Ургенчского филиала Ташкентского университета

Scheme of anti-lock brakes

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“Young Scientist” .  #29.3 (133.3) .  December 2016
Anti-Lock Brake Types. Anti-lock braking systems use 
different schemes depending on the type of brakes in use. 
We will refer to them by the number of channels — that is, 
how many valves that are individually controlled — and the 
number of speed sensors.
Four-channel, four-sensor ABS — This is the best 
scheme. There is a speed sensor on all four wheels and a sep-
arate valve for all four wheels. With this setup, the controller 
monitors each wheel individually to make sure it is achieving 
maximum braking force.
Three-channel, three-sensor ABS — This scheme, com-
monly found on pickup trucks with four-wheel ABS, has a 
speed sensor and a valve for each of the front wheels, with one 
valve and one sensor for both rear wheels. The speed sensor 
for the rear wheels is located in the rear axle. This system pro-
vides individual control of the front wheels, so they can both 
achieve maximum braking force. The rear wheels, however, 
are monitored together; they both have to start to lock up be-
fore the ABS will activate on the rear. With this system, it is 
possible that one of the rear wheels will lock during a stop, 
reducing brake effectiveness.
One-channel, one-sensor ABS — This system is com-
monly found on pickup trucks with rear-wheel ABS. It has 
one valve, which controls both rear wheels, and one speed 
sensor, located in the rear axle.
This system operates the same as the rear end of a three-
channel system. The rear wheels are monitored together and 
they both have to start to lock up before the ABS kicks in. In a 
system it is also possible that one of the rear wheels will lock, 
reducing brake effectiveness. This system is easy to identify. 
Usually there will be one brake line going through a T-fit-
ting to both rear wheels. You can locate the speed sensor by 
looking for an electrical connection near the differential on 
the rear-axle housing. Following you can see location of an-
ti-lock brake components (Figure 2).
An autofocus (or AF) optical system uses a sensor, a con-
trol system and a motor or tunable optical element to focus 
automatically or on a manually selected point or area. An 
electronic has a display instead of the motor; the adjustment 
of the optical system has to be done manually until indica-
tion. Autofocus methods are distinguished by their type as 
being either active, passive or hybrid variants.
Active AF systems measure distance to the subject inde-
pendently of the optical system, and subsequently adjust the 
optical system for correct focus.
Passive AF systems determine correct focus by per-
forming passive analysis of the image that is entering the op-
tical system.
PDA (personal digital assistant) is a term for any small 
mobile hand-held device that provides computing and infor-
mation storage and retrieval capabilities for personal or busi-
ness use, often for keeping schedule calendars and address 
book information handy. The term handheld is a synonym. 
Many people use the name of one of the popular PDA prod-
ucts as a generic term.
The advantages of PDA (Personal Digital Assistant) [8].
Size. They are small and getting smaller! PDAs have in-
creased in power and decreased in size. They are designed to 
fit in the palm of your hand or your jacket pocket. How long, 
though, before you want something smaller yourself?
Storage. Appointments calendar, contact address book 
and an ability to keep notes and lists are typical features of 
a PDA. Spreadsheets, word documents and power points? 
Done. Want to read e-books and store photos on it? No 
problem. PDAs will help you prepare to pack before you 
travel. They will even store your shopping list!
Figure 2.