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especially useful in a noisy environment. Because of these reasons, resolvers are usually applied for the purpose of position and speed measurement in brake-by-wire systems. However, nonlinear and robust observers are required to extract accurate position and speed estimates from the sinusoidal signals provided by resolvers.
347:
Some x-by-wire technologies have been already installed on commercial vehicles such as steer-by-wire, and throttle-by-wire. Brake-by-wire technology has been widely commercialized with the introduction of
Battery Electric Vehicles and Hybrid Vehicles. The most widely used application by Toyota in the
780:
between the clamp force sensor and the point of contact of an inner pad with the rotor. This hysteresis prevents a true clamp force to be measured. Due to the cost issues and engineering challenges involved with including the clamp force sensor, it might be desirable to eliminate this component from
455:
EBS enhances the precision of the braking over conventional braking, which shortens the braking distance. The fall back of an EBS system in case of failure is to use the ordinary air brake control pressure, so even in the event of a failure of the electronics the vehicle shall be able to make a safe
734:
The caliper controller controls the position and speed of the brake actuator (besides its main task which is tracking of its reference brake command). Thus, position and speed sensors are vitally required in each e-caliper and an efficient design of a measurement mechanism to sense the position and
368:
The system includes all of the complexity of a vehicle stability control system (VSC), antilock brake system (ABS), and the requirement to use the
Regeneration Braking as the primary mode of slowing the vehicle unless the Traction Battery (high-voltage battery) state of charge is too high to accept
95:
in the event of a power failure or an electronic software or hardware fault. Traditionally this has been achieved by means of a mechanical linkage between the brake pedal and the brake master cylinder. With a mechanical linkage, the braking system still operates hydraulically via the pedal, whether
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is a relatively expensive component in an EMB caliper. The cost is derived from its high unit value from a supplier, as well as marked production expenses because of its inclusion. The later emanates from the complex assembly procedures dealing with small tolerances, as well as on-line calibration
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The highest potential risk for brake system failure has proven to be the Brake
Control System software. Recurring failures have occurred in over 200 cases documented in NTSB documents. Because each manufacturer guards the confidentiality of their system design and software, there is no independent
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respectively) to dispense with the traditional cable operated system (operated via a lever between the seats or via a foot pedal) which commonly acted on the rear wheels of a car. EPBs, however, use a motorized mechanism built into the rear disc brake caliper, and is signalled via a switch on the
364:
The hydraulic force generated by pressing the brake pedal is used only as a sensor input to the computer unless a catastrophic failure occurs including a loss of 12-volt electrical power. The brake actuator has an electric pump that provides the hydraulic pressure for the system, and valves to
355:
Brake-by-wire is used in most common hybrid and electric vehicles produced since 1998 including all Toyota, Ford, and
General Motors Electric and hybrid models. The Toyota Synergy Drive and the Rav4 EV use a system where a modified ABS (antilock brake system) actuator is coupled with a special
372:
The sensors monitored as inputs for the brake system include the wheel speed sensors, traction battery state of charge, yaw sensor, brake pedal stroke sensor, steering wheel angle, hydraulic actuator pressure, hydraulic pressures of each wheel caliper circuit, and accelerator position. Other
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are relative position sensors and their additive error needs to be calibrated or compensated for by different methods. Unlike the encoders, resolvers provide two output signals that always allow the detection of absolute angular position. In addition, they suppress common mode noise and are
356:
hydraulic brake master cylinder to create a hydraulic system, coupled with the brake control unit (computer). Ford's system is almost identical to the Toyota system, and the
General Motors system uses different nomenclature for components while the operation is virtually identical.
451:
EBS still relies on compressed air for braking and is only controlling the air through valves which means that it is not depending on higher voltages used by the electromechanical or electrohydraulical brake systems where electric power also is used to apply the brake pressure.
698:
As of 2016 the NTSB has not directly investigated passenger car and light truck brake-by-wire vehicle accidents, and the manufacturers have taken the position that their vehicles are completely safe, and that all reported accidents are the result of "driver error".
768:, then it will be subjected to severe temperature conditions reaching up to 800 Celsius that will challenge its mechanical integrity. Also temperature drifts must be compensated for. This situation can be avoided by embedding a clamp force sensor deep within the
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Electro-mechanical brakes offer the advantage of reduced braking system volume and weight, less maintenance, easier compatibility with active safety control systems, and absence of toxic braking fluid. Their novel actuation methods such as
838:
EPB systems afford packaging and manufacturing advances, since it allows for an uncluttered central console in the absence of the traditional handbrake lever (many manufacturers have used the freed up space to place the controls for their
601:
are vitally required to measure the position and speed of the actuator in each e-caliper. Because of the safety critical nature of the application, even missing a limited number of samples of these sensory data should be compensated for.
690:
In the current brake-by-wire systems used in passenger and light truck vehicles, the system is designed to use existing sensors that have been proven to be dependable in brake system components and systems including ABS and VSC systems.
581:(e-calipers) via a communication network. As this network might not be able to properly communicate with the e-calipers due to network faults, HMI sensory data are also directly transmitted to each e-caliper via a separate
592:
uses the brake command (received from ECU) as a reference input. The controller provides drive control commands for a power control module. This module controls three phase drive currents for the brake actuator which is a
781:
the EMB system. A potential opportunity to achieve this presents itself in accurate estimation of the clamp force based on alternative EMB system sensory measurements leading to the omission of a clamp force sensor.
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If the speed of the vehicle is above about 7 MPH, the vehicle traction motor generator is used as a generator to convert the kinetic energy to electric power, and stores the energy in the battery. This slows the
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for performance variability from one clamp force sensor to another. The successful use of a clamp force sensor in an EMB system poses a challenging engineering task. If a clamp force sensor is placed close to a
702:
Wheel speed data are also vital in a brake-by-wire system to avoid skidding. The design of a brake-by-wire car should provide safeguards against missing some of the data samples provided by the safety-critical
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is a vitally important characteristic of this system. As a result, a brake-by-wire system is designed in such way that many of its essential information would be derived from a variety of sources (
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must always be informed of the driver's intentions to brake or to stop the vehicle. Therefore, missing the pedal sensor data is a serious problem for functionality of the vehicle control system.
641:
Redundant copies of some signals that are of particular safety importance such as displacement and force measurements of the brake pedal copied by multiple processors in the pedal interface unit.
597:
DC motor, energised by 42 V sources. In addition to tracking its reference brake command, the caliper controller also controls the position and speed of the brake actuator. Thus, two
751:
Example of a solution for this problem: A hybrid resolver-to-digital conversion scheme with guaranteed robust stability and automatic calibration of the resolvers used in an EMB system.
392:
The Brake
Control Unit (computer) detects the inputs, and then checks the wheel speed sensors to determine vehicle speed, and to determine if a wheel lockup requires the ABS algorithm.
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or disconnection, a communication network fault, or a sudden increase in noise. In such cases, for a safe operation, the system has to be compensated for missing data samples.
253:
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and accuracy are the main targeted outcomes of the voting techniques that should be developed especially for redundancy resolution inside a brake-by-wire system.
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To use the existing redundancy, voting algorithms need to be evaluated, modified and adopted to meet the stringent requirements of a brake-by-wire system.
352:. Ford, General Motors, and most other manufacturers use the same general design, with the exception of Honda, who designed a notably different design.
405:
Once the vehicle speed drops below about 7 MPH, the hydraulic brake system will completely take over, as regenerative
Braking does not work effectively.
96:
or not electrical control is present. EHBs can be implemented by-wire, without legacy hydraulic systems and mechanical connections. In such a case,
719:. This may happen due to a temporary problem with the sensor itself or with the data transmission path. It may also result from an instantaneous
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protocol. The communication between trailer and towing vehicle shall be done through a specific connector dedicated to ABS/EBS following either
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If the operator (driver) presses the brake pedal harder, the system will apply hydraulic friction brakes to increase brake force.
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464:"Electro-mechanical brakes" redirects here. For train and tram brakes originally known as "electro-mechanical brakes", see
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centre console or dashboard. The electric parking brake is normally integrated with the vehicle's other systems via a
562:
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The Brake
Control System then checks the yaw sensor, steering wheel angle, and state of charge of the traction battery.
236:
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Example of a solution for this problem: Clamp force estimation from actuator position and current measurements using
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components, and their failure will disrupt the vehicle function and endanger human lives. Two examples are the brake
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84:(EMB) that use no hydraulic fluid, which as of 2020 have yet to be successfully introduced in production vehicles.
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Since by-wire systems have no mechanical linkages that would provide manual control over the brakes, they require
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If the yaw sensor detects vehicle yaw, the system will initiate vehicle stability algorithms and processes (VSC).
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Automatic engagement of the parking brake whenever the vehicle is stopped on an incline – known as "Hold Assist"
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may also suffer an intermittent (temporary) data loss. For example, sensor data can sometimes fail to reach the
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high volume Prius was preceded by the GM EV1, the Rav4 EV, and other EVs where the technology is required for
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Redundant hardware to perform important processing tasks such as multiple processors for the ECU in Fig. 1.
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Electro-hydraulic braking systems control or boost the pressure applied to the hydraulic pumps through the
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If the wheel speed sensors detect wheel lock-up, the system will initiate anti-lock algorithm (ABS).
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voter developed to fuse the information provided by three sensors devised in a brake pedal design.
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to provide accurate and continuous measurements for both absolute position and speed of the
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Example of a solution for this problem: Missing data compensation by a predictive filter.
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428:). This system provides electronic activation of all braking system components including
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Please help update this article to reflect recent events or newly available information.
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Please help update this article to reflect recent events or newly available information.
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pressurize each wheel caliper to apply the friction brake when required by the system.
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have kept them, as of 2020, from successfully being introduced in production vehicles.
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systems), plus it reduces manufacturing complexity since it removes the need to route
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is implemented, allowing the vehicle to brake even if some of the brake systems fail.
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through electronic means, without a mechanical connection that transfers force to the
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the stroke sensor measures the pedal movement to identify a "panic stop" condition
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the additional energy or a panic stop or ABS situation is detected by the system.
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speed of the actuator is required. Recent designs for brake-by-wire systems use
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622:) and be handled by more than the bare necessity hardware. Three main types of
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Vehicle
Technology: Technical foundations of current and future motor vehicles
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Vehicle
Technology: Technical foundations of current and future motor vehicles
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Measurement and/or estimation of clamp force in the electromechanical calipers
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Accurate estimation of position and speed of brake actuators in the e-calipers
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EPB has gradually filtered down to cheaper vehicles, for instance within the
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car is shown in Fig. 1. The system mainly comprises five types of elements:
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and as of 2020 have found small-scale usage in the automotive industry; and
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The master cylinder converts the brake pedal movement to hydraulic pressure
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806:. The electronic parking brake (EPB) was introduced in the early 2000s by
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Brake-by-wire exists on heavy duty commercial vehicles under the name
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941:, ika – Institute for Motor Vehicles of RWTH Aachen University, 2016
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Brake by wire is now a mature concept in its application to vehicle
707:. Popular solutions are to provide redundant sensors and to apply a
195:
copy edit to normal prose rather than QA sections, check and update.
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which have, since the turn of the 21st century, become more common;
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Dieter Schramm; et al. (2020), "1 Introduction and overview",
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network, and can provide additional functionality such as:
577:(VSC). These command signals are sent to the four electric
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Dieter Schramm; et al. (2020), "5 Braking systems",
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The pressure transducer provides the brake force desired.
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SpeedE, an academic concept car developed for studying
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Automatic release of the parking brake upon moving off
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mechanism. In addition to a complete sensor loss, the
68:The three main types of brake-by-wire systems are:
376:The standard or typical operation is as follows:
854:, EPB became now a standard fitment on the 2006
245:but its sources remain unclear because it lacks
76:(EHB) which can be implemented alongside legacy
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191:needs attention from an expert in Automobiles
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380:The vehicle operator presses the brake pedal
373:information and inputs are also monitored.
169:Learn how and when to remove these messages
772:. However, embedding this sensor leads to
659:Example of a solution for this problem: A
91:. Safety requires that the system remains
671:In a brake-by-wire car, some sensors are
626:usually exist in a brake-by-wire system:
330:Learn how and when to remove this message
276:Learn how and when to remove this message
123:. Redundant power supplies, sensors, and
610:A brake-by-wire system, by nature, is a
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57:from a driver input apparatus such as a
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201:may be able to help recruit an expert.
511:General architecture of an EMB system
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38:technologies such as brake-by-wire
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150:This section has multiple issues.
540:(mainly integrated into the ECU)
534:(ECU) and other local processors
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158:or discuss these issues on the
814:on their top line models (the
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634:components such as the brake
981:Vehicle braking technologies
938:SpeedE – Forschungsplattform
561:command to the system via a
695:validation of the systems.
515:General architecture of an
193:. The specific problem is:
113:fail-operational redundancy
98:fail-operational redundancy
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862:introduced it on the 2008
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519:braking (EMB) system in a
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49:is the ability to control
956:, De Gruyter Oldenbourg,
918:, De Gruyter Oldenbourg,
667:Missing data compensation
575:vehicle stability control
557:Once the driver inputs a
553:Communication network(s).
484:This section needs to be
460:Electro-mechanical brakes
444:for 24 V systems or
422:Electronic Braking System
301:This article needs to be
82:electro-mechanical brakes
70:electronic parking brakes
847:underneath the vehicle.
571:anti-lock braking system
360:Electro-hydraulic brakes
231:This section includes a
74:electro-hydraulic brakes
18:Electro-mechanical brake
792:Electric parking brakes
717:electronic control unit
713:electronic control unit
685:electronic control unit
563:human–machine interface
532:electronic control unit
448:for 12 V systems.
260:more precise citations.
199:WikiProject Automobiles
55:physical braking system
776:that is influenced by
565:– HMI (e.g. the brake
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125:communication networks
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962:10.1515/9783110595703
924:10.1515/9783110595703
630:Redundant sensors in
614:system and therefore
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466:electromagnetic brake
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27:Automotive technology
745:Incremental encoders
588:In each e-caliper a
350:regenerative braking
115:as specified by the
798:Electric park brake
681:wheel speed sensors
47:automotive industry
876:Regenerative brake
786:sensor data fusion
743:of the actuators.
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233:list of references
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152:Please help
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106:wedge brakes
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886:Fly-by-wire
856:Passat (B6)
650:Reliability
258:introducing
89:brake pedal
892:References
774:hysteresis
624:redundancy
590:controller
528:Processors
446:ISO 7638-2
442:ISO 7638-1
343:Prevalence
266:April 2017
155:improve it
858:, whilst
766:brake pad
737:resolvers
709:fail-safe
573:(ABS) or
549:Actuators
438:ISO 11992
207:July 2018
161:talk page
119:standard
117:ISO 26262
975:Category
870:See also
864:Insignia
816:7 Series
778:friction
583:data bus
579:calipers
430:retarder
399:vehicle.
825:CAN bus
770:caliper
705:sensors
620:sensors
599:sensors
544:Sensors
486:updated
303:updated
254:improve
121:level D
761:sensor
683:. The
606:Voting
538:Memory
456:stop.
51:brakes
741:rotor
677:pedal
661:fuzzy
636:pedal
567:pedal
559:brake
239:, or
63:lever
59:pedal
860:Opel
818:and
812:Audi
810:and
432:and
958:doi
920:doi
808:BMW
426:EBS
416:EBS
61:or
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