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Technical Paper

Predicting the Effects of Muscle Activation on Knee, Thigh, and Hip Injuries in Frontal Crashes Using a Finite-Element Model with Muscle Forces from Subject Testing and Musculoskeletal Modeling

2009-11-02
2009-22-0011
In a previous study, the authors reported on the development of a finite-element model of the midsize male pelvis and lower extremities with lower-extremity musculature that was validated using PMHS knee-impact response data. Knee-impact simulations with this model were performed using forces from four muscles in the lower extremities associated with two-foot bracing reported in the literature to provide preliminary estimates of the effects of lower-extremity muscle activation on knee-thigh-hip injury potential in frontal impacts. The current study addresses a major limitation of these preliminary simulations by using the AnyBody three-dimensional musculoskeletal model to estimate muscle forces produced in 35 muscles in each lower extremity during emergency one-foot braking.
Technical Paper

Comparison of ATD and Driver Knee Positions

2009-04-20
2009-01-0390
Contact between the knees and knee bolster commonly occurs in frontal collisions. The contact region on the bolster and the knee anatomy involved are related to the pre-crash positioning of the knees. The location of the distal (or infra-) patella was recorded on volunteers of widely varying stature after they had selected a comfortable driving position in mockups of three vehicles representing a large variation in size and shape: sedan, crossover SUV, and full-size pickup. On average, the right knees were grouped more tightly and were located more forward and lower than the left knees. On average, the knees were positioned 200 mm from the knee bolster for all subjects. The range of distance separating the distal patellae (within subject knee-to-knee distance) varied from 184–559 mm for all subjects for the three vehicles.
Journal Article

An Eyellipse for Rear Seats with Fixed Seat Back Angles

2011-04-12
2011-01-0596
This paper describes the development of the fixed seat eyellipse in the October 2008 revision of SAE Recommended Practice J941. The eye locations of 23 men and women with a wide range of stature were recorded as they sat in each of three second-row bench seats in a laboratory mockup. Testing was conducted at 19-, 23-, and 27-degree seat back angles. Regression analysis demonstrated that passenger eye location was significantly affected by stature and by seat back angle. The regression results were used to develop an elliptical approximation of the distribution of adult passenger eye locations, applying a methodology previously used to develop the driver eyellipse in SAE J941-2002.
Technical Paper

Understanding Work Task Assessment Sensitivity to the Prediction of Standing Location

2011-04-12
2011-01-0527
Digital human models (DHM) are now widely used to assess worker tasks as part of manufacturing simulation. With current DHM software, the simulation engineer or ergonomist usually makes a manual estimate of the likely worker standing location with respect to the work task. In a small number of cases, the worker standing location is determined through physical testing with one or a few workers. Motion capture technology is sometimes used to aid in quantitative analysis of the resulting posture. Previous research has demonstrated the sensitivity of work task assessment using DHM to the accuracy of the posture prediction. This paper expands on that work by demonstrating the need for a method and model to accurately predict worker standing location. The effect of standing location on work task posture and the resulting assessment is documented through three case studies using the Siemens Jack DHM software.
Technical Paper

Measurement of the Contour and Deflection of Vehicle Seats for Comparison with the FMVSS 213 Dynamic Test Bench

2011-04-12
2011-01-0265
Federal Motor Vehicle Safety Standard (FMVSS) 213 specifies a bench seat that is used in dynamic testing of child restraint systems. To assess the representativeness of the FMVSS 213 bench, data from 54 passenger cars, minivans, and SUVs were analyzed to quantify the side-view profile of the seat centerlines in second-row, outboard seats. SAE J826 H-point measurements were performed on all seats and on the FMVSS 213 bench. A landmark-based resampling method was used to obtain a meaningful average seat contour after aligning on H-point. Principal component analysis and regression were conducted to quantify the effects of seat cushion angle, cushion length, and back angle on the seat profile. When aligned on H-point, the cushion length and surface angles of the FMVSS 213 bench were similar to the mean contour, except that no seats were as flat as the bench profile.
Technical Paper

Design and Testing of a Child Restraint for Developing Countries Using Low-Technology Manufacturing Methods

2011-04-12
2011-01-0260
As passenger car use becomes more common in developing countries, the number of child passengers killed and injuries also increases. Rates of child restraint use appear to be much lower in developing countries than in the U.S. or Europe. One barrier to increased restraint use is the relatively high cost of child restraints in low- and middle-income countries, where the cost of child restraints can be similar to the U.S. but incomes and typical vehicle prices are much lower. As part of a broader effort to improve child passenger safety worldwide, a team at the University of Michigan has begun development of a child restraint that is intended to be fabricated using low-cost technology in developing countries with minimal capital investment. Providing a design that has been tested successfully to regulatory standards may reduce barriers to entry and allow the restraints to be marketed at low prices.
Technical Paper

Simulating Complex Automotive Assembly Tasks using the HUMOSIM Framework

2009-06-09
2009-01-2279
Efficient methods for simulating operators performing part handling tasks in manufacturing plants are needed. The simulation of part handling motions is an important step towards the implementation of virtual manufacturing for the purpose of improving worker productivity and reducing injuries in the workplace. However, industrial assembly tasks are often complex and involve multiple interactions between workers and their environment. The purpose of this paper is to present a series of industrial simulations using the Human Motion Simulation Framework developed at the University of Michigan. Three automotive assembly operations spanning scenarios, such as small and large parts, tool use, walking, re-grasping, reaching inside a vehicle, etc. were selected.
Technical Paper

Validation of the Human Motion Simulation Framework: Posture Prediction for Standing Object Transfer Tasks

2009-06-09
2009-01-2284
The Human Motion Simulation Framework is a hierarchical set of algorithms for physical task simulation and analysis. The Framework is capable of simulating a wide range of tasks, including standing and seated reaches, walking and carrying objects, and vehicle ingress and egress. In this paper, model predictions for the terminal postures of standing object transfer tasks are compared to data from 20 subjects with a wide range of body dimensions. Whole body postures were recorded using optical motion capture for one-handed and two-handed object transfers to target destinations at three angles from straight ahead and three heights. The hand and foot locations from the data were input to the HUMOSIM Framework Reference Implementation (HFRI) in the Jack human modeling software. The whole-body postures predicted by the HFRI were compared to the measured postures using a set of measures selected for their importance to ergonomic analysis.
Technical Paper

Modeling Ascending and Descending Stairs Using the Human Motion Simulation Framework

2009-06-09
2009-01-2282
The Human Motion Simulation Framework (Framework) is a hierarchical set of algorithms for predicting and analyzing task-oriented human motion. The Framework was developed to improve the performance of commercial human modeling software by increasing the accuracy of predicted motions and the speed of generating simulations. This paper presents the addition of stair ascending and descending to the Transition Stepping and Timing (Transit) model, a component of the Framework that predicts gait and acyclic stepping.
Technical Paper

Dynamic Performance of Child Restraints with Two-Point Belt Securement

2009-10-06
2009-36-0183
Three different models of forward-facing CRS were evaluated dynamically using a two-point belt fixation (FMVSS 213 Standard). Ann additional test was conducted with one same model of CRS but using the three-point belt fixation. Results showed that CRS performance differ strongly according to belt fixation being the two-point belt securement dangerously inefficient for children transportation safety.
Journal Article

Postural Behaviors during One-Hand Force Exertions

2008-06-17
2008-01-1915
Posture and external loads such as hand forces have a dominant effect on ergonomic analysis outcomes. Yet, current digital human modeling tools used for proactive ergonomics analysis lack validated models for predicting postures for standing hand-force exertions. To address this need, the effects of hand magnitude and direction on whole-body posture for standing static hand-force exertion tasks were quantified in a motion-capture study of 19 men and women with widely varying body size. The objective of this work was to identify postural behaviors that might be incorporated into a posture-prediction algorithm for standing hand-force tasks. Analysis of one-handed exertions indicates that, when possible, people tend to align their bodies with the direction of force application, converting potential cross-body exertions into sagittal plane exertions. With respect to the hand-force plane, pelvis position is consistent with a postural objective of reducing rotational trunk torques.
Technical Paper

Modeling Vehicle Ingress and Egress Using the Human Motion Simulation Framework

2008-06-17
2008-01-1896
The ease of getting into and out of passenger cars and light trucks is a critical component of customer acceptance and product differentiation. In commercial vehicles, the health and safety of drivers is affected by the design of the steps and handholds they use to get into and out of the cab. Ingress/egress assessment appears to represent a substantial application opportunity for digital human models. The complexity of the design space and the range of possible biomechanical and subjective measures of interest mean that developing useful empirical models is difficult, requiring large-scale subject testing with physical mockups. Yet, ingress and egress motions are complex and strongly affected by the geometric constraints and driver attributes, posing substantial challenges in creating meaningful simulations using figure models.
Technical Paper

Characterization of Knee-Thigh-Hip Response in Frontal Impacts Using Biomechanical Testing and Computational Simulations

2008-11-03
2008-22-0017
Development and validation of crash test dummies and computational models that are capable of predicting the risk of injury to all parts of the knee-thigh-hip (KTH) complex in frontal impact requires knowledge of the force transmitted from the knee to the hip under knee impact loading. To provide this information, the knee impact responses of whole and segmented cadavers were measured over a wide range of knee loading conditions. These data were used to develop and help validate a computational model, which was used to estimate force transmitted to the cadaver hip. Approximately 250 tests were conducted using five unembalmed midsize male cadavers. In these tests, the knees were symmetrically impacted with a 255-kg padded impactor using three combinations of knee-impactor padding and velocity that spanned the range of knee loading conditions produced in FMVSS 208 and NCAP tests. Each subject was tested in four conditions.
Technical Paper

Comparison of Methods for Predicting Automobile Driver Posture

2000-06-06
2000-01-2180
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.
Technical Paper

Anthropometry for WorldSID A World-Harmonized Midsize Male Side Impact Crash Dummy

2000-06-19
2000-01-2202
The WorldSID project is a global effort to design a new generation side impact crash test dummy under the direction of the International Organization for Standardization (ISO). The first WorldSID crash dummy will represent a world-harmonized mid-size adult male. This paper discusses the research and rationale undertaken to define the anthropometry of a world standard midsize male in the typical automotive seated posture. Various anthropometry databases are compared region by region and in terms of the key dimensions needed for crash dummy design. The Anthropometry for Motor Vehicle Occupants (AMVO) dataset, as established by the University of Michigan Transportation Research Institute (UMTRI), is selected as the basis for the WorldSID mid-size male, updated to include revisions to the pelvis bone location. The proposed mass of the dummy is 77.3kg with full arms. The rationale for the selected mass is discussed. The joint location and surface landmark database is appended to this paper.
Technical Paper

Improved ATD Positioning Procedures

2001-03-05
2001-01-0117
Current anthropomorphic test device (ATD) positioning procedures for drivers and front-seat passengers place the crash dummy within the vehicle by reference to the seat track. Midsize-male ATDs are placed at the center of the fore-aft seat track adjustment range, while small-female and large-male ATDs are placed at the front and rear of the seat track, respectively. Research on occupant positioning at UMTRI led to the development of a new ATD positioning procedure that places the ATDs at positions more representative of the driving positions of people who match the ATD's body dimensions. This paper presents a revised version of the UMTRI ATD positioning procedure. The changes to the procedure improve the ease and repeatability of ATD positioning while preserving the accuracy of the resulting ATD positions with respect to the driving positions of people matching the ATD anthropometry.
Technical Paper

Anthropometric and Postural Variability: Limitations of the Boundary Manikin Approach

2000-06-06
2000-01-2172
Human figure models are commonly used to facilitate ergonomic assessments of vehicle driver stations and other workplaces. One routine method of workstation assessment is to conduct a suite of ergonomic analyses using a family of boundary manikins, chosen to represent a range of anthropometric extremes on several dimensions. The suitability of the resulting analysis depends both on the methods by which the boundary manikins are selected and on the methods used to posture the manikins. The automobile driver station design problem is used to examine the relative importance of anthropometric and postural variability in ergonomic assessments. Postural variability is demonstrated to be nearly as important as anthropometric variability when the operator is allowed a substantial range of component adjustment. The consequences for boundary manikin procedures are discussed, as well as methods for conducting accurate and complete assessments using the available tools.
Technical Paper

Development of Seatbelt Fit Assessment Components for the ASPECT Manikin

2002-03-04
2002-01-0686
As part of the Automotive Seat and Package Evaluation and Comparison Tools (ASPECT) program, UMTRI researchers developed a new H-point manikin that is intended to replace the current SAE J826 manikin. The original manikin is used in many automotive applications, including as a platform for a belt-fit test device (BTD). In the current project, components and procedures were developed to measure belt fit using the ASPECT manikin. Contoured lap and torso forms were constructed using anthropometric data from an earlier UMTRI study. Prototype forms were mounted on the ASPECT manikin for testing in a laboratory fixture and in vehicles. The testing demonstrated that the ASPECT-BTD produces consistent measures of belt fit that vary in expected ways with belt geometry.
Technical Paper

Characterization of Driver Seatbelt Donning Behavior

2002-03-04
2002-01-0783
Improvements in the accessibility and ease of use of seatbelts require an understanding of driver belt donning behavior. Participants in a study of driving posture were videotaped as they put on their belts in their own vehicles, either an SUV or a midsize sedan. The participants were unaware that the purpose of the videotaping was related to the seatbelt. Videos from 95 men and women were analyzed to identify several categories of belt-donning behavior and to analyze the influence of body dimensions. The results have applicability to seatbelt system design, including the use of human figure models to assess seatbelt accessibility.
Technical Paper

Investigating Driver Headroom Perception: Methods and Models

1999-03-01
1999-01-0893
Recent changes in impact protection requirements have led to increased padding on vehicle interior surfaces. In the areas near the driver's head, thicker padding can reduce the available headspace and may degrade the driver's perception of headroom. A laboratory study of driver headroom perception was conducted to investigate the effects of physical headroom on the subjective evaluation of headroom. Ninety-nine men and women rated a range of headroom conditions in a reconfigurable vehicle mockup. Unexpectedly, driver stature was not closely related to the perception of headroom. Short-statured drivers were as likely as tall drivers to rate a low roof condition as unacceptable. Statistical models were developed from the data to predict the effects of changes in headroom on the percentage of drivers rating the head-room at a specified criterion level.
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