Search Results

The heads of auto racing drivers and military pilots are usually not supported so that neck fatigue and injury can be a serious problem. A new Head And Neck Support (HANS) is being developed to reduce head motions and neck loads. The biomechanical performance of HANS has been evaluated by crash victim modeling with CAL 3-D and by impact sled testing with a Hybrid III dummy. Modeling and testing were conducted at 30 and 35 mph BEV and with acceleration directions from the front, right front, and right lateral. The model and test results show that head motions, neck loading, and the potential for neck injury are all significantly reduced with HANS compared to without HANS.

SAE Recommended Practice J941 describes the eyellipse, a statistical representation of driver eye locations, that is used to facilitate design decisions regarding vehicle interiors, including the display locations, mirror placement, and headspace requirements. Eye-position data collected recently at University of Michigan Transportation Research Institute (UMTRI) suggest that the SAE J941 practice could be improved. SAE J941 currently uses the SgRP location, seat-track travel (L23), and design seatback angle (L40) as inputs to the eyellipse model. However, UMTRI data show that the characteristics of empirical eyellipses can be predicted more accurately using seat height, steering-wheel position, and seat-track rise. A series of UMTRI studies collected eye-location data from groups of 50 to 120 drivers with statures spanning over 97 percent of the U.S. population. Data were collected in thirty-three vehicles that represent a wide range of vehicle geometry.

A new approach to driver seat-position modeling is presented. The equations of the Seating Accommodation Model (SAM) separately predict parameters of the distributions of male and female fore/aft seat position in a given vehicle. These distributions are used together to predict specific percentiles of the combined male-and-female seat-position distribution. The effects of vehicle parameters-seat height, steering-wheel-to-accelerator pedal distance, seat-cushion angle, and transmission type-are reflected in the prediction of mean seat position. The mean and standard deviation of driver population stature are included in the prediction for the mean and standard deviation of the seat-position distribution, respectively. SAM represents a new, more flexible approach to predicting fore/aft seat-position distributions for any driver population in passenger vehicles. Model performance is good, even at percentiles in the tails of the distribution.

New models are being developed to represent the geometry and movements of people in seated postures. The positions and motions of the torso skeletal structures for different amounts of lumbar curvature have been studied and represented in side view, two dimensional computer models of the average man, small woman, and large man. Some further developments for the average man include: 1. two dimensional, articulated drafting template, 2. three dimensional computer model of the skeletal system with soft tissue thicknesses added to represent the external body contours on the back of the torso, and 3. model of forces and moments between body segments based on seated posture, body segment masses, and seat surface forces. This paper describes these new biomechanical models and their potential uses in designing seats that more comfortably fit and move with people.

Although driver-side airbag systems provide protection against serious head and chest injuries in frontal impacts, injuries produced by the airbag itself have also been reported. Most of these injuries are relatively minor, and consist primarily of skin abrasions and burns. Previous investigations have addressed the mechanisms of airbag-induced skin abrasion. In the current research, laboratory studies related to the potential for thermal burns due to high-temperature airbag exhaust gas were conducted. A laboratory apparatus was constructed to produce a 10-mm-diameter jet of hot air that was directed onto the leg skin of human volunteers in time-controlled pulses. Skin burns were produced in 70 of 183 exposures conducted using air temperatures ranging from 350 to 550°C, air velocities from 50 to 90 m/s, and exposure durations from 50 to 300 ms.

Dynamic seat-position testing conducted recently at UMTRI on several different vehicles indicates that, in many cases, the current seating accommodation model represented in SAE J1517 does not accurately predict the distribution of driver seat positions. In general, J1517 tends to predict population percentile seat positions that are forward of observed percentile seat positions, and differences can be as much as 60 mm. It was hypothesized that vehicle factors other than seat height can have substantial and independent effects on driver seat position. The effects of steering-wheel position, seat height, seat-cushion angle, and transmission type on driver fore/aft seat position are being investigated, and results are being used to develop a new driver seating accommodation model called SAM.

Deformations of soft tissues and seat cushion foam are significant factors in determining the interface contours between the seat and the back of the thigh. This paper describes the measurement of forces, deformations, and contours of people's thighs and seat cushion materials. The goal of this work is to represent the human interactions with seats. A two-dimensional, plane strain finite element method was used to develop a contact model between the cross section of the human mid-thigh and flat surfaces, which can be a flat, rigid surface or a flat, foam cushion of various thicknesses and densities. Results of human and seat interactions for various subjects were measured, modeled, and compared. The present work showed a good agreement between experiments and models for various subjects and foam densities. The important results showed that the stiffness of the foam does not depend on the foam thickness.

To assist automotive seat development and evaluation, a technique for predicting the posture of seated occupants has been developed. The method involved modeling the torso geometry and articulation of a mid-size male, based on information presented in SAE paper number 930110 [1]. This mid-size male model, known as 2-D JOHN, was developed in a commercial kinetic modeling software and used in a comparative seat evaluation study between a current production automotive seat and a prototype articulating seat. The 2-D JOHN model was supported a greater range of postures, defined as Total Lumbar Curvature (TLC) and Torso Recline Angle (TRA), in the prototype seat than the automotive seat.

The purpose of this study was to assess, by use of computer simulations, the effectiveness of motorcycle helmets in reducing head and neck injuries in motorcyclist impacts. The computer model used was the MVMA Two-Dimensional Crash Victim Simulator. The study investigated a wide variety of impact conditions in order to establish a broad overall view of the effectiveness of helmets. It was found that helmet use invariably reduces dynamic responses which have a role in producing head injury and, in addition, almost always reduces the severity of neck response as well. For no configuration or condition does the helmet greatly increase the likelihood of neck injury. Thus, these simulations of a wide spectrum of motorcyclist impacts provide further evidence that helmet use significantly reduces the likelihood and severity of both head and neck injuries. This study was supported by the Insurance Institute for Highway Safety.

Human anthropometry was used as input to the design of the GM ATD 502 crash test dummy. The spinal column of an average adult male was located for an erect seated position leading to guidelines for placement of dummy components and sectioning of the dummy into segments. The weight and weight distribution of these dummy segments were defined based on anthropometric data. These results provide some assurance that the size, relative location, and weight distribution of dummy structures are representative of human characteristics.

The geometric, inertial, and joint characteristics of two Part 572 crash test dummies were measured to provide input to the MVMA 2-D occupant model. Segments of the dummies were defined which correspond to the links of the model and coordinate axes were defined for each segment. The center of gravity of each segment was located and its coordinates were measured along with the locations of joint centers, instrument mounts, and other significant geometric features. The mass moment of inertia for each segment about a lateral axis through its center of gravity was measured. The geometric and inertial measurements are presented on summary sheets for each segment with the hardware definition, coordinate system, and special notes for that particular segment. These summary sheets present the data in a format that is readily usable for defining computer model input.

Properties of the human neck which may influence a person's susceptibility to “whiplash” injury during lateral impact have been studied in 96 normal subjects. Subjects were chosen on the basis of age, sex, and stature and data were grouped into six primary categories based on sex (F, M) and age (18-24, 35-44, 62-74). The data include: measures of head, neck and body anthropometry in standing and simulated automotive seating positions, three-dimensional range of motion of the head and neck, head/neck response to low-level acceleration, and both stretch reflex time and voluntary isometric muscle force in the lateral direction. Reflex times are found to vary from about 30 to 70 ms with young and middle aged persons having faster times than older persons, and females having faster times than males. Muscle strength decreases with age and males are, on the average, stronger than females.

The objectives of this study are to quantify the biomechanical properties of the human neck which govern head and neck dynamic response and to establish the mechanisms responsible for primary aspects of response. Computer simulations with the MVMA 2-D and VOM 3-D occupant dynamics models were performed using head and neck sled input response data from human subjects at the Naval Biodynamics Laboratory for input and comparison. Predicted dynamic response data and preliminary values for biomechanical parameters in a three-dimensional head/neck model capable of accurately simulating response for −X, +Y, and −X+Y sled acceleration vectors are presented. The established analytical model should accurately predict head and neck responses in simulations of real-world automobile crashes where direct head impact is not involved. Additionally, the model can be used to assist in development of a design plan for the neck of advanced anthropomorphic test dummies.

Recent research in the ASPECT (Automotive Seat and Package Evaluation and Comparison Tools) program has led to the development of a new method for automobile driver posture prediction, known as the Cascade Model. The Cascade Model uses a sequential series of regression functions and inverse kinematics to predict automobile occupant posture. This paper presents an alternative method for driver posture prediction using data-guided kinematic optimization. The within-subject conditional distributions of joint angles are used to infer the internal cost functions that guide tradeoffs between joints in adapting to different vehicle configurations. The predictions from the two models are compared to in-vehicle driving postures.

Few studies have systematically examined the effects of truck and bus workstation geometry on driver posture and position. This paper presents methods for determining drivers' postural responses and preferred component locations using a reconfigurable vehicle mockup. Body landmark locations recorded using a three-dimensional digitizer are used to compute a skeletal-linkage representation of the drivers' posture. A sequential adjustment procedure is used to determine the preferred positions and orientations of key components, including the seat, steering wheel, and pedals. Data gathered using these methods will be used to create new design tools for trucks and buses, including models of driver-selected seat position, eye location, and needed component adjustment ranges. The results will also be used to create accurate posture-prediction models for use with human modeling software.

A new method of predicting automobile occupant posture is presented. The Cascade Prediction Model approach combines multiple independent predictions of key postural degrees of freedom with inverse kinematics guided by data-based heuristics. The new model, based on posture data collected in laboratory mockups and validated using data from actual vehicles, produces accurate posture predictions for a wide range of passenger car interior geometries. Inputs to the model include vehicle package dimensions, seat characteristics, and occupant anthropometry. The Cascade Prediction Model was developed to provide accurate posture prediction for use with any human CAD model, and is applicable to many vehicle design and safety assessment applications.

To provide contours for the new ASPECT manikin, the contours of the thighs and buttocks of mid-size male subjects were measured using a specially built chair. The subjects' body surfaces that were not in contact with the chair and their postures were measured using a video-based position measurement system. Using computer aided design methods, the measured contours were splined and sectioned relative to the local anatomical coordinates for each subject. These local sections were combined and analyzed, with comparison to SAE J826 manikin contours, to provide a thigh and buttocks contour for the ASPECT manikin that represent the mid-size male.

The ASPECT (Automotive Seat and Package Evaluation and Comparison Tools) manikin provides new capabilities for vehicle and seat measurement while maintaining continuity with previous practices. This paper describes how the manikin is used in the development of new designs, the audit verification of build, and in benchmarking competitive vehicles and seats. The measurement procedures are discussed in detail, along with the seat and package dimensions that are associated with the new tool.

The ASPECT program was conducted to develop new Automotive Seat and Package Evaluation and Comparison Tools. This paper presents a summary of the objectives, methods, and results of the program. The primary goal of ASPECT was to create a new generation of the SAE J826 H-point machine. The new ASPECT manikin has an articulated torso linkage, revised seat contact contours, a new weighting scheme, and a simpler, more user-friendly installation procedure. The ASPECT manikin simultaneously measures the H-point location, seat cushion angle, seatback angle, and lumbar support prominence of a seat, and can be used to make measures of seat stiffness. In addition to the physical manikin, the ASPECT program developed new tools for computer-aided design (CAD) of vehicle interiors. The postures and positions of hundreds of vehicle occupants with a wide range of body size were measured in many different vehicle conditions.

The primary objective of the ASPECT (Automotive Seat and Package Evaluation and Comparison Tools) program was to develop a new generation of the SAE J826 H-point manikin. The new ASPECT manikin builds on the long-term success of the H-point manikin while adding new measurement capability and improved ease of use. The ASPECT manikin features an articulated torso linkage to measure lumbar support prominence; new contours based on human subject data; a new weighting scheme; lightweight, supplemental thigh, leg, and shoe segments; and a simpler, user-friendly installation procedure. This paper describes the new manikin in detail, including the rationale and motivation for the design features. The ASPECT manikin maintains continuity with the current SAE J826 H-point manikin in important areas while providing substantial new measurement capability.