Exit warning system warns the occupants in a car of the vehicles approaching from behind as they open the doors of their car. This system scans the area behind the parked vehicle and keeps the doors locked unless the coast is clear to protect other passing vehicles.
Audi had first introduced this feature in it's A4 and Q7 models in 2015. It would only alert the driver of any approaching vehicles through warning lights. In 2018, Audi upgraded the technology by physically blocking the doors until the approaching vehicle passes by. It doesn't lock the door forever but for a mere 0.8 seconds which should be enough for a vehicle to pass by. It was installed in A8 model.
Seat belts are also known as safety belts which are designed
to safeguard a passenger from getting seriously injured in the event of a
collision. The basic idea is to prevent the occupant from being thrown towards
the windshield or dashboard.
Law of motion:
Newton’s first law of motion states that “Every object in a
state of uniform motion tends to remain in that state of motion unless an
external force is applied to it.” This means that when we (as passengers) are
travelling in a car at a particular speed, then we will continue to move
forward at that same speed even after brakes are applied due to the momentum
our body gains. The momentum is higher if there is a collision and hence our
body is thrown in front and we get seriously injured.
If a car is travelling at 60 kmph, then everything in the
car is in inertia. If the car hits a pole on the road, then the car abruptly
stops, but the occupants in the car will be hurdled in front due to the inertia
that they carry. Seat belts act against this inertia to slow us down.
Three Point
Retractable Lap and Shoulder Seat Belts:
This is the most commonly used seat belt system for
passenger cars worldwide.
Seat Belts Working
(Retractor mechanism):
This is the most commonly used mechanism in seat belts. The
retractor mechanism uses a spool as its central element. The spool is attached
to one end of the webbing. A spring is available inside the retractor that
provides a rotational force.
When we pull the webbing (fabric belt) out, the spool rotates
in anti-clockwise direction. The rotation of spool also rotates the attached
spring in the same direction. The spring will resist the twisting motion and
will want to return to the original shape. As soon as we release the webbing,
the spring untwists itself in clockwise direction and therefore the spool also
rotates in clockwise direction until there is no more slack in the webbing.
The Retractor Locking
Mechanism:
In the event of a collision, the retractor has a locking
mechanism that stops the spool from rotating. The basic idea of a locking
system is to lock the spool from rotating in order to prevent the occupant from
being thrown towards the dashboard.
The locking mechanism nowadays uses two sensors to lock the
spool. The first is the vehicle deceleration
sensor that detects any sudden deceleration in the vehicle and the second
is the webbing sensor to detect any
violent pull outs of the webbing.
A centrifugal clutch system is used to lock the spool. When
the spool rotates slowly, the centrifugal lever doesn’t pivot at all. When
there is a violent rotation of the spool, the lever’s centrifugal force
overcomes the spring force and the clutches get locked with the teeth of the
spool. The video will clearly show you how this works.
Pretensioners:
A conventional seat belt locking mechanism will only lock
the rotation of the spool. A pretensioner
will actually pull the belt in once the car comes to an abrupt stop.
Therefore, it helps move the occupants in the opposite direction of the
momentum that tends to carry them forward.
Modern day pretensioners use pyrotechnics to pull in the
belt. It consists of a separate gas chamber with an igniter material. When the
sensor detects collision, the igniter material is ignited by passing electric
current through it. The collision is detected by a central processor which then
sends the electric current to the igniter. The ignition releases gases at a
huge pressure which pushes the piston upwards. A rack gear is provided at the
top of the piston which moves up and engages with the spool gear and rotates
the spool forcefully to pull the belt inside.
Another angle of the pre-tensioner
Load Limiter:
In very violent crashes, seat belts can incur serious
damages on the occupants, especially the old people who cannot take much load
on their rib cages. The harder the impact of collision, the harder will be the
force of the seat belt to stop the occupant.
The basic idea of introducing a load limiter is to limit the
force of the pretensioner on the occupants. Load limiter allows the belt or
webbing to extend a bit more when a great deal of impact is applied on it. The
best way to achieve this is by integrating a torsion bar with the retractor
mechanism. The torsion bar is attached to the locking mechanism on one end and
the spool on the other end.
When the impact force is less, the torsion bar will be
steady and will allow the spool to be locked along with the locking mechanism. When
the impact is very high, then the force will twist the torsion bar slightly,
thus allowing the spool to rotate and extend the webbing a bit more.
Seat belts work in combination with the airbags and hence it
is necessary that the airbags deploy in order to save the occupant from
injuries.
Newton’s first law of motion states that “Every object in a state
of uniform motion tends to remain in that state of motion unless an external
force is applied to it.” This means that when we (as passengers) are travelling
in a car at a particular speed, then we will continue to move forward at that
same speed even after brakes are applied due to the momentum our body gains. The
momentum is higher if there is a collision and hence our body is thrown in
front and we get seriously injured. Air bags provide a cushion to our body in
the event of a collision to prevent any serious injury.
Air bag is a safety device used in vehicles that consists of
a flexible fabric bag that inflates instantaneously in the event of a collision
to protect the driver and passengers from serious injury to their head, face
and chest. Air bags are like a soft pillow to land against in the event of a
crash. The purpose of an air bag is to slow the forward motion of the passenger
in a fraction of a second.
Air bags were first introduced commercially for automobiles
in 1980. Looking at the reduction in fatalities, U.S made it mandatory for all
cars to be installed in cars since 1998.
Where is air bag
installed?
Typically air bags are installed in the steering wheel for
driver and in the instrument panel for the front passenger. Apart from that, in
high end luxury models, door mounted side air bags and seat mounted air bags
are also installed.
Working of an air
bag:
The air bag consists of a thin nylon bag which is folded
inside the steering wheel or dashboard. There is a crash sensor that detects
any crash when the vehicle collides. The crash sensor signals the inflator to
inflate the air bag when necessary.
Air bags will inflate only if the vehicle achieves a minimum
speed of 16 to 14 kmph. When crash occurs, accelerometer sends the information
to the crash sensor. The crash sensor then actuates the inflation system. The
inflation system in older air bags sets off a chemical reaction between sodium
azide (NaN3), potassium nitrate (KNO3) and silicion
dioxide (SiO2) to form nitrogen gas. The hot blast of nitrogen gas
inflates the nylon bag. The bag is covered with talcum powder for its
lubrication and to help it inflate smoothly.
Solid propellant
inflators:
Solid propellant inflation systems are used to rapidly
produce nitrogen gas in huge amount to inflate the nylon bag. The airbag
circuit passes the current to the heating element. The heating element heats up
sodium azide (NaN3) which acts as an explosive.
Sodium azide
decomposes at 300°C to form sodium and nitrogen gas. The highly reactive Na metal is removed by
KNO3 and SiO2 and in turn produces nitrogen gas. The K2O
and Na2O formed suring second reaction is highly reactive and reacts
with SiO2 in the third reaction to form silicate glass which is
harmless and stable.
The gas travels at more than 300 kmph and inflates the bag
completely in 60 to 80 milliseconds from point of collision. The bag has small
pores which lets the nitrogen gas to escape after few seconds of inflation.
Safety Concerns with
Airbags:
Airbags best work as a supplement to seat belts. Hence, it
is also known as Supplement Restraint
System (SRS). The force of an airbag can also hurt if the driver is sitting
too close to the steering wheel. It is recommended to be at least 10 inches
away from the air bag or steering wheel.
Run flat tires are tires that can run even after it’s
punctured. These tires are specifically designed to run for a short duration
after it is punctured so that you get enough time to run the vehicle to an auto
repair shop.
Run flat tires are becoming more common in everyday cars.
Goodyear started manufacturing run flat tires for NASCAR cars in 1966. It was
introduced in the mid-1980s specifically for commercial purpose. As the
technology proved its usefulness, most of the standard car models are equipped
with such tires.
Run flat tires can run for about 80 km after it suffers a
punctured wound. This grace period allows the driver to drive the car to his
garage or repair shop.
Types of Run Flat
Tires:
There are 2 types of run flat tires:
·Self supporting type
·Support ring type
Self Supporting
System:
In a self supporting type, the tire features a reinforced
side wall construction that will continue supporting the wheels in the event of
air pressure loss. This design helps to operate the tires even after loss of
air from the tires for the specified distance.
Support Ring System:
In a support ring system, a ring of hard rubber is provided
within the tire to support the weight of the vehicle in the event of air loss.
Tire Pressure
Monitoring System (TPMS):
Vehicles employing run flat tires are installed with tire
pressure monitoring system to monitor pressure losses in the tires. Drivers
might be unaware that their vehicle’s tires are punctured in the case of run
flat tires. TPMS alerts the driver of any pressure losses in the tires.
Advantages of Run
Flat Tires:
·We don’t have to change the tires in dangerous
situations. If there is a tire burst while driving on a highway, we don’t have
to immediately stop and change the tires. An average run flat tire can run up
to 80 km after tire burst.
·It provides better control over the vehicle. In
a conventional tire burst, drivers might panic and lose control which can be hazardous.
Disadvantages of Run
Flat Tires:
·It is expensive than a normal tire.
·The driving experience is not comfortable. Since
run flat tires are stiff, they tend to provide a harsh ride.
·There is no wide range of specialized tread
types in run flat tires. Tires especially for off road experience have not been
specifically designed.
ABS is
the short form for Anti lock Braking System which is a safety device installed
in vehicles.
Why is ABS used?
ABS is
used to prevent wheel locking while applying brakes to the wheels. In certain
scenarios owing to the surrounding conditions (such as wet roads, dry surface,
snowy surface, loose gravel, etc.), wheels might skid when brakes are applied
suddenly.
In
other words, wheels might get locked which increases the stopping distance of
the vehicle and also defies the driver the control on the
steering, leading to fatal injuries and in certain cases can lead to
death. ABS helps in maintaining the traction between the wheels and the
surface, thereby preventing the wheels from locking. It also allows the driver
to steer the vehicle and avoid obstacles.
When was ABS introduced?
ABS was
developed in the year 1929 by Gabriel Voisin, a French national who designed it
only for aircraft. It was in the year 1958 that ABS was experimented on a Royal
Enfield Super Meteor Motorcycle and it greatly reduced the stopping distance of
the motorcycle. The system was however not used for commercial purpose.
Later
in the year 1970, Ford added an electronic ABS system called 'sure-track' on
the rear wheels of the Lincoln Continental model as optional for the customers.
A year later, Ford made it standard in Lincoln models. Chrysler, along with the
Bendix corporation, developed a computerized three channel, four sensor all
wheels ABS called 'Sure Brake' for its Imperial model launched in 1971.
In the year 1978, Mercedes Benz introduced the second generation ABS
with the help of Bosch. Mercedes Benz was the first company to introduce
commercial cars with ABS and also ensured large scale production of ABS. This
was all possible due to the revolution in electronics. Integrated circuits and
computers could be built which with the help of computer codes could detect the
speed of the wheels and actuating the valves in no time and made the process
simpler and accurate.
ABS Components:
ABS has
4 main components:
1.Speed sensors: ABS has to know when the
wheel is about to lock up. So sensors are located over the wheels to
provide this information.
2. Valves: Valves are located in the
brake line of each brake which can be controlled by the ABS. Valve has 3
positions in some systems:
In position one,
the valve is open and the pressure from the master cylinder is passed
right through it to the brake.
In position two,
the valve is closed, thereby blocking the pressure from the master
cylinder to the brake.
In position three,
the valve releases some amount of pressure from the brake. The
controller signals the valve to release the pressure once the sensor
senses the wheel is about to slip.
3. Pump: Pump is used to restore
the pressure that was released from the brakes. The controller will control the
pump and makes it pump the required amount of pressure to the brake.
4.Controller: Controller
is the brain of the ABS, also called the Electronic Control Unit (ECU) which
receives the signals from the wheel speed sensors and modulates the ABS system
by controlling the braking valves. If the vehicle is about to slip, controller
will release the pressure from the brakes through the valve.
ABS Working:
Thecontroller (ECU) continuously monitors the speed of each
wheel with the help of speed sensors. If the ECU detects that one wheel is
rotating slower (for a 4 wheeled vehicle) than the other wheels, then it
actuates the valve to reduce the braking pressure on that particular wheel so
that it can start rotating faster and match the speed of the other wheels.
Conversely,
for a wheel rotating faster than the other wheels, the controller actuates the
valve to increase the braking pressure on that particular wheel to slow it down
and match other wheels' speed.
The
driver can feel the ABS working through his or her foot through the brake
pedals which will be pulsating. In some cases, ABS can release or apply the
brake pressure 15 times per second.
Types of ABS:
ABS can
be classified into various types based on the number of speed sensors and
valves:
1.Three channel, three
sensor ABS: This system has a speed sensor and a valve for each of the front
wheels, and a common speed sensor and a valve for both the rear wheels. For
rear wheels, it is located on the rear axle. This system provides maximum
efficiency for the front wheels. In the case of rear wheels, both the wheels
have to lock up for the ABS to function. There is always a possibility of one
of the rear wheels to lock up, reducing the effectiveness of ABS.
2.One channel, one sensor
ABS: This system is commonly used only for rear wheels which will
have a common valve and a speed sensor. Both the rear wheels have to lock up so
that the ABS can work. This is a rather ineffective system.
3.Three Channel, four
sensor ABS: This system employs separate speed sensors for each wheel and
separate valves for each of the front wheels. A common valve is used for the
rear wheels. If the controller detects lock up of one of the rear wheels, then
brake pressure will be applied on both the rear wheels.
4.Four channel, four sensor
ABS: Separate speed sensors and valves are used for each wheel. This
system provides the maximum brake effectiveness.
5.Two channel, two sensor
ABS: Separate speed sensors are used on each wheel and separate
valves are used for both front and rear axle. If there is a wheel lock up on
any wheel (say front left wheel), then braking pressure will be applied to both
the front wheels.
Kill switch is a safety device found in most of the modern day motorbikes. It is also known as 'Engine cut-off switch'. The purpose of a kill switch is to simply switch off the engine by cutting off the engine ignition. When you insert the key in the ignition switch, the current from the ignition switch is fed to the kill switch and then passed to the fuel pump relays and engine control relay.The engine's ignition will be turned ON only when the circuit is complete.
Kill switch was mainly introduced for emergency situations such as sudden accidents when the biker cannot reach for the ignition key to turn off the engine. It is of prime importance to turn OFF engines in such emergency situations to prevent any bigger danger such as fire accidents.
Kill switch can also be used when a bike is stationary. It is always recommended to turn ON the kill switch when a vehicle is parked. However, turning ON the kill switch won't turn off the electric supply to other electrical equipments such as horns, headlights, turn indicators, etc. Therefore, it has to be ensured that the ignition switch is also switched OFF after turning OFF the engine to prevent the battery from draining.
