Search Results

In this paper, dynamics and stability of an articulated vehicle in the yaw plane are examined through analysis, simulations, and vehicle testing. Control of a vehicle-trailer combination using active braking of the towing vehicle is discussed. A linear analytical model describing lateral and yaw motions of a vehicle-trailer combination is used to study the effects of parameter variations of the trailer on the dynamic stability of the system and limitations of different control strategies. The results predicted by the analytical model are confirmed by testing using a vehicle with a trailer in several configurations. Design of the trailer makes it possible to vary several critical parameters of the trailer. The test data for vehicle with trailer in different configurations is used to validate the detailed non-linear simulation model of the vehicle-trailer combination.

The primary function of an airbag control module is to detect crashes, discriminate and predict if a deployment is necessary, then deploy the restraint systems including airbags and where applicable, pretensioners. At General Motors (GM), the internal term for airbag control module is Sensing and Diagnostic Module (SDM). In the 1994 model year, GM introduced its SDM on some of its North American airbag-equipped vehicles. A secondary function of that SDM and all subsequent SDMs is to record crash related data. This data can include data regarding impact severity from internal accelerometers and pre-crash vehicle data from various chassis and powertrain modules. Previous researchers have addressed the accuracy of both the velocity change data, recorded by the SDM, and the pre-crash data, but the assessment of the timing of the pre-crash data has been limited to a single family of modules (Delphi SDM-G).

With the wider use of biofuels in the marketplace, a program was conducted to study the deposit forming tendencies and performance of E85 (85% denatured ethanol and 15% gasoline) in a modern Flexible Fuel Vehicle (FFV). The test vehicle for this program was a 2006 General Motors Chevrolet Impala FFV equipped with a 3.5 liter V-6 powertrain. A series of 5,000 mile Chassis Dynamometer (CD) Intake Valve Deposits (IVD) and performance tests were conducted while operating the FFV on conventional (E0) regular unleaded gasoline and E85 to determine the deposit forming tendencies of both fuels. E85 test fuels were found to generate significantly higher levels of IVD than would have been predicted from the base gasoline component alone. The effects on the weight and composition of IVD due to a corrosion inhibitor and sulfates that were indigenous to one of the ethanols were also studied.

Computer simulation was used as a complement to crash and injury field data analysis and physical sled and barrier tests to investigate and predict the spinal injuries of a rear impact in an IndyCar. The model was expected to relate the spinal loads to the observed injuries, thereby predicting the probability and location of spinal fractures. The final goal is to help reduce the fracture risk by optimizing the seat and restraint system design and the driver's position using computer modeling and sled testing. MADYMO Full FE Human Body Model (HBM) was selected for use because of its full spinal structural details and its compatibility with the vehicle and restraint system models. However, the IndyCar application imposed unique challenges to the HBM. First, the driver position in a race car is very different from that in a typical passenger car.

Advanced chassis control systems enable a vehicle to achieve new levels of performance in handling stability and responsiveness. In recent work by NHTSA and others, the performance of Electronic Stability Control (ESC) systems has been studied with focus on yaw stability and roll stability of vehicles on high friction surfaces. However, it is recognized that vehicle handling responsiveness is also an important aspect that should be maintained. This paper explores the trade-offs between yaw rate, side slip, and roll motions of a vehicle, and their relationships to handling stability and handling responsiveness. This paper further describes how various control systems are able to manage these motions. The paper also discusses methods to assess vehicle stability and responsiveness using specific maneuvers and measurements, and it includes data from vehicle tests on a slippery surface.

The paper describes the development of a vehicle stability indicator based on the correlation between various current vehicle chassis sensors such as hand wheel angle, yaw rate and lateral acceleration. In general, there is a correlation between various pairs of sensor signals when the vehicle operation is linear and stable and a lack of correlation when the vehicle is becoming unstable or operating in a nonlinear region. The paper outlines one potential embodiment of the technology that makes use of the Mahalanobis distance metric to assess the degree of correlation among the sensor signals. With this approach a single scalar metric provides an accurate indication of vehicle stability.

In a CAS system, the distance and relative velocity between front and host vehicles are estimated to calculate time-to-collision (TTC). The distance estimates by different methods will certainly include noise which should be removed to ensure the accuracy of TTC calculations. Kalman filter is a good tool to filter such type of noise. Nevertheless, Kalman filter is a model based filter, which means a correct model is important to get the good filtering results. Usually, a vehicle is either moving with a constant velocity (CV) or constant acceleration (CA) maneuvers. This means the distance data between front and host vehicles can be described by either constant velocity or constant acceleration model. In this paper, first, CV and CA models are used to design two Kalman filters and an interacting multiple model (IMM) is used to dynamically combine the outputs from two filters.

Both Crash-Avoidance and Pre-Crash active safety technologies are being developed to help reduce the number of crashes and minimize the severity of crashes. The root basis in the development of new and improved active safety technologies always begins with gaining further knowledge about crash kinds and causes. The dynamics of crashes are quite complex. The evolving precursor crash situation initiated in the Crash-Avoidance time-period will vary from the imminent crash situation in the Pre-Crash time-period. As such, in order to develop the appropriate requirements for both crash-avoidance and pre-crash technologies, they must be analyzed from their respective crash data. A data-driven methodology process has been developed which partitions the field data with a perspective to crash-avoidance and pre-crash.

Improving fuel economy, emissions, passenger comfort and convenience, safety, and vehicle performance in the automobile is resulting in the growth of electrical loads. In order to meet these electrical load demands and to meet the requirement of power generation when the engine is off, several technologies are on the horizon for on-board power generation in the vehicles. In this paper, new on-board power generation technologies based on the solid oxide fuel cell (SOFC), proton exchange membrane (PEM) fuel cell, thermo-photovoltaic (TPV) system, and diamond or carbon nanostructures are compared in terms power density, cost, and long term feasibility for automotive applications.

In this paper, a comparative study of the production applications of hybrid electric powertrains is presented. Vehicles studied include the Toyota Prius, Honda Insight, Toyota Estima, Toyota Crown, Honda Civic Hybrid, and Nissan Tino. The upcoming Ford Escape Hybrid and General Motors Parallel Hybrid Truck (PHT) will also be included, although advance information is limited. The goal of this paper is to look at what hybrid drivetrain architectures have actually been selected for production and what are the underlying details of these drivetrains. Since hybridizing a powertrain involves significant changes, the powertrain architectures are presented in diagram form, with analysis as to the similarities and advantages represented in these architectures. The specific hybrid functions used to save fuel are discussed. Peak power-to-weight ratio and degree of hybridization are plotted for the vehicles. System voltage versus electric power level are also plotted and analyzed.

Data suggest that in response to substantial educational efforts, more children are being placed in the rear seats of vehicles. As this transition occurs, it is important to make efforts to optimize the performance of rear seat restraints for children. Prior to developing new restraints for children for the rear seat, a better understanding of child responses in various crash scenarios is needed. The objective of this study was to evaluate the performance of various restraint systems and countermeasures for child occupants in different crash scenarios. Sled tests were carried out with a Hybrid III 6 year old anthropomorphic test device (ATD) in frontal, oblique and side impact configurations. The performance of a highback and a backless booster seat was assessed. The results were compared with two standard 3 point belt restraint systems: 1. a package shelf mounted belt, and 2. a C-pillar mounted belt.

This paper provides an overview of rollover crash safety, including field crash statistics, pre- and rollover dynamics, test procedures and dummy responses as well as a bibliography of pertinent literature. Based on the 2001 Traffic Safety Facts published by NHTSA, rollovers account for 10.5% of the first harmful events in fatal crashes; but, 19.5% of vehicles in fatal crashes had a rollover in the impact sequence. Based on an analysis of the 1993-2001 NASS for non-ejected occupants, 10.5% of occupants are exposed to rollovers, but these occupants experience a high proportion of AIS 3-6 injury (16.1% for belted and 23.9% for unbelted occupants). The head and thorax are the most seriously injured body regions in rollovers. This paper also describes a research program aimed at defining rollover sensing requirements to activate belt pretensioners, roof-rail airbags and convertible pop-up rollbars.

Automotive rollover is a complex mechanical phenomenon. In order to understand the mechanism of rollover and develop any potential countermeasures for occupant protection, efficient and repeatable laboratory tests are necessary. However, these tests are not well understood and are still an active area of research interest. It is not always easy or intuitive to estimate the necessary initial and boundary conditions for such tests to assure repeatability. This task can be even more challenging when rollover is a second or third event (e.g. frontal impact followed by a rollover). In addition, often vehicle and occupant kinematics need to be estimated a-priori, first for the safe operation of the crew and equipment safety, and second for capturing and recording the event. It is important to achieve the required vehicle kinematics in an efficient manner and thus reduce repetitive tests. Mathematical modeling of the phenomenon can greatly assist in understanding such kinematics.

Adaptive Cruise Control (ACC) technology is presently emerging in the automotive market as a convenience function intended to reduce driver workload. It allows the host vehicle to maintain a set speed and distance from preceding vehicles by a forward object detection sensor. The forward object detection sensor is the focal point of the ACC control system, which determines and regulates vehicle acceleration and deceleration through a powertrain torque control system and an automatic brake control system. This paper presents a design of an automatic braking system that utilizes a microprocessor-controlled brake hydraulic modulator. The alternatively qualified automatic braking means is reviewed first. The product level requirements of the performance, robustness, and durability for an automatic brake system are addressed. A brief overview of the presented system architecture is described.

This paper proposes the concept of Generalized Diagnostic Component (GDC) and presents a modular fault diagnostic strategy for safety critical automotive systems. The diagnostic strategy makes full use of hierarchical techniques, integrates the generalized diagnostic design into all-purpose vehicle diagnoses based on reconfiguration of the GDCs, and inherits the model-based diagnostic algorithms developed for Steering/Braking-By-Wire systems. The GDC-based approach simplifies the design and integration of diagnostics in complex dynamical control systems, and has been successfully implemented in an eight degrees of freedom NAVDyn (Non-Linear Analysis of Vehicle Dynamics) simulation model using Matlab Simulink. The simulation results are provided in this paper to testify that the diagnostic strategy and implementation are feasible, efficient and dependable.

A new single-brick Ba + alkali metals NOx-Trap catalyst has been developed to replace a two-brick NOx-Trap system containing a downstream three-way catalyst. Major development efforts include: 1) platinum group metals selection for higher HC oxidation with potassium-containing washcoat, 2) alumina and ceria selection, and Rh architecture design for more efficient NOx reduction and 3) NiO to suppress H2S odor. Mitsubishi Motors' 1.8L GDI™ with this Delphi new NOx-Trap catalyst with H2S control achieves J-LEV standard with less cost and lower backpressure compared to the previous model. It is further discovered that incorporation of NiO into the NOx-Trap washcoat is effective for H2S control during sulfur purge but has a negative impact on thermal durability and sulfur resistance. Further study to improve this trade-off has been made and preliminary results of an advanced washcoat design are presented in this paper. Details will be reported in a future publication.

Among the performance concerns in brake design, drag and fluid displacement are getting more attention in the requirement definition. High drag not only affects fuel efficiency and lining life, it is also a contributing factor to rotor thickness variation and brake pulsation. In this paper, a system approach to drag performance of a disc brake caliper is presented. A one-dimensional simulation model, which considers all the significant factors, including lining stiffness and hysteresis, housing stiffness, seal/groove characteristic, and stick-slide behavior between the seal and piston, is developed to capture the interactive impact of each parameter to caliper drag performance. The system model is validated with experimental measurements for caliper fluid displacement and piston retraction. A parameter study is then conducted to investigate the component interactive impact to the drag performance.

Since its invention in early 1990s, the side curtain airbag has become an important part of the occupant restraint system for side impact and rollover protection. Computer Aided Engineering (CAE) is often used to help side curtain airbag design. Because of the unique characteristics of side curtain airbag systems, the simulation of side curtain airbag systems faces different challenges in comparison to the simulation of driver and passenger airbag systems. The typical side curtain airbag CAE analysis includes, but is not limited to, cushion volume evaluation, cushion coverage review, cushion shrinkage and tension force review, deployment timing review and seam shape and location review. The commonly used uniform pressure airbag models serve the purpose in most cases.

In 2002, NHTSA statistics indicate air bag deployments saved an estimated 1,500 lives; however, reports of occupants having serious or fatal injuries during air bag deployment appear low relative to the number of accidents with air bag deployments. To avoid air bag induced injuries, a variety of occupant sensing technologies are being developed. One of the critical logic deployment challenges faced by these technologies is whether the system can accurately determine if the occupant is in a posture or a position such that air bag deployment may result in an injury. To improve accuracy, it is necessary to understand what postures the occupants are likely to assume during a ride and how often. For this purpose, Delphi Corporation has conducted a survey to solicit opinions on the posture usage rate. With 560 responses, the frequencies for 29 sitting postures for adult passengers and 13 child postures or positions were estimated.

This paper presents the development of coordinated control of vehicle systems, specifically for controlled brakes and controlled steering systems. By utilizing a control structure to oversee a four-wheel-steer (4WS) system and a brake-based vehicle stability enhancement (VSE) system, it is possible to achieve improvements in vehicle stability and driver workload/comfort, and to reduce compromises in vehicle handling. The coordinated control is designed to leverage the unique strengths of 4WS and VSE, and to prevent conflicts between them. Vehicle test results prove the viability of the concept.