098
In 2007, a software model of a Roll Stability Control (RSC) system was developed based on test data for a Volvo tractor at NHTSA's Vehicle Research and Test Center (VRTC). This model was designed to simulate the RSC performance of a commercially available Electronic Stability Control (ESC) system. The RSC model was developed in Simulink and integrated with the available braking model (TruckSim) for the truck. The Simulink models were run in parallel with the vehicle dynamics model of a truck in TruckSim. The complete vehicle model including the RSC system model is used to simulate the behavior of the actual truck and determine the capability of the RSC system in preventing rollovers under different conditions. Several simulations were performed to study the behavior of the model developed and to compare its performance with that of an actual test vehicle equipped with RSC.
Technical Paper

Microstructural Characteristics of Die Cast AZ91D and AM60 Magnesium Alloys

1999-03-01
1999-01-0928
Die cast AZ91D and AM60 magnesium alloy components are finding increasing usage in automotive applications. Both hot and cold chamber die cast components of these alloys generally exhibit several common microstructural features, including “skin”, porosity banding, and porosity distributed about the component centerline. Methods for quantitatively characterizing these microstructural features are described and representative values for skin thicknesses, porosity band dimensions and porosity band locations from selected die castings will be presented. The expected influence of these common microstrucutral features on mechanical properties and acceptability of die cast magnesium components for given applications are discussed.
Technical Paper

Measured Vehicle Center-of-Gravity Locations - Including NHTSA's Data Through 2008 NCAP

2010-04-12
2010-01-0086
This paper is a printed listing of public domain vehicle center-of-gravity (CG) location measurements conducted on behalf of the National Highway Traffic Safety Administration (NHTSA). This paper is an extension of the 1999 SAE paper titled “Measured Vehicle Inertia Parameters - NHTSA's Data Through November 1998” ( 1 ). The previous paper contained data for 496 vehicles. This paper includes data for 528 additional vehicles tested as part of NHTSA's New Car Assessment Program (NCAP) for year 2001 through year 2008 ( 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ). The previous data included center-of-gravity location and mass moments-of-inertia for nearly all of the entries. The NCAP involves only the CG location measurements; so the vehicles listed in this paper do not have inertia data. This paper provides a brief discussion of the entries provided in the tabular listings as well as the accuracy of CG height measurements.
Journal Article

Integration of a Torsional Stiffness Model into an Existing Heavy Truck Vehicle Dynamics Model

2010-04-12
2010-01-0099
Torsional stiffness properties were developed for both a 53-foot box trailer and a 28-foot flatbed control trailer based on experimental measurements. In order to study the effect of torsional stiffness on the dynamics of a heavy truck vehicle dynamics computer model, static maneuvers were conducted comparing different torsional stiffness values to the original rigid vehicle model. Stiffness properties were first developed for a truck tractor model. It was found that the incorporation of a torsional stiffness model had only a minor effect on the overall tractor response for steady-state maneuvers up to 0.4 g lateral acceleration. The effect of torsional stiffness was also studied for the trailer portion of the existing model.
Technical Paper

Establishing Occupant Response Metrics on a Roll Simulator

2012-04-16
2012-01-0099
This paper presents the results of an in-depth study of the measurement of occupant kinematic response on the S-E-A Roll Simulator. This roll simulator was built to provide an accurate and repeatable test procedure for the evaluation of occupant protection and restraint systems during roll events within a variety of occupant compartments. In the present work this roll simulator was utilized for minimum-energy, or threshold type, rollover events of recreational off-highway vehicles (ROVs). Input profiles for these tests were obtained through a separate study involving autonomous full vehicle tests [1]. During simulated roll events anthropomorphic test device (ATD) responses were measured using on-board high speed video, an optical three-dimensional motion capture system (OCMS) and an array of string potentiometers.
Technical Paper

Empirical-Numerical Simulation Technique for Improving the Quality of Rolled Rods by Roll Pass Design

1992-02-01
920783
Improper roll pass designs can lead to either underfill which results in the formation of hairline cracks on the surface of the finished bars or overfill which results in roll overloading and the formation of fins. Therefore to reduce downtime, and improve yield and quality, it becomes important to design an acceptable roll pass in reasonable time. This paper presents a methodology for roll pass design which uses a three dimensional finite element technique along with an empirical procedure to arrive at an iterative scheme for reducing the number of passes and improving metal flow in the passes. This methodology is applied to improving an existing seven pass square - to - round rolling sequence, resulting in the reduction of the number of passes and improved distributions of effective strains in the rolled product.
Technical Paper

Dynamic Analysis of Layshaft Gears in Automotive Transmission

1997-05-20
971964
In this paper, we will present parametric results of performing dynamic analysis of layshaft gear trains typically used in automotive transmissions with emphasis on the vibratory response due to transmission error excitation. A three-dimensional multiple degrees of freedom lumped parameter dynamic model of a generic layshaft type geared rotor system (with three parallel rotating shafts coupled by two sets of gear pairs) has been formulated analytically. The model includes the effects of both rotational and translational displacements of each gears, and bounce and pitch motions of the counter-shaft. The natural frequencies and mode shapes are computed numerically by solving an eigenvalue problem derived from applying harmonic solutions to the equations of motion. The complete set of mode shapes are then used in forced response calculations based on the modal expansion method to predict gear accelerations, dynamic transmission errors, mesh force and bearing loads.
Technical Paper

Combine Tractive Devices: Effects on Soil Compaction

1995-09-01
952159
Soil response to differences in tire size and inflation pressure was measured for a JD 9600 combine with 18.4R38 dual tires, 30.5L32 single tires, 68x50.00-32 single tires at 103 and 166 kPa inflation pressure and a John Deere half-track system on two different soils (Kokomo and Crosby) near Urbana, Ohio. A loaded 42.3 m3 grain cart was included on the Kokomo soil for comparative purposes. The Ohio State Soil Physical Properties Measurement System was used to sample and measure the bulk density, air-filled porosity, air permeability and cone penetration resistance between 10 and 50 cm depths. The results for Kokomo soil show the grain cart had the greatest effect with an average decrease in total porosity of 12.90 percent, compared to 7.95%, 6.05%, 4.56%, 3.06%, and 2.04% for singles, tracks, duals, wide overinflated, and wide rated pressure tires, respectively, on the combine.
Technical Paper

An Investigation of the Effect of Post Forging Cooling Rate on the Microstructure and Properties of Microalloyed Steels

1993-03-01
930961
Medium carbon steels have been traditionally used for high strength forging applications. These steels contain several alloying elements like chromium, nickel and molybdenum which enable them to attain excellent hardenability and toughness upon heat treatment (quenching and tempering). Microalloyed (MA) medium carbon forging steels are gaining acceptance as a replacement for the traditional quenched and tempered grades as they do not require post forging heat treatment and hence represent substantial savings in manufacturing costs. Since the chief advantage of MA steels lies in the savings of heat treatment costs, the post-forging cooling rate is one of the primary parameters for controlling microstructure and toughness of the forged part. This paper investigates the effect of different cooling rates on the microstructure and mechanical properties of MA steels. Experiments were conducted by cooling test billets in different media.
Journal Article

Advanced Control Strategies for a Roll Simulator - A Feedback Linearization Technique Explored

2013-04-08
2013-01-0683
This paper presents a feedback linearization control technique as applied to a Roll Simulator. The purpose of the Roll Simulator is to reproduce in-field rollovers of ROVs and study occupant kinematics in a laboratory setting. For a system with known parameters, non-linear dynamics and trajectories, the feedback linearization algorithm cancels out the non-linearities such that the closed-loop dynamics behave in a linear fashion. The control inputs are computed values that are needed to attain certain desired motions. The computed values are a form of inverse dynamics or feed-forward calculation. With increasing system eigenvalue, the controller exhibits greater response time. This, however, puts a greater demand on the translational actuator. The controller also demonstrates that it is able to compensate for and reject a disturbance in force level.
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