Editing Anti-lock braking system (section)

==ABS on motorcycles==
[[File:ABS-Sensor.jpg|thumb|upright=1.34|The ABS sensor of a BMW K 1100 LT]]
[[File:BMW R1150GS front discs.jpg|thumb|A toothed-wheel ABS sensor. These are the front brake discs on a BMW R1150GS. The toothed ABS ring indicates that this bike was manufactured before November 2002.]]
[[File:ABS Vorderrad BMW K75.jpg|thumb|Another toothed-wheel ABS sensor. This is on a [[BMW K75]] motorcycle.]]
On a motorcycle, an anti-lock brake system prevents the wheels of a [[motorcycle]] from locking during [[Brake|braking]] situations. Based on information from [[wheel speed sensor]]s the ABS unit adjusts the pressure of the brake fluid in order to keep [[Traction (engineering)|traction]] during deceleration to avoid accidents. Motorcycle ABS helps the rider to maintain stability during braking and to decrease the stopping distance. It provides traction even on low [[friction]] surfaces.

While older ABS models are derived from cars, recent Motorcycle ABS is the result of research, oriented to the specifics of motorcycles in case of size, weight, and functionality. National and international organizations have evaluated Motorcycle ABS to be an important factor in increasing safety and reducing the number and severity of motorcycle crashes and collisions. The [[European Commission]] passed legislation in 2012 that made the fitment with ABS for all new motorcycles above 125cc to be mandatory from 1 January 2016. ''Consumer Reports'' said in 2016 that "ABS is commonly offered on large, expensive models, but it has been spreading to several entry-level sportbikes and midsized bikes".<ref>{{cite web|title=Motorcycle Buying Guide|publisher=Consumer Reports|website=official website|date=April 2016|url=https://www.consumerreports.org/cro/motorcycles-scooters/buying-guide/index.htm|access-date=2018-06-28|archive-date=2018-06-28|archive-url=https://web.archive.org/web/20180628233513/https://www.consumerreports.org/cro/motorcycles-scooters/buying-guide/index.htm}}</ref>

===History of motorcycle ABS===
In 1988, BMW introduced an electronic/[[Hydraulics|hydraulic]] ABS for motorcycles, ten years after Daimler Benz and Bosch released the first four-wheel vehicle ABS for series production. Motorcycles of [[BMW K100]] series were optionally equipped with the ABS, which added 11&nbsp;kg to the bike. It was developed together with [[Schaeffler Group|FAG Kugelfischer]] and regulated the pressure in the braking circuits via a plunger [[piston]].<ref>{{cite web|url=http://www.spiegel.de/spiegel/print/d-40616291.html |title=DER SPIEGEL 26/1978 - Nachschlag für Abs |website=Spiegel.de |date=1978-06-26 |access-date=2013-02-12}}</ref><ref>{{cite web |url=http://media.daimler.com/dcmedia/0-921-657486-49-803841-1-0-0-0-0-1-11701-614318-0-1-0-0-0-0-0.html |title=Mercedes-Benz und die Erfindung des Anti-Blockier-Systems: 1978 ist ABS serienreif &#124; Daimler Global Media Site > Classic > Daimler AG > Technologie > Sicherheit |website=Media.daimler.com |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20140301092935/http://media.daimler.com/dcmedia/0-921-657486-49-803841-1-0-0-0-0-1-11701-614318-0-1-0-0-0-0-0.html |archive-date=2014-03-01 }}</ref> Japanese manufacturers followed with an ABS option by 1992 on the [[Honda ST1100]] and the [[Yamaha FJ1200]].<ref>{{Citation |title= Speed with style: GT bikes, backroads and anti-lock braking|magazine=[[Cycle World]] |publisher=[[Hachette Filipacchi Media U.S.]] |issn=0011-4286 |location=Newport Beach, California |date= July 1992 |pages=48–55 |url=https://books.google.com/books?id=eToxUA1LZbsC&pg=RA6-PA48 |access-date=June 5, 2015 }}</ref>

Continental presented its first Motorcycle Integral ABS (MIB) in 2006. It has been developed in cooperation with BMW and weighed 2.3&nbsp;kg.<ref>[http://www.conti-online.com/generator/www/com/de/continental/presseportal/themen/pressemitteilungen/1_topics/messen_veranstaltungen/pr_2006_10_10_intermot/gt_pr_intermot_abs_de.html] {{dead link|date=February 2013|fix-attempted=y}}</ref>
While the first generation of motorcycle ABS weighed around 11&nbsp;kg, the generation (2011) presented by Bosch in 2009 weighs 0.7&nbsp;kg (ABS base) and 1.6&nbsp;kg (ABS enhanced) with integral braking.<ref>{{cite web |url=http://world.honda.com/motorcycle-technology/brake/p2.html |title=Honda Worldwide &#124; Technology Close-up |website=World.honda.com |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20130506051356/http://world.honda.com/motorcycle-technology/brake/p2.html |archive-date=2013-05-06 }}</ref><ref>{{cite web|url=http://www.bmbikes.co.uk/photos/press%20PDF/1988%20ABS%20Press.pdf|title=1998 ABS Press|website=Bmbikes.co.uk|access-date=2018-06-28|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304062932/http://www.bmbikes.co.uk/photos/press%20PDF/1988%20ABS%20Press.pdf|url-status=dead}}</ref><ref>{{cite web |url=http://www.motorradonline.de/de/motorraeder/abs-spezial/102945?seite=5 |title=ABS-Spezial - Die Geschichte - Motorräder - MOTORRAD online |website=Motorradonline.de |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20100726045035/http://www.motorradonline.de/de/motorraeder/abs-spezial/102945?seite=5 |archive-date=2010-07-26 }}</ref>

===Basic principle===
Wheel speed [[sensor]]s mounted on the front and rear wheel constantly measures the rotational speed of each wheel and delivers this information to an [[Electronic control unit|Electronic Control Unit]] (ECU). The ECU detects two things: 1) if the deceleration of one wheel exceeds a fixed threshold and 2) whether the brake slip, calculated based on information of both wheels, rises above a certain percentage and enters an unstable zone. These are indicators for a high possibility of a locking wheel. To countermeasure these irregularities the ECU signals the hydraulic unit to hold or to release pressure. After signals show the return to the stable zone, the pressure is increased again. Past models used a piston for the control of the [[Fluid pressure#Fluid pressure|fluid pressure]]. Most recent models regulate the pressure by rapidly opening and closing [[solenoid valve]]s.
While the basic principle and [[architecture]] has been carried over from passenger car ABS, typical motorcycle characteristics have to be considered during the development and application processes.
One characteristic is the change of the dynamic wheel load during braking. Compared to cars, the wheel load changes are more drastic, which can lead to a wheel lift up and a fall over. This can be intensified by a soft suspension. Some systems are equipped with a rear-wheel lift-off mitigation functionality. When the indicators of a possible rear lift-off are detected, the system releases brake pressure on the front wheel to counter this behavior.<ref>{{Cite web |url=http://news.consumerreports.org/cars/2012/04/the-most-valuable-motorcycle-feature-antilock-brakes.html |title=The most-valuable motorcycle feature: antilock brakes<!-- Bot generated title --> |access-date=2018-12-03 |archive-url=https://web.archive.org/web/20130615102218/http://news.consumerreports.org/cars/2012/04/the-most-valuable-motorcycle-feature-antilock-brakes.html |archive-date=2013-06-15 }}</ref>
Another difference is that in the case of the motorcycle the front wheel is much more important for stability than the rear wheel. If the front wheel locks up between 0.2-0.7s, it loses gyrostatic forces and the motorcycle starts to oscillate because of the increased influence of side forces operating on the wheel contact line. The motorcycle becomes unstable and falls.

===Anti-lock Braking System (ABS)===
''Piston Systems'': The pressure release in this system is realized through the movement of a spring-tensioned piston. When pressure should be released, a linear motor pulls back the plunger piston and opens up more space for the fluid. The system was used for example in the ABS I (1988) and ABS II (1993) of BMW. The ABS II differed in size and an electronically controlled [[Clutch#Friction clutches|friction clutch]] was mounted on the shaft instead of a plunger. Further [[Displacement measurement|displacement sensors]] record the travel distance of the piston to allow the control unit a more precise regulation. Honda also uses this system of pressure modulation for big sports and [[Touring motorcycle|touring bikes]].<ref>{{cite web|url=http://www.largiader.com/abs/abs2.html |title=BMW description of ABS2 |website=Largiader.com |access-date=2013-02-12}}</ref><ref>{{cite web |url=http://world.honda.com/motorcycle-technology/brake/p6.html |title=Honda Worldwide &#124; Technology Close-up |website=World.honda.com |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20130819032525/http://world.honda.com/motorcycle-technology/brake/p6.html |archive-date=2013-08-19 }}</ref>

''Valve and Pump Systems'': The main parts which are part of the pressure modulation system are solenoid inlet and outlet valves, a pump, motor, and accumulators/reservoirs. The number of the valves differs from model to model due to additional functionalities and the number of brake channels. Based on the input of the ECU, coils operate the inlet and outlet valves. During pressure release, the brake fluid is stored in accumulators. In this open system approach, the fluid is then brought back in the brake circuit via a pump operated by a motor that is felt through pulsation on the brake lever.<ref>{{cite web|author=Matthias Becker |url=http://www.biat.uni-flensburg.de/msc/system/abssystem.htm#Grundkonzepte |title=ABS/ASR-Systemerklδrung |website=Biat.uni-flensburg.de |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20130422102905/http://www.biat.uni-flensburg.de/msc/system/abssystem.htm |archive-date=2013-04-22 }}</ref>

===Regenerative Anti-Lock Braking for Electric 2-wheel vehicles (eABS)===
Electric vehicles can recapture the energy from rear wheel braking.<ref>{{Citation | vauthors=Robinson J, Singh T | year=2013 | title=eABS: Regenerative Anti-Lock Braking for Electric Motorcycles | journal=SAE International Journal of Passenger Cars - Mechanical Systems | volume=6 | issue=3 | pages=1484–1492 | publisher=SAE International | doi=10.4271/2013-01-2064 | url=http://dx.doi.org/10.4271/2013-01-2064 |access-date=June 27, 2022}}</ref>

===Combined Braking System (CBS)===
Contrary to how the wheels on cars and trains react collectively to brakes when applied, on motorcycles the rear wheel brake and front wheel brake are controlled separately. If the rider only brakes with one wheel, this braked wheel tends to lock up faster than if both brakes had been applied. A [[Combined braking system|Combined Braking System]] therefore distributes the brake force also to the non-braked wheel to lower the possibility of a lock-up, increase deceleration and reduce [[Suspension (motorcycle)|suspension]] pitch.

With a single [rear] CBS the brake pressure applied on the rear brake (pedal) is simultaneously distributed to the front wheel. A delay valve cuts the hydraulic pressure to assure that only when strong braking is applied, the pressure is also created at the front wheel. Honda's first street motorcycle with a combined braking system (then called Unified Braking) was the 1983 [[Gold Wing#GL1100|GL1100]]. This system was derived from the 1970s [[Honda RC series|RCB1000]] world endurance race bike.<ref>{{cite web|title=Advanced brake introduced for motorcycles by Honda ahead of others|url=http://world.honda.com/motorcycle-technology/brake/p2.html|work=Honda Worldwide|publisher=Honda Motor Co|access-date=July 9, 2018|archive-url=https://web.archive.org/web/20160310200739/http://world.honda.com/motorcycle-technology/brake/p2.html|archive-date=March 10, 2016|df=mdy-all}}</ref><ref>{{cite web|title=Combined Braking System (CBS)|url=http://powersports.honda.com/experience/articles/090111c08139be28.aspx|work=Honda Powersports|publisher=American Honda Motor Co|access-date=July 9, 2018|date=9 December 2013|archive-url=https://web.archive.org/web/20180710010624/http://powersports.honda.com/experience/articles/090111c08139be28.aspx|archive-date=10 July 2018}}</ref>

Larger models with two front [[Disc brake|discs]] use a dual CBS System. The system was first installed by Moto Guzzi in 1975.<ref>{{citation|title=Motorcycle Handling and Chassis Design: The Art and Science
|first=Tony |last=Foale|year=2006|pages=12–16|publisher=Tony Foale |edition=Second|isbn=8493328634|url=https://books.google.com/books?id=84hF-qoR5I8C}}</ref> Here, applied brake pressure at the front is also applied to the rear wheel and vice versa. If the front lever is applied, the pressure is built up at 4 of the 6 pots in the 2 calipers at the front. A secondary master cylinder at the front wheel distributes remaining pressure to the rear wheel through a proportional control valve and acts on 2 of the 3 calipers. If a strong brake force is applied at the rear wheel force is also distributed to 2 of the 6 pots of the front wheel. More modern dual CBS use front and rear calipers (and all pots) according to a preset load ratio of front to rear. The proportioning was originally controlled by complex all-hydraulic systems interlinking the front and rear, with a fixed delay or by sensing weight distribution changes. As early as 2001 an electrohydraulic system was introduced by BMW.<ref>{{citation |title= New integral ABS from BMW Motorrad |last1= Braunsperger |first1=M. |last2=Beulich |first2=S. |last3=Wagner |first3=HA |journal= ATZ Worldwide |year=2001 |volume= 103 |number= 5 |pages= 5–8 |doi= 10.1007/BF03226430}}</ref>

===CBS and ABS===
CBS helps to reduce the danger of wheel locks and fall downs but in certain situations, it is possible that CBS causes a fall down. If brake pressure is distributed from the rear wheel to the front wheel and the friction of the surfaces changes suddenly (puddle, ice on the street) the front wheel might lock even if only the rear brake has been applied. This would lead to a loss of stability and a fall down. CBS is therefore combined with ABS to avoid this on a motorcycle.
Different approaches are possible to realize this combination:
''Without active pressure Build up''
Single Version: A third additional channel links the rear wheel circuit through a delay valve to the front brake. Strong brake pressure at the rear wheel (or both wheels) pressurizes both brake circuits however this pressure is adjusted according to wheel speed and brake slip.

The dual version combines Hondas Dual CBS with a secondary master cylinder and a proportional control valve [with Piston ABS] A modulator regulates the pressure for each<ref name="honda5">{{cite web |url=http://world.honda.com/motorcycle-technology/brake/p5.html |title=Honda Worldwide &#124; Technology Close-up |website=World.honda.com |access-date=2013-02-12 |archive-url=https://web.archive.org/web/20131228002749/http://world.honda.com/motorcycle-technology/brake/p5.html |archive-date=2013-12-28 }}</ref>
''With Active Pressure Build up''
In 2009, Honda introduced the electronic controlled combined ABS for its high-performance sports bikes which utilize brake by wire technology. The brake input of the rider is measured by pressure sensors and the information is provided to an ECU. Together with the information of the wheel speed sensors, the ECU calculates the optimal distribution of pressure to prevent lockups and to provide the best possible deceleration. Based on this output a motor for each wheel operates a pump that builds up and regulates the brake pressure on the wheel. This system offers a fast reaction time because of the brake by wire functionality.

The MIB (Motorcycle integral Braking system) from Continental Teves and the eCBS (electronic CBS) in the enhanced Motorcycle ABS from Bosch are results of another approach. These systems are based on the pump and valve approach. Through additional valves, stronger pumps and a more powerful motor the system can actively build up pressure. The input pressure of the rider is measured with pressure sensors at the lever and pedal. The pump then builds up additional pressure adjusted to riding conditions. A partial integral System is designed for working in one direction only: front→rear or rear→front. A fully-integrated system works in both directions.

Because these systems are electronically controlled and are able to build up pressure actively, they offer the opportunity to adjust the motorcycle braking behavior to the rider. CBS and ABS can be switched off by experienced riders and also different regulation modes with higher and lower thresholds can be chosen, such as the rain or slick mode in the BMW S1000RR.