1. Ultrasonic Sensor-Aided Intelligent
Walking Stick for Visually Impaired1
A. Allen Selvanayagam
Department of Biomedical Engineering,
SBST,
VIT University,
Vellore 632014, India
R. Harish Kumar
Department of Biomedical Engineering,
SBST,
VIT University,
Vellore 632014, India
A. Ganesh Prashanth
Department of Biomedical Engineering,
PSG College of Technology,
Coimbatore 641004, India
S. Vidhya
Department of Biomedical Engineering,
SBST,
VIT University,
Vellore 632014, India
1 Background
The visually challenged people face several challenges while
they try navigating at home or other places. These problems are
generally addressed by conventional walking sticks. Later, devel-
opments in the walking sticks were done using a numerous meth-
odology with an enormous improvement being made on the
previous models. The electronic sector intervened and changed
the way the walking sticks were made and now they are termed as
“smart sticks” [1]. Unfortunately, the increased use of sensors
hiked the cost thereby making it unaffordable by the needy. This
project aims on the usage of reduced number of sensors and
thereby reducing the cost of the device while meeting the required
accuracy and facilities. This system will be able to detect the
obstacle present in various directions with a single sensor. A new
way of alerting mechanism has been approached in this project
which is simple and more efficient to let people know in which
direction the object is present. This system also aims on maximum
accuracy at a lower cost without compromising the safety of the
person.
2 Methods
The currently available walking sticks make use of ultrasonic
sensors to detect the obstacles in their pathway [2]. The complex-
ity of the device demands an increase in the number of the sensors
used. People of underdeveloped countries find it unacceptable to
pay for such an expensive device. Hence, this project focuses on
reducing the cost of the device. The number of sensors used is
reduced by placing the sensor over a stepper motor, and the motor
is rotated in a programed speed, for 180 deg to and fro. This facili-
tates the area in front of the person to be covered completely. This
ensures the whole area in front of the person to be covered, by
using a single sensor without the need for an increased number of
sensors. The circuit diagram of the system is shown in Fig. 1.
2.1 Motor Unit. Stepper motors are DC motors that are used
mainly in the applications where there is a need for step count or
precision. The stepper motor has four coils that are activated
according to the pulse given by the microcontroller, and the rota-
tion required is achieved. They provide a very high-precision
movement at a very low cost. The stepper motor has four inputs
each with respect to the four coils available. The motor used
in this project has a holding torque of about 4.2 kg cm which is
sufficient enough to serve the purpose. The control driver and the
microcontroller control the motor by providing a pulse signal. The
motor driver bridges the microcontroller and the motor. Motor
driver receives the inputs from the microcontroller at lower vol-
tages and runs the motor at higher voltages after processing it.
2.2 Detection Unit. The detection unit consists of an ultra-
sonic sensor which helps in detecting the obstacles in the pathway.
The ultrasonic sensor works on the principle of the basic radar.
The sensor has a transmitter and a receiver. When an input
signal is given from the microcontroller, eight cycles of 40 MHz
ultrasound waves are being transmitted for 10 ls [3]. Later, the
transmitter is switched to low and the transmission is stopped.
The reflected wave produced by striking the obstacles is received
by the receiver. With the time taken for the waves to reflect from
the object, the distance between the object and the device can be
calculated using the formula
Distance ¼ ðH Â CÞ=2
where H is the time for which the receiver is in ON state and C is
the velocity of sound. The conversion of the result to centimeters
or inches can be done by
uS=58 ¼ cm; uS=148 ¼ in:
2.3 Control Unit. Microcontroller serves as the control unit
of the system. The programing is done in the software ARDUINO
which is the integrated development environment for coding the
controller. In this system, the microcontroller controls the motor,
the sensor, and the vibrators. The microcontroller is powered by
an external battery packed in the device. The microcontroller has
an inbuilt timer and oscillator, so that it makes it easier to get the
time difference between the transmission and reception of the
signals.
Fig. 1 Circuit diagram
1
Accepted and presented at The Design of Medical Devices Conference
(DMD2016), April 11–14, 2016 Minneapolis, MN, USA.
DOI: 10.1115/1.4033761
Manuscript received March 1, 2016; final manuscript received March 17, 2016;
published online August 1, 2016. Editor: William Durfee.
Journal of Medical Devices SEPTEMBER 2016, Vol. 10 / 030928-1Copyright VC 2016 by ASME
Downloaded From: http://tribology.asmedigitalcollection.asme.org/ on 01/03/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use

2. 2.4 Alerting Unit. A new approach for the alerting
mechanism has been implemented. Two vibrator motors and a
buzzer are used. The two vibrators are placed in two different
areas in the body so that there is no perplexing scenario faced by
the person. One of the vibrator motors is placed on the arm and
the other motor is to be worn on the fingers of the person as a
ring. So veritably, these two vibrators simplify the intricate detec-
tion process. It is programed in such a way that at least one of
these three conditions is satisfied. If the obstacle is in the range of
0–70 deg, the vibrator present on the arm vibrates, and if the
obstacle is in the range of 110–180 deg, the ring vibrator vibrates.
If the range is between 70 deg and 110 deg, both the vibrators are
put to high and it indicates to the person that the obstacle is in
front of him/her. The buzzer triggers whenever the range of the
sensor reading goes below 0.5 m. Thus, the person is given an
alert without any complexion or bewilderment, as to where the
obstacle is present. Figure 2 shows the flow of signals from the
various modules used in the system.
2.5 Process. The system functions as follows. The sensor
reading is monitored regularly while the motor rotates for 180 deg
to and fro. When an obstacle is detected, the motor is stopped
immediately. The degree where the motor halts is noted, the range
is considered, and accordingly, the corresponding vibrator is trig-
gered. If the range attains a much lower value than the programed
value, the buzzer is triggered. Until this point, the motor is made
to be still, and after a provided delay time, the motor is switched
on again. If the patient is in a closed environment, the sensor
range need not be higher as the objects are nonmoving unlike an
open environment where the objects are moving, and in some
cases, they might be fast as well. Hence, this system is provided
with two modes which can be swapped based on the environment.
In one mode, the range is lower, and in the other, the range is
programed to be higher.
3 Results
The proposed system works efficiently when tested in various
conditions. It is found to be cost-effective and the safety of the
user is satisfactory. The system is reliable and fast with a mini-
mized mechanism used. The two modes of the system assure
more safety, which is very useful for the users to maneuver
through any kind of environment. The new approach for the alert-
ing mechanism is very helpful and simpler. The mechanism of the
device makes it much cheaper, making it affordable for all classes
of people, rather than choosing other luxurious smart walking
sticks (Fig. 3). On a large-scale production, the cost of the stick is
estimated to be 2500–3000 INR.
4 Interpretation
This new system helps the visually challenged people to be safe
in both the open and closed environment. The system is pictured
to accept any modifications that are expected to be made in the
future. By integrating global positioning system (GPS) technology
in the stick, people will eventually find it easier to navigate to
desired places [4]. The use of the two vibrator system for alerting
replaces the need for a costly voice-controlled system. Consider-
ing the cost of this stick, the limitations such as detection of drop-
offs and over-head hazards could be foreseen with an addition of
a stationary sensor. Using slender and lightweight electronic com-
ponents, the weight and balance can be compromised and
improved prospectively.
References
[1] Kim, S. Y., and Cho, K., 2013, “Usability and Design Guidelines of Smart Canes
for Users With Visual Impairments,” Int. J. Des., 7(1), pp. 99–110.
[2] Mahmud, M. H., Saha, R., and Islam, S., 2013, “Smart Walking Stick—An
Electronic Approach to Assist Visually Disabled Persons,” IJSER, 4(10),
pp. 111–114.
[3] Gayathri, G., Vishnupriya, M., Nandhini, R., and Banu Priya, M., 2014, “Smart
Walking Stick for Visually Impaired,” IJECS, 3(3), pp. 4057–4061.
[4] Alam, U. K., Al-Amin, Md., Rabby, F., Chowdhury, N. B., and Islam, M. T.,
2014, “Study of Construction a Technical Device Named Walking Stick for the
Blind Using GPS,” Int. J. Novel Res. Eng. Sci., 1(1), pp. 30–36.
Fig. 2 Algorithm that controls the flow of work
Fig. 3 Image of the designed walking stick
030928-2 / Vol. 10, SEPTEMBER 2016 Transactions of the ASME
Downloaded From: http://tribology.asmedigitalcollection.asme.org/ on 01/03/2017 Terms of Use: http://www.asme.org/about-asme/terms-of-use