EC-0123
SOS TRANSMISSION
Through Cellular phones to save Accident Victims
-Boon for the cellular phone users
Abstra
This paper describes an ORIGINAL IDEA to help cellular phone users caught in an
accident. The idea has been developed keeping in mind the considerations of cost and
compatiblity with existing system, The Short Message Service or SMS as it is popularly referred to,
is made use of for this purpose.
The solution offered is the Force-Transducer method. The victim is assumed to be
unconscious and the accident is detected automaticaly. Detailed simulation results at a scaled
down level are provided for this solution. The threshold level is set based on data collected from
the experiments.
One major problem in such design is the technique to find the vietim's position. The Global
Positioning System (GPS) is found fo be costly. So, an unorthodox design using Radio Direction
Finders (RDF) and beacon signals is described. The Goniometer or Crossed Loop Antenna is used
for this purpose, This reduces cost effectively when compared with the GPS system. The paper
proceeds to suggest an abstract view of the software robo! required to perform the Save Our Souls
(SOS) message routing task. It uses a special hierarchical message dispatch system wherein
people nearby and more Ikely fo help are contacted. The robot also acts as a proxy to the vietin
and monitors responses for him.
This paper as a whole gives a cost-effective, high performance system which can be
introduced in the market i any of the cellular companies are wiling to encourage it
Key Words: Short message service, force transducer, Radio detection finder, global positioning
system, goniometer, robot
Conclusion: The system though complete presents a few limitations. They are, the system
requires the user to place the cellular phone in a stand or connect the transducer to the vehiole in
case of four wheelers. Though this might seem as if taking choice fram the user, the fact that the
system deals with a question of lile or death is more important. The system needs detailed
surveying to decode the position of the user in polar coordinates to actual localities. This however
isa one time job. This can be reduced by ringing the cellular phone every time an SOS is sent and
thereby warning the user. The data collected are approximate. However, accurate data can be
collected i the system is tested in real time as a commercial venture.
Thus, if implemented this system would prove to be a boon to all the people out there driving with
hands-free earphone in their ears,1. Introduction
Cellular phones are turning out to be a menace on the road. This is @ mejor problem for the
cellular phone manufacturers, This paper provides a solution which transmits @ SOS signal to save
the accident victim. It describes in detail a cost-effective foolproof solution.
There are many factors to be considered when designing such a system. In most of the
accidents, the viotim becomes unconscious, How is @ SOS transmitted then? Here, many ideas
can be implemented, One such solution is described here. The cell phone is fitted with a
transducer, which detects shocks. The cell phone automatically transmits the SOS if the shock
level goes beyond a certain percentage. The cell phone must not trigger an accidental SOS. To
‘ensure this, the shock level that triggers the SOS must be high enough. Based on the frst
‘condition, ifthe shock level is made very high, then an accident might not be identified at al
Fig: Antenna used in RDF to identify the position of the victim
Having thus identifed the situations in the accident, one needs to understand the actual
requirements in each case. They are given below.
The solution requires a software robot resident in the cellular phone provider's server, which can
transmitthe SOS signal in an inteligent manner and monitor responses for the victim
i)Similarly, the solution needs @ Positioning System to transmit the vietim’s whereabouts to others.
This has to be a cheap system and should not increase the cell phone receiver's cost greatly.
i)The solution requires a high fidelity shock transducer and decoding circuit fo identify the shock
‘magnitude
ihe SOS has to be transmitted as soon as possible, So all systems must have a very small time
delay
ivjAbove al, the new system must fit in with the present system (.e.,) there mustbe no difference in
the information received between a user who requests this option and one who does not
The detailed description of the solution willbe presented now.
2. The Toy Car Experiment
Incase the victim becomes unconscious, the system must be able to automatically detect an
‘accident and transmit the SOS automatically. In order to achieve this, a shock transducer is used
to measure the jerk experianced through the accident and trigger the SOS circuit f the force level
is very high. This system needs statistical data acquisition to find out the exact threshold level of
the force in an accident. Its highly expensive to simulate the accident in real tne, So, a scaled
down experiment is used, Here, a pair of toy cars of mass 200g is made to collide with each other.
The force caused by them is measured by simple piezoelectric transducers. The results of this
‘experiment are tabulated below.Fig : Toy car experiment to verify the working of the system
Table 21
ample Measured Voltage Actual Force
lo, mv) Newion }
fr [13.2 a7
2. l127 972
143 985
fas 387
b 133 978
jean (1136 980)
‘As seen from the experiment, the average force acting ona loy car in case of an accident is
approximately 1N. For a car measuring 960kg and moving at 70kmph speed, the force will be
scaled 18000 limes ot 18kN. These practical results can be verified by a simple theoretical
calculation. A car weighing 960kg decelerates from approximately 7Okmph to Okmph in 2 seconds
in case of an accident. Hence, the force is given by F =ma which is, 960°70" 1000/3600 or 18.67kN
approximately. This confirms with the scaled down experimental results. However, in afour-
wheeler, all ofthe total force does not act inside the vehicle. As per information got from Mercedes
Benz, only 10% of the total force acts inside the car (Acknowledgement (4)). Thus, the threshold
canbe sel to approximately at 1kN. The scaled down experiment used a cheaper transducer that
does no! measure high forces. The transducer required for the actual system costs Rs. 1000 a par.
Based on the statistical dala collected above, the approximate threshold level is determined. More
accurate results can be determined if the experiments are carried in real time to the exact detail
In order to ensure that the force caloulated above acts on the cell phone, itis essential fo place the
phone in the stand thal normally comes as a standard part of cars. This stand requires a slight
modification to provide the cell phone a small moving space so that iis jerked when an accident
oocurs. The alternate and belter solution would be to attach the transducer to some part of the
\ehiole itself and connect the cell phone to it whenever the user is driving hi/her car. This solution
would require that the transducer be properly protected, The problem of finding the position’s victim
is now dealt with
3. Identifying the Position of the Victim
The problem of knowing where we are has been an interesting and difficult problem through
the ages. Yeats of research have resulled in the Global Posttioning System (GPS). This technique
Uses three satelites and pin points the location by the triangulation process, wherein the user's
postion is located as the point of intersection of the three circles corresponding to the satelites.
Instaling such a system is quite simple. Bul the major constraint here isthe cost. A normal hand-
held GPS costs around $100 and weighs quite heavy. Minimizing the above apparatus will
increase the cost further. This would mean an extra cost of Rs. 10000 to Rs, 15000 forthe Indian
user.