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Technical Paper

Validation of the SIMON Model for Vehicle Handling and Collision Simulation - Comparison of Results with Experiments and Other Models

2004-03-08
2004-01-1207
SIMON is a new 3-dimensional vehicle dynamic simulation model. The capabilities of the model include non-linear handling maneuvers and collision simulation for one or more vehicles. As a new model, SIMON must be validated by comparison against actual handling and collision experiments. This paper provided that comparison. Included in the validation were lane-change maneuvers, alternate ramp traversals, limit maneuvers with combined braking and steering, vehicle-to-vehicle crash tests and articulated vehicle handling tests. Comparison against other models were included. No metric was provided for handling test comparisons. However, statistical analysis of the collision test results revealed the average path range error was 6.2 to 14.8 percent. The average heading error was -4.7 to 0.7 percent. Delta-V error was -1.6 to 7.5 percent. VEHICLE SIMULATION has many uses in the vehicle design and safety industries.
Technical Paper

A Simulation Model for Vehicle Braking Systems Fitted with ABS

2002-03-04
2002-01-0559
Most vehicles built today are fitted with anti-lock braking systems (ABS). Accurate simulation modeling of these vehicles during braking as well as combined braking and steering maneuvers thus requires the effects of the ABS to be included. Simplified, lump parameter models are not adequate for detailed, 3-dimensional vehicle simulations that include wheel spin dynamics. This is especially true for simulating complex crash avoidance maneuvers. This paper describes a new ABS model included in the HVE simulation environment. It is a general purpose model and is available for use by any HVE-compatible vehicle simulation model. The basic operational and control characteristics for a typical ABS system are first reviewed. Then, the specific ABS model and its options as implemented in the HVE simulation environment and employed by the SIMON vehicle simulation model are described. To validate the model, pressure cycles produced by the model are compared with stated engineering requirements.
Technical Paper

Single Vehicle Wet Road Loss of Control; Effects of Tire Tread Depth and Placement

2002-03-04
2002-01-0553
When an automobile is driven on wet roads, its tires must remove water from between the tread and road surfaces. It is well known that the ability of a tire to remove water depends heavily on tread depth, water depth and speed, as well as other factors, such as tire load, air pressure and tread design. It is less well known that tire tread depth combined with placement can have an adverse effect on vehicle handling on wet roads. This paper investigates passenger car handling on wet roads. Flat bed tire testing, three-dimensional computer simulation and skid pad experimental testing are used to determine how handling is affected by tire tread depth and front/rear position of low-tread-depth tires on the vehicle. Some skid pad test results are given, along with corresponding simulations. A literature review also is presented. Significant changes in tire-road longitudinal and lateral friction are shown to occur as speed, tread depth and water depth vary, even before hydroplaning occurs.
Technical Paper

Why Simulation? An Interesting Case Study

2016-04-05
2016-01-1484
This paper presents an example application for vehicle dynamics simulation software. This example investigates the validity of the vehicle motion presented in the famous car chase scene from the 1968 movie Bullitt. In this car chase, a 1968 Ford Mustang, driven by Det. Frank Bullitt of the San Francisco Police Department, is chasing a criminal driving a 1968 Dodge Charger through the streets of the Russian Hill district of San Francisco. The purpose of the simulation was to reconstruct the chase scene to determine the level of realism in the movie, in terms of conformance to Newton’s Laws of motion. To produce the simulation, several city blocks of the pertinent area of the city were surveyed and exemplar vehicles were measured and inspected. Three-dimensional computer models of the scene and vehicles were built. The movie footage was analyzed to determine vehicle speeds and driver inputs. The event was then simulated using three-dimensional vehicle dynamics simulation software.
Technical Paper

Applications and Limitations of 3-Dimensional Vehicle Rollover Simulation

2000-03-06
2000-01-0852
Vehicle crashes often involve rollover. A vehicle rollover is a complex, 3-dimensional event that is quite difficult to model successfully. As a result, crash investigators often make simplifying assumptions that compromise the quality of the information learned from the analysis. Advances in vehicle simulation modeling have greatly reduced the amount of work required to perform rollover simulations. Rollover simulation holds promise as a tool to learn more about crashes involving rollover. This paper describes how the EDVSM simulation model calculates 3-dimensional forces and moments on the sprung mass (i.e., body exterior) and how these forces and moments are integrated into the equations of motion. The paper also provides some examples of the use of rollover simulation. Finally, the paper addresses the practical and theoretical limitations of rollover simulation as a tool for routine reconstruction of on-road and off-road crashes. VEHICLE ROLLOVER is a significant safety problem.
Technical Paper

Validation of DyMESH for Vehicle vs Barrier Collisions

2000-03-06
2000-01-0844
A new three-dimensional collision simulation algorithm, called DyMESH (Dynamic MEchanical SHell) was recently introduced.[1]* This paper presents a validation of DyMESH for vehicle vs. barrier collisions. The derivation of the three-dimensional force vs. crush relationship was described previously.[1] Here the application of three-dimensional force vs. crush curves using the outlined methodology is shown to be effective. Nonlinear force versus crush relationships are introduced for use in DyMESH. Included are numerous DyMESH collision simulations of several types of vehicles (e.g., light and heavy passenger car and sport utility) compared directly with experimental collision test results from various types of barrier tests (e.g., full frontal, angled frontal, and offset frontal). The focus here is not on the vehicle’s change in velocity, but on the acceleration vs. time history.
Technical Paper

Integrating Design and Virtual Test Environments for Brake Component Design and Material Selection

2000-03-06
2000-01-1294
A new, systematic approach to the design-evaluation-test product development cycle is described wherein the vehicle design and simulation environments are integrated. This methodology is applied to brake mechanical design and material selection. Time-domain computations within a vehicle dynamic simulation environment account for brake and lining geometry and material properties, actuator properties, and temperature effects. Two examples illustrate the utility of this approach by examining: the effect of varying hydraulic cylinder diameter on passing federally mandated stopping distance tests, and the effect of S-cam actuator adjustment on the performance of air brakes on a tractor-trailer. The simulation results are compared with experimental vehicle stopping distance tests to assess the validity of the simulations.
Technical Paper

The DyMesh Method for Three-Dimensional Multi-Vehicle Collision Simulation

1999-03-01
1999-01-0104
Two-dimensional collision simulation has been used successfully for two decades. Two- and three-dimensional momentum methods are also well known. Three-dimensional collision simulation can be accomplished using finite element methods, but this is not practical for interactive collision simulation due to long mesh generation times and run times which may take several days. This paper presents an approach to collision simulation using a new algorithm to track interacting vehicle surface meshes. Three-dimensional forces due to vehicle crush are taken into account during the solution and the damage profile is visualized at run time. The new collision algorithm is portable in that it takes as input vehicle material properties and surface geometries and calculates from their interaction three-dimensional forces and moments at the vehicle center of gravity. Intervehicle mesh forces may be calculated from a user-defined force-deflection relationship. The derivation is discussed.
Technical Paper

Differences Between EDVDS and Phase 4

1999-03-01
1999-01-0103
Motor vehicle safety researchers have used the Phase 4 vehicle simulation model for several years. Because of its popularity and ability to simulate the 3-dimensional dynamics of commercial vehicles (large trucks and truck tractors towing up to three trailers), the Phase 4 model was ported to the HVE simulation platform. The resulting model is called EDVDS (Engineering Dynamics Vehicle Dynamics Simulator). This paper describes the procedures used in porting Phase 4 to the HVE platform. As a result of several assumptions made during the development of Phase 4, the port to EDVDS required substantial changes. The most significant modeling difference is the removal of the small angle assumption, allowing researchers to study complete vehicle rollover. Also significant is EDVDS’s use of HVE’s Get Surface Info () function, allowing the vehicles’ tires to travel over any 3-D terrain of arbitrary complexity. These and other changes in the model are described in the paper.
Technical Paper

An Overview of the EDSMAC4 Collision Simulation Model

1999-03-01
1999-01-0102
The EDSMAC simulation model has been in widespread use by vehicle safety researchers since its introduction in 1985. Several papers have been published that describe the model and provide validations of its use. In 1997, the collision and vehicle dynamics models were extended significantly. The main control logic was also extended and generalized. The resulting model was named EDSMAC4. This paper describes the EDSMAC4 model with particular attention to the extensions to the original algorithms. The paper also provides a validation of the new model by direct comparison to staged collision experiments and the results from the previous EDSMAC model.
Technical Paper

Differences Between EDCRASH and CRASH3

1985-02-25
850253
Motor vehicle accident researchers have used the CRASH computer program for some time. Over the years, the code was upgraded until it reached its present and popular form, CRASH3, which runs on a mainframe computer or minicomputer with a sizeable memory capacity. A new version of the program, EDCRASH, has been developed which runs on personal computers using 128K of memory. This paper describes and compares this program with its mainframe counterpart. The program performed the same function as CRASH3, but was designed as a screen-oriented program utilizing the environment of the personal computer. Its design also allowed for file saving, graphics, routing of output, and interfacing with other accident reconstruction programs. For most accident types, the results for both programs were identical. However, for some types the results were different.
Technical Paper

A Computer Graphics Interface Specification for Studying Humans, Vehicles and Their Environment

1993-03-01
930903
This paper describes a general purpose computer graphics interface for performing detailed two- and three-dimensional studies involving the dynamic response of humans and vehicles during the pre-crash, crash and post-crash phases of a motor vehicle accident. Specifications are provided for human, vehicle and environment models which can be constructed and analyzed using the interface. The requirements of analysis methods which may be incorporated into the interface are examined, and several examples are provided. Finally, the paper illustrates how the interface is used for creating high-level animations to view the resulting human and/or vehicle motion on various output devices such as computer displays, printers, plotters and video tape recorders.
Technical Paper

Further Validation of EDSMAC Using the RICSAC Staged Collisions

1990-02-01
900102
The accuracy of the SMAC computer program was evaluated in terms of its ability to predict the correct paths and damage profiles for vehicles involved in a crash. A comparison of the results from SMAC and EDSMAC were presented along with measured results from twelve staged collisions. Statistical analysis of those results revealed the average path error was 25 to 29 percent and the average damage profile error was 109 to 287 percent. A procedure was presented for improving the match between simulated and measured paths. After using this procedure, the average path error was reduced to -2 to 7 percent and the average damage profile error was 54 to 186 percent. CDC predictions were very good. Damage profile errors, which did not reduce the program's overall effectiveness, were the result of the way the program computes inter-vehicle forces, leading to a recommendation that the algorithm be reformulated to include an initial force coefficient.
Technical Paper

Application and Misapplication of Computer Programs for Accident Reconstruction

1989-02-01
890738
Several computer programs are used by accident investigators to reconstruct motor vehicle accidents. These programs are seen as valuable tools by most investigators. However, it is also clear the programs are sometimes misused. This paper addresses five different types of computer programs used by accident investigators and discusses their proper and improper use. Most frequently, misuse is due to the lack of a thorough understanding of how the programs work. A series of recommendations is presented to help investigators properly use the programs.
Technical Paper

Further Validation of EDCRASH Using the RICSAC Staged Collisions

1989-02-01
890740
The accuracy of the CRASH computer program was evaluated in terms of its ability to estimate impact speed. A comparison of the results from CRASH2, CRASH3 and EDCRASH were presented along with measured results from twelve staged collisions. Statistical analysis of these results revealed the impact speeds estimated by these CRASH programs were within −6 to +7 percent of the combined impact speeds at a 95 percent level of confidence. Using EDCRASH's extended features to optimize the input data improved the range to within −3 to +3 percent of combined impact speeds. An example was used to illustrate the use of the confidence intervals to estimate the expected range of impact speed for a given reconstruction. The results for oblique collisions were found to be significantly more accurate than the results for collinear collisions.
Technical Paper

Case Studies Involving the Use and Non-Use of Seatbelts

1986-11-01
861091
This paper presents the case study results of several actual motor vehicle accidents which occurred in the western U.S. Each case was analyzed to determine the characteristics of impact to the vehicle and the resulting occupant injuries. The most frequent injury was facial laceration from impacting the windshield. The main benefit of restraint systems lies in their ability to reduce or prevent contact between the occupant and the interior during the crash.
Technical Paper

An Overview of the Way EDCRASH Computes Delta-V

1987-02-01
870045
The two procedures, DAMAGE and OBLIQUE IMPACT, which are used by EDCRASH for computing delta-V, are described in detail. Enhancements in EDCRASH Version 4 which improve the DAMAGE method of computing delta-V are also described. The advantages and disadvantages of each method are explored, and the numerical and graphical output and use of warning messages are reviewed. In general, it was found the two methods are complimentary: The DAMAGE procedure is best-suited for the conditions in which the OBLIQUE IMPACT procedure is least-suited, and vice-versa.
Technical Paper

An Overview of the Way EDSMAC Computes Delta-V

1988-02-01
880069
The EDSMAC personal computer program for use by accident investigators is described. The input data requirements are reviewed. The general calculation procedures are discussed and the specific procedures for computing delta-V are explained in detail. The method, based on equalizing the force between the vehicles at all times during the impact phase, is seen to be simple in concept but extremely complex in practice. The numerical and graphical output and warning messages are reviewed. Applications of the program are illustrated. The major benefit of EDSMAC is the ability, using graphics, to provide an analytical method illustrating how an accident may, or may not, have occurred.
Technical Paper

Vehicle Data Sources for Accident Reconstruction

1988-02-01
880070
A major component in reconstructing motor vehicle accidents is the use of accurate data about the vehicles involved in the accident. Whether the reconstruction is done manually or with the aid of computers, the accuracy of the reconstruction is directly proportional to the accuracy of the vehicle data. Unfortunately, the vehicle data is not always available from the actual vehicles involved in the accident. In these instances, the reconstructionist must obtain data that best approximates the original vehicles. In lieu of finding, measuring, and weighing identical vehicles, the data is available through publications, trade associations, and other common sources. This paper describes these sources and how the information can be obtained.
Technical Paper

A Personal Computer Program for Drawing Accident Sites

1988-02-01
880068
A personal computer program for drawing accident sites is described. The program design is reviewed and hardware requirements are defined. Standard features are explained and features unique to the needs of the accident reconstructionist, such as photogrammetry and a built-in accident site template, are presented. Its use with other computer accident reconstruction programs is illustrated. It is seen that the scaled accident site diagram provides an important element to the reconstruction, both as an analytical tool as well as a presentation tool.
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