Robert William McCoy

A literature review of rollover test methodologies

This paper presents a literature review of test methods that have been used to provide data for development of rollover occupant protection systems, including rollover sensor algorithms, test methodologies, and restraint-system performance. Test methods reviewed in this paper include SAE J2114, side curb trip, corkscrew ramp, critical sliding velocity, deceleration rollover sled, ditch/embankment, soil trip and various misuse tests. Historical development, procedure, application and the experience with these methods are discussed. Pros and cons of these test methodologies are summarised in relation to the rollover sensing algorithm and rollover occupant protection system development. Remarks related to test methodologies are made and issues pertaining to repeatability and dummy performance are discussed. Various component test methodologies are also reviewed and a newly developed component test device is presented. A brief review of CAE methodology and trends in test methods are also given.

Image Analysis of Rollover Crash Tests Using Photogrammetry

This paper presents an image analysis of a laboratory-based rollover crash test using camera-matching photogrammetry. The procedures pertaining to setup, analysis and data process used in this method are outlined. Vehicle roll angle and rate calculated using the method are presented and compared to the measured values obtained using a vehicle mounted angular rate sensor. Areas for improvement, accuracy determination, and vehicle kinematics analysis are discussed. This paper concludes that the photogrammetric method presented is a useful tool to extract vehicle roll angle data from test video. However, development of a robust post-processing tool for general application to crash safety analysis requires further exploration.

A Method to Quantify Vehicle Dynamics and Deformation for Vehicle Rollover Tests Using Camera-Matching Video Analysis

This paper examines the use of camera-matching video analysis techniques to quantify the vehicle dynamics and deformation for a dolly rollover test run in accordance with the SAE Recommended Practice J2114. The method presented enables vehicle motion data and deformation measurements to be obtained without the use of the automated target tracking employed by existing motion tracking systems. Since it does not rely on this automated target tracking, the method can be used to analyze video from rollover tests which were not setup in accordance with the requirements of these automated motion tracking systems. The method also provides a straightforward technique for relating the motion of points on the test vehicle to the motion of the vehicle’s center-of-mass. This paper, first, describes the specific rollover test that was utilized. Then, the camera-matching method that was used to obtain the vehicle motion data and deformation measurements is described. Finally, the data obtained from the video analysis is analyzed and compared to data obtained from on-board instrumentation. Ultimately, the camera-matching technique is shown to be a viable technique for obtaining three-dimensional vehicle motion during a rollover crash test. As a means of obtaining vehicle deformation, the technique will need further development. INTRODUCTION This paper examines the use of a camera-matching photogrammetric technique to track the motion and dynamic deformation of a vehicle during a SAE J2114 dolly rollover test. The methodology presented enables vehicle motion data and deformation measurements to be obtained without the use of the automated target tracking employed by motion tracking systems. Since it does not rely on this automated target tracking, the method can be used to analyze video from rollover tests which were not setup in accordance with the requirements of such motion tracking systems. The method also provides a straightforward technique for relating the motion of points on the test vehicle to the motion of the vehicle’s center-of-mass. In 2006, Chou, et al. (2006), reported video analysis results for a 500 millisecond segment of another dolly rollover test [1]. In this earlier research, the authors primarily examined the effectiveness of the technique for obtaining roll angles and roll velocities from the test. The analysis reported by Chou, et al., was limited because the characteristics and locations of the cameras that recorded the crash test were unknown, as was the exact geometry of the crash test facility and the crash test vehicle. 2008-01-0350 A Method to Quantify Vehicle Dynamics and Deformation for Vehicle Rollover Tests Using Camera-Matching Video Analysis Nathan A. Rose, William T.C. Neale, Stephen J. Fenton and David Hessel

Development of a finite element model for simulation of rollover crashes

Rollover crashes are complex by their very nature, and have stimulated many researches aimed at improved occupant safety. In order to investigate the vehicle crashworthiness during rollovers, several test modes are generally used to replicate different real world rollover scenarios. However, such tests are very expensive, especially during the development stage of a new car line. Computer modeling is a cost-effective way to study rollover crashes. However, a survey of literature showed that only rigid-body dynamics based models have been used for rollover simulations. It is well known that this class of models cannot be used to simulate component deformation and structural collapses. Finite element (FE) method, which has been widely used to simulate frontal and side crashes, was rarely used for simulating rollover crashes, due mainly to the relative long duration of a rollover crash. The objective of this study was to develop an FE model for investigating vehicle crashworthiness during three commonly used rollover tests. An FE model of an SUV was developed in this study. Several sub-models, namely the vehicle structure sub-model, the tire sub-model, the suspension system sub-model, the restraint system sub-model, and the dummy model were generated and integrated together. The structure model was first used to simulate the roof crush test as prescribed in FMVSS 216. The resulting load versus roof crush curve matched well against test results. The integrated model was then used to simulate three laboratory-based rollover test modes, namely the SAE J2114 dolly test, curb-trip test, and corkscrew test. For each test mode, up to 1.5 seconds of simulation time (about 1 full vehicle roll) were computed. The vehicle kinematics, including the angular velocity, lateral acceleration, and vertical acceleration during these three test modes were computed and compared with experimental data. The simulated dummy head accelerations, timing and location of the most severe impact to the dummy’s head were also compared with the experimental results. Results showed very good agreement between the tests and simulations. In order to reduce the computational time, multiple CPUs were used. Approximately ten hours were required to run a 1.5 second rollover simulation on eight CPUs. Thus, simulating rollovers using FE method is quickly becoming a reality.Copyright

Analysis of Vehicle-to-Ground Impacts During a Rollover with an Impulse-Momentum Impact Model

This paper explores the accuracy of a planar, impulse-momentum impact model in representing the dynamics of three vehicle-to-ground impacts that occurred during a SAE J2114 dolly rollover test. The impacts were analyzed using video analysis techniques in order to obtain the actual velocity conditions, accelerations, impact force components and the energy loss for each of the impacts. Next, these same impacts were analyzed using the known initial velocity conditions and the subject impact model. The equations of this impact model yielded calculated values for the velocity changes and energy loss for each impact. These calculated results were then compared to the actual dynamics data from the video analysis of the impacts to determine the accuracy of the impact model results. For all three vehicle-to-ground impacts considered in this study, the impact model results for the velocity changes and energy loss showed excellent agreement with the video analysis results for these parameters. These results suggest that it is reasonable to use this impact model to examine the influence of various factors on rollover dynamics.

Use of Photogrammetry in Extracting 3D Structural Deformation/Dummy Occupant Movement Time History During Vehicle Crashes

The ability to extract and evaluate the time history of structural deformations or crush during vehicle crashes represents a significant challenge to automotive safety researchers. Current methods are limited by the use of electro-mechanical devices such as string pots and/or linear variable displacement transducers (LVDT). Typically, one end of the transducer must be mounted to a point on the structure that will remain un-deformed during the event; the other end is then attached to the point on the structure where the deformation is to be measured. This approach measures the change in distance between these two points and is unable to resolve any movement into its respective X, Y, or Z directions. Also, the accuracy of electro-mechanical transducers is limited by their dynamic response to crash conditions. The photogrammetry technique has been used successfully in a wide variety of applications including aerial surveying, civil engineering and documentation of traffic accidents. It has the potential to be used as a method to extract the time history of structural deformations during vehicle crash testing from film analysis without resorting to physical measurement of the points of interest. The procedure consists of first placing coded targets at the points of interest. Each targets motion is recorded using two digital high speed video cameras positioned at discrete angles to capture the motion of each target from two perspectives. Processing and analysis of the captured motion will yield the X, Y, and Z coordinates of these targets in a three dimensional space as a function of time. This paper describes in detail, the application of photogrammetry in crash safety analysis. It demonstrates the technique through examples carried out in dummy occupant motion and structural deformation analyses for a variety of crash tests and modes.

Analysis of a Prototype Electric Retractor, a Seat Belt Pre-Tensioning Device and Dummy Lateral Motion Prior to Vehicle Rollover

Vehicle motion prior to a rollover can influence an occupants position in the vehicle. Lateral deceleration prior to a tripped rollover may cause the occupant to move outboard. This outboard motion may have several effects on the occupant such as, repositioning the occupant with relation to the seat and seat restraint, and allowing the occupants head to travel further into the side curtain deployment zone. To reduce occupant lateral motion, the effectiveness of applying tension to the seatbelt was evaluated. The evaluation consisted of two test conditions simulating vehicle lateral motion prior to a trip using a Deceleration Rollover Sled [1]. The test conditions were designed to ensure a vehicle experiences a period of pure lateral motion before the onset of a lateral trip. A standard seat belt combined with various means of applying tension and activated at different times during the test were evaluated. The conclusions were based on analyzing the dummy lateral motion, belt loads, and dummy head and chest acceleration from these tests.

Vehicle Rollover Sensor Test Modeling

A computational model of a mid-size sport utility vehicle was developed using MADYMO. The model includes a detailed description of the suspension system and tire characteristics that incorporated the Delft-Tyre magic formula description. The model was correlated by simulating a vehicle suspension kinematics and compliance test. The correlated model was then used to simulate a J-turn vehicle dynamics test maneuver, a roll and non-roll ditch test, corkscrew ramp and a lateral trip test, the results of which are presented in this paper. The results indicate that MADYMO is able to reasonably predict the vehicle and occupant responses in these types of applications and is potentially suited as a tool to help setup a suite of vehicle configurations and test conditions for rollover sensor testing. A suspension system sensitivity study is presented for the laterally tripped non-roll event. Copyright

Early Detection of Rollovers with Associated Test Development

A number of studies, using data from NASS-CDS, have shown a large percentage of rollover crashes can be classified as tripped events. In many cases, the requirements for a tripped rollover detection algorithm are driven by the timely activation of an occupant containment device. To meet these requirements rollover detection algorithms have been developed by utilizing vehicle roll rate, lateral and vertical accelerations data collected primarily from laboratory tests. This study identifies and examines several challenges associated with developing a rollover detection algorithm with enhanced capabilities. Enhancement of the detection algorithm is explored by considering additional vehicle responses: forward velocity and sideslip angle. With the additional signals, discrimination of rollover crashes from other crash modes is discussed. Potential field/laboratory test modes are proposed to generate the additional vehicle signals. The new test modes are designed to challenge the detection algorithm, better represent field conditions and be used in development of strategies for occupant restraint system devices.