Stopping a car in a precipitation on a slippy road can be very thought-provoking . Anti - lock braking system ( ABS ) take a circumstances of the challenge out of this sometimes cheek - wreck consequence . In fact , on tricky surfaces , even professional driver ca n’t turn back as quickly without ABS as an average driver can with ABS .
In this article , the last in a six - part serial on brakes , we ’ll acquire all about anti - lock braking systems – why you need them , what ’s in them , how they work , some of the common case and some colligate problems .
The ABS System
The theory behind anti - lock brake is simple . Askidding wheel(where the tire contact patch is sliding relative to the route ) has lesstractionthan a non - skidding wheel . If you have been stick on ice-skating rink , you be intimate that if your wheel are reel you have no grip . This is because the contact patch is slide relative to the ice ( seeBrakes : How Friction Worksfor more ) . By keeping the wheels from skidding while you slow down down , anti - lock brakes benefit you in two way : You ’ll stop faster , and you ’ll be able tosteerwhile you stop .
There are four main components to an Bachelor of Arts system :
Speed Sensors
The anti - lock braking system demand some way of roll in the hay when a wheel is about to lock up up . The hurrying sensor , which are locate at each wheel , or in some cases in thedifferential , provide this information .
Valves
There is a valve in the pasture brake line of eachbrakecontrolled by the ABS . On some system , the valve has three positions :
Pump
Since the valve is able-bodied to release air pressure from the brakes , there has to be some means to put that pressure back . That is what the ticker does ; when a valve reduces the pressure in a melodic line , the pump is there to get the pressure back up .
Controller
The controller is a computer in the railcar . It catch the upper sensors and controls the valves .
ABS at Work
There are many unlike variations and restraint algorithms for ABS organization . We will discuss how one of the simpler systems works .
The controller monitors the speed sensors at all time . It is looking fordecelerationsin the wheel that are out of the average . Right before a wheel locks up , it will experience a rapid slowing . If provide unchecked , the wheel would cease much more cursorily than any car could . It might take a car five seconds to finish from 60 mph ( 96.6 kph ) under idealistic term , but a wheel that interlace up could discontinue twirl in less than a second .
The AB controller have intercourse that such a rapid slowing is unacceptable , so it reduces thepressureto that brake until it sees an acceleration , then it increases the pressure until it sees the deceleration again . It can do this very quick , before thetirecan in reality significantly deepen pep pill . The result is that the tire slow down at the same rate as the car , with the brakes sustain the tires very near the point at which they will start to operate up . This gives the system maximum braking power .
When the ABS organization is in cognitive process you will feel apulsingin the pasture brake pedal point ; this comes from the rapid opening and closing of the valves . Some ABS systems can cycle up to 15 times per second .
Anti-Lock Brake Types
Anti - lock braking systems expend dissimilar schemes depending on the eccentric of brakes in use . We will name to them by the telephone number of channels – that is , how many valve that are separately control – and the figure of swiftness sensor .
Four-channel, four-sensor ABS
This is the best scheme . There is a speed sensing element on all four wheels and a disjoined valve for all four wheels . With this setup , the restrainer monitor each bike on an individual basis to check that it is achieving maximum braking forcefulness .
Three-channel, three-sensor ABS
This dodge , commonly found on pickup trucks with four - bike Ab , has a upper sensor and a valve for each of the front wheel , with one valve and one detector for both rear wheel . The pep pill sensing element for the rear wheel is located in the rear axle .
This system provides individual control condition of the front wheel , so they can both achieve maximum braking forcefulness . The rearward wheels , however , are supervise together ; they both have to start to lock up before the AB will activate on the rear . With this organization , it is potential that one of the rear cycle will lock during a stop , reducing bracken potency .
One-channel, one-sensor ABS
This system is commonly found on pickup trucks with rear - wheel ABS . It has one valve , which controls both rear cycle , and one speed sensor , located in the rearward axle .
This organization operate the same as the rear end of a three - line system . The rear wheel are monitor together and they both have to start up to mesh up before the ABS kicks in . In this system it is also potential that one of the rear wheels will interlace , reducing bracken effectiveness .
This organisation is loose to identify . commonly there will be one brake ancestry going through a thyroxine - fitting to both rearward wheels . you may turn up the speed sensor by looking for an electrical connecter near the differential on the rear - axle housing.
ABS Questions
Should I pump the brake pedal when stopping in slippery conditions?
You absolutely should not pump the brake pedal in a car with group AB . Pumping the bracken is a technique that is sometimes used in slippery conditions to allow the wheel to unlock so that the vehicle stay fairly straight during a stopover . In a car with BA the wheels should never shut up in the first office , so pumping the brakes will just make you take longer to stop .
In an emergency brake stop in a motorcar with ab , you should apply the brake foot lever firmly and bear it while the ABS does all the work . You will feel a pulsing in the foot lever that may be quite violent , but this is normal so do n’t let off the Pteridium aquilinum .
Do anti-lock brakes really work?
Anti - lock brakes really do serve you cease easily . They prevent cycle from locking up and provide the shortest stopping distance on slippery control surface . But do they really preclude accidents ? This is the true measure of the effectiveness of Av system of rules .
TheInsurance Institute for Highway Safety(IIHS ) has conduct several field trying to ascertain if motorcar equipped with ABS are involved in more or fewer fatal accidents . It ferment out that in a 1996 study , vehicles equipped with ABS were overall no less potential to be need in fatal accidents than vehicle without . The study actually stated that although gondola with Av were less probable to be involve in accidents disastrous to the occupier of other cars , they are more likely to be involved in accidents calamitous to the occupants of the ABS car , especially single - fomite accident .
There is much speculation about the reason for this . Some people think that drivers of ABS - equipped cars use the AB incorrectly , either by pumping the brakes or by releasing the brake when they feel the arrangement pulsate . Some people think that since ABS allow you to head during a terror point , more people run off the route and crash .
Some more recent selective information may indicate that the accident rate for Artium Baccalaurens cars is improving , but there is still no evidence to show that ABS improve overall condom .
Anti-Lock Brake Diagram
Now let ’s put the parts together to see how anti - lock brakes work out as a whole . This diagram provides both a closeup view and an example of where the brakes are located in your vehicle .
For more information on anti - lock brakes and related topics , check out the connection on the next page .
