Browse Topic: Brake-by-wire

Items (48)
Simulation Based Control Strategy Design of All Wheel Drive Electric Vehicle Regenerative Braking System2018-01-04114/3/2018
Maximising the recovered regenerative braking energy during the deceleration can significantly reduce the Electric Vehicle (EV) energy consumption and increase the range. Compared with the Front Wheel Drive (FWD) or Rear Wheel Drive (RWD) EV, an All Wheel Drive (AWD) EV with 2 electric machines (e-machines) has more control degree freedom when developing the regenerative braking control strategy. By implementing the regenerative braking at the front axle, rear axle, or at the front and rear axles simultaneously, the amount of recovered kinetic energy will be affected. Furthermore, the e-machines at the front and rear axle in the AWD EV can have different sizes or be the same. Therefore, the ratio between front and rear e-machine power rating should also be investigated to understand its effect on the amount of recovered energy during deceleration. This paper starts with the analysis of the vehicle braking behaviour compared over different driving cycles, and the comparison of two configurations of regenerative braking system, Category A and B. Then, the AWD EV is modelled, and its regenerative braking controller is developed using Ricardo in-house, proprietary simulation tools. The power rating of front and rear axle e-machines in this model is varied. The regenerative braking controller simulates Category A or B regenerative braking system with various control strategies (such as front axle or rear axle only regenerative braking, and all wheel regenerative braking). Simulation is done to investigate: 1) the difference in recovered energy by implementing the regenerative braking at different axles with Category A or B systems, and 2) how the ratio between the front and rear axle e-machine power rating affects the amount of recovered regenerative braking energy. This in turn affects the overall brake balance distribution and impacts upon vehicle stability. Finally, the simulation result is analysed and discussed.
Bao, RanGriggs, PhilipBaxter, James
2021-12-29.TEST Design and Implementation of Adaptive Range LIDAR System (ARLS) for Autonomous Braking Assistance at High Speeds in Automobiles2018-01-00404/3/2018
Autonomous braking systems are prevalent in mid/upper-mid range vehicles today. The major drawback: acute boundary condition during which the system will function. The paper describes the implementation of Adaptive Range LIDAR Systems (ARLS) containing a state of the art collimator and wave shaper with a 140̊ sweep MEMS mirror, capable of calculating beam convergence as a function of distance, considering multiple obstacles ahead of it. The paper also describes the use of ARLS for ACC (Adaptive Cruise Control) and Autonomous braking, reinforcing the available software structure with more data points. Contrary to the other systems that detect objects/obstacles from a stationary point of reference, ARLS determines the velocity of obstacle with respect to the ground point of reference and computes most optimum brake effort curve. The brake curves are alike for every situation, as it is dynamic in nature, hence, additional electronics ensure physical curve tracing by manipulating the braking circuitry, or in some vehicles, by providing feedback to the Electronic Brakeforce Distribution Systems. Also, since the brake effort curve is dynamic with respect to time, rigorous braking is not imposed on the passenger, and that the retardation is smooth and well distributed in time.
Mishra, Jainendra
Estimation of Brake Friction Coefficient for Blending Function of Base Braking Control2017-01-25209/17/2017
The brake architecture of hybrid and full electric vehicle includes the distinctive function of brake blending. Known approaches draw upon the maximum energy recuperation strategy and neglect the operation mode of friction brakes. Within this framework, an efficient control of the blending functions is demanded to compensate external disturbances induced by unpredictable variations of the pad disc friction coefficient. In addition, the control demand distribution between the conventional frictional brake system and the electric motors can incur failures that compromise the frictional braking performance and safety. However, deviation of friction coefficient value given in controller from actual one can induce undesirable deterioration of brake control functions. The main objective of the presented study is to propose a method to compensate disturbances induced by variations of brake linings friction coefficient through modifications of the brake torque demand for the enhancement of both brake performance and active safety. The achievement of a compensation mechanism requires the estimation of relevant vehicle states. Hereunto, a novel technique based on a linear Kalman observer is proposed for the online estimation of the brake friction coefficient by relying upon the wheel speed sensors and inertia measurement unit (IMU). Such a tool enables a more efficient use of the frictional brakes aimed at minimizing losses of friction coefficient by keeping them in the optimal operational conditions. A simulation analysis will be carried out using the commercial vehicle dynamics simulation software IPG CarMaker to test the functionality of the developed estimator in the real-time mode. Experimental results from brake dynamometric test rig will be considered in the vehicle dynamics simulation software to reproduce the real behaviour of brake linings friction coefficient. The resulting improvements in brake control functions will be analysed against longitudinal base braking cases involving blending functions also in presence of failure of the electric motors.
Ricciardi, VincenzoSavitski, DzmitryAugsburg, KlausIvanov, Valentin
Research on Vehicle Stability Control Strategy Based on Integrated-Electro-Hydraulic Brake System2017-01-15653/28/2017
A vehicle dynamics stability control system based on integrated-electro-hydraulic brake (I-EHB) system with hierarchical control architecture and nonlinear control method is designed to improve the vehicle dynamics stability under extreme conditions in this paper. The I-EHB system is a novel brake-by-wire system, and is suitable to the development demands of intelligent vehicle technology and new energy vehicle technology. Four inlet valves and four outlet valves are added to the layout of a conventional four-channel hydraulic control unit. A permanent-magnet synchronous motor (PMSM) provides a stabilized high-pressure source in the master cylinder, and the four-channel hydraulic control unit ensures that the pressures in each wheel cylinder can be modulated separately at a high precision. Besides, the functions of Anti-lock Braking System, Traction Control System and Regenerative Braking System, Autonomous Emergency Braking can be integrated in this brake-by-wire system. A sliding mode variable structure vehicle dynamics stability controller based on hierarchical control framework is built in MATLAB/Simulink. The I-EHB actuator model and vehicle dynamic model with 15 degrees of freedom are built in simulation package AMESim through a parameterized and modularized method. Simulations are conducted via co-simulation platform using MATLAB/Simulink and AMESim under scenarios of the typical braking and NHTSA FMVSS 126 standard-Sine With Dwell. Simulation results show that hydraulic braking forces are coordinated well during typical braking process, verifying the feasibility and effectiveness of the models built and the control strategy proposed. Under Sine With Dwell maneuver, compared with the base systems equipped without/with the conventional ESP, the proposed stability control system has a good improvement on the vehicle dynamics.
He, XiangkunYang, KaimingJi, XuewuLiu, YahuiDeng, Weiwen
Analysis of Energy Consumption on Typical Main Cylinder Booster Based Brake-by-Wire System2016-01-19559/18/2016
The traditional vacuum booster is gradually replaced by Brake-by-Wire system (BBW) in modern passenger car, especially Electric Vehicle (EV). Some mechanical and hydraulic components are replaced by electronic components in Brake-by-Wire system. Using BBW system in modern passenger vehicles can not only improve the automotive safety performance, reliability and stability, but also promote vehicle maneuverability, comfort, fuel economy and environmental protection. Although vehicle's braking performance is greatly improved by using BBW, the system will inevitably consume some energy of the vehicle power supply, thus introducing unexpected drawback in comparison with the traditional vacuum assist braking system, since it doesn't need any electric power. Therefore, the analysis of energy consumption on typical main cylinder booster based BBW system under typical driving cycles will contribute to advanced design of current advanced braking system. In this paper, energy consumption of the typical main cylinder booster based BBW system is simulated by changing the brake response time and reduction ratio of the system under different driving cycles. The average power needed of conventional BBW system is also calculated. Energy consumption of the conventional and typical main cylinder booster based BBW systems is compared. The results show that the energy consumption of the typical main cylinder booster based BBW system is around 30W∼60W which is obvious better than the conventional BBW system with power need of 500W under typical driving cycles, such as USDC, EDC and JDC. The energy consumption of the Brake-by-Wire system can be reduced obviously through an optimal design on parameters of the system's actuator.
Yu, LiangyaoLiu, XiaohuiLiu, Xiaoxue
ASURT Formula Student Brake Design2014-01-24879/28/2014
The Braking System is the most crucial part of the racing vehicle. There is no doubt, that if only one minority failure in the braking system took place, this would be more than enough reason to cause the racing team disqualification from the competition. Time is the main and the most important criteria for any racing competition; on the other hand the formula student “FS UK SAE” competition care the most about developing the automotive engineering sense in the students by putting them under strict rules normally taken from the original version “formula 1” to encourage their creativity to reach the optimum performance under these strict rules. One of the most important rules is “No Braking by wire”, and the obvious consequences are more stopping distance and time. Braking distance is a critical facture in achieving racing success in a competitive domain. This report will cover using the bias bar, dynamic weight distribution “before and after braking” and carefully choosing the braking and suspension system components dimensions, in order to fulfill the main functions of “ABS and EBD” which are preventing the wheels from lock-up and preventing side skid of the vehicle during cornering in the different dynamic tests with full consideration of the maximum approachable deceleration of the vehicle without locking up without using any kind of electronic “actuators or control”. Mathematical model “Matlab” and Physical model “AME SIM” will be used to support the report's results.
Barakat, Mohamed Samy
Electro-Mechanical Brake for Front Wheel with Back-up Braking2014-01-25389/28/2014
Electro-Mechanical Brake (EMB) is the brake system that is actuated by electrical energy and has a similar design with the Electric Parking Brake (EPB). It uses motor power and gears to provide the necessary torque and a screw & nut mechanism is used to convert the rotational movement into a translational one. The main difference of EMB compared with EPB is that the functional requirements of components are much higher to provide the necessary performance for service braking such as response time. Such highly responsive and independent brake actuators at each wheel lead to enhanced controllability which should result in not only better basic braking performance, but also improvements in various active braking functions such as integrated chassis control, driver assistance systems, or cooperative regenerative braking. Although the EMB system has the potential for numerous advantages and innovations in braking, it has yet to be successfully introduced in series production mainly due to safety and cost concerns. Recent studies have been made to investigate the functional safety aspects[1] and additional mechanical backup measures[2] in this regard. Although the EMB is conventionally thought of as a solution for oil-free braking system[3-4], the EMB system introduced in the current paper includes a hydraulic piston to make several functions possible. First, the hydraulic system allows for a mechanical back-up mechanism that leads to increased reliability. Second, the clamping force for braking control can be measured with a pressure sensor. And finally, the dual piston structure proposed in the current paper, which leads to amplification of the force transmission, allows for the design of lower specification and higher cost effective motor and gear components. This new concept of EMB is termed the hEMB (hybrid EMB) in this paper. This study proposes to use a combined system of front hEMB and rear hydraulic caliper. This type of system has the potential of providing many advanced braking functions without the high cost associated with fully electric four wheel brake by wire systems. Prototypes of hEMB actuators were made and attached in a test vehicle. Results of bench and vehicle tests will be given to show the functionality of the system.
Kim, JongsungJo, ChjhoonKwon, YongsikCheon, Jae SeungPark, Soung JunJeon, Gab BaeShim, Jaehun
Novel Mechanism Using Differential Gears for the Electromechanical Brake2014-01-03844/1/2014
As is well known, the brake systems of vehicles are used in order to decelerate or stop the vehicle while the driving. The operational principle of the brake is the conversion of kinetic energy into thermal energy. In this case, the thermal energy is released to the atmosphere. Recently, electromechanical brakes (EMB) were developed in order to replace hydraulic brake calipers. Such brake-by- wire systems are composed of an electronic pedal, electronic control unit (ECU), wire, and an electromechanical caliper. A typical electromechanical brake is similar to existing floating brakes. In other words, an inner pad pushes out one side of a disc driven by the energy of a motor; by means of a screw-thread gear. Then, the caliper slides in the opposite direction by reaction force and moves the outer pad toward the other side of the disc. Then pads clamp both sides of the rotating disc and stop the wheel. While effective, this design has the problem that there is a difference in the wear of the inner and outer pads. In this paper, we describe a novel electromechanical brake design. Specifically, the proposed mechanism has some new features related to the presence of differential, and rack-pinion, gears. Furthermore, the wear difference of the inner and outer pads can be minimized by using our proposed mechanism. So to speak, both pads are clamped at the same time by the initial braking force. In addition, we focused on how to use the device to improve the braking force during the initial braking.
Park, Tae-SangJin, SunghoMoon, Jeon ILYang, Seung-Han
Regenerative Braking Control Algorithm for an Electrified Vehicle Equipped with a By-Wire Brake System2014-01-17914/1/2014
Regenerative braking, which can effectively improve vehicle's fuel economy by recuperating the kinetic energy during deceleration processes, has been applied in various types of electrified vehicle as one of its key technologies. To achieve high regeneration efficiency and also guarantee vehicle's brake safety, the regenerative brake should be coordinated with the mechanical brake. Therefore, the regenerative braking control performance can be significantly affected by the structure of mechanical braking system and the brake blending control strategy. By-wire brake system, which mechanically decouples the brake pedal from the hydraulic brake circuits, can make the braking force modulation more flexible. Moreover, its inherent characteristic of ‘pedal-decouple’ makes it well suited for the implementation in the cooperative regenerative braking control of electrified vehicles. With the aims of regeneration efficiency and braking performance, a regenerative braking control algorithm for electrified vehicles equipped with a brake-by-wire system is researched in this paper. The layout of the adopted brake-by-wire system is introduced. The proposed regenerative braking control algorithm is illustrated. To validate the control performance of the algorithm, hardware-in-the-loop simulations are carried out. The simulation results show that, based on brake-by-wire system, the proposed control algorithm, coordinating regenerative brake and hydraulic brake well, can further improving the regeneration efficiency of electrified vehicle and guarantee the braking performance in the meantime.
Lv, ChenZhang, JunzhiLi, YutongYuan, Ye
Multi-Objective Optimization and Robust Design of Brake By Wire System Components2013-01-20599/30/2013
A Brake By Wire (BBW) system is generally composed of electro-mechanical calipers at each wheel, a pedal simulator and a central controller. The brake demand is processed by the pedal and the central controller commands the brake distribution for each brake actuator. The highly responsive and independent brake actuators lead to enhanced controllability which should result in not only better basic braking performance, but also improvements in various active braking functions such as integrated chassis control, driver assistance systems, or cooperative regenerative braking. Although the BBW system has the potential for numerous advantages and innovations in braking, it has yet to be successfully introduced in series production mainly due to safety and cost concerns. Recent studies have been made to investigate the functional safety aspects and additional mechanical backup measures in this regard. Another area that needs to be considered is the optimization of key BBW system components to increase product competitiveness and cost effectiveness. In this study, optimization and robust design was carried out for the Electric Wedge Brake (EWB) caliper and the pedal simulator. First, the EWB actuator has a very uncommon wedge mechanism that needs to be designed in the caliper housing. This can lead to various designs of the caliper that can easily grow in size and weight. An optimal design is needed in order for the caliper to have a package competitive size while at the same time maintaining required stiffness. Second, the pedal simulator is the direct connection to the driver that provides the actual braking pedal feel. Thus it is imperative that the pedal simulator is designed to give driver friendly pedal feel without sacrificing its structural integrity. The multi-objective robust design concept based on the Non-dominated Sorting Genetic Algorithm-ii (NSGA-ii) was used as the optimization method in this investigation. This method considers multiple objective functions and external noise factors, and uses self-learning weight factors. The objective functions for the EWB caliper and pedal simulator were designated as caliper weight and stiffness, and pedal feel and rubber stiffness, respectively. And variations in operation direction were considered as the noise factors for both designs. Finally, Finite Element Analysis (FEA) based on the Design of Experiments (DOE) procedure was used to obtain data to define the objective functions and the resulting robust optimal designs were verified using FEA analyses and experiments.
Kwon, YongsikKim, JongsungCheon, Jae SeungMoon, Huyng-ilChae, Ho Joong
Energy and Timing Advantages of Highly Non-Linear EMB Actuation2013-01-20679/30/2013
With linear actuated brakes the actuation force (or torque) rises linearly from 0 to the full actuation force at full braking. This means that the actuation must be designed for the rare case of full-braking. The parts must be designed for this peak load (e.g. motor, gear) and the transmission ratio is determined by the full-braking actuation torque, which causes the highest transmission ratio and hence determines slow actuation dynamic. Ideally the actuation should make the fastest travel at low normal force and turn to slow movement and high force at the highest pad force. Mathematically the torque transmission ratio should optimally be an exact representation of the actuation characteristics (actuation torque over actuation movement), creating the highest torque-transmission ratio at highest force and the fastest movement at low pad force. This highly non-linear actuation characteristics means that the actuator motor is always running on constant load (although the pad pressing force changes dramatically). The resulting actuation timing is the fastest possible, because the actuation is as fast as possible at low force. The actuator electro motor is running at constant-load and hence can be operated in best efficiency, making the electrical power consumption the lowest possible. How can the optimal, variable transmission ratio (that is mathematically given by the actuation characteristics) be achieved in reality at the Vienna-Engineering EMB (Electro Mechanical Brake)? Firstly the VE-EMB has a non-linear actuation due to the principle of the eccentrics, which are turned to press the pad to the disc. Secondly the VE-EMB uses an approx. 90° angle-range at the eccentrics, making it easy to insert a non-linear gear between eccentrics and the motor gear. It is shown how the behavior can be optimized to the mathematical needs and how the characteristics can cover a wide range of changing transmission ratio. It is also discussed how the optimized non-linearity also assists to turn the brake back to “released” in the power-off case: At high actuation force the VE EMB always automatically rolls back to released by the high internal force and its efficiency of 90% and higher. At low force any EMB must overcome the motor cogging (“snapping” and friction) to roll back to released at power-off. The highly non-linear actuation of the VE-EMB makes it far easier, because at low force the transmission ratio turns to “fast pad movement”, assisting in turning the motor from the side of the pad-force. The VE-EMB Simulator is a detailed (and calibrated) representation of the brake in software, making it easy to accurately study improvements. It also can be used to study linear actuation on the same brake with the same motor. So this work also discusses timing and energy advantages by optimizations in the VE EMB and it also compares it to linear actuated brakes (e.g. screws, electro-over-hydraulic). By these optimizations an extremely simple EMB with the smallest possible electro motor can be shown.
Putz, Michael HerbertWunsch, ChristianMorgan, JohnSchiffer, MarkusBrugger, Johannes
An Approach to Vehicle Brake-By-Wire Optimal Control Tracking Strategy2013-01-06864/8/2013
In this paper, an optimal control tracking strategy for a brake-by-wire system is developed and tested on a laboratory setup consisting of a driving motor, clutch and gearbox system, rotating inertia and an electro-mechanical brake actuator. The presented brake by wire system consists of a brake pedal sub-system connected to the electro-mechanical brake actuator through an electronic control module handling the optimal control logic. A mathematical model of the proposed brake-by-wire control system is presented. The presented mathematical model is simulated and validated against the experimental data. The good agreement between both simulation results and experimental validates the mathematical model. The validated mathematical model is then used to test the proposed optimal control tracking strategy against different levels of disturbances that are difficult to emulate in the laboratory. The developed control logic ensures optimal control effort of the electro-mechanical brake actuator and, at the same time, efficient tracking between the brake pedal command and the braking deceleration profile. Consequently, the introduced logic plays a major role in keeping the tracking between the braking system command and its output as high as possible while not sacrificing the power supply (i.e. high drained electric current) in case of emergency situations. This provides acceptable braking performance while maximizing the system battery life and protects the brake actuator driver against high current.
Haggag, Salem A.Abidou, Diaa
A Control Allocation Algorithm for Improving the Fail-Safe Performance of an Electric Vehicle Brake System2013-01-01874/8/2013
The ample electrical power supply makes brake-by-wire technology more suitable for application in electric vehicles than in conventional vehicles. The fail-safe performance of a brake-by-wire system is a key factor regarding its application on production vehicles. A new control allocation algorithm for improving the fail-safe performance of an electric vehicle brake system is proposed. The electric vehicle is equipped with a four-wheel independent brake-by-wire and steer-by-wire system. The main objective of the algorithm is to maintain the vehicle braking performance as close to the desired level as possible by reallocating the control inputs to the actuators in cases of partial or full failure of the brake-by-wire system. The control algorithm is developed using a two degrees of freedom vehicle model. A pseudo control vector is calculated by a sliding mode controller to minimize the difference between the desired and actual vehicle motions. A pseudo-inverse controller then allocates the control inputs according to the pseudo control vector and the failure mode which is assumed to have been determined by some diagnostic algorithms. The control algorithm is evaluated in Matlab/Simulink. Cases of the brake-by-wire system's partial failure and full failure are all covered while performing the simulations. In cases of partial failure, the control algorithm reallocates the braking forces to the failure-free wheels and corrects the steering angles of the four wheels to compensate the yaw moment generated by the possible asymmetric braking. In the case of full failure, the wheels on each of the two axles are steered in opposite directions to generate braking forces. Simulation results show that the algorithm works effectively to ensure safe braking in case of brake system failures.
Feng, ChongDing, NenggenHe, YonglingXu, GuoyanGao, Feng
New Brake By Wire Concept with Mechanical Backup2012-01-18009/17/2012
Brake-By-Wire (BBW) is a term used to describe next generation brake systems that rely on motor driven electro-mechanical calipers in place of conventional hydraulic components such as the booster, master cylinder, hydraulic unit, and parking brake. Instead the system configuration is simplified to a pedal simulator, electro-mechanical calipers that require no boosting, and electric control units. The active, highly-responsive, and independent control of the brake actuators at each wheel allows for great control flexibility and improved brake performance. It is also very well-suited for easy integration with cooperative regenerative braking and driver assistance functions. Although such potential and innovations have driven the interest and research into BBW systems through the years, it has yet to be successfully introduced in series production mainly due to the underlying perception of the lack of reliability of electronic components and overall cost concerns. In the current investigation, a new concept of BBW system is proposed as a step towards overcoming such hurdles. The proposed concept provides a mechanical backup function that does not deter the system from the original performance benefits of a BBW system. It is hoped that such an addition, which provides emergency braking capability with no electrical power, will give the BBW system the ultimate reliability that can help persuade its penetration into the brake market. This system also has the potential to reduce the overall cost of the system since reliance on complex system architectures, redundancies, and highly reliable electrical components can be reduced. This study will investigate the feasibility and basic performance of the proposed BBW concept. First, prototype actuators for the proposed system were designed and manufactured. After checking the samples in bench tests, the actuators were built into a car to access the braking capability of the system.
Cheon, Jae SeungKim, JongsungJeon, Jaehan
Effects of Titanates in Low Steel Formulation: Prevention of Metal Pick Up Growth2012-01-17859/17/2012
Titanates are currently used in friction materials worldwide. This study investigates the effects of titanates in friction materials with Low Steel (LS) formulations. A kind of titanate compound is examined with a LS formulation. Test pieces both with and without the titanate are examined using small rotors of gray cast iron. The frictional performance tests use a 1/7 scale dynamometer. The surfaces and the cross-sections are closely observed using a Scanning Electron Microscopic analyzer. Results of the testing on samples without the titanate suggest that frictional effectiveness is sensitive to the load value especially in high speed braking conditions. A Metal Pick Up (MPU) phenomenon, which is one of the significant problems of friction materials, also occurs. The millimeter-sized picked-up metals consist of micron-sized wear debris of iron. The crystalline transformation of the steel fibers around the picked up metals is investigated. Results show that the crystalline structure of the steel fibers changes from ferrite to martensite. This results in hardening of the steel fibers. The frictional effectiveness may become unstable due to these changes. On the other hand, frictional effectiveness in high speed braking conditions is stabilized in the samples containing the titanate. The MPU phenomenon and the hardening of steel fibers are not found. Titanates seem to have the effect of stabilizing frictional effectiveness by preventing the MPU phenomenon in high speed braking conditions. There is a reason to suggest that titanates might be better classified as “modifiers” rather than lubricants or abrasives in LS formulations.
Kamada, ShogoInada, Kousuke
Brake By Wire Functional Safety Concept Design for ISO/DIS 262622011-01-23579/18/2011
The importance of functional safety design has recently grown with the increasing widespread application of electric/electronic (E/E) systems in today's automotive industry. Such E/E systems, usually composed of mechatronic actuators, various sensors, and electronic control units (ECU), have become too complex to be handled in the conventional quality management manner that was used for most predominantly mechanical applications. ISO/DIS 26262, an adaptation of the pre-existing IEC 61508 requirements specifically for the automotive industry, has been prepared as the global standard to meet such demands for a more structured and systematic approach to functional safety design. The functional safety concept design includes a hazard analysis and risk assessment phase that is based on ASIL (Automotive Safety Integrity Level) categorization. ASIL has four levels, A, B, C, and D, where A has the lowest risk and D has the highest. In this study, the concept phase of this ISO26262 standard for application to the Brake-by-Wire (BBW) system will be investigated. A BBW system is one in which the existing hydraulic system is replaced by motor driven electro-mechanical calipers. In this system a pedal simulator is used to provide pedal feel and recognize the driver brake demand. This demand signal is sent to the main controller which controls the independent actuators at each wheel. The target system structure of the current study is composed of conventional electro-mechanical brakes (EMB) on the rear axle and electric wedge brakes (EWB), which use self-reinforcement through the vehicle kinetic energy, on the front. Development of BBW began in the late 1990s but has yet to successfully be introduced in series production mainly due to cost, reliability, and safety concerns. The current investigation is an attempt to take a step forward in tackling the safety concerns.
Cheon, Jae SeungKim, JongsungJeon, JaehanLee, Sang Mok
Semiconductor Solutions for Braking Systems: New Partitioning and New Safety Concepts Increase Safety and Reduce System Cost2004-01-02513/8/2004
Braking systems require a high system safety level: New safety concepts need to be implemented by reducing the system complexity. Microcontrollers with special safety functions are available with implemented features, self detecting and compensating different types of faults. Today usually two microcontrollers are used to check each other. Power devices provide microcontroller supplies and drive motors and valves; internally the functions are supervised to avoid incorrect system behaviour due to wrong voltages, currents, missing loads or other malfunctions. Bus interfaces, signal conditioning and interfaces for high voltage signals are integrated into the power system ICs. Latest BIPOLAR-CMOS-DMOS power technologies enable the power semiconductors to integrate logic functions. This capability drives new partitioning of power ICs and microcontroller in ABS and ESP systems: Calculation tasks and microcontroller supervision functions migrate from the microcontroller into the power devices - Power devices get intelligence. Today, the microcontroller is loaded with current measurement and the generation of duty cycles to control the target pressure for each wheel. Intelligent power devices take over the current regulation control loop. The increasing data transfer between components and modules requires advanced interfaces as well as enhanced data coding and supervision. New balancing between the pure CMOS microcontroller and BCD mixed-signal power ICs is established. Individual component cost may increase, but the overall system cost is reduced with a higher safety level.
Diermeier, Andreavon Wendorff, Wilhard
Customer Orientation: A Further Target in Brake System Design2003-01-05993/3/2003
The attention to the perceived quality, e.g. the quality as it is evaluated by the final customer, is becoming more and more important for the car makers. The paper describes how such aspects of braking system feel quality, joined with brake thermal constraints and interactions with other vehicle subsystems, such as suspensions, tyres and rims, can become manageable by an engineering process. In order to do that experienced designers define: longitudinal brake performance, stability limits in braking in a turn by comparison with referenced cars; brake thermal constraints; brake system constraints due to interactions with other vehicle subsystems. For perceived quality, on the other hand, it's necessary to take a different kind of approach in order to define targets. Some fundamental and different steps are necessary: the definition of measurable performance for the subjective aspects; the identification of the target values for such aspects coherent with product positioning; the deployment of such overall values generally fixed at “system” level into sub targets at subsystem level expressed by measurable and predictable quantities. A design procedure has been developed which allows one to define braking subsystem main parameters (longitudinal tyre characteristics; disc, piston and pad dimensions; coefficient of friction; brake balance; pedal ratio, vacuum-assisted brake booster, pump, lines and calliper characteristics) during brake system design, using at first simple models and then other more and more complex subsystems and vehicle models. The targets of the procedure are objective indexes calculated in the processing of normalised road tests data and correlated with subjective evaluations of normal and professional drivers. These indexes are the output of the simulation since the earliest design phase and become the “virtual subjective evaluation” of the vehicle model. This new approach at car advanced design represents an evolution of the traditional approach because it tries to merge customer orientation with general criteria defined by experienced designers. The approach has been used with success during specification for innovative systems, such as brake by wire. In this case, since the connection between brake pedal and tyres is not mechanical, it is possible to impose the brake pedal feel defining the response of pedal group (travel and effort feel) and the characteristics for corners actuators (deceleration feel). In general, the methodology that will be described has the aims of reducing time to market and guaranteeing a “customer oriented fingerprinting” in braking performance and feel.
Pascali, LeonardoRicci, ClaudioCaviasso, GuglielmoPetruccelli, Luigi
Future Electrical Steering Systems: Realizations with Safety Requirements2000-01-08223/6/2000
Additional future requirements for automobiles such as improved vehicle dynamics control, enhanced comfort, increased safety and compact packaging are met by modern electrical steering systems. Based on these requirements the new functionality is realized by various additional electrical components for measuring, signal processing and actuator control. However, the reliability of these new systems has to meet the standard of today's automotive steering products. To achieve the demands of the respective components (e.g. sensors, bus systems, electronic control units, power units, actuators) the systems have to be fault-tolerant and/or fail-silent. The realization of the derived safety structures requires both expertise and experience in design and mass production of safety relevant electrical systems. Beside system safety and system availability the redundant electrical systems also have to meet economic and market requirements. Within this scope the paper discusses three different realizations of electrical steering systems 1 Electrical power steering system (mechanical system with electrical boosting) 2 Steer-by-wire system with hydraulic back-up and 3 Full steer-by-wire system The paper presents solutions for these systems and discusses the various advantages and disadvantages, respectively. Furthermore strategies for failure detection, failure localization and failure treatment are presented. Finally the various specifications for the components used are discussed.
Harter, WernerPfeiffer, WolfgangDominke, PeterRuck, GerhardBlessing, Peter
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