Sensors International 3 (2022) 100181
Contents lists available at ScienceDirect
Sensors International
journal homepage: www.keaipublishing.com/en/journals/sensors-international
Design and implementation of a solar powered navigation technology for
the visually impaired
Michael W. Apprey a, *, Kafui T. Agbevanu b, Gabriel K. Gasper a, Patrick O. Akoi c
a
b
c
Department of Electrical/Electronic Engineering, Ho Technical University, Ghana
Department of Computer Science, Ho Technical University, Ghana
Department of Electrical/Electronic Engineering, Accra Institute of Technology, Ghana
A R T I C L E I N F O
A B S T R A C T
Keywords:
Blind
Navigation
Arduino uno
1Sheeld
Solar panel
The Blind Navigation System using Arduino and 1sheeld is a system that intends to enhance blind peoples' access
to the environment, particularly in Ghana, Africa. This research aimed at designing a safe navigation system to
allow seamless transitions for visually impaired people from one location to another, as well as a tool to assist
them in communicating with their surroundings and guardians when in a difficult situation. The design uses PVC
pipe as the cane, 1Sheeld, Arduino Uno, ultrasonic and water sensors for processing and monitoring, a buzzer and
vibration motor to offer an alarm system via vibration and sound, housed within a circuit box and the handle, and
finally powered by a portable mini solar panel with a rechargeable battery. The phone of the blind is connected to
the 1sheeld board via Bluetooth link and the 1sheeld App is installed on the mobile phone. The guardian receives
a call or an SMS with the GPS coordinates, which can be tracked when the blind person is lost through Google
Map. The simulations related to the design's overall purpose were precise, and the trial findings from volunteers
obtained from the final test were encouraging and ensured the safety and speed of mobility. As a result, the goal of
designing a safe navigation system to detect impediments and provide the exact location of the visually impaired
through GPS/SMS processing and powered by a mini solar panel with rechargeable battery system were achieved.
1. Introduction
Most visually impaired individuals in the public arena are suffering
while practising the essential things of day-to-day existence, and that
could put lives in danger while moving around. There is a need these days
to give security and protection to these individuals [1].
Blindness occurs when a person's capacity to see is lost due to physiological or neurological factors [2]. Total blindness refers to the entire
loss of visual light perception, whereas partial blindness refers to a lack of
integration in the optic nerve's or the eye's visual centre's growth.
Because humans receive 83% of their information from their surroundings through sight, vision is the most essential aspect of their physiology
[3,4]. According to World Health Organization (WHO) figures from
2021, near or farsighted vision impairment affects at least 2.2 billion
individuals worldwide. Vision impairment may have been avoided or
managed in at least one (1) billion (or almost half) of these cases [5].
Again, there are 285 million visually impaired people on the globe, with
39 million blind and 246 million with limited vision. Around 65% of
visually impaired people and 82% of blind people are over the age of 50
[6–8].
Around 90% of the world's visually impaired people reside in poor
nations [9], including Ghana. A study in 2015 by the Ghana Health
Service (GHS) in conjunction with the Ghana Blindness and Visual
Impairment Study (GBVIS) projected that about 190,000 people in Ghana
are blind [10]. This is a very sad issue in the country since most of these
blind people are poor. For example, a study on poverty and its repercussions discovered that “although some people become handicapped
as a result of low income, a shocking 64% of people with disabilities were
* Corresponding author.
E-mail addresses: mapprey@htu.edu.gh (M.W. Apprey), kagbevanu@htu.edu.gh (K.T. Agbevanu), ggasper@htu.edu.gh (G.K. Gasper), akoi_p@yahoo.com
(P.O. Akoi).
Production and hosting by Elsevier
https://doi.org/10.1016/j.sintl.2022.100181
Received 26 March 2022; Received in revised form 17 May 2022; Accepted 17 May 2022
Available online 22 May 2022
2666-3511/© 2022 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).
M.W. Apprey et al.
Sensors International 3 (2022) 100181
which will be detected by the pressure sensor, and force will be applied to
the shoe. An alert is generated when the output exceeds the threshold
value.
The authors in Ref. [24] proposed a Smart Blind Stick in 2020. The
primary purpose of the technology is to aid blind people in walking with
complete relief and independence. The blind stick contains three ultrasonic sensors: a panic switch, a navigation switch, Bluetooth, a soil
moisture meter, and an Arduino UNO. The Smart Blind Stick employs
sensors to automatically detect the impediment in front of the user as
well as moisture detection at the bottom to detect the wetness of the soil
or ground, allowing the user to determine whether or not it is safe to walk
on that particular surface.
An ultrasonic transducer, a water circuit, and an RF transmitter and
receiver module were integrated into an electronic stick in Ref. [25]. The
ultrasonic sensor will detect an obstruction within the span and sound a
buzzer to alert the blind individual. The water circuit shorts out when it
comes into contact with water, causing the buzzer to ring. In addition, it
gives a means of locating a missing stick indoors. When the person hits
the remote's button, the stick will alert the blind person to the presence of
the stick. Because it is simple, inexpensive, and lightweight, it is easy to
carry. The prototype model was implemented, and the Arduino ATMEGA
328-PU was used to control all of the setup procedures.
The authors of reference [26] presented a smart walking stick for the
blind. The obstacle is recognized using a camera, and the distance between objects is measured using an ultrasonic sensor. If a blind person
encounters an impediment, the user can be alerted by hearing the sound
created by the headphone. The technique is extremely beneficial to
persons who are visually impaired and frequently require assistance from
others.
A blind stick is built and produced in Ref. [27] to aid and offer a clear
way for the blind person. An ultrasonic sensor is attached to the user's
stick as part of the system. While the user strolls, the ultrasonic sensor
attached to the stick with an Arduino mega tries to identify any obstacles
in the way. If the sensor detects an impediment, the recipient's output is
triggered, and the microcontroller detects this change since the receiver's
output is sent as inputs to the microcontroller. This stick detects the
object before the person and alerts the user through vibration.
A smart stick guiding concept for visually impaired persons was
demonstrated in Ref. [28]. This package included an Arduino-based
controlling system, an Ultrasonic sensor for detecting objects around
the user to avoid lethal injuries, a Light sensor module to monitor the
strength of the light in the surroundings, LED lights to send the signal to
the surroundings, a DC power system to operate the controlling module,
and a buzzer to detect obstacles around the stick. The majority of visually
assistive solutions, according to the report, are designed for users. The
suggested system, on the other hand, is not just for supporting visually
impaired users, but also for directing individuals navigating around them
to avoid inadvertent injury.
The publication [29] provided a thorough comparison of current assistive technologies for visually impaired persons. The functionality and
functioning principles of these strategies are used to classify them. These
methodologies' major characteristics, problems, and limits have been
addressed as well. Furthermore, a score-based quantitative analysis of
these devices is carried out to highlight their feature enrichment capabilities in each category. It could be useful in determining which gadget is
best for a certain situation.
The authors in Ref. [30] provided up-to-date assistive gadgets for the
blind using the Design for Six Sigma (DFSS) Methodology in medical
engineering. This study aims to show how a systematic design approach
was used in the development of the “Ocane,” an innovative smart cane
concept for visually impaired patients that was created in response to the
needs of the end-user by incorporating an easy to transport, locate, and
adjust element with ultrasonic sensors and tactile feedback. First, the
Quality Function Deployment (QFD) method is presented and used to
gather final consumer demands, with benchmarking and similar-thought
items on the market rounding up the investigation. Following that, the
not poor before they became afflicted.” When compared to households
unaffected by disability who were not previously disadvantaged,
households impacted by disability had three times the chance of
becoming impoverished within one year after the beginning of impairment. Because of the additional expenditures and lower wages associated
with impairment, households impacted by disability have a lesser chance
of escaping poverty [11]. The blind also relies on additional aids such as a
white cane; information from strangers; trained dogs; and so on. Guide
dogs are effective, and they may be taught by specialists and cared for by
their owners. Their prices range from $12,000 to $20,000 [12–14],
making them prohibitively expensive for blind people in Africa, and more
specifically Ghana. However, this system has significant disadvantages,
such as the difficulty in understanding the complicated directions given
by these dogs and the person's inability to follow them in important
situations. The need for navigation and orientation assisting devices has
grown. Trained dogs and the white cane are the most basic and
cost-effective navigational instruments. Despite their popularity, these
technologies cannot offer the blind all of the information and functionality that persons with sight have access to for safe movement [15,16].
Many types of studies have been performed throughout the years to
create and develop technologies that could safeguard the visually
impaired from harm. The “white” walking stick is the most frequent item
used by the blind to assist their movement, especially while they are
moving around outside [17]. One of the new developments in rehabilitation engineering that helps blind individuals move about more simply
and pleasantly is the creation of an electronic walking stick. Because of
the rapid advancements in current technology, both on the hardware and
software fronts, intelligent navigation capabilities are now possible [18].
Intelligent systems use sensors to identify their surroundings and take
appropriate actions [19].
Authors in Ref. [20] proposed a smart walking stick for visually
challenged individuals that use ultrasonic sensors and Arduino. The
system is made up of obstacle and moisture detection sensors that
receive, process, and send signals to the alarm system, which then informs the user to take immediate action. The system was conceived,
coded in C, and tested and checked by a visually challenged individual
for accuracy. The gadget can identify impediments about 2 m around the
user.
The Blind Stick Navigator [21] was created utilizing an Arduino Uno
and a 1Sheeld in 2017. The prototype has a vibrating device for detecting
obstructions and a message system for alerting others in the event of an
emergency. The ability of the ultrasonic sensor on the stick improves a
blind person's awareness. The new approach of applying contemporary
technological components such as 1Sheeld aided in reducing the blind's
challenges in achieving greater feedback of their surroundings.
Mohapatra et al. in Ref. [22] provided a functioning model of a
walking stick with an ultrasonic sensor and a microcontroller integrated
with Electronic Save Our Souls (e-SOS technology. The sensor sends data
to the microcontroller when it detects impediments. The data is then
processed by the microcontroller, which determines if the impediment is
close enough. The loop accomplishes nothing if the obstacle is not close
enough. If an impediment is approaching, the blind person receives an
alert signal from the microcontroller When a blind person is having
difficulty navigating, he hits the e-SOS distress call button on the stick to
make a video call to a family member. The video is seen on an Android
phone via an Android app. The Android application also informs the
blind person's family members of his location.
Again [23], designed a robot cane that would continually monitor
upcoming events as well as enhance outdoor and indoor navigation by
detecting impediments at varying heights on a level road. The cane is also
designed to accommodate people's real-time motions when walking or
their various walking patterns by counting each step and distance travelled. A threshold level for acceleration is established when a person
walks. At the tip of the shoe, an ultrasonic sensor and a force sensor are
integrated to help detect the distance between the stick and the leg. If a
person is prone to falling, their hands will exert more effort than usual,
2
M.W. Apprey et al.
Sensors International 3 (2022) 100181
or unable to find their way in complex locations; proximity sensors (Ultrasonic sensors), a water detection sensor, a vibrator, and a buzzer. The
software used to program the microcontroller is C-Programming in the
Arduino IDE environment. 1Sheeld is a new Arduino shield that is simple
to set up. It is linked to a mobile app that lets you include all of your
Android phone's features, including the LCD screen, switches, LEDs,
accelerometer, GSM, Wi-Fi, GPS, and so on, into your Arduino code.
The main advantage of this design is that the microcontroller and
power circuitry (solar and battery-based), real-time GPS technology with
the 1sheeld App, and the alert signals (vibration and buzzer) are the
crucial parts of the scheme, and they provide great coordination between
this hardware to provide safe guidance. At the same time, the simplicity
of the design makes it convenient to use by any blind person, and at the
same time, the cost of manufacturing the stick is kept low.
Fig. 1 depicts an overview of the prototype architecture which demonstrates how sensor signals respond when they encounter an obstruction, as well as the feedback given to the mobile device.
Stylistic Design Engineering (SDE) technique is revealed by finding and
developing the “Ocane” concept and advancing toward the conclusion of
an inventive product.
In [31], the authors presented a low-cost 3D intelligent walking
gadget. This gadget depends on sensors, which may enhance the world
through diagnostics in a variety of applications and aid in performance
improvement. The gadget is fabricated with an ARM controller, IR sensors, a vibration sensor, and GSM and GPS for position sharing. Along
with this, a speech module is created to guide in audio format. To optimize the machine, this Entered gadget is programmed using basic machine learning algorithms.
The goal of research work [32] is to create a technology that can
identify impediments for blind individuals. The HC-SR04 ultrasonic
sensor is also used in this gadget. This research resulted in a prototype
design stick for blind people that uses sensor technology to notify and
move blind persons who can detect items at a distance of 7 cm using
sound and vibration output. The resultant stick comprises a 0.5-inch PVC
frame and is divided into two parts: the stick rod and the sensor unit.
Finally, the system in Ref. [33] was designed at a low cost to give
artificial vision and object identification, as well as real-time help
through GPS, using Raspberry Pi. This system comprises ultrasonic sensors, a GPS module, audio feedback, and voice output through TTS (text
to speech). This technology recognizes an object in its environment and
offers feedback in the form of voice, alarm messages sent via earphones,
and GPS navigation to a specified area.
To overcome certain constraints of existing devices, the suggested
system has to meet specific requirements, such as selecting low-cost
components with higher precision to make the system economical and
dependable for the blind. Thus, the goal of this study is to create a simple
and low-cost [34,35] intelligent electronic orientation aid (EOA) system
that can aid the blind without requiring the assistance of a sighted person
and also assist them in communicating with their surroundings and
guardian when in a difficult situation. The main benefits of the system
design are that the microcontroller and power circuitry (mini solar panel
with rechargeable battery system), calling, SMS, and real-time GPS
technology with 1sheeld module connected via Bluetooth to the blinds'
phone and alert signals (vibration and beeping sound) are critical components of the scheme and provide excellent coordination between these
hardware to ensure safe navigation. The design's simplicity makes it easy
for any blind person to use while keeping the cost of producing such
sticks comparatively cheap. When a blind person uses this stick, they may
affirm that they have arrived at their desired destination or obtain the
assistance they require when they are locked up in a difficult environment. It is simple to keep up with and a pleasure to use.
2.2. System block diagram
In Fig. 2, the block diagram depicts how each module of the prototype
is connected. A 9 V power supply is required to run the circuit. This
power supply consists of a mini solar panel with a charging circuit for
charging a battery. After receiving data from the ultrasonic sensor, the
microcontroller analyses the information by measuring the time in microseconds and converting it to inches. This conversion is used to reduce
the range of values that may be communicated from the ultrasonic sensor
to the microcontroller. This transformed value is then mapped to the
preset values for identifying obstructions ranging from 80 cm to 100 cm,
which then triggers the vibration motor and buzzer when the range set is
captured. The Arduino Uno, in conjunction with the 1sheeld module, is
used to process sensor feedback and deliver notice from the blind person's mobile device to the guardian's mobile device.
2.3. System algorithm
Fig. 3 illustrates the flow chart of programming the sensors in the C
language for detecting obstacles and alerting the guardian. All the sensors begin to scan as soon as the power is switched on. To precisely estimate the sensor-to-target distance, the system monitors the time delay
between each emitted and echo pulse. The water sensor measures the size
of traces of water droplets through the line with a series of parallel lines
exposed on the sensor. When the sensor value increases or decreases and
falls in between the ranges of the programmed value, the buzzer buzzes
2. Materials and methods
The SDLC (System Development Life Cycle) approach was employed
in the creation of this system as a research method. The process of
building and updating systems, as well as the models and processes used
to develop an application, is referred to as the System Development Life
Cycle (SDLC) [2]. These processes for the design are as follows;
2.1. System design overview
To address some of the constraints of existing devices, the suggested
system had to meet specific criteria, such as the device's components
having to be low-cost and accurate for the system to be economical and
dependable in this part of the world, specifically in Africa.
The proposed device is based on a design model and a system concept
of EOA to provide a smart electronic aid for the blind with navigation
technology. Two major parts fulfil the design specification, and these
involve the hardware and software parts. The hardware consists of the
electronic walking stick itself, the microcontroller (Arduino Uno þ
1sheeld) to give the blind's location and finally send emergency notification via SMS to their guardian or authority whenever they are in need
Fig. 1. Architecture diagram of the proposed system.
3
M.W. Apprey et al.
Sensors International 3 (2022) 100181
2.5. System circuit simulation
Proteus is a piece of software that allows one to simulate microprocessors, record schematics, and design printed circuit boards (PCBs).
Proteus-VSM (Virtual System Modelling) enables the co-simulation of
embedded software and hardware designs for common microcontrollers
[37]. As indicated in Fig. 5, the software was utilized to simulate the
design circuit. The simulation began when a hex file was prepared using
the Arduino IDE and uploaded to the microcontroller in Proteus. Because
1sheeld was not available in the proteus library, a combination of the
SIM900D module and the GPS module was utilized to provide the SMS
and GPS position for the simulation.
2.6. 1Sheeld application interface
In certain cases, visually impaired people confront several challenges
in a new area or are experiencing health problems and desire to call their
Fig. 2. Block diagram of the proposed system.
and the vibrator vibrates discontinuously. If the blind perceive a constant
beep from the buzzer or the vibrator or even both, then there are too
many obstructions on the pathway and they need to press the toggle
switch for an SMS of their location to be sent to the contact person's
mobile device for the search to begin or to call the phone and speak
directly to them.
2.4. Programming Code development
One of the most important aspects of developing the project's algorithm is programming development. It includes a C program for the AVR
microcontroller, ADC value declarations for the sensors, a vibrator, LED,
and buzzer, and sensor coordination programming [36]. As illustrated in
Fig. 4, the system software was developed in C for the Arduino and
programmed via the ICSP interface with a specialized programmer. The
software was created and explained as well as the circuit functionality.
Without the library, the Arduino Uno and 1Sheeld þ boards will not be
able to run the sketch code.
Fig. 4. Programming code development with Arduino IDE.
Fig. 3. Flow chart diagram.
4
M.W. Apprey et al.
Sensors International 3 (2022) 100181
Fig. 5. Circuit simulation with Proteus Suite 8.0.
guardian. Normally, the blind must rely on others for assistance, but an
emergency application comes in these cases [38]. An Android-based
emergency application is utilized in this system, which may be downloaded from the open-source Google Play store or IOS for communication
between the 1sheeld module and the mobile phone of the blind through
Bluetooth. For this project, the 1sheeld app was downloaded and
installed on an Android phone from the Play Store. Fig. 6 illustrates the
process of launching the 1sheeld app.
2.7. Selection of material
The blind stick is made mostly of PVC tubing, as seen in Fig. 7. Several
variables contribute to the benefits of using PVC pipes. Any used wire
(main circuit wiring) can be stored within the PVC pipe. Apart from that,
PVC pipe is a non-toxic and safe material that lasts for a long time with no
maintenance and is readily recyclable. The complete assembly is mounted on a 100-cm-long PVC pipe. The length of the PVC pipe was chosen
because it is appropriate for use by a blind person. Besides, the complete
circuitry is housed in a closed box, which is located on the pipe's top half
section.
assessment performance of the solar-powered navigation technology for
the visually impaired. To evaluate the overall system performance,
important tests were performed in the laboratory environment through
simulations and real testing. The responses to the proposed EOA device
are discussed.
3. Results and discussions
3.1. Final system design
This section delves deeper into sustainable solar power performance,
system sensing performance, energy consumption analysis, and system
A system architecture was built to test the EOA device as illustrated in
Fig. 8, with the ultrasonic sensors positioned at 30 and 10 beneath the
Fig. 7. ½ inch PVC pipe.
Fig. 6. 1sheeld application interface.
5
M.W. Apprey et al.
Sensors International 3 (2022) 100181
solar energy harvesting system, allowing it to prolong its energy autonomy. The power stage, as depicted in Fig. 9, provides 9Vdc to charge the
battery. The design of the Proteus 8 program is shown, and a DC Voltmeter was installed at the output section of the circuit to assess the output
supply voltage value necessary to power the AVR microcontroller, which
was derived from the design. The DC voltmeter was used to measure the
requisite 5 V DC to power the microcontroller at the output section of the
power supply circuit, and the LED was turned on when the switch was
closed. As a result, the power supply circuit was easy to create.
The system power supply circuit was monitored in the lab, and then
measurements were collected with the Hantek DSO5072P dual-channel
digital oscilloscope to evaluate the photovoltaic (PV) system electrical
performance and the battery charging performance. The solar system was
able to fully charge the battery. Fig. 10a and b shows the outcomes of
recognition and communication.
Several criteria should be examined while evaluating the suggested
guidance system's performance. The first and most important parameter
is the system's power consumption and how long it will work before
needing to be recharged [37]. Although the device consumes power, the
power source needs to be of optimum capacity to enable the device to
operate for a long time before it gets drained. This system comprises solar
power and a rechargeable battery system that is capable of delivering the
required power to drive these tremendous sensors and circuit designs for
longer periods. The navigation system's average operating current was
around 0.253 A or (253 mA), and the battery capacity was 2000 mAh.
The average battery life was evaluated using equation (1).
BL ¼
Fig. 8. Overall system design.
BC
LC
(1)
where;
circuit box on the stick for direct and ground detection, respectively. A
water detection sensor was also installed at the bottom edge of the stick
to detect water on the pathway of the blind person. Above the top ultrasonic sensor, a circuit unit box was installed on the middle section of
the stick, and the mini solar panel was placed directly on top for detecting
direct sunlight to charge the battery.
BL→(Battery life in hours); BC →(Estimated battery capacity in mAh)
and LC →(Estimated load current in A or mA).
From the equation and the values stated above, the average life of the
battery estimated in a day is roughly 8 h. As the blind person strolls
during the day, the battery recharges, and this allows the system to
perform magnificently. The system is powered by a 9 V rechargeable
battery that can last for at least 8–9 h or even beyond each day when
energy-saving techniques such as turning the device off when not in use.
The battery life will be affected if the blind encounter too many
3.2. Power supply circuit and energy consumption analysis
The power supply for the circuit was simulated using the Proteus 8
software to analyse the circuit of the design components and determine
the required output. The proposed gadget would be powered by a fixed
Fig. 9. Power supply circuit test.
6
M.W. Apprey et al.
Sensors International 3 (2022) 100181
Fig. 10. Laboratory results of the solar charging system.
indicating that an obstacle exists ahead of the blind person. The visually
impaired must then decide whether to adjust the pathway or halt. In
place of the monitor, a buzzer and a vibrator were utilized as output
devices to warn the blind about making a decision.
Again, one of the primary requirements for the many types of barriers
being explored was distinction by material. Five materials; Humans,
metal, wood, stone, and plastic were all put through rigorous testing. The
ultrasonic sensor's produced signal was evaluated at varied distances for
each substance studied. The microcontroller collects reflected information from the barriers by measuring the breadth of the echo pulse signal.
It was demonstrated that the distance between the nearest barrier and the
pulse width are closely connected. Obstacles were placed at intervals of
50–200 cm. The mean distance values for the five materials selected are
summarized in Table 1.
It was discovered that ultrasonic sensors could identify barriers
properly, and the calculated distance to the obstacles was also roughly
right. A graph was produced between the recorded value and the real
value to compare the obtained distance to the real distance, as illustrated
obstructions because the output devices will trigger with virtually every
detection. This will have an impact on the duration of the power supply.
During such times, the blind user should not stroll outside for a longer
time. The user can also charge the battery with a 9 V-1A AC to DC adapter
charger to sustain the battery power when the weather of the day is partly
cloudy. The standard charging rate of the battery is 16hrs.
The most important element is the framework's power consumption
and how long it will operate without the need to recharge the battery
often. The following evaluations are taken into account: electrical power
usage of 0–0.5 W is regarded as low power utilization, 0.5–1 W is
considered medium power utilization, and greater than 1 W is considered
high power utilization [35]. This design consumes a total power of 1.265
W, which falls on the medium power utilization scale. Because of the
absolute number of segments associated with the framework for a viable
route to be accomplished, the blind can use the electronic stick for a
significant number of hours before charging the battery.
3.3. Sensors performance test and results
The ultrasonic sensors on the upper portion of the stick were tested by
placing various obstacles in front of them to check whether the sensor
could detect the obstacles within the distances set in the programme
code. The distances to which the impediments were recognized were
monitored using the serial monitor in the Arduino software system. The
output results from the test are shown in Fig. 11. It can be observed that
the sensor did not perceive any impediments ahead within certain distances and so displayed a “No Obstacle Ahead” or “No Ground Obstacle”
message, indicating that the blind person's route was clear of hazards. At
other defined distances, the sensor identifies impediments ahead and
displays an “Obstacle Ahead” or “Ground Obstacle Ahead” message,
Table 1
Experimental results of selected material.
S/
No.
Selected
material
Obstacle
positioned range
(cm)
Mean distance
measured (cm)
Calculated
marginal error
1.
2.
3.
4.
5.
Human
Metal
Wood
Plastic
Stone
50
100
150
180
200
46
92
144
174
197
0.04
0.08
0.06
0.06
0.03
Fig. 11. Obstacles detection test and results.
7
M.W. Apprey et al.
Sensors International 3 (2022) 100181
represented as guardians of the blindfolded volunteers to track their
position on a mobile phone when an SMS is received from the blindfolded person under test. The purpose of the learning and familiarization
test was to gather usability feedback data from our volunteers to enhance
our system performance in training the blind. The functioning of the
buzzer, vibrator, and emergency systems, i.e., the calling and SMS features provided on the navigation system were explained to the volunteers
before they were blindfolded to grasp its usage when they found it
difficult to navigate. When a participant is assigned to the start region,
the timer begins and ends when the participant has completed the route.
Table 2 describes the yield signals for obstacle, ground, and water
identifications.
The response time, performance and feedback of each group of volunteers are recorded in Table 3. The findings imply that the majority of
participants were aware of warning signals provided by our system and
could utilize them to avoid obstructions. In all, the navigation system
built for the blind operated admirably and with less trouble than most
volunteers had expected. Other volunteers serving as guardians were able
to track their partners when the emergency button was pressed, allowing
them to send an SMS to their guardian. Also, the speed of mobility of the
users was slightly above the stipulated time, whiles other participants
could not appropriately interpret the difference in the warning signals
assigned to each sensor when an obstacle or water is detected on their
pathway, and this might be attributed to their first-time usage. The
inability of the guardian participants to track their blindfolded partners
was due to inexperience in the use of high-grade mobile phones or the
inconsistency in the use of most applications on the mobile phone. This
will be considered to enhance training sessions.
To determine if the intended design was capable of delivering its
purpose, we examined the gadget's most fundamental, yet critical,
properties as shown in Table 4. In addition, we gave a quantitative
assessment of the intended system's development based on the key
criteria that must be offered by any system that provides a service to
visually impaired persons. It has been established that a system designed
for the blind person must have several features, including clear and
concise information in seconds, consistent performance during the day
and night, indoors and outdoors operation; detects objects from close and
far distances; and detects static and dynamic objects to handle any sudden appearance of objects; otherwise, the user's life is in danger [15].
Table 4 shows the results of the assessment and score of the Smart
Cane navigation system's characteristics, such as solar battery charging,
Bluetooth connectivity, sensor detection responses, GPS/SMS processing,
and so on. The assessed elements are fundamental features for designing
and relying on assistive technology for blind persons. As a result, weights
of 5.0 or 10.0 (representing the number of trial times) were assigned
because each feature has a considerable influence on the system performance. We then assigned a performance rate to each feature of the system created based on the data we gathered through calculations after
each independent assessment. The authors assumed the following formula shown in equation (2) for calculating the performance rates of each
system parameter under test;
in Fig. 12. According to Table 1, there is a modest disparity between the
estimated and observed attributes. The graph depicts a linear curve,
indicating that the error in distance measurement was marginally
insignificant. In any instance, the error edge displayed illustrates that the
sensor execution is still accurate regardless of the little difference.
3.4. Emergency system test and results
The prototype system has emergency-calling and SMS features that
allow the blind individual to contact their family or guardian in the event
of an emergency or during panic situations. The 1Sheeld can identify the
blind person's position by turning on the Bluetooth and both the call and
GPS functions in the Android smartphone widget menu. A calling signal
is sent from the blind person's phone to the guardian's phone when the
toggle switch placed beside the circuit box is hit once, or an emergency
SMS generated from the program code is sent when the button is touched
twice. The Blind Stick Navigator offers longitude and latitude coordinates
for the visually impaired and therefore serves as a provider of real-time
GPS position for this procedure, in addition to the vibrator and buzzer
as warning signs. The smartphone sends an SMS alert with GPS coordinates displayed and searches for them through Google Map to obtain
the exact position of the blind. These demo processes are similar to
research done by Ref. [38]. The operation and results of the demos are
shown in Fig. 13.
3.5. System assessment performance
A usability test for system accuracy performance, which includes
collecting measurements with the top and lower sensors in line of sight
was carried out on the field. We conducted user research in a real-world
outdoor setting to see if our system might assist visually impaired people
in following a prioritized path without losing their orientation or clashing with barriers. Obstructions seen from a blind person's upper torso are
detected by the upper sensor, which has a line of sight of 100 cm. To
detect ground impediments and other obstacles, the bottom sensor has
been set with an 80 cm line of sight from the lower body. The system was
put to the test with barriers of various materials and forms placed at
various distances. When an impediment was identified above and below
the knee level within the predefined range selected, the buzzer and
vibrator were activated. The experiment's findings from the system accuracy test were quite positive. It demonstrated an efficient accuracy,
indicating that the system is effective and unique in its capacity to
describe the source and distance of the barriers and water encountered by
the user. Fig. 14 shows the field test process.
Following the usability test, five volunteers were blindfolded and
instructed to navigate through Ho Technical University's campus within a
specified route for a set duration of five (5) minutes without clashing
with objects above and below the knee level that were positioned at
various spots along the pathway. Another five volunteers were
PR ð%Þ ¼
NS NF
100
NT
(2)
where;
PR →(Percentage performance rate); NS →(Estimated proportion of
success); NF →(Estimated proportion of failure) and NT →(Total
number of trials).
Fig. 12. Analysis
measured values.
of
the
distance
between
the
actual
values
In brief analysis, the solar power and battery charging system was
tested five (5) times. The solar panel was directed to sunlight until the
battery indicator LED started to blink to indicate the charging process. In
all, the system responded accordingly in all five (5) trials. Therefore, it
can be concluded that the estimated proportion of success is five (5), the
and
8
M.W. Apprey et al.
Sensors International 3 (2022) 100181
Fig. 13. Results of emergency system test (calling, SMS and tracking).
Fig. 14. System accuracy test for obstacle detection.
Table 2
Output signal process for the stick.
Table 3
Volunteer performance and response.
S/
No.
Sensor type
Distance (from the
stick in cm)
Type of signal
1.
Ultrasonic Sensor 1
(Direct Detection)
Ultrasonic Sensor 2
(Ground Detection)
Water Detection Sensor
100
Longer and faster beep þ
vibration þ buzzer
Longer and slower beep þ
vibration þ buzzer
short and slower beep þ
vibration þ buzzer
2.
3.
80
–
estimated proportion of failure is zero (0) and the number of trials is five
(5), providing a result of 100% of PR.
Again, the ultrasonic sensors for direct and ground obstacle detection
were tested ten (10) times. It can be concluded based on the results that
the estimated proportion of success is nine (9), the estimated proportion
User
(blindfolded)
Average
time to
complete
(mins)
Easy to
navigate
Encounter
collision
Ability to
use
emergency
features
(SMS/
Calling)
Ability to
track with
google
map
(guardian)
1
2
3
4
5
7:08s
9:13s
8:48s
6:11s
7:28s
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
of failure is one (1) and the number of trials is ten (10), providing a result
of 80% of PR. The overall system average performance rate was
9
M.W. Apprey et al.
Sensors International 3 (2022) 100181
The EOA development, on the other hand, proved to be extremely
essential since the quantity of information gathered from the environment was far greater than any traditional navigation aid.
Any new technology should be compared to what is presently available and current technology, as stated in the literature study. The
designed system is compared with the blind Stick Navigator developed in
2017 by Sri Banu et al. [21]. This Blind Stick Navigator was created
utilizing an Arduino Uno and 1Sheeld to fix the shortfalls of the inspirational classic white cane. This research project is a step forward from
the previous effort, the white cane, which assisted blind people while
travelling. The prototype has a vibrating device for detecting obstructions and a message system for alerting others in the event of an emergency. The ability of the ultrasonic sensor to interact with two sensors on
a stick improves blind people's awareness. The new approach of applying
contemporary technological components such as 1Sheeld aided in
reducing the blind's challenges in achieving greater feedback of their
surroundings. However, a few challenges were identified during the
development and testing stage of the system design. It was noted that
when the power supply to the microcontroller board was not enough, the
prototype lacked the resilience to continue in operation for a longer time.
Therefore, the prototype requires a steady power supply. The microcontroller will be damaged or crashed if more power is supplied to it
[21].
Several ideas were suggested to improve the project's function and
implementation in the future by the noble authors. For improved
mobility and durability, as suggested by the authors, the power source
may be converted to be rechargeable using solar technology. This is
where the novelty of including the solar chargeable system was implemented in this system since this type of energy provides electricity from
renewable clean energy that is accessible daily and even on overcast
days. Whether active or not, this smart cane with a rechargeable battery
automatically regulates the energy consumption by providing a low
power supply to the microcontroller and its associated peripherals to
reduce power consumption and extend the life of the device [39]. The
designed EOA technology also circumvents the constraints of GPS/SMS
processing. The calling capability has also been included so that if the
blind sends an SMS and does not receive a response, they may use it to
contact the guardian. There are several advantages to employing the
newly built system, especially at this early stage of its implementation.
First and foremost, it is safe, economical, and portable due to its lightweight; when impediments are detected, the system warns the user
through a buzzer and a vibrator, allowing them to get a better awareness
of the environment around them.
Table 4
Summary of assessment and score for system parameters tested.
S/
No
System Parameter
Under Test (N)
No. of
Trials
(NT)
Remarks
Performance
Rate (PR%)
1.
5
4.
SMS feature
5
5.
Calling feature
5
6.
10
10
Detected obstacles on
the ground level
80
5
10.
Buzzer
10
Detected water at an
appreciable level
The system vibrated
accordingly per
detection
The System buzzed
accordingly per
detection
80
9.
Ultrasonic sensor
A (Direct
detection)
Ultrasonic Sensor
B (Ground
obstacle
detection)
Water detection
sensor
Vibrator
Able to charge battery
system
Paired with the App
via Bluetooth link
Able to provide GPS
coordinates via SMS
Able to Send SMS to
guardian's phone when
the switch is hit twice
Able to call guardian's
phone when the switch
is hit once
Detected obstacles
directly
100
3.
Solar power and
battery system
1sheeld App and
module
GPS coordinates
2.
7.
8.
5
5
10
Overall System Average Performance
100
100
100
100
80
100
100
94.0
calculated based on the following assumed formula shown in equation
(3).
P
AVPR ð%Þ ¼
PR
N
(3)
where;
P
PR →(Summation of performance rates); and N →(Total number of
tests performed).
The overall system average performance rate after calculation was
found to be 94%, indicating an excellent system that can provide a
navigation guide to the blind user. Any device with high scores has
higher-quality features [29].
During the assessment period, the sensors recognized a variety of
barriers within the defined ranges, however, in certain cases, there was
little interference (ultrasonic noise). Because the water detection sensor
was placed near the base of the stick, it appeared to detect water at a
reasonable level. The system's GPS, SMS, and calling services performed
admirably. Through the Bluetooth link, the installed 1sheeld app links
the system's circuitry to the mobile phone of the blind. The GPS menu
estimates the user's location (i.e., latitude and longitude) and provides
these coordinates through an SMS for the guardian to search for the blind
in the Google Maps application to help or save them. If a blind person is
out for a stroll or any other purpose and feels he/she is lost, they can
inform a guardian. On the stick, there is an alert button that when hit,
communicates the stick's coordinates to a pre-stored mobile number
through SMS or calls the number directly to speak with this guardian.
Finally, the warning systems responded to each sensor detection. The
design's warning mechanisms, a buzzer, and a vibrator were able to
notify the blind individual of the danger ahead when obstructions are
detected. The performance rates from each parameter tested are based on
the response of every system under test.
The quantity of information necessary for blind persons' safe and
rapid mobility was not being produced by conventional navigation aids.
3.6. System design limitations
Wireless access control solutions do have limitations, which must be
understood alongside the benefits and use cases to achieve the most
balanced outcome. During the circuit design, various challenges and
limitations were found. The most prominent and often overlooked
feature is the detection by the sensors. Ultrasonic sensors work similarly
as optical sensors, in that, they send out a pulse of sound at an ultrasonic
frequency and measure how long it takes for the sound to bounce back.
The distance may be determined using the known sound speed and the
time gap between the pulse and the echo. If there are other sources of
ultrasonic noise in the area, the sensor will pick them up and give an
incorrect distance reading. It is also conceivable for a prior pulse to
reverberate off many surfaces, causing the sensor to trigger prematurely.
Although ultrasonic sensors should theoretically work properly indoors,
we encountered slight interference (ultrasonic noise) in some cases
during the test, resulting in slight inconsistency [40], thereby failing in
some trials and causing slight changes in the performance rate as indicated in Table 4.
Secondly, the Smart Cane is unable to notify its users of fast-moving
vehicles such as automobiles, motorcycles, and other similar vehicles,
which pose a considerable hazard to the visually impaired because they
10
M.W. Apprey et al.
Sensors International 3 (2022) 100181
participants who cordially responded to our calls.
are unable to notice them and are thus in continual danger while negotiating congested highways. Finally, if the circuit linking the Bluetooth
and the blind person's phone fails, the blind may be unable to contact
their guardian when difficulty arises. If either the blind person's or the
guardian's phone is turned off, contact between the two will be lost.
Furthermore, if one of them is outside of the service area or the mobile
phone has no airtime, it will result in a communication failure.
References
[1] J.J. Evangeline, Guide Systems for the Blind Pedestrian Positioning and Artificial
Vision, Int. J. Innovat. Stud. Eng. Technol. 1 (3) (2014) 42–44.
[2] A.A. Elsonbaty, Smart blind stick design and implementation, Int. J. Eng. Adv.
Technol. 10 (5) (2021) 17–20, https://doi.org/10.35940/ijeat.d2535.0610521.
[3] S. Dambhare, A. Sakhare, Smart stick for blind: obstacle detection, artificial vision
and real-time assistance via GPSe [Online], Int. J. Comput. Appl. (2011) 31–33.
Available: https://www.ijcaonline.org/proceedings/ncict/number6/4227
-ncict048.
[4] M.A. Therib, Smart blinding stick with holes, obstacles and ponds detector based on
microcontroller [Online], J. Univ. Bombay 25 (5) (2017) 1759–1768. Available:
https://www.iasj.net/iasj?func¼article&aId¼132299.
[5] Blindness and vision impairment. https://www.who.int/news-room/fact-sheets
/detail/blindness-and-visual-impairment, 2021. (Accessed 1 November 2021).
[6] G. Gayathri, M. Vishnupriya, R. Nandhini, M. Banupriya, Smart walking stick for
visually impaired, IJECS 3 (3) (2014) 4057–4061.
[7] A. Thakur, R. Singh, A. Gehlot, Smart Blind Stick For Obstacle Detection and
Navigation System, J. Emerg. Technol. Innovat. Res. 5 (October) (2018) 216–221.
[8] Y. He, et al., Prevalence and causes of visual impairment in population more than
50 years old: the Shaanxi Eye Study, Medicine 99 (20) (2020), https://doi.org/
10.1097/MD.0000000000020109.
[9] A. Nartey, The disability act of Ghana: building accessibility of visually impaired
persons in two districts in the ashanti region of Ghana, Adv. Ophthalmol. Vis. Syst.
8 (1) (2018) 4–9, https://doi.org/10.15406/aovs.2018.08.00257.
[10] B. Wiafe, Ghana blindness and visual impairment study [Online], Available: htt
ps://www.iapb.org/wp-content/uploads/Ghana-Study-BVIS-8_6_2017_-Final-edit.
pdf, 2015, 1-61(AInternational Agency for the Prevention of Blindness).
[11] Module 12_ poverty and blindness [Online], Available: https://www.uniteforsight.o
rg/community-eye-health-course/module13. (Accessed 9 December 2021).
[12] A. Yohannan, S. Shyam, Smart cane for blind and visually impaired people - smart
cane manufacturer and seller, Int. J. Creat. Res. Thoughts 8 (5 May) (2020)
2513–2517, https://doi.org/10.13140/RG.2.2.10908.51840.
[13] M.D. Messaoudi, B.-A.J. Menelas, H. Mcheick, Autonomous smart white cane
navigation system for indoor usage, Technol. 8 (3) (2020) 37, https://doi.org/
10.3390/TECHNOLOGIES8030037. Page 37, 8, Jun. 2020.
[14] D. Koester, R. Stiefelhagen, M. Awiszus, Mind the gap: virtual shorelines for blind
and partially sighted people, in: Proceedings - 2017 IEEE International Conference
on Computer Vision Workshops, ICCVW 2017 2018-Janua, Jul. 2017,
pp. 1443–1451, https://doi.org/10.1109/ICCVW.2017.171.
[15] W. Elmannai, K. Elleithy, Sensor-based assistive devices for visually-impaired
people: current status, challenges, and future directions, Sensors 17 (3) (2017),
https://doi.org/10.3390/s17030565.
[16] A.J. Oak, A.S. Walde, Assistive navigation for blind people : a review, Int. Res. J.
Eng. Technol. 7 (5) (2020) 6072–6075.
[17] S. Singh, B. Singh, Intelligent walking stick for elderly and blind people, Int. J. Eng.
Res. Technol. 9 (2020) 19–22, 03.
[18] R. Marukatat, P. Manaspaibool, B. Khaiprapay, P. Plienjai, GPS navigator for blind
walking in a campus, World Acad. Sci. Eng. Technol. 46 (10) (2010) 89–92, https://
doi.org/10.5281/zenodo.1332552.
[19] E. Mbunge, S. Jiyane, B. Muchemwa, Towards emotive sensory Web in virtual
health care: trends, technologies, challenges and ethical issues, Sensors Int. 3
(August 2021), 100134, https://doi.org/10.1016/j.sintl.2021.100134, 2022.
[20] D.E. Gbenga, A.I. Shani, A.L. Adekunle, Smart walking stick for visually impaired
people using ultrasonic sensors and Arduino, Int. J. Eng. Technol. 9 (5) (2017)
3435–3447, https://doi.org/10.21817/ijet/2017/v9i5/170905302.
[21] S.B. Munisamy, D. Ab Kadir, M.H. Elias, Blind stick navigator, Malaysian J. Ind.
Technol. 2 (2) (2017).
[22] S. Mohapatra, S.H. Rout, V. Tripathi, T. Saxena, Y. Karuna, Smart walking stick for
blind integrated with SOS navigation system, in: Proc. 2nd Int. Conf. Trends
Electron. Informatics, ICOEI 2018, 2018, pp. 441–447, https://doi.org/10.1109/
ICOEI.2018.8553935. May.
[23] S. Srinivasan, M. Rajesh, Smart walking stick, in: Proc. Int. Conf. Trends Electron.
Informatics, ICOEI 2019, 2019, pp. 576–579, https://doi.org/10.1109/
ICOEI.2019.8862753. Icoei.
[24] S. Grover, A. Hassan, K. Yashaswi, N.K. Shinde, Smart blind stick, Int. J. Electron.
Commun. Eng. 7 (5) (2020) 19–23, https://doi.org/10.14445/23488549/ijecev7i5p104.
[25] S.R. Bhavani, Development of a smart walking stick for visually impaired people,
Turk. J. Comput. Math. Educ. 12 (2) (2021) 999–1005, https://doi.org/10.17762/
turcomat.v12i2.1112.
[26] D. Sathya, S. Nithyaroopa, P. Betty, G. Santhoshini, S. Sabharinath, J. Ahanaa, M,
Smart walking stick for blind person, Math. Appl. Sci. Comput. 118 (20) (2018)
4531–4536.
[27] T. Tirupal, B. Venkata Murali, M. Sandeep, K. Sunil Kumar, C. Uday Kumar,
A. Professor, Smart blind stick using ultrasonic sensor [Online], J. Remote Sens. GIS
Technol. (7) (2021). Available: www.matjournals.com.
[28] M.M. Shah, M.N.R. Khan, M.R.A. Khan, M.M.H. Plabon, M.A. Razzak, A costeffective smart walking stick for visually impaired people, in: Proceedings of the 6th
International Conference on Communication and Electronics Systems, ICCES 2021,
Jul. 2021, pp. 1582–1585, https://doi.org/10.1109/ICCES51350.2021.9489010.
4. Conclusion
A solar-powered smart walking stick for the visually impaired was
developed and built to serve as a useful helper and support in their
environment. This study provided a comprehensive comparison of assistive devices for the visually impaired. The device is classified based on
its usefulness and working mechanism. The power supply provided the
needed force to drive these tremendous circuits through the solar panel
and the charge controller circuit developed. The system sensors were able
to identify objects and water within the defined ranges during the testing
of the electronic walking stick developed. The warning mechanisms of
the design, a buzzer and a vibrator were able to notify the blind individual of the danger ahead. The GPS menu estimates the location of the
user and provides the coordinates through an SMS for the guardian to
search for the blind in the Google Maps app to help or save them. This
system is a simple gadget that can be carried for a long distance and
requires no additional training. The design also eliminates the constraints
associated with the majority of mobility issues that may affect blind
people in their environment while using a white walking stick. The trial
test results along an obstructed path were promising and very good. The
simulations performed were accurate and relevant to the ultimate goal of
the design implementation. Hence, the electronic walking stick developed can be used to guide the visually impaired.
Based on the limitations discovered, we can state that this gadget is
not optimal. Therefore, an intelligent system that can cover all of the
necessary elements to support the blind and yet can be affordable as
advised is required.
Future development will focus on improving the system's performance and decreasing the stress on the user by replacing the buzzer with
an actual human voice to precisely guide the blind. Furthermore, a shape
identification test with sophisticated cameras for objects moving at
varying speeds, such as automobiles, will be examined.
Data availability statement
The data (Programming Code) that support the finding of this study
are available from the corresponding author upon request.
Funding
This research received no external funding.
Declaration of competing interest
TITLE: Design and Implementation of a Solar Powered Navigation Technology for the Visually Impaired.
The authors whose names are listed immediately below certify that
they have NO affiliations with or involvement in any organization or
entity with any financial interest (such as honoraria; educational grants;
participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony
or patent-licensing arrangements), or non-financial interest (such as
personal or professional relationships, affiliations, knowledge or beliefs)
in the subject matter or materials discussed in this manuscript.
Acknowledgements
We acknowledge the support of research assistants and the study
11
M.W. Apprey et al.
Sensors International 3 (2022) 100181
[35] K. Dalton H, K. Sarah E, Access to assistive technology among students with visual
impairment in higher education institutions in Tanzania, Univ. Dar es Salaam Libr.
J. 15 (2) (2020) 137–151.
[36] F. Kulor, D.E. Markus, M.W. Apprey, K.T. Agbevanu, G. Gasper, Design and
implementation of a microcontroller based printed circuit scrolling message
notification board, IOP Conf. Ser. Mater. Sci. Eng. 1088 (1) (2021), 012057,
https://doi.org/10.1088/1757-899x/1088/1/012057.
[37] A.S. Al-Fahoum, H.B. Al-Hmoud, A.A. Al-Fraihat, A smart infrared microcontrollerbased blind guidance system, Act. Passive Electron. Components (2013), https://
doi.org/10.1155/2013/726480.
[38] N. Sahoo, H.W. Lin, Y.H. Chang, Design and implementation of a walking stick aid
for visually challenged people, Sensors 19 (1) (2019), https://doi.org/10.3390/
s19010130.
[39] K.C. Sung Yeon Kim, Usability and design guidelines of smart canes for users with
visual impairments, Int. J. Des. 7 (1) (2013) 99–110.
[40] M. McNally, Interference in Ultrasonic and IR | UNH Connectivity Research Center,
University of New Hampshire, 2017. https://connectivity.unh.edu/blog/interferen
ce-in-ultrasonic-and-ir-range-sensors.html. (Accessed 9 December 2021).
[29] S. Zafar, et al., Assistive devices analysis for visually impaired persons: a review on
taxonomy, IEEE Access 10 (2022) 13354–13366, https://doi.org/10.1109/
ACCESS.2022.3146728.
[30] L. Frizziero, A. Liverani, G. Donnici, P. Papaleo, C. Leon-Cardenas, Smart cane
developed with dfss, qfd and sde for the visually impaired, Inventions 6 (3) (2021),
https://doi.org/10.3390/inventions6030058.
[31] N.D. Kumar, A.S. Mala, Practical implementation of 3D smart walking stick for
blind people, in: Proc. Int. Conf. Women Res. Electron. Comput., 2021,
pp. 391–398, https://doi.org/10.21467/proceedings.114.51. Wrec.
[32] S. Budilaksono, et al., Designing an ultrasonic sensor stick prototype for blind
people, J. Phys. Conf. Ser. 1471 (1) (2020), https://doi.org/10.1088/1742-6596/
1471/1/012020.
[33] P.R. More, P.S. Raut, P.M. Waghmode, Virtual eye for visually blind people, Int. J.
Adv. Sci. Res. Eng. Trends 5 (12) (2021) 562–566, https://doi.org/10.51319/24560774.2021.6.0087.
[34] D.A.H. Fakra, D.A.S. Andriatoavina, N.A.M.N. Razafindralambo, K.A. Amarillis,
J.M.M. Andriamampianina, A simple and low-cost integrative sensor system for
methane and hydrogen measurement, Sensors Int. 1 (June) (2020), https://doi.org/
10.1016/j.sintl.2020.100032.
12