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A new optimal control strategy for dealing with braking actuator failures in a vehicle equipped with a brake-by-wire and steer-by- wire system is described. The main objective of the control algorithm during the failure mode is to redistribute the control tasks to the functioning actuators, so that the vehicle performance remains as close as possible to the desired performance in spite of a failure. The desired motion of the vehicle in the yaw plane is determined using driver steering and braking inputs along with vehicle speed. For the purpose of synthesizing the control algorithm, a non-linear vehicle model is developed, which describes the vehicle dynamics in the yaw plane in both linear and non-linear ranges of handling. A control allocation algorithm determines the control inputs that minimize the difference between the desired and actual vehicle motions, while satisfying all actuator constraints.

Electro-mechanical brakes (EMBs) are emerging as a new approach to enhance brake system features as well as braking performance. This paper takes a fresh look at the switched reluctance (SR) drive as a possible prime mover technology for EMB applications. The switched reluctance motor has attractive potential, in view of its robustness, dynamic bandwidth and fault tolerance. An overall assessment of the approach is made based on bench performance of a prototype EMB caliper with an SR drive executing typical braking patterns. It is shown that the SR motor can provide the required overall brake actuator performance. Various implementation options are examined to lower cost, with particular focus on electronic design, control algorithms and motor position sensing.

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.

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.

In the field of vehicle diagnostics accurate instantaneous engine speed information enables the detection and diagnosis of many engine problems, even subtle ones. Currently, there is a limited choice in the ways of obtaining such information. For example, it is known that one can tap into the crank sensor wiring, or use a separate, intrusive method, such as mounting a sensor in the bell housing to sense the rotation of the ring gear. However, the shortcomings of these approaches are locating and gaining access to the crank sensor connector, the location of which varies from vehicle to vehicle. Thus, authors proposed a novel, robust and manufacturing friendly speed sensor. The concept is based on the Villari effect. The sensor, which is attached to the front end of the engine crankshaft, consists of a coil of magnetostrictive wire supplied with AC current. During engine rotation the magnetostrictive wire become stressed due to centrifugal force.

This study utilizes complex eigenvalue analysis to investigate the sensitivity of dynamic system stability to the mechanical properties of the friction material. The friction material is modeled as a transverse isotropic material exhibiting different in-plane and out-of-plane moduli. Parametric studies are performed to evaluate system stability under various combinations of these properties. The initial analysis results show good correlation with laboratory testing for both squeal frequency and mode shape. Additional laboratory testing reveals a change in friction material can have a significant effect on the noise performance of a system. Analysis was performed with corresponding friction materials and the results were directionally consistent. This helped to validate the analysis model and establish confidence in the analysis results. In general, for the specific system considered, decreasing both in-plane and out-of-plane moduli encouraged system stability.

The intensity of a combustion flame ionization current signal (ionsense) can be used to monitor and control combustion in individual cylinders during a cold engine start. The rapid detection of poor or absence of combustion can be used to determine fuel delivery corrections that may prevent engine stalls. With the ionsense cold start control active, no start failures were recorded even when the initially (prior to ionsense correction) commanded fueling had failed to produce a combustible mixture. This new dimension in fuel control allows for leaner cold start calibrations that would still be robust against the possible use of low volatility gasoline. Consequently, when California Phase 2 fuel is used, cold start hydrocarbon emissions could be lowered without the risk of an engine stall if the appropriate fuel is replaced with a less volatile one.

Modern military ground vehicles are dependent not only on armor and munitions, but also on their electronic equipment. Advances in battlefield sensing, targeting, and communications devices have resulted in military vehicles with a wide array of electrical and electronic loads requiring power. These vehicles are typically designed to supply this power via a main internal combustion engine outfitted with a generator. Batteries are also incorporated to allow power to be supplied for a limited time when the engine is off. It is desirable to use a subset of the battlefield electronics in the vehicle while the engine is off, in a mode called “silent watch.” Operating time in this mode is limited, however, by battery capacity unless an auxiliary power unit (APU) is used or the main engines are restarted.

The industry strategy for automotive safety systems has been evolving over the last 20 years. Systems, such as frontal and side airbags, are available today on the worldwide market that provide proven safety benefits. Interest in advanced safety systems for occupant protection and accident avoidance, is focused on making further reductions in road fatalities and injuries. Interior occupant sensing systems for advanced restraint systems, trapped occupant sensing, and driver monitoring are today under intense development as part of the industry's safety vision. In this paper, we will discuss the need for and requirements of interior occupant sensing systems, as well as applicable technologies

In dynamic rollover tests many vehicles experience sustained body roll oscillations during a portion of road edge recovery maneuver, in which constant steering angle is maintained. In this paper, qualitative explanation of this phenomenon is given and it is analyzed using simplified models. It is found that the primary root cause of these oscillations is coupling occurring between the vehicle roll, heave and subsequently yaw modes resulting from suspension jacking forces. These forces cause vertical (heave) motions of vehicle body, which in turn affect tire normal and subsequently lateral forces, influencing yaw response of vehicle. As a result, sustained roll, heave and yaw oscillations occur during essentially a steady-state portion of maneuver. Analysis and simulations are used to assess the influence of several chassis characteristics on the self-excited oscillations. The results provide important insights, which may influence suspension design.

A typical problem that is encountered by drivers of vehicles with manual transmissions is rollback on an incline. This occurs when the driver is trying to coordinate the release of the brake pedal with the release of the clutch pedal and application of the accelerator all at the same time. If not done in harmony, the vehicle will roll down the incline. While the Hill Hold function is a highly desirable feature in manual transmission vehicles, it also enhances the driving experience in automatic transmission vehicles equipped with hybrid powertrains. The Hill Hold feature supports the Stop and Go performance associated with a hybrid powertrain by holding the vehicle on an incline and preventing undesired motion. The objective of this paper is to describe the implementation of the Hill Hold feature using an electric and / or a hydraulic brake control system. The paper describes the moding states in implementing the Hill Hold function at various levels of design complexity.

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.

Since more occupants are using rear seats of vehicles, a better understanding of priorities for rear occupant protection is needed as future safety initiatives are considered. A two-part study was conducted on occupant injuries in rear seating positions. In Part I, adult and teenage occupants ≥13 years of age are investigated. In Part II, children aged 4-12 years old and toddlers and infants aged 0-3 are studied separately because of the use of infant and child seats and boosters involve different injury mechanisms and tolerances. The objectives of this study on adult and teenager, rear-seated occupants (≥13 years old) are to: 1) review accident data, 2) identify the distribution of rear occupants, and 3) analyze injury risks in various crash modes, including rollovers, frontal, side and rear impacts. Three databases were investigated: NASS-CDS, GES and FARS.

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.

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.

In this paper the effects of rear brake imprecision on vehicle braking performance and yaw dynamics are investigated for a vehicle with individually controlled brake actuators. The effects of side to side brake force imbalance on vehicle yaw rate and path deviation during straight line braking and in braking in turn maneuvers are examined through analysis, simulations and vehicle testing. These effects are compared to the influences of disturbances encountered during normal driving such as side winds and bank angles of the road. The loss of brake efficiency due to imprecision in generating actuating force is evaluated for different types of vehicles and different levels of vehicle deceleration. Requirements regarding path deviation during straight line braking and braking efficiency on low friction surfaces were found to lead to the most stringent specifications for actuator accuracy in realizing the desired braking forces.

In this paper a method of mitigating the consequences of potential brake actuator failure in vehicles with brake-by-wire (BBW) and possibly with steer-by-wire (SBW) systems is described. The proposed control algorithm is based on rules derived from general principles of vehicle dynamics. When a failure of one actuator is detected, the algorithm redistributes the braking forces among the remaining actuators in such a way that the desired deceleration of vehicle is followed as closely as possible, while the magnitude and the rate of change of the yaw moment caused by asymmetric braking are properly managed. When vehicle is equipped with BBW system only, or when the desired deceleration can be obtained by redistributing of braking forces, without generating an undesired yaw moment, no steering correction is used. Otherwise, a combination of brake force redistribution and steering correction (to counter the yaw moment generated by non-symmetric braking) is applied.

In occupant sensing system development, the Anthropomorphic Test Dummy (ATD) and the Occupant Classification ATD (OCATD) are frequently used to simulate live human subjects in the testing and validation of weight based occupant sensing systems. A study was conducted to investigate the range of loading differences between these ATDs and live human subjects over various seating postures and conditions. The results of the study revealed that differences in seat load patterns could be significant, even though both the ATD and live humans are in the same weight and body size categories. Seat loading was measured using Hybrid III (5th percentile female, 50th percentile male, and 3 year old) ATDs, OCATDs (OCATD5 - 5th percentile female, and OCATD6 - 6 yr old child), and a CRABI (12-month old) dummy. Human subjects in the same weight and height categories as the above listed ATDs were also measured.

Implementation of engine turnoff at idle is desirable to gain improvements in vehicle fuel economy. There are a number of alternatives for implementation of the restarting function, including the existing cranking motor, a 12V or 36V belt-starter, a crankshaft integrated-starter-generator (ISG), and other, more complex hybrid powertrain architectures. Of these options, the 12V belt-alternator-starter (BAS) offers strong potential for fast, quiet starting at a lower system cost and complexity than higher-power 36V alternatives. Two challenges are 1) the need to accelerate a large engine to idle speed quickly, and 2) dynamic torque control during the start for smoothness. In the absence of a higher power electrical machine to accomplish these tasks, combustion-assisted starting has been studied as a potential method of aiding a 12V accessory drive belt-alternator-starter in the starting process on larger engines.

Electro-hydraulic actuation has been used widely in automatic transmission designs. With greater demand for premium shift quality of automatic transmissions, higher pressure control accuracy of the transmission electro-hydraulic control system has become one of the main factors for meeting this growing demand. This demand has been the driving force for the development of closed loop pressure controls technology. This paper presents the further research done based upon a previously developed closed loop system. The focus for this research is on the system requirements, such as solenoid driver selection and system latency handling. Both spin-stand and test vehicle setups are discussed in detail. Test results for various configurations are given.