Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
Research Paper
AUTOMATIC SEAT BELT FOR PASSENGER VEHICLE
R.Prakash*1, R.Prakash1, K.SaiKrishna1, C.Sathishkumar1,
S.Vivekanandan1
Address for Correspondence
* Mechanical Engineering, SSN College of Engineering, Anna University, Chennai, Tamil Nadu, India
ABSTRACT:
1
The system consists of a ring gear setup which lies below the seat. The seat belt is mounted on the ring gear which is meshed
with a pinion driven by a motor. Provisions are made to adjust the ring gear setup based on the position of the buckle which
can be altered according to the convenience of the passenger. The ring gear is designed to follow maximum possible
projectile to accommodate passengers of different size. Once the passenger occupies the seat, the motor is switched on in the
forward direction. The belt is carried by the curved ring gear and locked with the buckle. Once the seat belt is locked with
the buckle, the motor runs in the backward direction till the ring gear is brought back to its initial position. In the existing
scenario of automatic seat belts, belts are attached to doors. A crash that causes the doors to open leaves the passenger
unprotected. The foremost advantage of this type of automatic seat belt is that it is attached to a sturdier portion i.e. frame of
the car instead of doors.
KEYWORDS: Injuries, Safety, ANSYS, Pressure Sensor, Infrared Sensor, Color Sensor, Microcontroller.
1 INTRODUCTION
Seats belts play a vital role in the safety of
passengers. Seat belts are designed to keep the
passengers from being thrown from the car. They are
also designed to absorb the impact of a crash. Seat
belts also stretch slightly so our body doesn't stop
abruptly, and they prevent us from colliding with a
part of the car or another person. Death as a result of
ejection of unrestrained occupants from the vehicle is
the major cause of fatalities in vehicle crashes.
However the importance of wearing a seat belt is
often overlooked. An automatic seatbelt system can
go a long way in ensuring usage of seatbelts.
Automatic seat belts have been introduced as early as
1975 but there is no such arrangement in the industry
at present. Such belts were discarded because of
various disadvantages. Also it gets in the way of side
curtain air bags.
1.1 Why passengers fail to use seat belt?
Major cause of fatalities in road is due to non-usage
of seatbelt by passengers which can be attributed to
various reasons like
 Carelessness and forgetfulness of the
passengers.
 Absence of concrete legislative laws for
wearing seat belts.
 Ignoring the importance of seat belts.
1.2 Importance of seat belt
Ejection from the vehicle is one of the most
injurious events that can happen to a person in a
crash.
The fig. 1 clearly shows that more than 70% of
the injuries incur to passengers of trucks and
automobiles.
Fig. 1. The percentage of injuries
Fig. 2. Fatality to injury ratios for occupants using seat
belt and not using seat belt by age
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From fig. 2 , as the age of the occupant increases,
the fatalities per 1000 injuries also increases. This
can be attributed to the fact older the occupant higher
the mortality rate.According to the National Highway
Traffic Safety Administration (NHTSA) in fatal
traffic crashesabout 79% of passengers who were
totally ejected from the vehicle were killed and
about60 percent of passengers who were not wearing
safety belts were killed.
Fig. 3.The percentage of drivers and passengers
wearing seatbelts
From Fig. 3 use of seat belt by drivers has
increased from 45% to 77% and the use of seat belt
by passengers has increased from 37% to 68%.
Research has found that lap/shoulder seat belts, when
used, reduce the risk of fatal injury to front-seat
passenger car occupants by 45 percent and the risk of
moderate-to-critical injury by 50 percent. For lighttruck occupants, seat belts reduce the risk of fatal
injury by 60 percent and moderate- to-critical injury
by 65 percent.
Fig. 4.Cumulative estimated number of lives saved by
seat belts
Fig. 4 shows the cumulative number of lives
saved by using seat belts. Studies by road safety
authorities conclude that seat belt legislation has
reduced the number of casualties in road accidents.
Experiments using both crash test dummies and
human cadavers also indicated that wearing seat belts
should lead to reduced risk of death and injury in car
crashes. According to a WHO report, India has the
highest number of road deaths in the world – 105,725
Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
in 400,000 accidents, followed by China (96,611),
the US(42,642) and Russia(35,972). Of these deaths,
25% can be avoided by making seat belt usage
compulsory. Though there are no concrete laws to
enforce the use of seat belts in India, it was made
compulsory that all cars manufactured after March
25, 1994 should be equipped with front seat belts.
The rule was extended for rear seats in 2002.
2. LITERATURE SURVEY
Ooka M, Sugiura F, proposed an automatic seat
belt applying device on October 22, 1974 where the
seat belt is fastened over the occupant automatically
in correspondence with opening or closing of the
door of a vehicle. A conventional seat belt guide rail
is arranged to form a virtually linear line along a
diagonal connecting the lower section in the rear on
the internal surface of a door.
MasaharuSaji and KamiMigusa proposed an
automatic seatbelt on August 21, 1990 where lap seat
belt and shoulder seat belt are automatically set to
restrain a seated person end of each belt is in a guide
ran diagonally disposed on the inner surface of the
door. Second ends of the belts are on the inner side of
the bottom seat and on the inner side of the seat back
respectively.
Jesse R. Hollins proposed automatic seatbelt
buckle and unlatching mechanism on June 15, 1976
and a seat belt buckle automatic unlatching
mechanism including a seat belt arrangement
comprised of a first seat belt strap and a second seat
belt strap. Attached to one end of the first seat belt
strap is a latching tongue and attached to one end of
the second seat belt strap is a tongue latching
mechanism. Chris Lee, discussed Analysis of injury
severity of drivers involved in single and two-vehicle
crashes on highways in Ontario on 1st February 2014.
This study analyzed driver’s injury severity in single
and two-vehicle crashes using the 5-year crash
records in Ontario, Canada. To account for variations
in unobserved effects of variables on injury severity
among observations, Heteroscedastic Ordered Logit
(HOL) models were developed for identifying the
association between injury severity and explanatory
variables. For two-vehicle crashes, crash records
were separated into nine data sets of different
combinations of vehicle types considering the
differential impacts of the collision on vehicles due to
difference in their size and weight. Vehicles were
classified into cars, light trucks, and heavy trucks.
Timo Lajunen discussed “Why Turks do not use
seat belts?” an interview study on 12 November
2006.Despite the effectiveness of seat belt use and
legislation, seat belt use rate is low in Turkey. The
aim of this study was to investigate the motives to
use and not to use a seat belt in different traveling
conditions in a sample of car drivers and passengers.
Interviews were made face to face with 221
interviewees from different age and occupation
groups. Frequently reported reasons for using a seat
belt were traveling conditions, safety, situational
conditions, habit of using a seat belt, and avoiding
punishment.
2.1 Inference based on the survey
Various publications regarding automatic seat
belts were studied and several reasons, as to why
these belts were discarded, were found. Even though
shoulder belts were automated, passengers must still
fasten the lap belt manually, thus rendering the
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E-ISSN 0976-3945
automation of the shoulder belt redundant. Motorized
or door-affixed shoulder belts hinder access to the
vehicle, making it difficult to enter and exitparticularly if the occupant is carrying items such as
a box or a purse. Vehicle owners tend to disconnect
the motorized or door-affixed shoulder belt to
alleviate the nuisance of entering and exiting the
vehicle, leaving only a lap belt for crash protection.
Despite the proven effectiveness of seat belt use and
enacted seat belt legislation, a high amount of car
occupants fail to use seat belt. This system
concentrates on eliminating these discrepancies.
3. METHODOLOGY
The design of the system was prepared using Solid
Works software. The process to select the most
suitable material for the design of the gears was then
started. Aluminium was chosen but reinforced fibers
can also be used. The specifications for the gear
design were determined. The size of the seat from
real to prototype and the size of the gear to the
prototype were scaled accordingly. The next step was
machining the gear and the guideway setup. This was
done by gear shaping machine. The guideway was
made by cutting two parallel arc shaped strips out of
sheet metal using gas cutting. These two curved
plates were then welded by arc welding. The rollers
were machined by centre lathe and a hole in the
centre of the rollers was made and fixed with help of
nails which were welded to the guideway. The
electronic equipment necessary for the project was
then procured namely Arduino microcontroller,
pressure sensor, IR sensor, color sensor and
programmed as needed. After programming the
microcontroller the whole setup was assembled and
simulation and analysis were carried out with the
help of ANSYS. It was found that the maximum
stress induced was less than the ultimate stress and
hence the design was considered to be safe.
Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
4. BASIC DESIGN OF AUTOMATIC SEATBELT
Fig. 5 shows the basic design concept for the
automatic seat belt system .The ring gear is situated
beneath the seat and is will be inclined at an angle
between 35 to 45  according to the buckle on the
other side. The potentiometer and servomotor setup
causes the guide way along with the ring gear to get
synchronized with the position of the buckle. The
potentiometer is attached to the buckle rod. The
servomotor is attached to the guide way setup by a
clamp made of stainless steel. The potentiometer
transmits voltage to the servomotor which rotates to
adjust the position of the guide way according to the
position of the buckle rod. The ring gear slides over a
guide way with the help of rollers as shown. A pinion
mated with the ring gear is connected to the dc
motor.
Fig. 5. Basic arrangement of automatic seatbelt
Fig. 6. Ring gear and pinion arrangement
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4.1 Stress with deflection analysis
Fig. 9. Nodal solution for the stress analysis on the ring
gear
In Fig 9. A denotes the end of the gear on which the
seat belt latch is mounted, while B denotes the free
end. It can be observed that the stress is maximum
near end A while lesser at the end B.
Working stress is approximately = 3000 N/mm2
The stress acting on the A portion is maximum
because starting torque is applied by the pinion gear
at this position to set the ring gear in motion.
Fig. 10 shows curved ring gear analysis. The curved
ring gear is analyzed based on the stress and
displacement method on the material aluminum of
density 2750 kg/m3. The problem was theoretically
solved by use of maximum load carrying capacity
technique.
The factor of safety of aluminum was assumed as 2.
The analysis was done using ANSYS version 14.5.
The deflection of the gear was found to be 0.128 m
when a dynamic load of 1 N was applied on the gear
teeth at the end of the gear locks. Hence the design is
safe. In the figure illustrated above maximum stress
and maximum strain are noted to find the ultimate
stress and yield point of the material.
Fig.6 Shows ring gear which is used in seat belt.
Ring gear is cut as per the angle of 210 because the
passenger will be sitting in between the gap of two
edges.
Fig. 10. Analyzed curved ring gear
Fig. 7.Guideway with rollers
The guideway is illustrated in the fig. 7. It
consists of two parallel arc shaped sheet metals
bound together by rectangular sheet metal plates by
arc welding. Rollers have also been fixed at certain
positions along the guideway for smooth motion of
the gear. A hole has been drilled inside each roller to
which a nail had been fixed and welded to the
guideway. 6 pairs of mild steel rollers were used
throughout the length of the guideway each pair
located at an arc angle of 30˚. The steel roller is
shown fig. 8.
Fig. 8. Magnified view of rollers
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5.
ELECTRONIC COMPONENTS
Pressure Sensor:
Pressure sensor is located at the bottom of the
passenger seat. It works based on the capacitance
varying signals.
Infrared Sensors:
Infrared sensor is located at the end of belt lock
system. This purpose of the sensor is to detect the
belt lock or unlock position.
Color Sensor:
Color sensor is located inside the side mirror of
the automobile, it detects the white and yellow
colors.
Microcontroller & Motor:
Arduino is a simple microcontroller board and
open source development environment that allows
you to make computers that drive both functional and
creative projects alike. It is shown in fig. 11.
DC geared motors 200RPM 12V for robotics
applications, very easy to use and available in
Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
standard size.Nut and threads on shaft to easily
connect and internal threaded shaft for easily
connecting it to wheel.
Fig. 11. Arduino microcontroller
Arduino Uno consists of 14 digital input/output
pins (of which 6 can be used as PWM outputs), 6
analog inputs, a 16 MHz crystal oscillator, a USB
connection, a power jack, an ICSP header, and a reset
button
Power Jack:
Arduino can be powered either from the pc
through a USB or through external source like
adaptor or a battery. It can operate on an external
supply of 7 to 12V. Power can be applied externally
through the pin Vin or by giving voltage reference
through the IORef pin.
Digital Inputs:
It consists of 14 digital inputs/output pins, each of
which provide or take up 40mA current. Some of
them have special functions like pins 0 and 1, which
act as Rx and Tx respectively , for serial
communication, pins 2 and 3-which are external
interrupts, pins 3,5,6,9,11 which provides pwm
output and pin 13 where LED is connected.
Analog inputs:
It has 6 analog input/output pins, each providing a
resolution of 10 bits.
ARef:
It provides reference to the analog inputs
Reset: It resets the microcontroller when low.
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Sensors based upon the capacitive sensing
technique are strain-based sensors. Fig. 14 shown
where the sensor capacitances are arranged in a pushpull, half-bridge configuration where both capacitors
are parameter modulated. Simple media isolation is
achieved when one capacitance is parametermodulated and the other capacitance within the halfbridge circuit is an unmodulated reference
capacitance. Capacitive sensors require a dynamic
excitation and all capacitive designs contain an
internal oscillator and signal demodulator to provide
static capable outputs. In most cases these
components will limit the useful operating
temperature range from -40ºC to +120ºC.
Fig. 14. Capacity varying section
5.2 Working of IR Sensor
An IR sensor is a device which detects IR radiation
falling on it. There are numerous types of IR sensors
that are built and can be built depending on the
application. Proximity sensors (Used in Touch
Screen phones and Edge Avoiding Robots), contrast
sensors (Used in Line Following Robots) and
obstruction counters/sensors (Used for counting
goods and in Burglar Alarms) are some examples,
which use IR sensors.
Fig.12 shows Arduino structural view.
Fig. 15. IR sensor
Fig. 12. Arduino structural view
Fig 13. Pressure sensor
5.1 Working of Pressure Sensor
The capacitive pressure sensor uses a diaphragm
and pressure cavity to create a variable capacitor to
detect strain due to applied pressure. Common
technologies use metal, ceramic, and silicon
diaphragms. Generally, these technologies are most
applied to low pressures (Absolute, Differential and
Gauge). It is shown in fig. 13.
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5.3 Working Mechanism
An IR sensor is basically a device which consists of a
pair of an IR LED and a photodiode which are
collectively called a photo-coupler or an optocoupler. The IR LED emits IR radiation, reception
and/or intensity of reception of which by the
photodiode dictates the output of the sensor. Now,
there are so many ways by which the radiation may
or may not be able to reach the photodiode.
Direct incidence
The IR LED may be directly held in front of the
photodiode, such that almost all the radiation emitted,
reaches the photodiode. This creates an invisible line
of IR radiation between the IR LED and the
photodiode. Now, if an opaque object is placed
obstructing this line, the radiation will not reach the
photodiode and will get either reflected or absorbed
by the obstructing object. This mechanism is used in
object counters and burglar alarms.
Indirect Incidence
High school physics taught us that black color
absorbs all radiation, and the color white reflects all
radiation. This very knowledge was used to build the
IR sensor. If the IR LED and the photodiode are
placed side by side, close together, the radiation from
Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
the IR LED will get emitted straight in the direction
to which the IR LED is pointing towards, and so is
the photodiode, and hence there will be no incidence
of the radiation on the photodiode. Please refer to the
right part of the illustration given below for better
understanding. If an opaque object is placed in front
the two, two cases occur:
1. Reflective Surface
If the object is reflective, (White or some other light
color), then most of the radiation will get reflected by
it, and will get incident on the photodiode. For
further understanding, please refer to the left part of
the illustration below.
2. Non-reflective Surface
If the object is non-reflective, (Black or some other
dark color), then most of the radiation will get
absorbed by it, and will not become incident on the
photodiode. It is similar to there being no surface
(object) at all, for the sensor, as in both the cases, it
does not receive any radiation.
The IR sensor acts as Proximity Sensors to detect the
presence of the seat belt latch.
Reflective indirect incidence
It is used for making proximity sensors. The radiation
emitted by the IR LED is reflected back on the
photodiode by an object. Closer the object, higher
will be the intensity of the incident radiation on the
photodiode. This intensity is made analogous to a
voltage by a circuit, which is then used to determine
the distance.This is shown in fig. 16.
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5.5 Circuit process flow diagram
Initially if the pressure sensor senses the pressure and
IR sensor senses the lock position as unlocked, after a
delay for a specific time they are checked again (in
case the passanger was seated only for a short
duration of time ) and if the same output is obtained
from the sensors the indication to switch on the
motor is sent. After a given delay the motor is
switched on. The gear traverses a curved path along
theguideway untill it locks itself with the other
section section of the setup. Once the lock is sensed
by the IR sensor there is another delay after which
the motor reverses its direction of rotation. It is
shown in fig. 19.
6. WORKING OF AUTOMATIC SEATBELT
When a passenger sits on the seat, the pressure sensor
is actuated followed by a 10 second delay to check
whether the seatbelt is locked or not and whether the
passenger is still sitting on the seat and then the
signal is sent to the Arduino microcontroller after
which there is a 5 second delay and then the motor is
switched on in forward direction. The belt is carried
by the curved ring gear and is locked to the buckle
situated on the left hand side of the seat.An IR sensor
is located near the lock which senses whether the belt
is locked or not. If the belt is locked the sensor sends
a signal to the microcontroller which is followed by a
5 second delay and then the microcontroller reverses
the direction of roatation of the DC motor. Hence the
curved ring gear traverses its path back to the initial
position whereas the seat belt remains in locked
position. After the gear returns back to its initial
position,i.e.,after a delay of 8 seconds the motor is
switched off. Once the seatbelt is disengaged after
the travel, the passenger has to fix the seatbelt tongue
to the provision at the beginning of the ring gear
which would be at the right bottom side of the seat.
Fig. 16. Indirect incidence of IR radiation
5.4 Circuit Diagram
The block diagram is shown in fig. 17.
Fig. 17. Block diagram of the components
The connected components with Arduino is shown in
fig., 18. The Pressure sensor which is located at the
bottom of the seat is connected to the microcontroller
that in turn is connected to the DC Motor drive. The
DC Motor drive is given a DC Power supply. The
drive is connected to the DC motor. The Lock
sensor/IR sensor is also connected to the
microcontroller. The main function of the lock sensor
is to sense whether the seat belt is locked and give
indication to the microcontroller accordingly.
Fig. 18. Components connected to Arduino
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Fig. 19. Circuit process flow diagram
Prakash Ramasamy et al., International Journal of Advanced Engineering Technology
Arduino programming
The above mentioned programme is programmed by
the using Arduino Software. The software is used as
the control of electronics parts.
The community of Arduino enthusiasts is vast, and
includes region specific groups and special interest
groups. The open-source Arduino Software (IDE)
makes it easy to write code and upload it to the
board. It runs on Windows, Mac OS X, and Linux.
7. CONCLUSIONS
Occupant safety has been a subject of intense debate
for nearly as long as automobiles have been on the
roads. Seatbelts, credited with being the most
important and effective safety feature currently
available in cars, have been both a point of
contention among and a focal point of efforts
undertaken by advocates, manufacturers, and
government in improving traffic safety.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
Nissan Motor (Oct 28, 1975),”Passive seat belt
arrangement for automotive vehicles”Publication dateJul 22, 1980. Patent No: US4213637.
Juichiro Takada, “Movable inboard belt guide for use
in passive vehicle occupant restraint system”
Publication date – Mar 2, 1982. Patent No: US
4258933.
Toyota- Jidosha, KogyoKabushiki ,“Automatic seatbelt
system” Publication date: Feb 15, 1983. Patent No:
US4372580.
Nissan motor co. Ltd, “Seatbelt device for an
automotive seat occupant” Publication date: Sep 20,
1983. Patent No: US4413841.
Honda - Giken Kogyoand Kabushiki Kaisha“Seatbelt
device” Publication date: Jan 13, 1987. US4635963.
John Barker, “Safety enhancement for a safety belt”
Publication date: Apr 29, 2014. Patent No: US8708370.
AsmoCo,Ltd , “Auxiliary mechanism for seat belt
apparatus” Publication date: Jul 19, 2011. Patent No:
US7980635.
Michael Bouju,“ Seat belt security release mechanism”
Publication date: Sep 20, 1977. Patent No: US4049293.
GeorgeCoulombe,“Automatic releasing seat belt”
Publication date: Jul 31, 1979, Patent No: US4162715.
Nippon Soken , “Automobile seat belt system with
automatic unlocking function” Published date: Nov 19,
1985. Patent No: US4553625.
Fleming JosepA, “Thermally actuated seat belt
fastener” Publication date: Dec 19, 1987. Patent No:
US4715096.
MeckewJames,“Automatic
time-delayed
release
buckle” Publication date: Mar 14, 1991. Patent No:
US5014810.
Wesley T, Leedy“ Automatic restraint belt release
system” Publication date: Nov 26, 2013. Patent No:
US8590935.
Bilyeu&Dant, “Child-proof seat belt locking assembly”
Publication date: May 12, 1998. Patent No:
US5749130.
Tk Holdings Inc,“ Remotely actuated seat belt buckle”
Publication date: Aug 14, 2012. Patent No:
US7905789.
GavriHerzl , “A self-releasable safety belt” Publication
date: Dec 12, 1996. Patent No: WO1996039316A1.
BayerischeMotorenWerkeAg,“Safety-belt buckle in a
motor vehicle” Publication date: Dec 28, 1989. Patent
No: DE3821066A1.
Trw Inc., “Seat belt tightening apparatus” Publication
date: Apr 10, 2001. Patent No: US6213512.
Joseph A Tabe,“Smart seatbelt control system”
publication date: Nov 4, 1999. Patent No:
WO19999055560A1.
Daimler Chrysler Ag,“Motor vehicle comprising means
for vehicle occupants” publication date: Oct 27, 2005.
Patent No: WO2005100102A1.
Hughes A, “Compulsory seat belts” Publication date:
Jun 4, 1974. Patent No: US3815086.
Lindblad O L has published a patent of “Safety belt
arrangement for individuals” Publication date: Dec 23,
1975. Patent No: US3927902
http://www.nhtsa.gov
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