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Current state-of-the-art vehicles implement pedestrian protection features that rely on pedestrian detection sensors and algorithms to trigger when impacting a pedestrian. During the development phase, the vehicle must “learn” to discriminate pedestrians from the rest of potential impacting objects. Part of the training data used in this process is often obtained in physical tests utilizing legform impactors whose external biofidelity is still to be evaluated. This study uses THUMS as a reference to assess the external biofidelity of the most commonly used impactors (Flex-PLI, PDI-1 and PDI-2). This biofidelity assessment was performed by finite element simulation measuring the bumper beam forces exerted by each surrogate on a sedan and a SUV. The bumper beam was divided in 50 mm sections to capture the force distribution in both vehicles. This study, unlike most of the pedestrian-related literature, examines different impact locations and velocities.

In the automotive industry, FMEA occurrence ranking is made to a standard such as SAE J1739. The SAE J1739 standard, as does other comparative standards, provides numerical probability criteria to aid ranking. Problems arise when the part or system under analysis is new, and there is no field data to estimate the probability of failure occurrence. Attempts to use qualitative verbal criteria or to go by the “feel” often result in inconsistency or large variability across and within FMEA projects. This paper presents a case study in which this problem was solved by the development of a tool that enables consistent - and efficient - FMEA occurrence rankings. The tool takes input from the user in the form of multiple-choice answers and calculates the final solution.

Power steering systems provide significant design challenges. They are detrimental to fuel economy since most require the continuous operation of a hydraulic pump. This generates heat that must be dissipated by fluid lines and heat exchangers. This paper presents a simple one-dimensional transient model for power steering components. The model accounts for the pump power, heat dissipation from fluid lines, the power steering cooler, and the influence of radiation heat from exhaust system components. The paper also shows how to use a transient thermal model of the entire system to simulate the temperatures during cyclic operation of the system. The implications to design, drive cycle simulation, and selection of components are highlighted.

Computer Simulation was extensively utilized in the design and development of the Active Roll Control (ARC) system on LandRover 4X4 vehicle. An ADAMS model was developed integrating the electronic controller, hydraulic activation and vehicle model into one system of various degrees of complexity. Simulation results not only correlated well with vehicle test results, but also provided invaluable design guidelines crucial for solving key stability issues and successful product launch.

In 1972, the first SAE paper describing the use of computer simulation as a design tool for automotive air conditioning was written by these authors. Since then, many such simulations have been used and new tools such as CFD have been applied to this problem. This paper reviews the work over that past 35 years and presents several of the improvements in the basic component and system models that have occurred. The areas where “empirical” information is required for model support and the value of CFD cabin and external air flow modeling are also discussed.

While much research has focused on improving terrain mobility, energy and fuel efficiency of terrain trucks, only a limited amount of investigation has gone into analysis of power distribution between the driving wheels. Distribution of power among the driving wheels has been shown to have a significant effect on vehicle operating characteristics for a given set of operating conditions and total power supplied to the wheels. Wheel power distribution is largely a function of the design of the driveline power dividing units (PDUs). In this paper, 6×6/6×4 terrain truck models are analyzed with the focus on various combinations of PDUs and suspension systems. While these models were found to have some common features, they demonstrate several different approaches to driveline system design.

One Dimensional models for front end air flows through the cooling system package are very useful for evaluating the effects of component and front end geometry changes. To solve such models for the air flow requires a robust iterative process that involves a number of non-linear sub-models. The cooling fan (s) constitute a major part of the difficulty, especially when they employ a viscous or “thermal” fan drive. This drive varies the torque coupling between the input and output shafts based on the radiator outlet air temperature. The coupling is achieved by viscous shear between two grooved disks and is regulated by a bimetal strip valve that varies the amount of fluid between the disks. This paper presents a mathematical model by which the input/output speed ratio may be determined as a function of the air temperature and input speed. Coefficients in the model are estimated from standard supplier performance information.

Simple component models are advantageous when simulating vehicle AC systems so that overall model complexity and computation time can be minimized. These models must be robust enough to avoid instability in the iteration method used for determining the AC system operating or “balance” point. Simplicity and stability are especially important when the AC system model is coupled with a vehicle interior model for studies of transient performance because these are more computationally intensive. This paper presents a semi-empirical modeling method for compressors based on dimensionless parameters. Application to some sample compressor data is illustrated. The model equations are simple to employ and will not introduce significant stability problems when used as part of a system simulation.

A new system reliability allocation methodology was applied on a steering product. The methodology makes use of design failure modes and effects analysis (DFMEA) and allows the allocation percentages to reflect differences in the criticality levels of the subsystems or components. The methodology was applied in conjunction with system reliability target setting. The paper first explores existing reliability allocation methods. It then introduces the new methodology. Finally, a real-life case is presented to show how the methodology was adopted and how and why it was modified. The approach presented here is one more way to make full use of the analytical efforts that have gone into the DFMEA.

One of the most important means used for suppressing squeal noise in disc brakes is the application of shims on the pad backplates. In many cases this proves a very efficient tool depending on the type of shim applied in the specific cases. Building up knowledge on the effects of shims have been ongoing for several years, and measuring the important parameters characterizing the shims is crucial for understanding how to develop and implement the shims in an optimal way. Several methods are described in literature for measuring the constrained layer damping effect and one method is described for direct measurement of the shear stiffness and shear damping properties. However, up to now no method has been available that can measure and characterize the normal stiffness and damping properties of shims. This is one of the most important properties of shims as it controls the de-coupling effect in the direction of the normal forces.

A biaxial test procedure is used to assess the constitutive properties of polymers in tension. The constitutive constants are derived for high strain rate applications such as those associated with crashworthiness studies. The test procedure is used in conjunction with a time- and strain-dependent quasi-linear viscoelastic constitutive law consisting of a Mooney-Rivlin formulation combined with Maxwell elements. The procedure is demonstrated by describing the stress vs. strain relationship of a rubber specimen subjected to a step-relaxation input. The constitutive equation is transformed from a nonlinear convolution integral to a set of first order differential equations. These equations, with the appropriate boundary conditions, are solved numerically to obtain transient stresses in two principal directions. Material constants for use in the explicit LS-Dyna non-linear finite element code are provided.

Biomechanical data are often assumed to be doubly censored. In this paper, this assumption is evaluated critically for several previously published sets of data. Injury risk functions are compared using simple logistic regression and using survival analysis with 1) the assumption of doubly censored data and 2) the assumption of right-censored (uninjured specimens) and uncensored (injured) data. It is shown that the injury risk functions that result from these differing assumptions are not similar and that some experiments will require a preliminary assessment of data censoring prior to finalizing the experimental design. Some types of data are obviously doubly censored (e.g., chest deflection as a predictor of rib fracture risk), but many types are not left censored since injury is a force-limiting phenomenon (e.g., axial force as a predictor of tibia fracture). Guidelines for determining the censoring for various types of experiment are presented.

Children under six years of age who are prematurely restrained in adult seat belts are at more than 3 times increased risk of injury as compared with children in child restraint systems (CRS). As a result, CRS (child safety seats and booster seats) are recommended as appropriate restraints for young children and use of different types of child restraints is increasing rapidly. The objective of this study was to begin to evaluate the performance of multiple restraints at a range of speeds, utilizing the Hybrid III 3- and 6-year-old child dummies. Injury measurements were compared for a 3-year old restrained in a forward facing convertible child restraint, a backless belt-positioning booster seat and in a lap shoulder seat belt; and, for a 6-year old restrained in a backless belt-positioning booster seat, a high back belt-positioning booster seat, and a lap shoulder seat belt. A matrix of tests (total of 18) at speeds of 24, 40, and 56 kph were used in the evaluation.

Injuries of the Occipitoatlantoaxial (Occ-C2) region (also known as atlanto-occipital injuries) are the most common form of cervical injury in children aged ten years and younger. The crash studied in this paper is unique in that there were three children ages 3, 6 and 7 involved in a frontal crash with a delta V of 28mph with each child receiving a nonfatal Occ-C2 injury of varying degrees. The 3 and 6 year-old children were remarkably similar in height and weight to the 3 and 6 year-old Hybrid III ATD's. Also, unique to this case is the fact that the right rear 6 year-old occupant likely sustained an Occ-C2 injury prior to impact with the frame of the front passenger seat. This crash environment was recreated utilizing MADYMO occupant simulation software. The models for the Hybrid III 3 and 6 year-old ATDs were used to represent the occupants in this crash.

An ABS/TC proportional pressure control can be achieved by using some of the control technology applied to an electro-hydraulic brake (EHB) system. This paper describes a new method for reducing the calibration time of an EHB, and this method may be used for potential advanced ABS/TC proportional control systems. A mathematical model is established to analyze the system and by using the model some common physical relationships are identified. Calibration values of a proportional system in certain pressure ranges can be estimated instead of requiring measurement.

Strategies for the inoculation of bioreactors for long-term space missions include communities of diverse composition or, alternatively, communities of a few organisms selected for their ability to efficiently catalyze reactions of interest in the reactor. The concept of functional redundancy states that in a diverse community, several different organisms may be present that are capable of effecting processes necessary to the maintenance of the system function. The concept implies that if some members of the community are lost, others will be able to keep the system from failing in the critical reactions that take place therein. In a sewage reactor in the laboratory, a diverse community at steady state was perturbed by elimination of aeration for seven days. Chemical pools (NH4+, NO3-, dissolved O2), pH, and CO2 evolution were monitored before, during, and after the perturbation.

Studies show that the pedestrian population at high risk of injury consists of both young children and adults. The goal of this study is to gain understanding in the mechanisms that lead to injuries for children and adults. Multi-body pedestrian human models of two specific anthropometries, a 6year-old child and a 50th percentile adult male, are applied. A vehicle model is developed that consists of a detailed rigid finite element mesh, validated stiffness regions, stiff structures underlying the hood and a suspension model. Simulations are performed in a test matrix where anthropometry, impact speed and impact location are variables. Bumper impact occurs with the tibia of the 50th percentile adult male and with the thigh of the 6-year-old child. The head of a 50th percentile male impacts the lower windshield, while the 6-year-old child's head impacts the front part of the hood.

This research investigates the variation of pedestrian stance in pedestrian-automobile impact using a validated multi-body vehicle and human model. Detailed vehicle models of a small family car and a sport utility vehicle (SUV) are developed and validated for impact with a 50th percentile human male anthropometric ellipsoid model, and different pedestrian stances (struck limb forward, feet together, and struck limb backward) are investigated. The models calculate the physical trajectory of the multi-body models including head and torso accelerations, as well as pelvic force loads. This study shows that lower limb orientation during a pedestrian-automobile impact plays a dominant role in upper body kinematics of the pedestrian. Specifically, stance has a substantial effect on the subsequent impacts of the head and thorax with the vehicle. The variation in stance can change the severity of an injury incurred during an impact by changing the impact region.

Computer simulations, dummy experiments with a new enhanced upper extremity, and small female cadaver experiments were used to analyze the small female upper extremity response under side air bag loading. After establishing the initial position, three tests were performed with the 5th percentile female hybrid III dummy, and six experiments with small female cadaver subjects. A new 5th percentile female enhanced upper extremity was developed for the dummy experiments that included a two-axis wrist load cell in addition to the existing six-axis load cells in both the forearm and humerus. Forearm pronation was also included in the new dummy upper extremity to increase the biofidelity of the interaction with the handgrip. Instrumentation for both the cadaver and dummy tests included accelerometers and magnetohydrodynamic angular rate sensors on the forearm, humerus, upper and lower spine.

The control of fuel delivery to minimize drivetrain oscillations is a major benefit to vehicle refinement and driveability. This paper describes the application of robust H-infinity loop-shaping control to the speed-fuel control loop. A one-degree-of-freedom controller structure (feedback only) is examined and applied to a small passenger car. Using careful implementation, the control algorithm is of low order and efficient requiring only limited microprocessor resources. The robust controller gives excellent performance when operated synchronously to engine rotation, where the dynamics become speed-dependent. Alternatively it can be operated satisfactorily at a fixed sample rate, asynchronous to engine rotation. The design is found to be eminently suitable for production.