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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.
336:
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
769:
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
444:
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
723:
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
357:
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
84:
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
752:
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
683:
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
811:
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
353:
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
344:
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
361:
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
736:
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
345:
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.
440:
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.
687:
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".
757:, 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
92:
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
827:
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
590:
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.
679:
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.
570:(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
581:
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
770:
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.
387:
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
753:
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
691:
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
607:
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 (
676:
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.
630:
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.
586:
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
740:
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.
381:
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.
712:
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.
645:
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.
637:
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.
341:. Ford, General Motors, and most other manufacturers use the same general design, with the exception of Honda, who designed a notably different design.
394:
Once the vehicle speed drops below about 7 MPH, the hydraulic brake system will completely take over, as regenerative
Braking does not work effectively.
430:
85:
or not electrical control is present. EHBs can be implemented by-wire, without legacy hydraulic systems and mechanical connections. In such a case,
708:. 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
429:
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.
969:
453:"Electro-mechanical brakes" redirects here. For train and tram brakes originally known as "electro-mechanical brakes", see
812:
centre console or dashboard. The electric parking brake is normally integrated with the vehicle's other systems via a
384:
The Brake
Control System then checks the yaw sensor, steering wheel angle, and state of charge of the traction battery.
773:
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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73:(EMB) that use no hydraulic fluid, which as of 2020 have yet to be successfully introduced in production vehicles.
100:
Since by-wire systems have no mechanical linkages that would provide manual control over the brakes, they require
397:
If the yaw sensor detects vehicle yaw, the system will initiate vehicle stability algorithms and processes (VSC).
823:
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
434:
143:
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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
633:
Redundant hardware to perform important processing tasks such as multiple processors for the ECU in Fig. 1.
76:
Electro-hydraulic braking systems control or boost the pressure applied to the hydraulic pumps through the
551:
558:), four independent brake commands are generated by the ECU based on high level brake functions such as
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225:
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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.
8:
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733:
417:). This system provides electronic activation of all braking system components including
35:
19:
479:
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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611:) 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
905:
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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852:
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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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912:
795:. The electronic parking brake (EPB) was introduced in the early 2000s by
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729:
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Brake-by-wire exists on heavy duty commercial vehicles under the name
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426:
105:
930:, 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
696:. Popular solutions are to provide redundant sensors and to apply a
184:
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:
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566:(VSC). These command signals are sent to the four electric
903:
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
57:The three main types of brake-by-wire systems are:
365:The standard or typical operation is as follows:
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843:, EPB became now a standard fitment on the 2006
234:but its sources remain unclear because it lacks
65:(EHB) which can be implemented alongside legacy
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180:needs attention from an expert in Automobiles
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369:The vehicle operator presses the brake pedal
362:information and inputs are also monitored.
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158:Learn how and when to remove these messages
887:
780:
761:. However, embedding this sensor leads to
648:Example of a solution for this problem: A
80:. Safety requires that the system remains
660:In a brake-by-wire car, some sensors are
615:usually exist in a brake-by-wire system:
319:Learn how and when to remove this message
265:Learn how and when to remove this message
112:. Redundant power supplies, sensors, and
599:A brake-by-wire system, by nature, is a
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46:from a driver input apparatus such as a
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190:may be able to help recruit an expert.
500:General architecture of an EMB system
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27:technologies such as brake-by-wire
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139:This section has multiple issues.
529:(mainly integrated into the ECU)
523:(ECU) and other local processors
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281:
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147:or discuss these issues on the
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803:on their top line models (the
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623:components such as the brake
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970:Vehicle braking technologies
927:SpeedE – Forschungsplattform
550:command to the system via a
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684:validation of the systems.
504:General architecture of an
182:. The specific problem is:
102:fail-operational redundancy
87:fail-operational redundancy
10:
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851:introduced it on the 2008
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508:braking (EMB) system in a
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38:is the ability to control
945:, De Gruyter Oldenbourg,
907:, De Gruyter Oldenbourg,
656:Missing data compensation
594:
564:vehicle stability control
546:Once the driver inputs a
542:Communication network(s).
473:This section needs to be
449:Electro-mechanical brakes
433:for 24 V systems or
411:Electronic Braking System
290:This article needs to be
71:electro-mechanical brakes
59:electronic parking brakes
836:underneath the vehicle.
560:anti-lock braking system
349:Electro-hydraulic brakes
220:This section includes a
63:electro-hydraulic brakes
781:Electric parking brakes
706:electronic control unit
702:electronic control unit
674:electronic control unit
552:human–machine interface
521:electronic control unit
437:for 12 V systems.
249:more precise citations.
188:WikiProject Automobiles
44:physical braking system
765:that is influenced by
554:– HMI (e.g. the brake
501:
404:
114:communication networks
28:
951:10.1515/9783110595703
913:10.1515/9783110595703
619:Redundant sensors in
603:system and therefore
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455:electromagnetic brake
22:
16:Automotive technology
734:Incremental encoders
577:In each e-caliper a
339:regenerative braking
104:as specified by the
787:Electric park brake
670:wheel speed sensors
36:automotive industry
865:Regenerative brake
775:sensor data fusion
732:of the actuators.
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222:list of references
34:technology in the
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485:October 2013
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302:October 2013
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141:Please help
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95:wedge brakes
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31:
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875:Fly-by-wire
845:Passat (B6)
639:Reliability
247:introducing
78:brake pedal
881:References
763:hysteresis
613:redundancy
579:controller
517:Processors
435:ISO 7638-2
431:ISO 7638-1
332:Prevalence
255:April 2017
144:improve it
847:, whilst
755:brake pad
726:resolvers
698:fail-safe
562:(ABS) or
538:Actuators
427:ISO 11992
196:July 2018
150:talk page
108:standard
106:ISO 26262
964:Category
859:See also
853:Insignia
805:7 Series
767:friction
572:data bus
568:calipers
419:retarder
388:vehicle.
814:CAN bus
759:caliper
694:sensors
609:sensors
588:sensors
533:Sensors
475:updated
292:updated
243:improve
110:level D
750:sensor
672:. The
595:Voting
527:Memory
445:stop.
40:brakes
730:rotor
666:pedal
650:fuzzy
625:pedal
556:pedal
548:brake
228:, or
52:lever
48:pedal
849:Opel
807:and
801:Audi
799:and
421:and
947:doi
909:doi
797:BMW
415:EBS
405:EBS
50:or
966::
889:^
855:.
809:A8
777:.
641:,
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232:,
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