Browse Topic: Rollover accidents

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Identification of Dynamic Rollover Precursors for Enhanced Helicopter Flight Data Monitoring (HFDM) ApplicationsF-0081-2025-01465/20/2025
Dynamic rollovers represent a major hazard for helicopters during near-ground operations, often resulting in significant aircraft damage and passenger injuries. To improve safety in operations, recent studies have focused on developing a Helicopter Flight Data Monitoring framework to provide data-driven insights on operational safety. This work contributes to that effort by proposing an approach to identify precursors to dynamic rollovers. According to NTSB reports, approximately 60% of such incidents occur during in-flight phases like hover, hover-taxi, or landing. To capture the complex non-linear dynamics of helicopters, physics-based simulations were conducted to estimate a first hitting time metric, defined as the time until blade-ground contact, across a wide range of initial conditions for an inflight initial state of the helicopter. Eight parameters were identified as driving the first hitting time, and a probabilistic model was created to predict the distribution of that metric for different values of those parameters. Based on the predicted distributions, a risk-based metric was derived to robustly assess the risk of dynamic rollover and identify safer operational boundaries.
Johnson, Charles, Mavris, Dimitri
REDUCED ORDER MODELLING METHOD (ROMM) FOR GROUND VEHICLE ROLLOVER PROTECTION M&S2024-01-390311/15/2024
ABSTRACT The performance of ground vehicles during a rollover event is an important safety and occupant protection requirement for military vehicles. Modeling and simulation is a very useful tool in study and investigation of vehicle rollover characteristics and countermeasure concepts. This study presents two methods of simulating the rollover events. The first one uses Full System Method (FSM), where all the components are modelled as is and are evaluated. The second method is a reduced order modelling method (ROMM) using integration of the resulted kinematics data from FSM into the vehicle model with occupant & restraints. The FSM & ROMM methods were applied to simulate two HMMMV rollover events, and the results from both methods show that simulation and test data agreed fairly well. Computational time reduced by the ROMM was about 53% of that of the FSM. ROMM approach not only saves significant computational time but also increases robustness of the simulation. Citation: V. Babu, J. Kang, S. Kankanalapalli, J. Sheng, M. Vunnam, S. K. Karwaczynski, C. Jessup, M. Duncan, K. Paulson, “REDUCED ORDER MODELLING METHOD (ROMM) FOR GROUND VEHICLE ROLLOVER PROTECTION M&S”, In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 10-12, 2021.
Babu, V., Kang, J., Kankanalapalli, S., Sheng, J., Vunnam, M., Karwaczynski, S. K., Jessup, C., Duncan, M., Paulson, K.
Articulated Vehicle Lateral Stability Management via Active Rear-Wheel Steering of Tractor Using Fuzzy Logic and Model Predictive Control02-13-02-00087/1/2020
In-phase rear-wheel steering, where rear wheels are steered in the same direction of front wheels, has been widely investigated in the literature for vehicle stability improvements along with stability control systems. Much faster response can be achieved by steering the rear wheels automatically during an obstacle avoidance maneuver without applying the brakes where safe stopping distance is not available. Sudden lane change movements still remain challenging for heavy articulated vehicles, such as tractor and semitrailer combinations, particularly on roads with low coefficient of adhesion. Different lateral accelerations acting on tractor and semi-trailer may cause loss of stability resulting in jackknifing, trailer-swing, rollover, or slip-off. Several attempts have been made in the literature to use active steering of semi-trailer’s rear wheels to prevent jackknifing and rollover. However, loss of stability in an articulated vehicle is usually caused by an oversteered tractor, and the semitrailer’s rear wheels have little effect on the tractor’s directional control. In this study, viability of active rear-wheel steering of tractor to maintain the stability of an articulated vehicle during a high-speed obstacle avoidance maneuver is investigated. Two different controllers, fuzzy logic and linear model-based predictive controllers, are proposed to minimize the off-tracking behavior of an articulated vehicle. The controllers were tested in IPG/TruckMaker environment with MATLAB/Simulink interface on roads with various coefficient of adhesions, performing single lane change maneuvers. The simulated results showed that jackknifing occurring right after sudden lane changes can be successfully prevented using the tractor’s active rear-wheel steering based on model predictive control algorithm when the feedback gains are tuned correctly.
Sahin, Hasan, Akalin, Ozgen
A Novel Prediction Algorithm for Heavy Vehicles System Rollover Risk Based on Failure Probability Analysis and SVM Empirical Model2020-01-07014/14/2020
The study of heavy vehicles rollover prediction, especially in algorithm-based heavy vehicles active safety control for improving road handling, is a challenging task for the heavy vehicle industry. Due to the high fatality rate caused by vehicle rollover, how to precisely and effectively predict the rollover of heavy vehicles became a hot topic in both academia and industry. Because of the strong non-linear characteristics of Human-Vehicle-Road interaction and the uncertainty of modeling, the traditional deterministic method cannot predict the rollover hazard of heavy vehicles accurately. To deal with the above issues, this paper applies a probability method of uncertainty to the design of a dynamic rollover prediction algorithm for heavy vehicles and proposes a novel algorithm for predicting the rollover hazard based on the combined empirical model of reliability index and failure probability. Moreover, the paper establishes a classification model of heavy vehicles based on the support vector machine (SVM) and uses the Monte Carlo method to calculate the failure probability of rollover limit state of heavy vehicles. The fishhook, double lane change, and slalom maneuver tests of heavy vehicles are used to predict and validate the proposed algorithm in real-time. The simulation results show that the rollover prediction method based on failure probability is accurate and real-time, and can effectively improve the rollover prediction accuracy. Meanwhile, the proposed approach reduces the external interference of strong non-linear characteristics of Human-Vehicle-Road interaction and the uncertainty of the modeling to the system, thus significantly improving the prediction accuracy of active safety performance of heavy vehicles.
Zhu, Tianjun, Yin, Xiaoxuan, Wang, Zhenfeng, Wang, Dong, Li, Fei, Wang, Xinyu, Ma, Wei, Wang, Zheng
SUV Kinematics during a Steer-Induced Rollover Resolved Using Consumer-Grade Video, Laser Scans and Match-Moving Techniques2020-01-06424/14/2020
Rollover crashes are complex events that generate motions in all six degrees of freedom (6DOF). Directly quantifying the angular rotations from video can be difficult and vehicle orientation as a function of time is often not reported for staged rollover crashes. Our goal was to evaluate the ability of using a match-moving technique and consumer-grade video cameras to quantify the roll, pitch and yaw angles and angular velocities of a rollover crash. We staged a steer-induced rollover of an SUV at 106 km/h. The vehicle was fitted with tri-axial accelerometers and angular rate sensors, and five consumer-grade video cameras (2 on tripods, 2 on drones, 1 handheld, ~30 fps) captured the event. Roll, pitch and yaw angles were determined from the video using specialized software. We then compared the vehicle orientation angles from the video data to the integrated angular rate data measured by onboard sensors, and also compared the angular rates from the differentiated video data to the angular rates measured directly by the sensors. We found that both methods of measuring the 3D angles and angular rates generated similar results. The integrated sensor data drifted a maximum of 13° relative to the video-based angles, with RMS differences of ±2.7° or less when the drift was removed. The differentiated video data did not drift relative to the sensor data, with RMS differences of ±0.22 rad/s or less. These findings indicate that both methods generate similar results and are suitable for reconstructing rollovers. Given the drift we observed in the integrated sensor data, we recommend using angle measurements from the video to quantify the amount of drift in integrated sensor data if accurate knowledge of the vehicle’s orientation as a function of time is important.
Young, Cole R., King, David J., Siegmund, Gunter P.
Accuracy and Sensitivity of Yaw Speed Analysis to Available Data2019-01-04174/2/2019
Accident reconstructionists rarely have complete data with which to determine vehicle speed, and so the true value must be bracketed within a range. Previous work has shown the effect of friction uncertainty in determining speed from tire marks left by a vehicle in yaw. The goal of the current study was to assess improvements in the accuracy of vehicle speed estimated from yaw marks using progressively more scene and vehicle information. Data for this analysis came from staged S-turn maneuvers that in some cases led to rollover of sport utility vehicles. Initial speeds were first calculated using the critical curve speed (CCS) formula on the yaw marks from the first portion of the S-maneuver. Then computer simulations were performed with progressively more input data: i) the complete tire marks from the whole S-maneuver, ii) measured vehicle mass, iii) measured suspension stiffness and damping, and iv) measured steering history. Simulations based on the complete tire marks reduced the average error compared with the CCS equation if measured accelerations were also matched. Adding the remaining input data to the simulations did not further improve the accuracy of the reconstructed vehicle speed.
Heinrichs, Bradley, Lee, Janice, Young, Cole
An Analytical Review and Extension of Two Decades of Research Related to PC-Crash Simulation Software2018-01-05234/3/2018
PC-Crash is a vehicular accident simulation software that is widely used by the accident reconstruction community. The goal of this article is to review the prior literature that has addressed the capabilities of PC-Crash and its accuracy and reliability for various applications (planar collisions, rollovers, and human motion). In addition, this article aims to add additional analysis of the capabilities of PC-Crash for simulating planar collisions and rollovers. Simulation analysis of five planar collisions originally reported and analyzed by Bailey [2000] are reexamined. For all five of these collisions, simulations were obtained with the actual impact speeds that exhibited excellent visual agreement with the physical evidence. These simulations demonstrate that, for each case, the PC-Crash software had the ability to generate a simulation that matched the actual impact speeds and the known physical evidence. Simulation of a full-scale rollover test reported by Asay [2010] is also examined. For this test, we obtained a simulation that exhibited an excellent visual match with the pre-roll tire marks and furrows and in which the vehicle rolled 7 times, just as it did in the actual test. The rest position of the vehicle was well matched, though a portion of the simulated roll trajectory did not match the actual roll trajectory. These areas of additional analysis extend the prior literature.
Rose, Nathan A., Carter, Neal
Study on the Handling Stability for an Articulated Truck with Four Motor-Driven Wheels2017-01-18336/5/2017
Articulated engineering vehicle travels on complex road, its working condition is bad and because of the non-rigid connection between the front and rear body, additional DOF is brought in and the transverse stiffness is relatively weak. When the articulated vehicle runs in a high speed along a straight line, it is easy to cause the transverse swing and the poor handling stability. If it is serious enough, it will lead to "snakelike" instability phenomenon. This kind of instability will increase driving resistance and tire wear, the lateral dynamic load and aggravate the damage of the parts. The vehicle will have a lateral migration of center of gravity (CG) when steering, which will lead a higher probability of rollover accident. A dynamic mathematical model for a 35t articulated truck with four motor-driven wheels was established in this paper, to study the condition for its stable driving and the influence of the vehicle structural parameters. This part research focused on the position changes of the pivot and front and rear axle center, which impact the handling stability. Then a multi-body dynamic model was built in ADAMS and simulation of steady state circular test and steering wheel angle step input test were conducted to observe the handling stability of vehicle and compare the results in empty load, full load and different steering angle step inputting. On this basis, the influence of the CG position of rear body on truck handling stability was studied. The results of simulation has a good reference value for the articulated truck handling stability design and verify the correctness of the models.
Qin, Bonan, Yang, Jue, Zhao, Xinxin
Investigation of Rollover Prevention with Coupling from Driver Yaw Control Using a Scaled Vehicle2017-01-15793/28/2017
The development of an integrated controller for a 4WS/4WD electric bus is investigated. The front wheel steering angle is assumed to be controlled by the human driver. The vehicle is controlled by the rear wheel steering and the yaw moment that can be generated by the differential torque/brake control on each wheel. The high speed cornering is used as the testing scenario to validate the designed controller. Due to the highly nonlinear and the multiple-input and multiple-output nature, the control design is separated into different stages using the hierarchical layer control concept. The longitudinal speed is controlled using a PI controller together with a rule-based speed modification. The other two control inputs, namely the rear wheel steering and the DYC moment, are then designed using the state-dependent Riccati equation method. The designed controllers are evaluated using computer simulations first, and the simulations showed promising results. A scaled electric bus is being constructed to serve as the experimental platform for the designed controllers. In the future the designed controllers will be evaluated with TruckSim simulations and the scaled electric bus experiments.
Chen, Liang-kuang, Chen, Chien-An
Active Hydraulically Interconnected Suspension. Modeling and Simulation2017-01-15613/28/2017
Rollover prevention is one of the prominent priorities in vehicle safety and handling control. A promising alternative for roll angle cancellation is the active hydraulically interconnected suspension. This paper represents the analytical model of a closed circuit active hydraulically interconnected suspension system followed by the simulation. Passive hydraulically interconnected suspension systems have been widely discussed and studied up to now. This work specifically focuses on the active hydraulically interconnected suspension system. Equations of motion of the system are formalized first. The system consists of two separate subsystems that can be modeled independently and further combined for simulation. One of the two subsystems is 4 degrees of freedom half-car model which simulates vehicle lateral dynamics and vehicle roll angle response to lateral acceleration in particular. The other subsystem is active hydraulically interconnected suspension system which is responsible for active roll angle reduction. The subsystems are coupled via hydraulics-to-mechanical boundary condition. The methodology used is based on obtaining the equations of motion for the hydraulically interconnected suspension system as well as the half-car model. Standard Lagrange method is used for the half-car model. Hydraulic impedance method and the Kirchhoff's laws for hydraulics are used for the hydraulic circuit. Under a certain simplification, the state-space model of the whole system can be obtained with all states measurable. In simulation part, the system response is examined under a number of typical input tests including NHTSA J-turn maneuver and NHSTA fishhook maneuver. The ability of the active system in roll angle reduction is compared with the conventional car suspension and passive hydraulically interconnected suspension system.
Tkachev, Anton A., Zhang, Nong
An Analysis of Recreational Off Road Vehicle Tire Performance Characteristics2016-01-16354/5/2016
Recreational Off Road Vehicles (ROVs) which are sometimes referred to as side-by-sides, have increased in popularity over the last decade. These vehicles are available in many different sizes and performance characteristics from a host of different manufacturers and also have a variety of different missions, just as there are many types of off road terrain. The United States Federal Government, through the Consumer Product Safety Commission (CPSC), has advocated and proposed vehicle handling and rollover resistance standards for the side-by-sides which have a top speed above 25 miles per hour (these are not defined as “low speed vehicles”). For the sake of repeatability, the proposed maneuvers are to be performed on a high friction hard surface (like asphalt) as opposed to the off road surfaces (i.e. grass, sand, dirt, mud. rocks, etc.) that these vehicles are designed to be operated on. Since ROV tires are designed for off road use only, their force and moment characteristics on an asphalt or concrete surface has not been studied in depth. This paper discusses a technical analysis of tire force and moment properties of two types of ROV tires, a bias ply and a radial ply both of the same size. The tests were conducted on an MTS Flat Trac III tire machine where slip angle sweep tests were performed at various vertical loads. Comparisons between the two ROV tire types, as well as comparisons to common passenger vehicle tires are made. Repeated step input of slip angle runs were also made to study how the ROV tire performance characteristics change as they wear during severe cornering in limit maneuvers.
Tandy, Donald F., Bae, Jung, Colborn, Jason, Coleman, Clay
Development of a Biofidelic Rollover Dummy-Part II: Validation of the Kinematic Response of THOR Multi-Body and Finite Element Models Relative to Response of the Physical THOR Dummy under Laboratory Rollover Conditions2016-01-14864/5/2016
While over 30% of US occupant fatalities occur in rollover crashes, no dummy has been developed for such a condition. Currently, an efficient, cost-effective methodology is being implemented to develop a biofidelic rollover dummy. Instead of designing a rollover dummy from scratch, this methodology identifies a baseline dummy and modifies it to improve its response in a rollover crash. Using computational models of the baseline dummy, including both multibody (MB) and finite element (FE) models, the dummy’s structure is continually modified until its response is aligned (using BioRank/CORA metric) with biofidelity targets. A previous study (Part I) identified the THOR dummy as a suitable baseline dummy by comparing the kinematic responses of six existing dummies with PMHS response corridors through laboratory rollover testing. In this study (Part II), the whole-body kinematic responses of the THOR MB and FE models were validated with responses of the physical THOR dummy in experiments that simulated rollover conditions. This step is necessary to ensure accuracy of the computer-aidedengineering dummy design, thereafter improving confidence in the proposed rollover dummy design modifications. In addition, to ensure the robustness of the model validation, the sensitivities of the THOR dummy computational model responses to parameters with uncertainty in the experiment were assessed, including seatbelt pretension, friction, and dummy seating posture. In summary, both the THOR MB and FE model responses matched well with its physical counterpart. Future studies (Part III) will focus on using these validated dummy models for rollover dummy design modification and evaluation.
Zhang, Qi, Gepner, Bronislaw, Toczyski, Jacek, Kerrigan, Jason
Responses of the Q6/Q6s ATD Positioned in Booster Seats in the Far-Side Seat Location of Side Impact Passenger Car and Sled Tests2015-22-001211/9/2015
Passenger car side impact crash tests and sled tests were conducted to investigate the influence of booster seats, near-side occupant characteristics and vehicle interiors on the responses of the Q6/Q6s child ATD positioned in the rear, far-side seating location. Data from nine side impact sled tests simulating a EuroNCAP AEMD barrier test were analyzed with data obtained from 44 side impact crash tests. The crash tests included: FMVSS 214 and IIHS MDB, moving car-to-stationary car and moving car-to-moving car. A Q6 or prototype Q6s ATD was seated on the far-side, using a variety of low and high back booster seats. Head and chest responses were recorded and ATD motions were tracked with high-speed videos. The vehicle lateral accelerations resulting from MDB tests were characterized by a much earlier and more rapid rise to peak than in tests where the bullet was another car. The near-side seating position was occupied by a Hybrid III 10-year-old ATD in the sled tests, and a rear or front facing child restraint or a 5th percentile side impact ATD in the crash tests. Head impacts occurred more frequently in vehicles where a forward facing child restraint was present behind the driver seat for both the low and high back booster seats. Pretensioners were found to reduce lateral head displacements in all sled test configurations but the greatest reduction in lateral excursion was obtained with a high back booster seat secured with LATCH and tested in combination with pretensioners.
Tylko, Suzanne, Bohman, Katarina, Bussières, Alain
Handling-Stability Oriented Parameter Optimization for a Tractor Semi-Trailer Vehicle2015-01-27539/29/2015
Tractor semi-trailer as a widely-used heavy duty freight vehicle has caused many fatal accidents every year and one of the main factors of which may relate to its relatively poor lateral dynamics performance compared to the passenger cars [1, 2, 3]. In this paper, attention is concentrated on the parametric design for a tractor semi-trailer by optimizing the configuration parameters aiming to comprehensively improve the lateral dynamics performance. According to the previous public reports, the performance measures such as Load Transfer Ratio (LTR), Static Rollover Threshold (SRT), Rearward Amplification Ratio (RAR) and Ratio of Yaw Rate (RYR) are very effective measures and often be used to evaluate the handling and stability performances for tractor-trailer vehicles. However, each of those measures only pays attention to a certain aspect of vehicle lateral dynamics which is closely related to vehicle configuration parameters. Especially, the load scenario in transport which often varies from one task to another can make the lateral dynamics change considerably. Therefore it is difficult for a vehicle to obtain a comprehensively satisfying handling-stability performance in a wide range of load scenarios. In this work, two relatively comprehensive measures which directly link with vehicle configuration parameters have been formulated based on multivariable linear regression (MVLR) method respectively corresponding to the body roll and yaw dynamics in order to facilitate the implementation of handling- stability oriented design method. As an example, an optimal design scheme based on Multi-Objective Linear Programming (MOLP) method is presented and a set of optimum parameters are obtained. The handling and stability performances after optimization have been compared with those before optimization by simulations in TruckSim.
Yang, Xiujian, Zhu, Ruocheng, Gao, Jin
Vertical Occupant Loading in Car Crashes; Test Methods and Countermeasures2015-01-14594/14/2015
Vertical loading can cause thoracic and lumbar spine injuries to a car occupant. Crashes potentially causing occupant vertical loads include; rollover events or free flying events when the car lands on its wheels, and run off road events when the car goes into the ditch and collides with an embankment. To date, there is no standardized test method evaluating this occupant loading mechanism. The aim of this study was to develop test methods addressing vertical occupant loading for car occupants and to evaluate countermeasures for reduction of such loads. Based on real world run off road crashes, representative test track methods were developed. These complete vehicle test track methods were used to provide input to a simplified and repeatable rig test method. The rig test method comprises a dummy positioned in a seat attached to a frame and exposed to a vertical acceleration. Vertical pelvis acceleration is monitored, as an indication of potential loads through the spine. Two different seat designs are compared. The modified seat concept includes a deformation element which is built into the rear part of the seat connection to the seat frame. The deformation element allows for a controlled deformation of up to 25 mm. The space under the seat is cleared to allow for total occupant movement up to 150 mm. During this movement, energy is absorbed by the deformation element as well as the springs and seat cushion material. Compared to the reference production seat, the dummy pelvis vertical acceleration is reduced by 25-32% in the situations tested in this study.
Jakobsson, Lotta, Björklund, Magnus, Axelson, Anders
A Comparison of Bayesian Speed Estimates from Rollover and Critical Speed Methods2015-01-14344/14/2015
Martinez and Schlueter [6] described a three-phase model for reconstructing tripped rollover crashes, where the vehicle's path is divided into pre-trip, trip, and post-trip phases. Brach and Brach [9] also described this model and noted that the trajectory segmentation method for the pre-trip phase needed further validation. When a vehicle leaves a measurable yaw mark at the start of its pre-trip phase it might be possible to compare estimates from the three-phase model to those obtained using the critical speed method, and this paper describes Bayesian reconstruction of two such cases. For the first, the 95 percent confidence interval for the case vehicle's initial speed, estimated using the critical speed method, was (64 mph, 81 mph) while the 95 percent confidence interval via the three-phase model was (66 mph, 79 mph). For the second case an initial inconsistency between the two estimates suggested a modification to the three-phase model, leading to confidence intervals of (72 mph, 91 mph) and (79 mph, 92 mph) for the critical speed method and three-phase model, respectively.
Davis, Gary A.
Glass Debris Field Longevity for Rollover Accident Reconstruction2015-01-14274/14/2015
Vehicles involved in rollover crashes can leave debris trails which can include glass from broken windows. The glass patterns can be useful to identify the vehicles path during the rollover and the location and orientation of the vehicle at various vehicle-to-ground impacts. The location of glass, which is often window specific, can be used to identify where the window fractured during the rollover sequence. The longevity of the glass debris fields, subject to various real-world conditions and disturbances (i.e. slope, weather, mowing, soil type, etc.), was tested over a period of two years. The glass debris fields were placed and mapped in multiple locations across the United States. Periodically during each year, the glass debris fields were examined and the new field extents were mapped. The comparison between the original debris field and the subsequent debris fields are presented. At the completion of the research, the glass debris fields were collected and compared to what was initially placed at each location. This research concluded that a glass debris field remained in its approximate original location and can be relied upon as a source of accident reconstruction evidence for some time after the rollover occurred.
Przybyla, Jay, Jupe, Jason, Rush, Thomas, Keller, Rachel
The Influence of Body Mounted Shoulder Seat Belt Anchor (D-Ring) Displacement During Dynamic Vehicle-to-Ground Impacts2015-01-17564/14/2015
For more than 30 years, field research and laboratory testing have consistently demonstrated that properly wearing a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes. In severe rollover crashes, deformation to vehicle body structures can relocate body-mounted seat belt anchors altering seat belt geometry. In particular, roof pillar mounted shoulder belt anchors (“D-rings”) are subject to vertical and lateral deformation in the vehicle coordinate system. The ROllover Component test System (ROCS) test device was utilized to evaluate seat belt system performance in simulated severe rollover roof-to-ground impacts. A mechanical actuator was designed to dynamically relocate the D-ring assembly during a roof-to-ground impact event in an otherwise rigid test vehicle fixture. Anthropomorphic test device (ATD) kinematics and kinetics and seat belt tensions were compared between tests with and without D-ring relocation. Results indicate that the displacement of the shoulder belt anchor does not have a substantial effect on either ATD axial neck loads or the restraint provided by the seat belt system while limiting the vertical motion of the ATD during a single roof-to-ground impact.
Toomey, Daniel E., Marth, Debora R., Ballard, William G., Belwafa, Jamel E., Burnett, Roger, McCoy, Robert W.
Implementation and Experimental Study of a Novel Air Spring Combined with Hydraulically Interconnected Suspension to Enhance Roll Stiffness on Buses2015-01-06524/14/2015
Air spring due to its superior ride comfort performance has been widely used in distance passenger transporting vehicles. Since the requirements for ride comfort and handling performance are contradict to each other, handling performance and even roll stability are sacrificed to some extent to obtain good ride comfort. Due to the complex terrain and limited manufacturing level, in the past several years, bus rollover accidents with serious casualties have been reported frequently and bus safety has attracted more and more attention from bus manufacturers in China. On one hand the bus standards have to be raised, and on the other hand, novel solutions which can effectively improve the roll stability of air spring bus are needed to replace the inadequacy of anti-roll bars. This paper starts from experiment-based system parameter estimation to identify the handling issues of the new bus and redefine the design scope, then a combination design of air spring with an anti-roll hydraulically interconnected suspension is proposed, aiming to improve the cornering stability, ride comfort in roll direction, while maintaining the softness in the bounce mode. Experimental results of the bus fitted with the roll-enhanced air spring suspension are provided and compared with the original bus. Dynamic responses, such as roll angle, lateral acceleration and bounce acceleration are used to evaluate the handling stability and ride comfort of the bus. Results show that the new design can effectively improve the bus handling while maintaining the ride comfort.
Hua, Hui, Wang, Lifu, Qi, Hengmin, Zhang, Jie, Zhang, Nong
Analyzing Rollover Indices for Critical Truck Maneuvers2015-01-15954/14/2015
Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in different situations. In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8×4 twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal maneuvers with different rollover indices, thus limiting the vehicle's maneuvering envelope with respect to each rollover index. The resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the conservativeness of the indices for assessing the risk of rollovers are discussed.
Lundahl, Kristoffer, Lee, Chih Feng, Frisk, Erik, Nielsen, Lars
Effects of Liquid Cargo on Lateral Stability of B-Train Combination2014-01-23199/30/2014
Road train vehicles have been applied as one of the common and efficient ways for transportation of goods, specifically hazardous liquid cargos, in different nations. These vehicles have a wide variety of lengths and towing systems such as the fifth wheel or the dolly draw-bar. Based upon specific regulations, they could be authorized to move on specific roads. In order to avoid hazard and danger in case of accidents, safety performance of a B-train vehicle as a specific type of road train vehicles is investigated in this paper. A Multi-Body Dynamic (MBD) model, which consists of a prime mover and two trailers coupled by fifth wheels, are simulated in the initial phase of the study. The developed dynamic model is capable of simulating required tests as well as the SAE lane change, along with a constant radius turn for the purpose of roll and yaw stability analysis and safety evaluation. The effects of variation of the fluid fill level are considered in this research. The trammel pendulum concept is adopted for simulation of fluid movements, known as sloshing, in two articulated tankers of the model. Moreover, a preview driver controller is integrated to the MBD model to provide the follow-up the path during the lane-change and constant radius turn maneuvers. Compared to the results from the simulation of fixed liquid cargo, the critical behavior of the vehicle in terms of rollover at lower speeds is observed when the movement of fluid is taken into account. The results show that transportation of a high density fluid yields a more critical condition compared to a low density one, when the same axle load is retained.
Hazrati Ashtiani, Iman, Abedi, Mehrnoosh
Simulations of Heavy Truck Rollovers and Sleeper Restraint System Effectiveness2014-01-24209/30/2014
Federal Motor Carrier Safety Requirement (FMCSR) 393.76(h) states that “a motor vehicle manufactured on or after July 1, 1971 and equipped with a sleeper berth must be equipped with a means of preventing ejection of the occupant of the sleeper berth during deceleration of the vehicle.” [1] Furthermore, this standard requires that “the restraint system must be designed, installed and maintained to withstand a minimum total force of 6,000 pounds applied toward the front of the vehicle and parallel to the longitudinal axis of the vehicle.” [1] Today, sleeper berths are equipped with sleeper restraint systems that function to contain the sleeper occupant inside the sleeper berth during reasonably foreseeable crashes. To assess the effectiveness of sleeper restraint systems, computer simulation models of the sleeper cab environment and these restraint systems were developed, with a simulated supine occupant in the sleeper. The model was evaluated using two different rollover crash scenarios. The first rollover scenario used measurements from a previously reported tractor-trailer, driver side leading, and quarter-turn rollover crash test. [2] The second rollover scenario was based on reconstruction of a very severe crash that occurred on a mountain road, where a tractor-trailer rolled, passenger side leading. When the tractor was in approximately the 90 degree roll position, the trailer landed and pivoted on a guardrail. As the trailer was crushing the guardrail, the top passenger side of the tractor's cab struck the guardrail. The inertia of the truck, combined with the guardrail impacts, continued the roll and the truck became airborne as it entered a 25 ft. deep ravine. The truck impacted the bottom of the ravine and came to rest with the tractor completing approximately 360 degrees of roll and the trailer completing approximately 315 degrees of roll. This simulation effort demonstrated that tenting style and blanket style sleeper cab restraints contain a supine sleeper occupant in the sleeper berth, preventing ejection, in two rollover crash scenarios when the sleeper compartment itself remains intact.
Chinni, James, Butler, Robert, Yang, Shu
High Speed Optimal Yaw Stability of Tractor-Semitrailers with Active Trailer Steering2014-01-00934/1/2014
Most tractor-semitrailers are fitted with multi-axle trailers which cannot be actively steered, and such vehicles with an articulated configuration are inclined to exhibit instability such as trailer swing, jack-knifing, and rollover at high speed. Proposed in this paper is an optimal control of the yaw stability of tractor-semitrailers at high speed by applying an active trailer's steering angle. An optimal control algorithm is designed by employing a 3-DOF vehicle model in the yaw plane. The optimal linear quadratic regulator (LQR) approach is used with a cost function including sideslip angles, yaw rates of both tractor and trailer, and trailer's steering angle. The yaw stability at the high speed is also quantified by the dynamic performance measurements of lateral path deviation, hitch angle and rearward amplification (RA). The algorithm is evaluated by co-simulations using TruckSim and Matlab/Simulink softwares. Simulation results under double lane change maneuvers show that trailer swing and jack-knifing are suppressed with a small path-tracking error and it is concluded that the optimal control of semi-trailer steering can improve the yaw stability at high speed.
Lin, Xiaomin, Ding, Nenggen, Xu, Guoyan, Gao, Feng
Implementation of Real-Time Vehicle Rollover Prevention System2014-01-01494/1/2014
Vehicle Rollover Prevention/Warning Systems have recently been an important topic in Advanced Driver Assistance Systems (ADAS) of automotive electronics field. This paper will propose a rollover-prevention system implementation with vehicle dynamic model, video-detection technique and rollover index to help the driver avoid accidents as driving into a curve. Due to the reason that vehicle rollover motion analysis needs complicated computation and accurate parameters of vehicle stability in real time, in the first stage a vehicle dynamic model based on Extended Kalman Filter (EKF) algorithm is built, which can estimate vehicle roll/yaw motion in the curve by vehicle sensors. And then the image-based technique will be employed in detecting the front road curvature, and combined in the system to predict vehicle steering status. The final stage is to apply the vehicle rollover index with estimated vehicle motion to predict the dangerous level to drivers for warning. In the system validation, a Digital Signal Processor (DSP) with Microcontroller Unit (MCU) hardware structure is equipped and implemented in our vehicle experimental platform. The simulated and experimental results indicate that the proposed vehicle rollover prevention system can work properly and provide a driver an early warning to reduce the rollover accidents happening.
Yao, Chi-Chun, Hsu, Jin-Yan, Liao, Yu-Sheng, Li, Ming Hung
Improving Stability of a Narrow Track Personal Vehicle using an Active Tilting System2014-01-00874/1/2014
A compact sized vehicle that has a narrow track could solve problems caused by vehicle congestion and limited parking spaces in a mega city. Having a smaller footprint reduces the vehicle's total weight which would decrease overall vehicle power consumption. Also a smaller and narrower vehicle could travel easily through tight and congested roads that would speed up the traffic flow and hence decrease the overall traffic volume in urban areas. As an additional benefit of having a narrow track length, a driver can experience similar motorcycle riding experience without worrying about bad weather conditions since a driver sits in a weather protected cabin. However, reducing the vehicle's track causes instability in vehicle dynamics, which leads to higher possibility of rollovers if the vehicle is not controlled properly. A three wheel personal vehicle with an active tilting system is designed in MapleSim. The vehicle is driven by constant rotational input which is applied to the rear wheel. Simulation results indicate that for the case when the tilting vehicle is moving at 45 km/h and the front wheel's steering angle is 4°, the resulting turning circle's diameter without rollovers is found to be 9.5 m less than the non-tilting vehicle moving at the same condition as the tilting vehicle.
Kim, Shinhoon, McPhee, John, Lashgarian Azad, Nasser
Effect of Terrain Roughness on the Roll and Yaw Directional Stability of an Articulated Frame Steer Vehicle2013-01-23669/24/2013
Compared to the vehicles with conventional steering, the articulated frame steer vehicles (ASV) are known to exhibit lower directional and roll stability limits. Furthermore, the tire interactions with relatively rough terrains could adversely affect the directional and roll stability limits of an ASV due to terrain-induced variations in the vertical and lateral tire forces. It may thus be desirable to assess the dynamic safety of ASVs in terms of their directional control and stability limits while operating on different terrains. The effects of terrain roughness on the directional stability limits of an ASV are investigated through simulations of a comprehensive three-dimensional model of the vehicle with and without a rear axle suspension. The model incorporates a torsio-elastic rear axle suspension, a kineto-dynamic model of the frame steering struts and equivalent random profiles of different undeformable terrains together with coherence between the two tracks profiles. The simulations are performed to determine the stability limits of the ASV models while operating on different terrains, namely: a perfectly smooth surface, plowed field, pasture, gravel road, and the MVEE random course. The directional stability limits are defined in terms of the static and dynamic rollover thresholds, rearward amplification ratio, and critical speed corresponding to snaking instability under steady and transient steering inputs. The results suggest that the tire interactions with the rough terrains affect the stability limits of both the unsuspended and suspended vehicles in a highly adverse manner. The suspended vehicle responses, however, show less sensitivity to variations in the road roughness profile.
Pazooki, Alireza, Rakheja, Subhash, Cao, Dongpu
Performance Analysis of Active Independent Front Steering (AIFS) for Commercial Vehicles with Greater Lateral Load Shift Propensity2013-01-23559/24/2013
An Active Independent Front Steering (AIFS) offers attractive potential for realizing improved directional control performance compared to the conventional Active Front Steering (AFS) system, particularly under more severe steering maneuvers. The AIFS control strategy adjusts the wheel steer angles in an independent manner so as to utilize the maximum available adhesion at each wheel/road contact and thereby compensate for cornering loss caused by the lateral load transfer. In this study, the performance potentials of AIFS are explored for vehicles experiencing greater lateral load transfers during steering maneuvers such as partly-filled tank trucks. A nonlinear yaw plane model of a two-axle truck with limited roll degree-of-freedom is developed to study the performance potentials of AIFS under different cargo fill conditions. The lateral movement of the cargo within a partly-filled cylindrical tank is described by the resulting lateral load shift, lateral force and the roll moment using the quasi-static fluid motion. The AIFS control strategy based on a simple PI controller is subsequently integrated and simulations are performed under different loading conditions for a steady- turning maneuver. Simulation results in general show that while both the AFS and AIFS can achieve the target response to a steering command, the AFS control causes the inner wheel to saturate under lateral accelerations well below the rollover threshold limit. The AIFS strategy, on the other hand, realizes the target response at far greater speeds, while the steered wheels do not encounter cornering force saturation until the vehicle approaches rollover condition. The results further show superior tire work-load performance of the vehicle with AIFS, irrespective of the load.
Farazandeh, Azadeh, Ahmed, A. K. W., Rakheja, S.
Design for Vehicle Rollover Warning System2013-01-06754/8/2013
Rollover accidents are a serious and too frequent incident at many locations on the road. Especially in the condition of trucks or Sport Utility Vehicles (SUV) travelling at high speeds require a greatly reduced speed when meeting the exit ramps and tight curves. The usual cause of rollovers is driving behavior, typically excessive speed while cornering which adversely affects the stability of the vehicle. Sudden or severe changes in direction can create a potential risk to rollover. By the time drivers see or feel something wrong, it is usually too late to prevent a rollover. Although some papers discuss many methods to eliminate the rollover phenomenon, it could not provide early warning for the driver. These systems usually work in the condition of slipping or near rollover. To overcome the problem, an alternate approach is to incorporate an image-based detection technique with rollover prediction model. This paper estimates the maximum rollover threshold speed in real time by using the vehicle speed, acceleration and roll angle. The goal of this paper is to provide more than 90% precision of lane radius detection. In our test results, the average error of image recognition is within ± 6 m and affects 3% error of the maximum rollover threshold speed. It detects the lane radius effectively. The predicted value of the maximum rollover threshold speed is verified by measured slip angle. Compared to traditional methods, we could offer 2 or 3 seconds early warning before the vehicle rollover occurs, and hence the proposed approach is potentially suitable for application in rollover prevention systems.
Chen, Chun Hsiung, Yao, Chi-Chun, Liao, Yu-Sheng
A Methodology to Assess Road Tankers Rollover Trend During Turning2013-01-06824/8/2013
An experimental methodology is proposed to measure the rollover propensity of road tankers when subjected to lateral perturbations derived from steering manoeuvers. The testing principle involves subjecting a scaled down sprung tank to the elimination of a lateral acceleration, to analyze its rollover propensity as a function of various vehicle's operational and design parameters. Initial acceleration is generated through putting the scaled tank on a tilt table supported by a hydraulic piston. The controlled release of the fluid in the hydraulic system generates a perturbation situation for the tank, similar to the one that a vehicle experiences when leaving a curved section of the road and going to a straight segment. Durations for the maneuver and initial tilt angles characterize both the corresponding intensities of the steering maneuver. The use of this methodology to analyze the effect of fill level, initial acceleration and tank shape on the rollover propensity of a sprung tank suggests that for high fill levels an oval tank is up to three times more prone to rollover than the circular tank, while for low fill levels such tank is up to two times less prone to rollover than the circular tank. It is suggested that the proposed methodology be used to realistically analyze the effectiveness of alternative tank shapes and slosh suppression devices, as well as suspension dimensions and characteristics.
Romero, Jose Antonio, Betanzo-Quezada, Eduardo, Lozano-Guzman, Alejandro
The Front Center Airbag2013-01-11564/8/2013
General Motors and the Takata Corporation have worked together to bring to production a new, industry first technology called the Front Center Airbag which is being implemented on General Motors' 2013 Midsize Crossover Vehicles. This paper reviews field data, describes the hardware, and presents occupant test data to demonstrate in-position performance in far side impacts. The Front Center Airbag is an airbag that mounts to the inboard side of the driver front seat. It has a tubular cushion structure, and it deploys between the front seating positions in far side impacts, near side impacts and rollovers, with the cushion positioning itself adjacent the driver occupant's head and torso. This paper includes pictures of the technology along with a basic description of the design. In-position occupant performance is also described and illustrated with several examples. Single occupant and two front occupant far side impact test data are included, both with and without the airbag present. Resulting performance differences are discussed leading to the following test observations: a) In a far side impact with a single driver occupant present, the deployed airbag functions as a restraint to help keep the occupant away from the intruded passenger compartment structure. b) When two occupants are present, the deployed airbag functions as a cushion between the front occupants. In addition, field data from the Fatal Analysis Reporting System and National Automotive Sampling System - Crashworthiness Data System are initially presented to illustrate the challenges that this technology attempts to address.
Thomas, Scott D., Wiik, Richard A., Brown, Jacqueline E.
A Multi-Objective LMI-Based Antiroll Control System2012-01-19049/24/2012
A long standing problem with heavy vehicle stability has been rollover. With the higher center of gravity, heavier loads, and narrower tracks (as compared to passenger vehicles), they have a lower rollover stability threshold. In this paper, a rollover stability control algorithm based on a two-degrees-of-freedom (DOF) and a three-DOF vehicle model for a two-axle truck was developed. First, the 3DOF model was used to predict the future Lateral load Transfer Rate (LTR). Using this LTR value, the dynamic rollover propensity was estimated. Then, a robust output feedback gain control rollover stability control algorithm based on the combination of active yaw control and active front steering control was developed. A H₂/H∞/poles placement multi-objective control strategy was developed based on the 2DOF reference model. After the control objectives were determined, the Linear Matrix Inequality (LMI) technique was utilized to solve the restrictions and to carry out the output feedback gain for the multi-input multi-output (MIMO) system. Finally, utilizing the commercial software TruckSim, the rollover stability control was evaluated using fishhook and step steering maneuvers. The simulation results show that the LMI robust controller could effectively improve the vehicle rollover stability.
Zhao, Jian, Taheri, Saied
A Study of the Ditch Fall-over Test Method Using Numerical Simulation2012-01-00944/16/2012
Rollover tests are performed to design the algorithms for deployment of countermeasures to mitigate occupant ejection in rollover situations. The ditch fall-over test is one of the rollover test methods in which a vehicle on a steep slope, representing a ditch embankment, is subjected to a forced steering operation that results in a turnover. An accurate prediction method is needed to determine the specifications of the ditch fall-over test equipment and test conditions because a test-based trial-and-error process involves high cost of performing repeated experiments and preperation for various types of related test equipment. This paper presents a newly developed numerical simulation method for simulating vehicle behavior in ditch fall-over tests. The vehicle model used in the simulation incorporates a finite element tire model for calculating the contact forces to a steep slope in a rollover situation characterized by large contact patch deformation with very large camber angles relative to the slope, an operating condition that ordinary vehicles cannot handle. The vehicle model also includes the suspension systems, steering system and inertial properties of the vehicle. Under various test conditions, the simulation results agreed well with those of actual ditch fall-over test data to judge whether turnover occurred or not and also the dynamic response such as vehicle roll rate. Simulations were conducted to investigate the test equipment specifications and test conditions for a vehicle. It was found that the slope angle, the friction coefficient of the slope, initial vehicle velocity and the sectional shape of the slope at the top influence vehicle turnover behavior.
Fukushima, Tatsuya, Shitamichi, Masafumi, Nishikata, Osamu, Mori, Masamitsu, Hatano, Keiji, Torigaki, Toshikazu, Nishi, Masato, Miyachi, Takahiko
Seat Belt Restraint Evidence Generated in the Presence of Fractured Glass2012-01-00844/16/2012
Physical evidence on the seat belt restraint system is one source of data used by investigators to determine whether or not an occupant was wearing their seat belt during a crash. Evidence of occupant loading on seat belts generated during crash events has been thoroughly researched and is well documented in the literature. However, there is a paucity of data regarding the physical evidence produced when fractured glass is introduced into the restraint system during occupant loading events. The objective of this study is to characterize the physical evidence generated by glass-to-seat belt interaction during low-level impact loading, and compare this evidence with the types of seat belt marks that can be generated inadvertently by accident scene bystanders, emergency responders, and crash investigators. The presence of glass particles in and around the vehicle at the end of a crash event may contribute to the inadvertent generation of physical evidence. Movable side windows composed of tempered safety glass and laminated safety glass were fractured via impactor loading representative of occupant impact. The resulting glass fracture fragments were separated by size using a series of sieves, and the distribution of glass fragments size was quantified. New service-replacement seat belt retractor assemblies (including D-ring, latch plate, anchor, and webbing) were tested using a Seat Belt Load Simulator (SBLS) fixture, which simulates occupant loading by applying a repeatable load pulse to the restraint system. Each retractor assembly was mounted onto the SBLS fixture in a position representative of belt routing when installed in a vehicle. A repeatable lap-shoulder belt stroke pulse, representative of low-level restraint loading and consistent in magnitude and duration with loads produced during rollover, was applied using the SBLS with glass fragments of varying sizes introduced onto the webbing surface adjacent to the D-ring and latch plate surfaces. Additional test series were run to investigate the types of physical evidence generated in the presence of glass under non-crash loading scenarios. These scenarios included the extraction of webbing with glass fragments present adjacent to the D-ring and latch plate, extraction of webbing over glass fragments captured or fixed in a window seal, and the compression of webbing with various sizes of glass fragments interposed between the webbing and a reaction surface. Documentation of each restraint system was performed post-test. Seat belt loading events that occurred in the presence of fractured safety glass produced characteristic markings on the restraint system hardware and webbing. The tests conducted to examine non-crash loading evidence generated in the presence of fractured safety glass revealed markings on the restraint system that differed from those generated in a simulated loading event.
Moralde, Marie, Dibb, Alan, Smedley, Janine, Carhart, Michael, Cooper, Eddie
Influence of Complying with FMVSS 226 (Ejection Mitigation) on Side Airbag Occupant Out of Position Injury Assessment2012-01-04664/16/2012
The National Highway Traffic Safety Administration (NHTSA) has identified ejection mitigation as a top priority, issuing a final rule for FMVSS 226, Ejection Mitigation, in January of 2011 to set performance standards for a vehicle's ejection mitigation countermeasures to mitigate the risk of ejection through a vehicle's side window openings. The most likely countermeasures to be used for compliance with this standard are rollover activated curtain airbags that deploy from a vehicle's roof rail. However, this rule will most likely result in increases in the coverage area and inflator outputs of the curtain airbag; which may influence out-of-position occupant injury as measured in the test methods that have been outlined by the Side Airbag Out-of-Position Injury Technical Working Group (TWG). This paper presents a case study in which the out-of-position performance of a curtain airbag optimized for both ejection mitigation and side impact protection, as outlined per FMVSS 226 and FMVSS 214 respectively, is compared with that of one developed for side impact protection only for the same vehicle. Furthermore, the authors present a design concept that can be used to balance the requirements of FMVSS 226 with the injury risk from the deploying curtain airbag for out-of-position occupants.
Dix, Jeff, Hammoud, Selim, Cardinali, Alex, Mitchell, Abe, Fulk, Daniel
An Integrated Model of Rolling and Sliding in Rollover Crashes2012-01-06054/16/2012
Rollover crashes are often difficult to reconstruct in detail because of their chaotic nature. Historically, vehicle speeds in rollover crashes have been calculated using a simple slide-to-stop formula with empirically derived drag factors. Roll rates are typically calculated in an average sense over the entire rollover or a segment of it in which vehicle roll angles are known at various positions. A unified model to describe the translational and rotational vehicle dynamics throughout the rollover sequence is lacking. We propose a pseudo-cylindrical model of a rolling vehicle in which the rotational and translational dynamics are coupled to each other based on the average frictional forces developed during ground contacts. We describe the model as pseudo-cylindrical because vertical motion is ignored but the ground reaction force is not constrained to act directly underneath the center of gravity of the vehicle. The tumbling phase of a rollover is modeled in three distinct phases: an initial brief airborne phase between roll initiation and the first ground contact, an early phase in which relative sliding between the perimeter of the vehicle and the ground causes the roll rate to increase, and a later phase in which the vehicle rolls without sliding and the roll rate decreases. In the early phase, the average vehicle deceleration is higher and is governed by sliding friction. In the later phase, the average vehicle deceleration is lower and is governed by geometric factors. Model predictions were fit to data from 12 well-documented rollover crashes in order to derive empirical values for the model parameters. In 11 out of the 12 rollovers studied, the model predictions matched the actual results with good accuracy. The results validate the underlying physical principles of the model and provide data that can be used to apply the model to real world rollovers. The proposed model provides a physical basis for understanding vehicle dynamics in rollovers and may be used in certain cases to improve the accuracy of a rollover reconstruction.
Funk, James, Wirth, Jeffrey, Bonugli, Enrique, Watson, Richard, Asay, Alan
Comparison of Linear Variable Deceleration Rate Rollover Reconstruction to Steer-Induced Rollover Tests2012-01-04694/16/2012
A variable deceleration rate approach to rollover crash reconstruction was proposed in 2009 by Rose and Beauchamp. A detailed description of Rose and Beauchamp's method was outlined in 2010. The method used a Linearly Variable Deceleration Rate (LVDR) as a function of roll distance. Improvements in responses as a function of time was demonstrated by Rose and Beauchamp using test data from two 208 dolly rollover tests; however, they noted that additional validation work using steering-induced rollover tests would be desirable. This paper provides additional validation of the LVDR model using the steer-induced rollover test data reported in 2011 by Stevens et al. The Over-The-Ground Speed (OGS) and recorded roll rate results from the five steer-induced rollover tests reported by Stevens' in 2011 were compared to reconstructed speed and roll rates as a function of time using the 2010 Rose and Beauchamp LVDR method. Using an appropriate range of average drag factors, the LVDR method produced agreement with the measured results of the Stevens rollover tests. Comparisons showed agreement with the predicted rollover duration, the shape of the roll rate curve and the maximum roll rate. Calculated roll rates were high if the calculated roll duration was low. Low roll durations were found associated with a Constant Drag Factors (CDF) method and the LVDR method utilizing high average drag factors. Greater roll rate uncertainty occurred in roll segments that have long airborne duration and/or high speed change. The LVDR method significantly improves prediction of speed and roll rate time history compared to a CDF method.
Arndt, Mark W., Stevens, Don, Arndt, Stephen
Design of a Dynamic Rollover Test System2011-01-11164/12/2011
A dynamic rollover test system (DRoTS) capable of simulating rollover crashes in a laboratory was designed for research use at the University of Virginia. The goal of the current study is to describe the system's capabilities and specifications as well as to explore the limitations of the system's ability to simulate rollover crashes. The test apparatus was designed to permit simulation of a single roof-to-ground interaction of a rollover crash with the potential to be modified for evaluation of pre-roof contact occupant motion. Special considerations were made to permit testing of both dummies and post-mortem human surrogates in both production vehicles and a parametric test buck. DRoTS permits vertical translation, pitch, and roll of the test vehicle while constraining longitudinal and lateral translations and yaw. The study details the ranges of test parameters capable with the DRoTS and evaluates the limitations of the system relative to rollover crash conditions. Considerations on the use of the test system and the constraints applied to the vehicle are evaluated through analytical analysis and computational modeling. The results of the analyses suggest that the DRoTS design is capable of testing vehicles in a wide variety of conditions while maintaining reasonable fidelity to rollover crashes during the duration of a single vehicle roof-to-ground interaction.
Kerrigan, Jason R., Jordan, Acen, Parent, Daniel, Zhang, Qi, Funk, James, Dennis, Nate J., Overby, Brian, Bolton, Jim, Crandall, Jeff
Effects of Safety Belt Pretensioning on ATD Motion in Rigid Fixture Rollover Testing2011-01-11184/12/2011
General Motors conducted a series of subsystem rigid fixture sled rollover tests to evaluate the effects of various safety belt pyrotechnic pretensioners on Anthropomorphic Test Device (ATD) head motion. Twelve tests were conducted using a rigid fixture comprised of a modified compact sport utility vehicle (SUV) body encased in a rigid exoskeleton. The testing simulated the pre-trip/trip, free flight and first roof to ground impact phases of a field representative curb trip initiation rollover crash test with a roof to ground impact angle of approximately 180 degrees. Various combinations of safety belt lap anchor, buckle and retractor pretensioners were tested and film analysis was used to measure trailing side ATD head motion relative to the vehicle. Additionally, a new analysis technique of measuring the reduction of lap webbing length during the crash event was developed for evaluating the ability of a restraint system to reduce ATD head motion during the rollover tests. The results indicated that with deployment times prior to occupant belt loading, certain pretensioner combinations were able to reduce the lateral and vertical motion of the trailing side ATD head when compared to non-pretensioner baseline tests.
White, James, Sevigny, Jennifer, Antonucci, Antonio, Haldenwanger, Michael, O'Brien-Mitchell, Bridget M., Cassatta, Stephen Joseph, Wendzinski, Michael, Cooper, Gerald
A Study of Occupant Ejection Mitigation in Side Impact Crashes2011-01-01064/12/2011
The National Highway Traffic Safety Administration (NHTSA) has identified ejection mitigation as a top priority, issuing a notice of proposed ruling making (NPRM) in December of 2009. The NPRM proposes a linear impact test that uses a featureless head-form to impact a vehicle's side windows' daylight opening at various positions. The test measures the excursion of the head-form beyond the plane of the window glazing. The intention is to evaluate the ability of a vehicle's ejection mitigation system, such as the curtain airbag or other vehicle features, to manage the impactor energy and limit excursion. The NPRM proposes a test conducted 1.5 seconds after the ejection mitigation countermeasure is deployed at an impact speed of 24 km/h with a mass of 18 kg (400 Joules). This test condition is intended to consider both rollover and side impact crashes. While the majority of the research published to date has concentrated on occupant ejections in rollover crashes, there is little published literature focusing on side impact crashes. The authors will present the results of a study in which computer modeling using a generic vehicle environment was used to estimate an ejection representative energy level for side impact crashes that can be employed for evaluating ejection mitigation systems. The effects of factors such as vehicle architecture and interior layout were considered in this study.
Dix, Jeff, Sagawa, Koichi, Sahare, Lalitkumar, Hammoud, Selim, Fulk, Daniel, Cardinali, Alex
Evaluation of Dynamic Roof Deformation in Rollover Crash Tests2011-01-10934/12/2011
Although the measured amount of roof deformation associated with a given rollover crash test is often the residual or post test deformation, rollover crash test researchers are aware that roof deformation occurs dynamically throughout the rollover event with varying magnitude. The challenge to quantifying dynamic roof deformation has been the lack of a reliable method to measure and record the dynamic roof deformation during the rollover test. Researchers have explored various methods to measure dynamic roof deformation including the use of film analysis of external targets, accelerometers, string potentiometers, and 3D photogrammetry. This paper discusses a series of simulated curb trip rollover tests conducted to study and compare different methodologies to measure and record dynamic roof deformation. The tests involved midsize crossover utility vehicles instrumented with accelerometers on the roof rails at the A and B pillars and string potentiometer arrays at roof locations above the front driver and passenger seating locations. High speed digital motion cameras were rigidly mounted inside the vehicles to monitor the movement of the interior roof targets as the roof deformed during the rollover event. This paper discusses and compares the dynamic roof deformation data as measured by the roof string potentiometers and 3D photogrammetry as compared to post-test residual deformation measurements.
Harvin, Stuart W., O'Brien-Mitchell, Bridget M., Dwoinen, Andrew R., Nassoiy, Carol Ann, Motowski, Daniel F., Melocchi, Anthony G., Lu, Huizhen, Peace, Manuel V.
Occupant Kinematics and Injury Mechanisms During Rollover in a High Strength-to-Weight Ratio Vehicle2010-01-05164/12/2010
Rollover events involving multiple revolutions are dynamic, high-energy, chaotic events that may result in occupant injury. As such, there is ongoing discussion regarding methods that may reduce injury potential during rollovers. It has been suggested that increasing a vehicle's roof strength will mitigate injury potential. However, numerous experimental studies and published field accident data analyses have failed to show a causal relationship between roof deformation and occupant injury. The current study examines occupant kinematics and injury mechanisms during dolly rollover testing of a vehicle with a high roof strength-to-weight ratio (SWR = 4.8). String potentiometers and high-speed video cameras were used to capture and quantify the dynamic roof motion throughout the rollover. Instrumented Anthropomorphic Test Devices (ATDs) in the front occupant positions allowed for the assessment of occupant kinematics, loading, and injury mechanics during the rollover event. The quantification of the roof motion over the complete time course of the rollover combined with ATD neck loads demonstrated that neck loads in excess of the relevant Injury Assessment Reference Value (IARV) occurred as a result of the dynamic rollover circumstances independent of the vehicle roof motion. Injurious neck loads were observed with relatively small amounts of roof deformation, while relatively small neck loads were observed during large elastic and plastic roof deformations. The results of this testing are discussed in the context of other experimental and field accident data studies examining roof deformation and occupant injury.
Heller, Michelle F., Newberry, William N., Smedley, Janine E., Eswaran, Senthil K., Croteau, Jeffrey J., Carhart, Michael R.
Subsystem Rollover Tests for the Evaluation of ATD Kinematics and Restraints2010-01-05184/12/2010
The development of a repeatable dynamic rollover test methodology with meaningful occupant protection performance objectives has been a longstanding and unmet challenge. Numerous studies have identified the random and chaotic nature of rollover crashes, and the difficulty associated with simulating these events in a laboratory setting. Previous work addressed vehicle level testing attempting to simulate an entire rollover event but it was determined that this test methodology could not be used for development of occupant protection restraint performance objectives due to the unpredictable behavior of the vehicle during the entire rollover event. More recent efforts have focused on subsystem tests that simulate distinct phases of a rollover event, up to and including the first roof-to-ground impact. This paper explores two subsystem rollover test methods up to the first roof-to-ground impact, and highlights the importance of simulating the lateral vehicle acceleration that occurs during the pre-trip/trip phase of a rollover event in order to provide more realistic trailing-side Anthropomorphic Test Device (ATD) kinematics and enable more meaningful restraint evaluations.
Cassatta, Stephen J., Sevigny, Jennifer L., White, James P., O'Brien-Mitchell, Bridget M., Antonucci, Antonio, Haldenwanger, Michael J., Cooper, Gerald A.
Are Trauma Team Activations Essential and Cost Effective for Rollover Crashes?2010-01-05194/12/2010
Background: Motor vehicle crashes (MVCs) are the leading cause of death for ages 2-34 years. Rollover (RO) is defined as any vehicle rotation of ≥90° about any longitudinal or lateral axis occurring. The purpose of this study was to determine the cost effectiveness of RO mechanism as the sole triage criteria. Methods: Detailed patient injury, demographics, costs and crash information were obtained on patients ≻16 years and seen at an ACS COT-verified level I trauma center from 2007-2008. Analysis was performed using SPSS v 17. Results: 257 RO crash occupants were treated at this study center. The frequency of AIS ≤2 in these RO occupants was 74%. 62% (133/214) of patients triaged as partial TTA (PTTA) were discharged from the emergency department (ED), whereas all full TTA (FTTA) patients were admitted. 60% of all RO patients were reported to have utilized seat belts. Seat belt use decreased the risk of injury by four-fold (95% CI, 2.14-8.01). No other patient or crash characteristics contributed to this excess triage rate. Based on an average cost of $6,000/TTA and our excess ED discharge rate exceeding the accepted national average rate of 37%, this trauma center could save $498,000/year. Applying the same cost analysis to the NASS database could save $190 million annually to the trauma systems nationally. Conclusion: Consideration of physiometric data, and seat belt use in the triage of non-critically injured RO occupants could potentially save this trauma center up to $2.5 million over a five-year period and approximately $0.95 billion dollars for the trauma systems nationwide over the same period.
Aldaghlas, Tayseer, Burke, Christine, Sheridan, Michael J., Stadter, Greg W., Hanfling, Dan, Griffen, Margaret, Rizzo, Anne
Roll Stability Control for Torsionally Compliant Vehicles2010-01-01024/12/2010
Rollover prevention is now part of complete vehicle stability control systems for many vehicles. Given that rollover is predominantly associated with vehicles with high centers of gravity, the targeted vehicles for rollover protection include medium and heavy duty commercial vehicles. Unfortunately, the chassis designs of these vehicles are often so compliant in torsion that the ends of the vehicles may have significantly different roll responses at any given time. The potential need to assess and correct for the roll behavior of the front and rear ends of the vehicle is the subject of this paper. Most rollover mitigation research to date has used rigid chassis assumptions in modeling the vehicle. This paper deals with the roll control of vehicles with torsionally flexible chassis based on a yaw-correction system. A simplified model of a single-unit vehicle with chassis torsional compliance and an integrated roll controller is exercised using step, ramp and swept sine steering inputs to select the gains for a state feedback controller. Simulation results show that, for the vehicle considered, the performance of a locally selected controller that adds roll stability is more sensitive to payload than torsional compliance. Also, a set of controller gains selected as satisfactory for a soft or stiff chassis could give poor performance or even destabilize the vehicle when the torsional stiffness changes.
Sill, Justin, Arant, Michael, Mau, Robert, Ayalew, Beshahwired
Safety Belt Buckle Environment in Vehicle Rollover Crash Tests2009-01-12514/20/2009
A study was conducted by General Motors (GM) to further expand upon the currently available research regarding the safety belt buckle environment during full scale vehicle crash tests. A previous study by GM [1] focused on the environment experienced by safety belt buckles in planar, non-rollover, vehicle crash conditions. This study expands upon that work by measuring buckle acceleration and webbing tension in a variety of full scale vehicle rollover crash tests. A variety of test vehicles, rollover crash types, seating positions, roll directions, test speeds, and safety belt systems were included in the study. Emphasis was placed on examination of the buckle response data during vehicle-to-ground impacts (roof, body, and wheel). This study reports on data recorded from 20 full scale rollover crash tests with 40 instrumented end release safety belt buckles. Crash tests in this study were limited to rollover tests involving un-tethered vehicles where at least one-quarter turn or more occurred. Acceleration measurements were made using tri-axial accelerometers mounted onto the buckles. The accelerations were recorded in the axial, lateral, and perpendicular axes relative to the buckle. Belt webbing tension was also measured with load cells mounted on the lap and shoulder webbing. The data summarized in this study characterizes the environment for safety belt buckles during a variety of full scale vehicle rollover crash test conditions. In the 20 vehicle rollover crash tests included in this study, there were no buckle to latch plate separations.
Haldenwanger, Michael J., Antonucci, Antonio, Cooper, Gerald A., Malopolski, William A., Sevigny, Jennifer L., White, James P., Yee, Jack K.
Measurement and Modeling of Rollover Airborne Trajectories2009-01-01094/20/2009
Much has been written about reconstruction techniques and testing methods concerning vehicle rollovers. To date, most of the literature describes rollovers as one-dimensional events. Rollovers account for a disproportionate fraction of serious injuries and fatalities among all motor vehicle accidents. The three-dimensional nature of rollover sequences in which a rolling vehicle experiences multiple ground contacts contributes to the environment where such injuries occur. An analytical technique is developed to model the airborne segments of a rollover sequence as a parabolic path of the vehicle center of gravity. A formulation for the center of gravity descent from maximum elevation to full ground contact is developed. This formulation contains variables that may be readily determined from a thorough reconstruction. Ultimately, this formulation will also provide a vertical ground impact velocity at contact. Measurements of airborne segments from two high-speed rollover events – a dolly rollover test and a real-world rollover crash - are presented as a basis to evaluate the model. The ability to theoretically model two-dimensional trajectory paths is demonstrated and the concept of an effectively airborne rollover segment is presented. Comparisons between vehicle descent predicted by the model and from the rollover tests are presented. The measured values of descent distance from the rollover tests generally slightly exceed the predicted values. It is shown that accuracy may be improved by careful selection of drag factors based on non-uniform over-the-ground deceleration observed in on-road and soft surface vehicle rollover events. The application of the trajectory model to obtain vertical vehicle motion in real-world rollover crashes involves reconstruction based on the topography of the rollover path and physical evidence related to ground contacts.
Henry, Kevin C., Germane, Geoff J., Luepke, Peter, Carter, Jarrod
Development of a Variable Deceleration Rate Approach to Rollover Crash Reconstruction2009-01-00934/20/2009
The goal of this paper is to advance rollover crash reconstruction techniques beyond the assumption typically made that a rolling vehicle decelerates at a constant rate. The paper presents and applies a planar vehicle-to-ground impact model to explore the manner in which a vehicle’s deceleration rate would be expected to vary over the course of a rollover. Based on this analysis, several possible variable deceleration rate profile shapes are then suggested for rollover crash reconstruction. Then, two rollover crash tests are analyzed to determine the extent to which these suggested variable deceleration rate profiles can be expected to yield accurate reconstructions of the translational and angular velocity histories for actual rollovers. Overall, each of the suggested variable deceleration rate profiles represented a significant improvement over using a constant deceleration rate.
Rose, Nathan A., Beauchamp, Gray
Vehicle Stability Control Scheme for Rollover Prevention and Maneuverability/Lateral Stability Improvement2009-01-08264/20/2009
This paper describes vehicle stability control (VSC) scheme to prevent rollover and to improve both maneuverability and lateral stability by integrating individual chassis control modules such as electronic stability control (ESC), active front steering (AFS) and continuous damping control (CDC). The proposed VSC system consists of an upper and lower level controller. The upper level controller determines a control mode such as rollover mitigation, maneuverability and lateral stability, and it also calculate desired values for its objectives. The lower level controller determines longitudinal and lateral tire forces as inputs of each control modules such as the ESC and AFS. From the simulation results, it is shown that the proposed VSC system can prevent vehicle rollover, while at the same time improving both maneuverability and lateral stability
Yoon, Jangyeol, Cho, Wanki, Yi, Kyongsu, Koo, Bongyeong
Glass Debris in Rollover Accidents2008-01-01674/14/2008
Vehicles involved in rollover accidents almost always leave a debris trail. This debris trail is useful for the accident reconstructionist; it assists with identifying the vehicle path during the rollover and the location and orientation of the vehicle at various vehicle to ground contacts. Often it is helpful to know when and where various vehicle windows fractured. This is possible by comparing glass obtained from the accident site with glass samples still attached to the accident vehicle. The limit of this analysis is controlled by the manufacturing tolerance of the vehicle glass and the specified pane thickness. This paper presents a series of measurements made on various automotive tempered windows and presents: 1) the thickness range in individual panes, and 2) the thickness variation seen from pane to pane in the same vehicle.
Perl, T. R., Bready, J. E., Nordhagen, R. P., Warner, M. H.
Occupant Trajectory Model using Case-Specific Accident Reconstruction Data for Vehicle Position, Roll, and Yaw2008-01-05174/14/2008
In the fields of accident reconstruction and injury biomechanics, it is often of interest to know details of an occupant's ejection from a vehicle during a rollover. Current occupant trajectory models do not account for vehicle yaw and yaw rate. Such considerations are compulsory if the occupant's rest point has a non-trivial deviation from the vehicle's roll path. Moreover, many existing models use a single, generic function for the roll rate for all analyses. Such approaches intrinsically model all rollovers as identical events, regardless of the underlying uniqueness a particular accident may exhibit. The objective of this work is to model the trajectory of an occupant ejected from a vehicle in a rollover event. In particular, we model the vehicle's longitude, latitude, roll, yaw, and time derivatives thereof, based on data extracted from a particular accident reconstruction. We model the occupant moving in the vehicle and possibly ejected at any time during the rollover. For each admissible ejection time, we construct an occupant trajectory, landing point, and point of rest (POR). We illustrate the effectiveness of our model with a case-study where significant yaw occurs during the rollover. Our new model, when compared with existing approaches, provides an improved understanding of occupant ejection. Additionally, the new model eliminates spurious ejection solutions predicted by previous formulations. Finally, the new model is tailored to the underlying accident reconstruction data, producing a simulation that is based on the uniqueness of a particular rollover event.
Hovey, Chad B., Kaplan, Matthew L., Piziali, Robert L.
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