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Vehicle Noise, Vibration, and Harshness (NVH) performance has become an important indicator used in the “Customer Satisfaction” category in the automotive industry. Particularly, refinement of powertrain NVH performance in different vehicle operating conditions has had a major contribution to the perception of overall vehicle NVH performance. The powertrain system typically includes the engine and transmission (powerplant), driveline, axle, and induction/exhaust subsystems. This paper presents three areas of successful development work in resolving vehicle NVH issues using analytical and experimental tools: (1) powertrain bending induced vehicle NVH concerns at high speeds [1]; (2) exhaust modes induced - idle boom, vibrations, and normal vehicle speed moaning noise [2-3]; and (3) driveshaft modes and axle gear mesh force induced axle whine noise [4]. Each development work has resulted in design changes and improved NVH performance in production vehicles.

Harmonizing software and hardware in addition to facilitating the analysis of intricate electronic systems from the functional perspective down to its low-level hardware and electronic implementation, transpires as an objective for safety analysis. Improving this process and simplifying a complex task to enable domain experts to partake in many aspects of the safety analysis would aid in permitting further insight into how the system behaves. The process presented in this paper achieves these objectives whilst promoting and communicating safety to a broader audience via a common language and process that is easy to understand and embraces current development methods.

Roadway surfaces contaminated with gravel, sand, salt, or other debris may affect the stopping capability of a vehicle. This paper presents results of 96 skid-to-stop tests where the effects of roadway debris on vehicle deceleration were examined. Four vehicles of different types (light truck, sedan, sport, and sport utility vehicle) were tested, with and without the Anti-lock Brake System (ABS) enabled, on roadway surfaces with and without a gravel and salt mixture. Significant decreases in both maximum and average deceleration rates between normal and gravel-contaminated roadways for each vehicle were observed. The test results provide quantification of the reduction in vehicle deceleration when gravel contaminates the roadway. Also, the effectiveness of ABS on gravel surfaces was examined.

The results of a number of previous studies have demonstrated that seat-belted occupants can undergo significant upward and outward excursion during the airborne phase of vehicular rollover, which may place the occupant at risk for injury during subsequent ground contacts. Furthermore, testing using human volunteers, ATDs, and cadavers has shown that increasing tension in the restraint system prior to a rollover event may be of value for reducing occupant displacement. On this basis, it may be argued that pretensioning the restraint system, utilizing technology developed and installed primarily for improving injury outcome in frontal impacts, may modify restrained occupant injury potential during rollover accidents. However, the capacity of current pretensioner designs to positively impact the motion of a restrained occupant during rollover remains unclear.

Toyota developed the first-generation Intelligent Power Module (hereinafter referred to as IPM) that is the key part of the system for Hybrid Electric Vehicles (hereinafter referred to as HEV). It was installed in the inverter for Prius, which was launched in Japan in 1997, and recently, the demands for not only mileage performance but also power performance in an HEV have been increasing. For the inverter for Prius that was launched in 2003, we developed a new IPM for the high voltage and high power that is applied in the second generation Toyota Hybrid System (hereinafter referred to as THSII). In the second-generation IPM, the boost converter that raises the power-supply voltage was added in the inverter, and a low electric current in the IPM was achieved based on “Power = Voltage × Electric Current”. The IPM for the motor and the IPM for the generator were integrated by using the merits of the system.

Vehicle aspect ratio has been reported as a significant factor influencing the likelihood of fatality or severe injury/fatality during single-vehicle rollover crashes. To investigate this, dynamic simulations of friction-induced rollover accidents were performed using different roof heights, but otherwise identical vehicle parameters and initial conditions. Higher aspect ratios tended to cause the leading side roof to impact first, with significant impact force. The roof impact forces during the first roll of higher-roofed vehicles were primarily laterally directed with respect to the vehicle. Impact locations during subsequent rolls were less predictable. Lower aspect ratios produced higher impact forces on the trailing side roof that were more vertically oriented with respect to the vehicle. The vertically oriented forces potentially create greater risk for severe neck or head injuries.

Several studies have sought to investigate the biomechanics associated with “whiplash syndrome” by evaluating head kinematics in simulated low-speed rear-end collisions. However, the present study is the first to comprehensively measure head accelerations in six degrees of freedom for the purpose of estimating upper neck loads. In the first phase of the study, nine volunteers were instrumented with a sensor package to measure three-dimensional linear accelerations and angular velocities of the head during rear-end impacts while riding an amusement park bumper car. In the second phase, thirty volunteers were instrumented with the same sensors during selected vigorous activities, including hopping and skipping rope. The linear and rotational head accelerations as well as the calculated upper neck forces and moments for the two groups are presented and compared.

The growing concern surrounding Sports Utility Vehicle (SUV) rollover incidences and their consequences have prompted to investigate the sensitivity of critical vehicle parameters on rollover. In this paper, dynamic rollover simulation of Sports Utility Vehicles is carried out using a validated nonlinear vehicle model in Matlab/Simulink. A standard model is considered and critical vehicle parameters like CG height, track width and wheel base are varied within chosen specified limits to study its influence on roll behavior during Fishhook steering maneuver. A roll stability criterion based on two wheel lift off phenomenon is adopted for rollover propensity prediction. Further dynamic rollover characteristics of the vehicle are correlated with Static Stability Factor (SSF), Roll Stability Factor (RSF) and Two Wheel Lift off Velocity (TWLV).

Simple rigid body dynamics models are created to analyze the curb- and soil-trip types of rollover events and experimental methods that are used to simulate these events. Equations for the models are given, and they are integrated numerically to obtain the solution. Solutions of the models provide a break down of the energy during these events, which exposes the importance of energy absorption, unloading, and friction during the impact-and-roll process. Furthermore, the models are used to derive the critical sliding velocity under different test parameters. They are also used to understand near-critical state responses of the vehicle, and the corresponding characteristics of the signals in the phase space.

Three vehicle rollovers have been reconstructed based on driver interviews and approximate measurements of crash artifacts. The purpose of this work is to provide insight into sensor signals prior to the onset of rollover. The three events include: a car-to-car T-bone leading to a roll of 90 degrees; an impact-induced skid leading to a roll with 6 quarter turns; and a single vehicle partly on-road event with three complete rolls. Sensor signals are derived using the PC-Crash tool, and characteristic features are identified. Insights derived from these events can aid in development of robust rollover detection algorithms and calibrations. Furthermore, by studying how pre-roll maneuvers may presage a rollover event, key requirements for system-of-systems safety architectures can be derived.

With the stringent emission regulations and renewable energy concerns, hydrogen application either to direct injection combustion or fuel cell application attracts more attention. However, a major obstacle for vehicle utilization of hydrogen as a main fuel is onboard storage. Due to the low mass density, hydrogen has the lowest energy per unit volume among all potential fuels. One of the typical methods to store hydrogen is in very high pressure storage tanks. The high pressure (35 MPa and higher) combined with small size of hydrogen molecules makes the tanks and adjacent fittings prone to leakage, which may cause important potential safety issues, given the wide combustion range and easy ignition of hydrogen. Our research focuses on characterizing the relative importance of basic modes of hydrogen leakage at the joints of commercial stainless steel fittings.

The increasing demand of four-wheel drive vehicles is pushing the market for more optimized transfer cases. In modern cars the transfer case is usually controlled electronically because this provides more design freedom and the possibility of diagnostics feedback and direct control by the powertrain ECU. A typical transfer case control would include different sensors for angle-rotational speed and position sensing, a keypad for the mode selection by the driver, a microcontroller to compute the information and some high current drive circuitry for driving the actuators. But, while SUV's are known to provide ample space for the passengers, the electronics cannot claim that luxury. With every function added the available board space per function is getting smaller and the additional power dissipation is of concern. This is especially true for high current components like the transfer case motor driver.

Federal Motor Vehicle Safety Standard (FMVSS) 208 - Occupant Crash Protection establishes performance requirements to determine whether passenger vehicles, light multipurpose vehicles, and trucks meet conditions and injury criteria specified by the standard. On May 12, 2004, the National Highway Traffic Safety Administration (NHTSA) amended the standard to set the path for future air bag development [1, 2]. The amendment concerned the development of airbag systems that would be designed to minimize the risk of air bag induced injuries in comparison to current technologies. These new rules forward the framework for engineering of these systems without strictly regulating their design. This paper will discuss the test methodologies used from the initial design phase to the final validation phase of a vehicle. Strategies for advanced air bag system types, suppression and low risk occupant mixes, and the use of human subjects will be discussed.

General Motors has pursued research to develop systems intended to assist drivers in recognizing people or objects behind them when they are backing, and this paper summarizes results from this research. We are currently working with ultrasonic rear parking assist systems, rear radar backing warning systems, and rear camera systems, which are briefly described and their utility for assisting drivers in recognizing people or objects behind them discussed. Our research on driver performance with a prototype long range backing warning system found that audible and visual warning combinations may not be effective in warning distracted drivers about unexpected objects. Driver expectancy is thought to play a significant role in this result. However, further research found drivers were more likely to notice an unexpected obstacle behind their vehicle with a prototype rear view video camera system compared to ultrasonic rear parking assist and trials that had no system.

A separate measurement of these single jet flow injection quantities is absolutely necessary for the evaluation of the injection nozzles. However, so far this has not been possible in a satisfying way [7, 9]. A measuring adapter for determination of the injection quantities for individual spray hole was developed here. With measuring adapter the influence of variation in shape and geometry of the individual nozzle components on single jet flow injection quantities can be determined. The measurements are supported by simulation results. The spray hole shape is crucial for flow coefficient and cavitation in the spray hole. During fuel atomization the diameter and shape of the injecting holes and the pattern realized by the nozzle needle in addition to the injection pressure play a substantial role.

A suspension system does not merely isolate a vehicle from the shocks and vibrations induced by the road surface. It also keeps the wheels in contact with the road, ensuring vehicle stability and control. In order to properly determine the stiffness and damping parameters of a Formula SAE, models for a quarter car and a seven degree-of-freedom car (DOF-7) were developed based upon Newton's second law. These were built using MatLab/Simulink. The quarter car model was taken first, to study the effect of four (4) suspension parameters on the tires' vertical load fluctuations. The results were then used to optimize suspension parameters for the 7-DOF model, taking the bounce, roll and pitch motions of the chassis into account in addition to its four-wheel hops. Track data was acquired and used as input to the model. Nonlinear damping was implemented in the 7-DOF model to study the car's behavior.

This paper will discuss the vehicle top-down design approach that includes the non-linearity and sub-system interactions such as tire and road, (left and right) interaction between two or more parts connected by bushings, springs, bolts, stabilizer-bar, etc… The proposed method would allow for the inclusion of realistic boundary conditions and proper load simulation, and it would provide the ability to visualize and evaluate dynamic structural phenomena and complex component interaction. This approach would also facilitate the evaluation of design changes that may affect load propagation and/or load magnitude. All of the advantages of the sub-system analysis method mentioned above would allow for a greater understanding of the sub-system as a whole and help correctly identify the design requirements needed for the individual components that make up such chassis subsystems.

Durability of automotive structures is a primary engineering consideration that is evaluated during a vehicle's design and development. In addition, it is a basic expectation of consumers, who demand ever-increasing levels of quality and dependability. Automakers have developed corporate requirements for vehicle system durability which must be met before a products is delivered to the customer. To provide early predictions of vehicle durability, prior to the construction and testing of prototypes, it is necessary to predict the forces generated in the vehicle structure due to road inputs. This paper describes an application of the “virtual proving ground” approach for vehicle durability load prediction for a vehicle on proving ground road surfaces. Correlation of the results of such a series of simulations will be described, and the modeling and simulation requirements to provide accurate simulations will be presented.

Kinetic Pty Ltd and Tenneco Automotive have developed a passive suspension system hereafter referred to as a Kinetic2 system. The motivation for the design of the system is discussed, and the function of the system is briefly explained. In a previous paper, the system has been shown to improve the stability and rollover resistance of a small SUV. In this study vehicle response characteristics are found by simulating a typical sinusoidal sweep maneuver. Improved handling is evaluated by simulating NHTSA’s yaw acceleration feedback fishhook test. Lastly ride is studied by simulating the vehicle driving over a characteristic stretch of California Freeway #5. All of the simulations were performed on a small SUV in standard form and equipped with the Kinetic system. Results of the ADAMS simulation are presented, and benefits are discussed.