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This paper presents a brake pressure estimation algorithm for Delphi Traction Control Systems (TCS). A control oriented lumped parameter model of a brake control system is developed using Matlab/Simulink. The model is derived based on a typical brake system and is generic to other types of brake control hardware systems. For application purposes, the model is simplified to capture the dominant dynamic brake pressure response. Vehicle experimental data collected under various scenarios are used to validate the algorithm. Simulation results show that the algorithm gives accurate pressure estimation. In addition, the calibration procedure is greatly simplified

Lithium-based battery technology offers performance advantages over traditional battery technologies at the cost of increased monitoring and controls overhead. Multiple-cell Lead-Acid battery packs can be equalized by a controlled overcharge, eliminating the need to periodically adjust individual cells to match the rest of the pack. Lithium-based based batteries cannot be equalized by an overcharge, so alternative methods are required. This paper discusses several cell-balancing methodologies. Active cell balancing methods remove charge from one or more high cells and deliver the charge to one or more low cells. Dissipative techniques find the high cells in the pack, and remove excess energy through a resistive element until their charges match the low cells. This paper presents the theory of charge balancing techniques and the advantages and disadvantages of the presented methods.

Recent advances in dependable embedded system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to actively pursue development programs in computer-controlled, by-wire subsystems. These subsystems include steer-by-wire and brake-by-wire, and are composed of mechanically de-coupled sets of actuators and controllers connected through multiplexed, in-vehicle computer networks; there is no mechanical link to the driver. This paper addresses fundamental benefits and issues of steer-by-wire, especially those related to automated vehicle control and steering feel quality as perceived by the driver.

Hybrid electric vehicles have the potential to reduce air pollution and improve fuel economy without sacrificing the present conveniences of long range and available infrastructure that conventional vehicles offer. Hybrid vehicles are generally classified as series or parallel hybrids. A series hybrid vehicle is essentially an electric vehicle with an on-board source of power for charging the batteries. In a parallel hybrid vehicle, the engine and the electric motor can be used to drive the vehicle simultaneously. There are various possible configurations of parallel hybrid vehicles depending on the role of the electric motor/generator and the engine. In this paper, a comparative study of the drivetrains of five different hybrid vehicles is presented. The underlying design architectures are examined, with analysis as to the tradeoffs and advantages represented in these architectures.

The lateral runout of disc brake corner components can lead to the generation of brake system pulsation. Emphasis on reducing component flatness and lateral runout tolerances are a typical response to address this phenomenon. This paper presents the results of an analytical study that examined the effect that the attachment of the wheel to the brake corner assembly could have on the lateral distortion of the rotor. An analysis procedure was developed to utilize the finite element method and simulate the mechanics of the assembly process. Calculated rotor distortions were compared to laboratory measurements. A statistical approach was utilized, in conjunction with the finite element method, to study a number of wheel and brake corner parameters and identify the characteristics of a robust design.

This work examines the development and implementation of a pulsing brake control system as part of a Forward Collision Warning (FCW) System for an Adaptive Cruise Control (ACC) prototype vehicle. The brake pulse is a likely candidate to be employed with visual and auditory cues in the event of an imminent collision alert level when the driver is not in ACC mode.

This paper presents the objectives and preliminary results of the BRAKE project - a joint effort of Delphi Automotive Systems, Infineon Technologies, Volvo Car Corporation and WindRiver. The objective of this project is to use microelectronics technologies to design a distributed Brake-by-Wire system including: A distributed fault tolerant system for enhanced safety An extension of the OSEK based operating system for a distributed time triggered architecture An open interface between vehicle control, and brake system control The results comprise the requirements, interface specification (see [1]), a full simulation model, a hardware-in-the-loop bench, and a demonstration vehicle. The application has been developed using advanced automatic code generation for Infineon's TriCore based automotive microcontrollers.

Today automotive system suppliers develop more-or-less independent systems, such as brake, power steering and suspension systems. In the future, car manufacturers like Volvo will build up vehicle control systems combining their own algorithms with algorithms provided by automotive system suppliers. Standardization of interfaces to actuators, sensors and functions is an important enabler for this vision and will have major consequences for functionality, prices and lead times, and thus affects both vehicle manufacturers and automotive suppliers. The investigation of the level of appropriate interfaces, as part of the European BRAKE project, is described here. Potential problems and consequences are discussed from both a technical and a business perspective. This paper provides a background on BRAKE and on the functional decomposition upon which the interface definitions are based. Finally, the interface definitions for brake system functionality are given.

In vehicular mobility context, it is extremely important for the environmental sustainability that the available energy will be used as efficiently as possible, both in the use of internal combustion engines (ICE) as powertrain, as well in the application of Hybrid and Electric Vehicle Motors (HEV/EV). In this comparison, ICE has a lower efficiency when compared to electric motors, wasting much of the potential energy of the fuel in form of heat and noise. On the other hand, the electric vehicles face limitation in autonomy and recharge time, demanding for a more efficient use of energy stored in batteries. This study aims to present emerging technologies for reuse of energy within the automotive context, originally known as “Energy Harvesting” and “Renewable Energies”.

This paper investigates a method for improving vehicle stability by incorporating feedback from a yaw rate sensor into an electric power steering system. Presently, vehicle stability enhancement techniques are an extension of antilock braking systems in aiding the driver during vehicle maneuvers. One of the contributors to loss of vehicle control is the reduction in tactile feedback from the steering handwheel when driving on wet or icy pavement. This paper presents research indicating that the use yaw rate feedback improves vehicle stability by increasing the amount of tactile feedback when driving under adverse road conditions.

Brake squeal phenomenon often involves modal coupling between various component modes. In order to reduce or eliminate squeal, it is very important to understand the coupling mechanism so that the key component(s) can be modified accordingly. This paper demonstrates a quantitative method to define system mode shapes using the concept of modal participation factors. This method is implemented on a front disc brake system to identify the modal coupling mechanism associated with its high frequency squeal. Complex eigenvalue analysis is carried out and the squeal frequency is correlated. System mode shapes are then processed with an in-house program to calculate modal participation factors based on a complex MAC (Modal Assurance Criteria) algorithm. The coupling mechanism is identified and possible countermeasures are discussed.

Fuel cells show great promise in generating electrical power for a variety of uses. In the automotive realm, one focus has been on the use of fuel cells for primary vehicle propulsion. Another emerging application is the fuel cell as the primary provider of electrical power to the vehicle, augmenting or replacing the traditional alternator, while producing higher power levels. The advantage of the fuel cell in this role is that the fuel cell operation is de-coupled from that of the engine. High power levels can be achieved independent of engine speed and power can be produced without the engine running. This paper examines the application of a fuel cell auxiliary power unit (APU) to a dual-voltage 42V/14V automotive electrical system meeting the evolving 42V PowerNet specifications. An architecture for this electrical system is presented, followed by a sizing analysis to properly match the fuel cell stack to the voltage of the PowerNet and to a 42V battery pack.

The automotive industry is moving to a higher voltage for the electrical system. This change will occur because the total electrical power required by the vehicles will increase to a level where the current requirements at 14 volts will be impractical. Some of the new loads will change the duty cycle of the battery. The most notable change is the proposed start/stop mode of vehicle operation where the engine is stopped and restarted frequently to avoid prolonged operation at idle. An additional feature would be to use an electric motor to assist in acceleration and/or to actually launch the vehicle. This paper addresses the changes in battery requirements brought on by these new features. A means of analysis for choosing the appropriate battery technology is presented. We also propose a life test to establish a benchmark for current battery technology when it is used in a new duty cycle.

This paper documents the advantages of brake corner system modeling and simulation over traditional component analysis techniques. A better understanding of the mechanical dynamics of the disc-braking event has been gained through brake corner system modeling and simulation. Single component analyses do not consider the load transfer between components during the braking event. Brake corner system analysis clearly quantifies the internal load path and load transfer sequence between components due to clearances or tolerance variations in the brake assembly. By modeling the complete brake corner assembly, the interaction between components due to the contact friction loads and variational boundary conditions can be determined. The end result permits optimal design of brake corner systems having less deflection, lower stress, optimum material mass, and reduced lead-time for new designs.

Long repetitive braking, such as one which occurs during a mountain descent, will result in a brake fluid temperature rise and may cause brake fluid vaporization. This may be a concern particularly for passenger cars equipped with aluminum calipers and with a limited air flow to the wheel brake systems. This paper describes the computer modeling techniques to predict the brake fluid temperature rise as well as other brake component temperatures during braking and heat soaking. Numerical results are compared to the measured vehicle data and the effects of relevant brake system parameters on the fluid temperature are investigated. The techniques developed in this study will help brake engineers to build a safer brake system and reduce the extensive vehicle tests currently required.

The severe thermal distortion of a brake rotor can affect important brake system characteristics such as the system response and brake judder propensity. This paper will propose a technique to determine the thermal distortion under transient or steady state conditions. The technique involves utilizing a PC-based computer program to calculate the necessary thermal parameters and apply the results as input to a finite element-based thermal stress analysis. This unique approach provides a reliable methodology to determine the heat input and cooling characteristics of a given brake system in addition to resultant distortion and stress components within the brake rotor. Analysis results are also compared to measured temperature and distortion data.

A front disc brake system is used as an example for an investigation of low frequency squeal. Many different modifications to this disc brake system have been proposed and this paper focuses on a solution that reduces the stiffness of the rotor. This is accomplished by a reduction in the Young's modulus of the rotor material. The complex eigenvalue method is used for a detailed analytical study in order to obtain a better understanding of this solution technique. Modal participation factors are calculated to examine the modal coupling mechanism. Parametric studies are also performed to find out the effects of friction coefficient and rotor stiffness. Results show that shifting rotor resonance frequencies may ecouple the modal interaction and eliminate dynamic instability, which is in agreement with experimental results.

This paper describes a semi-active damping control system that responds in real-time to road and driving conditions based on body motions as determined through ABS wheel speed sensors. The use of these existing sensors for vehicle information eliminates the need for the additional sensors (e.g. accelerometers and body-to-wheel position/velocity sensors) that are commonly part of semi-active suspension systems. This technology also allows for further cost and part count reductions through the combination of the suspension and brake controls into a single electronic control unit. This paper has been previously presented in 1998 at the SAE Controlled Suspension System Toptec.

A double dielectric barrier discharge reactor driven by an alternating voltage is a relatively simple approach to promote oxidation of NO to NO2 for subsequent reduction in a catalyst bed. The chemical performance of such a non-thermal plasma reactor is determined by its current and electric field behavior in the gap, and by the fraction of the current carried by electrons, because the key reactants which initiate the NO oxidation and accompanying chemical changes are produced there, mostly by electron impact. We have tried to determine by models and experiments the bounds on performance of double dielectric barrier reactors and guidelines for optimization. Models reported here predict chemical results from time-resolved applied voltage and series sense capacitor data.

CFD analysis was performed using the FLUENT software to design the thermal system for a hybrid vehicle battery pack. The battery pack contained multiple modular battery elements, called bricks, and the inlet and outlet bus bars that electrically connected the bricks into a series string. The simulated thermal system was comprised of the vehicle cabin, seat cavity, inlet plenum, battery pack, a downstream centrifugal fan, and the vehicle trunk. The fan was modeled using a multiple reference frame approach. A full system analysis was done for airflow and thermal performance optimization to ensure the most uniform cell temperatures under all operating conditions. The mesh for the full system was about 13 million cells run on a 6-node HP cluster. A baseline design was first analyzed for fluid-thermal performance. Subsequently, multiple design iterations were run to create uniform airflow among all the individual bricks while minimizing parasitic pressure drop.