INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,  
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)  
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue V, May 2026  
Design and Development of anAutonomous Fire Extinguishing Robot  
using Arduino Mega and Dry-Powder Extinguisher for Class B Fires  
Idaraobong E. Ansa1; Ephraim R. Afia2; Immanuel H. Usoro3; Philip E. Philip4 Uduakobong U. Ekong5;  
Endiong C. Eshiet6; Nsikakabasi N. Inyang7  
1,5,6Department of Computer Science, Akwa Ibom State University, Ikot Akpaden, Akwa Ibom State,  
Nigeria.  
2Department of Mechanical Engineering, Federal University of Technology, Ikot Abasi (FUTIA), Akwa  
Ibom State, Nigeria.  
3,7Department of Electrical and Electronics Engineering, Federal University of Technology, Ikot Abasi  
(FUTIA), Akwa Ibom State, Nigeria.  
4Department of Mechanical Engineering, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria.  
Received: 07 June 2026; Accepted: 12 June 2026; Published: 25 June 2026  
ABSTRACT  
Firefighting is one of the most dangerous occupations, with firefighters frequently facing extreme heat, toxic  
smoke, explosions, and structural collapse. These adverse conditions lead to numerous injuries and fatalities  
each year. Although robotic systems have been proposed to reduce human exposure, many existing designs rely  
on remote control, use water or fans that are ineffective for flammable-liquid fires, or suffer from limited  
detection ranges and slow response times. This study addresses these gaps by designing and fabricating an  
autonomous fire-extinguishing- robot specifically targeting Class B fires (flammable liquids and gases). The  
robot employs an Arduino Mega 2560 microcontroller as the central processing unit, three flame sensors (left,  
forward, right) for fire localization within a range of 10ꢀcm to 90ꢀcm, four ultrasonic distance sensors for obstacle  
detection and avoidance, and a 1ꢀkg dry-powder extinguisher actuated by a 12ꢀV solenoid valve. A servo motor  
sweeps the nozzle from 50° to 130° and back to distribute the extinguishing agent over a calculated area of  
113.1ꢀcm². The drive system consists of four 9ꢀV DC gear motors controlled via an H-bridge driver, with speed  
ramped linearly from 0 to a maximum PWM value of 180 (achieving a measured maximum velocity of  
0.030ꢀm/s). The obstacle avoidance algorithm compares left and right distances; if an obstacle is closer than  
25ꢀcm in front, the robot turns toward the clearer side. Testing on a 1ꢀm² test area with controlled alcohol-based  
fires demonstrated that the robot reliably detects fire at up to 90ꢀcm, navigates around obstacles, and completely  
suppresses the fire within a single continuous run. The flame sensor output decays nonlinearly with distance,  
following an inverse-square trend, which allows approximate distance estimation but limits resolution beyond  
70ꢀcm. Across five repeated trials, mean fire detection time was 2.1 ± 0.3 s and mean extinguishing time was  
11.8 ± 0.8 s, with a 100% extinguishing success rate. Results confirm that the autonomous system performs  
consistently without human intervention, offering a scalable, low-cost solution to reduce firefighter casualties.  
Future improvements should focus on larger chassis, onboard battery integration, and autonomous extinguisher  
replacement.  
Keywords: Autonomous firefighting robot; Arduino Mega 2560; flame sensor; ultrasonic obstacle avoidance;  
Class B fire; dry-powder extinguisher; servo nozzle sweep; PWM motor control.  
INTRODUCTION  
Despite substantial advances in firefighting technologies and professional training over recent decades, fire  
suppression remains an intrinsically hazardous activity that continues to result in firefighter fatalities and serious  
injuries [1-2]. The hostile environmental conditions present during fire incidents, including extreme thermal  
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loads, toxic combustion products, structural instability or collapse, and the potential for explosions arising from  
gas leaks or volatile chemical substances far exceed the physiological tolerance limits of the human body [3–5].  
Fires occurring in natural or built environments often exhibit dynamics that surpass human predictive  
capabilities; the temperatures generated can exceed the range detectable or interpretable by human sensory  
systems, and deflagrations or explosions from flammable liquids and gases may occur with minimal or no  
perceptible precursors [6-8]. With global population growth and concurrent industrial and technological  
expansion, both the incidence and severity of fire-related emergencies have shown a corresponding increase [9-  
10]. Human physiological and perceptual constraints, including impaired visibility due to smoke, respiratory  
compromise in toxic or oxygen-deficient atmospheres, and limited capacity to safely enter confined, cluttered,  
or structurally compromised spaces render firefighting one of the most physically demanding and high‑risk  
occupations [11-13].  
Robotic systems have been proposed as a means of mitigating firefighter exposure to life‑threatening conditions;  
however, many current platforms remain teleoperated or semi-autonomous and therefore still require human  
operators to remain within hazardous zones or in close proximity to them [14-15]. Fully autonomous systems,  
by contrast, frequently exhibit restricted sensing and perception capabilities, suboptimal response latency, and  
limited capacity to prioritize and suppress high‑risk fire sources [5,16-17]. This persistent discrepancy between  
the theoretical potential of robotic and autonomous technologies and their current level of robust, life-preserving  
operational autonomy in real-world fire scenarios contributes to the continued exposure of human firefighters to  
preventable fatalities, injuries, and property losses [1,2,18]. A robot is typically defined as a multifunctional,  
reprogrammable system capable of executing tasks conventionally performed by humans, frequently in  
hazardous or otherwise inaccessible environments [4,6,10,19-20]. Fire-extinguishing robots, in particular,  
constitute specialized electromechanical platforms engineered to autonomously detect, localize, and suppress  
fires while minimizing direct human involvement [8,21-22].  
Several studies focus on low-cost autonomous firefighting robots. [15] and [14] implemented fire detection and  
extinguishing robots using basic flame and gas sensors, demonstrating feasibility for small-scale residential or  
educational applications. [11] and [9] similarly developed autonomous fire extinguishing robots with sensor-  
based obstacle detection and extinguisher triggers. While these systems are affordable and easy to deploy, they  
suffer from limited sensing range, high false-positive rates, and inability to discriminate fire classes. To overcome  
sensor limitations, recent studies integrate AI and deep learning. [3] introduced “Flame guard,” an AI-powered  
robot for fire detection and extinguishing. [12] developed an AI-based robot capable of fire scene patrol, using  
object detection to identify flames. [7] conducted a comparative analysis of object detection models for real-time  
wildfire and Class B fire detection, highlighting that model selection significantly affects detection speed and  
accuracy. These AI-driven approaches improve reliability in variable lighting and flame shapes but require  
substantial computational resources and training data. Furthermore, [4] developed a novel IoT-based smart  
firefighting robot for real-time detection and suppression, with sensor data transmitted wirelessly. [13] integrated  
the Thingspeak cloud server with an IoT-equipped robot, allowing users to monitor fire events remotely while  
[2] described an autonomous firefighting robot with likely IoT capabilities. While cloud connectivity enhances  
situational awareness, it introduces latency, dependency on network infrastructure, and potential single points of  
failure in disaster scenarios. Moreover, numerous studies have emphasized that many existing robotic systems  
rely on water which is ineffective and potentially hazardous for oil and grease fires or airflow-based suppression  
using fans which can disperse burning liquids and exacerbate fire spread, and are thus predominantly constrained  
to Class A fire scenarios. Consequently, a significant research gap persists: no existing system concurrently  
integrates a wide-range flame sensor with a detection span of approximately 10–90 cm, fully autonomous  
navigation and suppression capabilities incorporating obstacle avoidance via multiple ultrasonic sensors, a dry-  
powder fire extinguisher specifically engineered for Class B fires involving flammable liquids and gases, and an  
Arduino Mega 2560 platform capable of executing complex, real-time decision-making processes without  
human intervention.  
To address this gap, the present study aims to develop an autonomous fire-extinguishing robot capable of  
detecting fire locations and suppressing them without human intervention, thereby mitigating hazards and  
reducing casualties among firefighting personnel. The novelty of the proposed system lies in the concurrent  
integration of four elements not previously combined in a single low-cost Arduino-based platform: (i) a tri-  
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directional infrared flame sensing array with a validated detection range of 10–90 cm; (ii) fully autonomous  
closed-loop navigation with multi-sensor ultrasonic obstacle avoidance; (iii) a 1 kg dry-powder extinguishing  
agent specifically rated for Class B flammable-liquid fires; and (iv) a servo-driven nozzle sweep mechanism  
providing distributed agent coverage over a calculated area of 113.1 cm². Unlike prior Arduino-based robots that  
rely on water or fans and remain limited to Class A scenarios, or AI-based systems that require substantial  
computational infrastructure, the proposed platform achieves Class B suppression on an accessible, low-cost  
microcontroller without any remote-control dependency. The specific objectives are: to design and fabricate a  
fire-extinguishing robot that employs a dry-powder extinguisher suitable for Class B fires; to achieve fire  
detection using flame sensors with an operational range of 10 cm to 90 cm; and to implement all locomotion and  
behavioural control via an Arduino Mega 2560 microcontroller functioning as the central processing unit. The  
research methodology adopts a prototyping model, encompassing iterative requirements elicitation, rapid design,  
prototype construction, functional evaluation, and subsequent refinement. The significance of this work lies in  
its potential to substantially decrease firefighter injuries and fatalities, provide rapid autonomous responses to  
incipient fires in residential and industrial environments, and offer a scalable, low-cost solution that eliminates  
direct human exposure to hazardous conditions. By focusing explicitly on Class B fires, which are among the  
most explosive and hazardous fire categories, and by operating in a fully autonomous manner without reliance  
on remote control, this study addresses a critical technological gap in current firefighting robotics research and  
practice.  
MATERIALS AND METHOD  
System Overview  
An autonomous fire-extinguishing robot was designed and fabricated to detect, navigate to, and suppress Class  
B fires (flammable liquids and gases) using a dry-powder extinguisher. The robot operates autonomously,  
without remote human intervention. The system comprised five subsystems:  
sensor system, logic control system, traction and drive system, actuation extinguishing system, and power  
system. A high-level architectural diagram of the robotic system is shown in Figure 1.  
Figure 1: Architectural Diagram of the Robotic System  
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A
Motor  
Power  
Flame  
R
Right  
Left  
Relay  
D
U
I
Ultrasonic  
Pressure  
Solenoid  
Sprinkler  
LED  
Figure 2: Detailed System Design  
Hardware Components  
All components were assembled on a high-density- polymer chassis. The materials include:  
Microcontroller: Arduino Mega 2560 (ATmega2560) with 54 digital I/O pins, 16 analog inputs, and a  
16ꢀMHz crystal oscillator.  
Flame sensors: Six flame detection modules, three of which were used for localization (left, forward,  
and right).  
Ultrasonic distance sensors: Four HC-SR04 ultrasonic sensors for obstacle detection (front, left, and  
right).  
Fire extinguisher: 1ꢀkg dry-powder extinguisher.  
Solenoid valve: 12ꢀV DC solenoid valve attached to the extinguisher nozzle.  
Servo motor: One servo motor for nozzle sweeping.  
Drive motors: Four 9ꢀV DC gear motors.  
Motor driver: One H-bridge motor driver  
Relay module: One 5ꢀV relay for pump/solenoid control.  
Battery: 12ꢀV rechargeable DC battery.  
Distribution board, jumper wires, LEDs, buzzer, switch, nuts and bolts, and tubing  
Fabrication and Assembly  
The chassis was fabricated from a high-density polymer sheet. Holes were drilled to attach the motor clamps and  
wheels. Each of the four 9ꢀV motors was secured to the chassis using clamps, and the wheels were attached to  
the motor shafts. The bottom frame included pre-cut slots to house the battery and the Arduino Mega. Four  
threaded steel pins connected the bottom frame to the top frame. Figure 3 shows the driver assembly, and Figure  
4 presents the complete robot model.  
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Figure 3: The Driver Assembly  
Figure 4: The Complete Robot Model.  
The 1ꢀkg dry-powder extinguisher was fastened to the top frame using zip ties. A 12ꢀV solenoid valve was  
attached to the extinguisher nozzle, and a servo motor was fixed to the top frame; the servo’s link controlled the  
nozzle orientation. Three flame sensors were mounted on the front chassis: one at the centre, one on the right  
side, and one on the left side, each spaced 5–6ꢀcm apart. Four ultrasonic distance sensors were placed facing  
front, left, and right directions (one sensor per direction, with an additional sensor for redundancy or rear  
detection). The buzzer, LEDs, and relay module were soldered onto a distribution board and connected to the  
Arduino Mega via jumper wires. Figures 5–8 illustrate the progressive stages of robot assembly.  
Figure 5: Stage One of Robot Assembling  
Figure 6: Stage Two of Robot Assembling  
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Figure 7: Stage Three of Robot Assembling  
Figure 8: Stage Four of Robot Assembling  
Control System and Software Development  
Microcontroller and Programming Language  
The Arduino Mega 2560 served as the central processing unit (brain) of the robot. The choice of this  
microcontroller was justified by its large number of I/O pins (54 digital, 16 analog), sufficient memory for  
complex robotics applications, and ease of programming. The robot was programmed using the Arduino  
Integrated Development Environment (IDE), which employs a simplified version of C++ (Arduino programming  
language). The IDE was installed on a Windows operating system, and the Arduino core library was downloaded  
from the official website (https://www.arduino.cc) and added to the IDE via the Library Manager. Figure 9 shows  
the Arduino setup environment, and Figure 10 shows the IDE interface.  
Figure 9: Arduino Setup Environment  
Figure 10: Arduino IDE Program's Image  
Embedded Code Logic  
The program defined all input/output pins, global variables, and functions for motor control, sensor reading,  
obstacle avoidance, and fire extinguishing. The main loop continuously read the three flame sensors (left,  
forward, right) and executed the following decision rules:  
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No fire: All three sensors HIGH → robot stopped.  
Fire straight ahead: Forward sensor LOW → robot moved forward.  
Fire to the left: Left sensor LOW → robot turned left.  
Fire to the right: Right sensor LOW → robot turned right.  
Extinguishing routine: When a fire was detected (forward sensor LOW) and the robot was positioned  
near the fire, the put off fire function was called: motors stopped, buzzer sounded, solenoid valve opened  
(pump pin HIGH), a delay of 9630ꢀms allowed agent discharge, the servo swept from 50° to 130° and  
back (1° steps, 10ꢀms delay per step), then the solenoid and buzzer were deactivated.  
Obstacle Avoidance Algorithm  
The ultrasonic distance sensors were triggered and read using the pulse in function. Distances were calculated  
as:  
distance (cm) = duration (µs) × 10 / 292 / 2.  
The robot used three thresholds: front avoidance distance ≤ꢀ25ꢀcm, left and right avoidance distances ≤ꢀ20ꢀcm. If  
an obstacle was detected in front, the robot compared left and right distances: if left < right, it turned right; if left  
> right, it turned left. Similarly, if an obstacle was detected on the left, the robot turned right (or moved forward  
if the right was free); if on the right, it turned left. The avoid function integrated these checks and called the  
appropriate motor commands. Figure 11 shows robot’s obstacle avoidance  
Figure 11: Obstacle Avoidance  
Drive System and Power Supply  
2.6.1 Traction and Motor Control  
Four 9ꢀV DC gear motors provided locomotion. The motors were controlled through an H-bridge motor driver.  
The robot’s speed was ramped linearly from 0 to a maximum PWM value of 180, increasing by 2 units every  
5ꢀms. The measured maximum velocity of the robot was 0.030ꢀm/s (determined experimentally). Directional  
control functions (move Forward, move Backward, move Left, move Right, move Stop set the appropriate motor  
polarities and speeds. Figure 12 illustrates the robot’s drivetrain configuration including the H-bridge motor  
driver and gear motors  
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Figure 12: Robot’s Movement with the help of Motor Driver and Motor  
Power Distribution  
The entire system was powered by a 12ꢀV rechargeable DC battery. The Arduino Mega received power via its  
DC barrel jack or USB connector. The motors and solenoid valve drew 12ꢀV directly from the battery through  
the motor driver and relay, respectively. Sensors (flame, ultrasonic) and the servo motor were powered from the  
Arduino’s 5ꢀV pin. In early tests, the weight of the rechargeable 12 V battery prevented autonomous locomotion;  
therefore, during final validation the robot was powered via an AC-to-DC adapter plugged into a wall socket. A  
steady-state power consumption analysis was conducted to characterise system load. Under idle conditions  
(sensors active, motors stopped), the total current draw measured at the 12 V supply was approximately 0.38 A  
(4.6 W). During forward motion at maximum PWM, current increased to approximately 1.2 A (14.4 W) owing  
to the four gear motors. Peak current during solenoid valve actuation was 1.5 A (18.0 W). The estimated total  
energy consumed per extinguishing cycle (detection, navigation, and suppression over approximately 12 s) was  
0.06 Wh. These measurements indicate that a 12 V, 2.2 Ah LiPo battery, if appropriately mounted with a  
redesigned low-centre-of-gravity chassis, would provide an estimated operational endurance of approximately  
1.8 hours of idle monitoring or at least 120 complete extinguishing cycles, confirming the technical feasibility  
of untethered operation in future iterations.  
Working Principle  
Upon power-up, the robot initialized all sensors and set the servo to 90°. The flame sensors continuously  
monitored the environment within 10–90ꢀcm. When a fire was detected (output LOW), the robot moved toward  
the flame while the ultrasonic sensors scanned for obstacles. If an obstacle was encountered, the robot  
circumvented it by turning left or right. Once the robot reached a safe distance from the fire, it stopped, activated  
the solenoid valve, and swept the nozzle via the servo motor to disperse the dry-powder agent. The spraying  
action continued until the flame sensors no longer detected a fire, at which point the robot returned to its idle  
state. Figure 2 illustrates the detailed system design, and Figure 13 presents the system flow chart.  
Performance Testing  
Individual Subsystem Tests  
Each sensor was tested independently:  
Flame sensors: A lighter was placed at distances ranging from 10ꢀcm to 90ꢀcm. The analog readings  
were monitored on the serial monitor to confirm detection and sensitivity decay with distance (Figure  
14).  
Ultrasonic sensors: Distances to a flat obstacle were measured and compared with a ruler; accuracy was  
within ±1ꢀcm.  
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Motors: PWM speed commands were issued and rotational direction verified for both forward and  
reverse operation at incremental speed settings from 0 to PWM 180.  
Sensor Calibration Procedure  
Flame sensor calibration was performed by placing a standardised lighter flame at nine discrete distances (10,  
20, 30, 40, 50, 60, 70, 80, and 90 cm) from the sensor face in a controlled, draught-free environment. At each  
position, ten consecutive ADC readings were recorded via the Arduino serial monitor and averaged to reduce  
noise. The calibration curve (ADC output versus distance) confirmed the inverse-square relationship shown in  
Figure 17, with a coefficient of determination R² = 0.97, indicating a strong predictive fit. The digital detection  
threshold was set at ADC ≤ 512 (approximately 50% of full scale), corresponding to a maximum reliable  
detection range of 90 cm; below this threshold, the firmware asserts a LOW signal to the main control loop.  
Ultrasonic sensor calibration involved measuring distances to a flat reflective surface at ten known positions  
between 5 cm and 100 cm, comparing sensor output against steel-rule reference measurements. Mean absolute  
error was 0.8 cm (range: 0.2–1.4 cm), confirming the ±1 cm accuracy reported in Section 2.9.1. No firmware  
correction factor was applied, as the measured error remained within the acceptable operational tolerance for  
obstacle avoidance at the programmed thresholds of 25 cm (front) and 20 cm (sides).  
Integration and System Testing  
A complete system test was conducted on a 1ꢀm² test area. A controlled alcohol-based fire (Class B) was ignited  
as the primary test scenario. The robot’s response was evaluated across five repeated trials under identical  
conditions, recording: time to fire detection, navigation path (including obstacle-avoidance manoeuvres), and  
time to complete extinguishment. To quantify repeatability and measurement uncertainty, the mean and standard  
deviation were computed for each metric.  
Obstacle-avoidance capability was additionally assessed using three distinct obstacle configurations: a single  
centred obstacle, dual lateral obstacles, and an asymmetrically placed obstacle offset from the robot’s initial  
heading. Figures 15 and 16 show the robot navigating toward the fire location and suppressing it, respectively.  
The mean fire detection time across five trials was 2.1 ± 0.3 s (coefficient of variation, CV = 14.3%), and the  
mean time to complete extinguishment was 11.8 ± 0.8 s (CV = 6.8%), indicating consistent autonomous  
behaviour across all trials.  
The robot achieved a 100% extinguishing success rate for all five Class B trials. For comparative context, [9]  
and [11] reported flame sensor detection ranges below 60 cm with no statistical repeatability data, while [15]  
and [14] demonstrated extinguishing capability restricted to Class A fires without obstacle-avoidance validation.  
The concurrent integration of dry-powder suppression, tri-directional flame sensing to 90 cm, servo nozzle  
sweep, and multi-sensor ultrasonic obstacle avoidance on a single low-cost microcontroller represents a  
measurable advance over these prior platforms in both functional scope and operational autonomy.  
Performance metrics derived from the five repeated integration trials are summarised below and discussed in  
detail in Section 3.0. Table 1 presents a consolidated summary of all key performance indicators:  
Maximum fire detection distance: 90ꢀcm (depending on flame intensity).  
Robot maximum velocity: 0.030ꢀm/s (measured experimentally).  
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Start  
I/O settings  
Get data  
Data = 0  
Road obstacle  
sensor  
Stop  
Right = 1  
Right = 0  
Right = 1  
Right = 1  
Turn Right  
Move  
Forward  
Turn Left  
Stop  
Right = 0  
Figure 13: System Flow Chart  
Spray coverage area: 113.1ꢀcm² (calculated as arc length of 18.85ꢀcm × spray height of 6ꢀcm, where arc  
length = (180°/360°) × 2π × 6ꢀcm).  
The robot successfully avoided obstacles placed in its path and extinguished the fire within a  
run  
single continuous  
Figure 14: Flame Sensor with Buzzer Sound  
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Figure 15: Robot’s Movement towards Fire Location  
Figure 16: Robot Extinguishing Fire  
Challenges Encountered  
During implementation, the following challenges were noted: strong electric motors were not readily available  
in the local market, so the available motors were used, affecting torque; the large number of sensors drew  
considerable power, causing fluctuations in sensor readings; the battery weight prevented the robot from moving  
when the battery was onboard, so an external adapter was used for validation.  
Safety and Compliance  
The prototype was designed for low-scale demonstration using a 1ꢀkg dry-powder extinguisher. The solenoid  
valve and all electrical connections were rated for 12ꢀV DC operation. No high-voltage AC components were  
integrated. The dry-powder agent is non-toxic and suitable for Class B and C fires. All tests were conducted in  
a well-ventilated area with fire-extinguishing backup measures in place.  
RESULTS AND DISCUSSION  
Flame sensitivity vs. Distance  
Figure 17: Graph of Flame sensitivity vs. Distance  
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Figure 17 presents the relationship between fire distance (cm) and flame sensor output (ADC value, 0–1023).  
The data were acquired by placing a controlled flame (lighter) at incremental distances from 10ꢀcm to 90ꢀcm and  
recording the analog reading from a flame sensor mounted on the robot chassis. At a distance of 10ꢀcm, the  
sensor output was approximately 1000 ADC counts, indicating a very strong response. As the distance increased,  
the output decreased monotonically, falling to approximately 200 ADC counts at 50ꢀcm and approaching zero  
near 90ꢀcm. The decay was nonlinear, with a steeper initial decline followed by a shallower tail beyond 60ꢀcm.  
This pattern is consistent with the inverse-square law of radiation intensity, where the infrared energy emitted  
by the flame diminishes with the square of the distance from the source.  
The observed trend has direct practical implications for the autonomous fire extinguishing robot described in  
this study. The sensor’s high sensitivity at close range (10–30ꢀcm) ensures reliable fire confirmation before the  
robot activates its extinguishing mechanism, preventing false positives. The usable detection range of 10ꢀcm to  
90ꢀcm, as specified in the Arduino program is fully validated by the graph: beyond 90ꢀcm the output falls below  
the digital LOW threshold, meaning the robot will not perceive a fire. The steep decline between 10ꢀcm and  
40ꢀcm means that the robot can roughly estimate fire proximity from the analog value, a feature that could be  
exploited to adjust motor speed or spraying intensity. However, the exponential-like decay also implies that small  
changes in distance near the upper limit (e.g., 80–90ꢀcm) produce very small output variations, limiting distance  
resolution beyond 70ꢀcm. For reliable autonomous navigation, this reinforces the need to bring the robot closer  
(≤50ꢀcm) before triggering the extinguisher, which is consistent with the implemented algorithm that moves the  
robot until a safe but effective distance is reached.  
In conclusion, the flame sensor exhibits a strong, predictable relationship between output and fire distance over  
the specified range of 10–90ꢀcm. This characteristic makes it suitable for binary fire detection (fire/no fire) as  
well as approximate distance estimation. The nonlinear decay curve supports the design choice of using multiple  
sensors (left, forward, right) for directional localization rather than relying on precise analog triangulation.  
Future iterations could incorporate a calibrated look-up table to convert ADC values into estimated fire distance,  
enabling adaptive spraying or more efficient path planning.  
Robot speed vs. Time  
Figure 18: Graph of Robot’s Acceleration Profile  
Figure 18 shows the acceleration profile of the fire-extinguishing robot from rest to its maximum steady-state  
speed. The x-axis represents time in seconds, ranging from 0.0 to 0.4ꢀs, and the y-axis represents robot speed in  
meters per second, increasing from 0.000 to 0.030ꢀm/s. The data were obtained experimentally by recording the  
robot’s velocity during the initial phase of forward motion, while the control algorithm executed the programmed  
speed-ramping routine. The plot exhibits a linear increase in speed over the first 0.2ꢀs, reaching approximately  
0.015ꢀm/s, followed by a slightly moderated rise to the terminal velocity of 0.030ꢀm/s at approximately 0.45ꢀs.  
The smooth, monotonic ascent indicates that the motor driver and DC motors responded consistently to the  
incremental PWM commands, with no detectable stalling or overshoot.  
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The observed acceleration trend is a direct consequence of the robot’s embedded speed-control loop. The motor  
speed (PWM value) was increased from 0 to a maximum of 180 in steps of 2, with a 5ꢀms delay between each  
step, resulting in a total ramp-up time of about 0.45ꢀs. The measured terminal speed of 0.030ꢀm/s agrees with the  
calculated value based on the motor characteristics and the robot’s total mass (including the 1ꢀkg extinguisher  
and chassis). The linearity of the speed increase implies that the drivetrain operated well within its torque limits  
and that the wheels maintained sufficient traction on the test surface. From a practical standpoint, this smooth  
acceleration is highly desirable for a fire-extinguishing robot operating in cluttered indoor environments. Abrupt  
changes in velocity could destabilize the robot or cause the extinguisher cylinder to shift, whereas the gradual  
ramp-up ensures controlled navigation and reduces the risk of collisions with obstacles before the ultrasonic  
sensors can respond.  
The robot’s acceleration to its maximum speed of 0.030ꢀm/s is consistent with the programmed PWM ramping  
strategy and confirms the proper functioning of the motor driver, the DC motors, and the power supply under  
load. The relatively low maximum speed of 0.030ꢀm/s is appropriate for a small-scale prototype whose primary  
mission is accurate fire localization and extinguishing rather than rapid transit. This deliberate, controlled  
movement allows the ultrasonic obstacle-avoidance system to operate effectively and gives the flame sensors  
sufficient time to confirm the fire direction. The linear acceleration trend also serves as a validation of the code  
logic (for (speedSet = 0; speedSet < MAX_SPEED; speedSet += 2)) and the chosen delay intervals.  
Ultrasonic Sensor Distances During Obstacle Avoidance  
Figure 19: Graph of Ultrasonic Sensor Distances During Obstacle Avoidance  
Figure 19 presents the time-course of distance measurements (in cm) recorded by the three ultrasonic sensors  
mounted on the robot front, left, and right during an obstacle avoidance manoeuvre. The x(Time)axis spans 0 to  
10ꢀseconds, while the y(Distance) axis covers distances from 0 to 100ꢀcm. The trace representing the front sensor  
begins at approximately 100ꢀcm at time zero, then decreases steadily, reaching a minimum of about 40ꢀcm at  
3ꢀseconds. Simultaneously, the left and right sensor distances also decline but at different rates: the right sensor  
drops to nearly 25ꢀcm by 3ꢀseconds, whereas the left sensor remains above 60ꢀcm at 3 seconds. Between 4 and  
5ꢀseconds, the robot executes an avoidance action; the front distance momentarily stabilizes around 20ꢀcm, then  
begins to increase after 5ꢀseconds, recovering to approximately 100ꢀcm by 10ꢀseconds. The left and right traces  
diverge further during this period, with the left distance rising steeply to 80ꢀcm while the right distance slowly  
recovers to above 60ꢀcm.  
The trends observed directly reflect the obstacle-avoidance algorithm of the robot. The robot continuously  
monitors front distance; when the front sensor detected an obstacle at 25ꢀcm (the programmed  
threshold (maxFrontDistance), the controller compared the left and right distances. Because the right distance  
was smaller (closer obstacle on the right), the algorithm correctly turned the robot left, as evidenced by the sharp  
rise in left sensor distance after 5ꢀseconds (moving away from the left side) and the persistent low right distance  
(still near the obstacle). This behaviour matches the decision rule: if (left Distance(cm) < right Distance(cm)  
move Right; else if (left Distance(cm) > right Distance(cm) move Left; The front distance’s slow recovery after  
the turn indicates that the robot continued moving forward but at a slightly oblique angle, gradually increasing  
clearance from the obstacle. Practically, this demonstrates that the ultrasonic-based obstacle avoidance is  
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functional and allows the robot to navigate around barriers while still progressing toward the fire source which  
is a critical capability for autonomous firefighting in cluttered home or industrial environments.  
The ultrasonic sensor distance profiles confirm that the robot successfully detected an approaching obstacle,  
evaluated the relative clearance on both sides, and executed a turning manoeuvre (to the left) to avoid collision.  
The front distance never fell below 20ꢀcm, indicating that the robot maintained a safe minimum separation from  
the obstacle. The left and right traces clearly show which side was more obstructed, validating the logic that  
compares left and right distances to choose the escape direction. The time required for the front distance to return  
to open values (≈5ꢀseconds) is acceptable for a robot moving at a maximum speed of 0.030ꢀm/s, as the obstacle  
avoidance does not introduce excessive delays. The data also support the chosen threshold values (25ꢀcm for  
front, 20ꢀcm for sides), which strike a balance between safe stopping distance and unnecessary avoidance  
manoeuvres.  
Servo Nozzle Sweep During Fire Extinguishing  
Figure 20: Graph of Servo Nozzle Sweep during Fire Extinguishing  
Figure 20 illustrates the angular position of the servo motor (in degrees) as a function of time (in seconds) during  
the fire-extinguishing routine of the robot. The y-axis spans from 50° to 130°, and the x-axis covers 0.0 to 1.6ꢀs.  
The trace begins at 50° at tꢀ=ꢀ0.0ꢀs and increases linearly to 130° at approximately 0.8ꢀs. Immediately thereafter,  
the angle decreases linearly from 130° back to 50°, reaching the starting point at around 1.6ꢀs. The slope of the  
ascending and descending segments is constant, indicating that the servo moved at a uniform angular velocity  
without stalling or overshooting. The shape of the plot is therefore a symmetric triangular waveform, with a  
peak-to-peak amplitude of 80° and a full cycle period of 1.6ꢀs.  
This pattern directly corresponds to the programmed sweeping action and the put off fire function in the Arduino  
code. Specifically, the code executed a for loop that increases from 50 to 130 in steps of 1, with a 10ꢀms delay  
per increment. Since there are 80 steps (130 – 50 = 80), the total time for the forward sweep was 80ꢀ×ꢀ0.01ꢀs =  
0.8ꢀs. Asecond for loop then decreased from 130 back to 50 using the same step size and delay, requiring another  
0.8ꢀs, for a total sweep duration of 1.6ꢀs. The linearity of the trace confirms that the servo motor followed the  
position commands without mechanical binding or electrical lag. From a practical standpoint, this sweeping  
action is essential for covering a wider spray area than a fixed nozzle would allow, especially for Class B fires  
where the flammable liquid may spread over a surface. This performance validates the choice of a standard servo  
motor for nozzle orientation and confirms that the timing parameters (1° per 10ꢀms) are appropriate given the  
robot’s proximity to the fire (typically ≤50ꢀcm). The symmetric sweep ensures that both sides of the flame receive  
extinguishing agent, reducing the chance of re-ignition.  
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Motor Speed Ramping During Startup  
Figure 21: Graph of Motor Speed Ramping During Startup  
Figure 21 presents the relationship between loop iteration (x-axis) and motor PWM speed (y-axis, ranging from  
(0–180 PWM units) during the initial acceleration phase of the fire-extinguishing robot. The data were acquired  
by monitoring the speed Set variable in the Arduino code as it increased from zero toward the programmed  
maximum. The plot shows a perfectly linear, stepwise increase: at iteration 0, the PWM value is 0; at each  
successive iteration, the value increases by 2 units. The progression continues until the maximum PWM value  
of approximately 180 (100% duty cycle) is reached after about 90 iterations. The relationship between iterations  
and PWM value is deterministic, with a slope of 2 PWM units per iteration, and no overshoot or oscillation is  
observed because the ramping is implemented purely in software without feedback.  
This linear ramping profile is a direct implementation of the speed-control loop documented in the Arduino code.  
The constant increment of two (2) ensures a gradual increase in the pulse-width modulation (PWM) duty cycle  
applied to the DC motors, which in turn produces the smooth acceleration observed in Figure 18. The total  
number of iterations (90) multiplied by the delay per iteration (5ꢀms) gives a ramp-up duration of 450ꢀms,  
consistent with the time to reach maximum speed seen in Figure 18 (approximately 0.38–0.45ꢀs). From a practical  
standpoint, this stepwise ramping is crucial for several reasons: it prevents inrush current spikes that could  
destabilise the battery voltage, reduces mechanical stress on the gear motors and wheels, and allows the  
ultrasonic sensors to reliably measure distances without vibration-induced noise. The linear relationship also  
simplifies debugging, as any deviation would indicate a fault in the motor driver or power supply.  
In conclusion, the motor speed ramping profile is linear, deterministic, and matches the programmed increment  
of 2 PWM units per iteration over 90 iterations, achieving a maximum PWM value of 180 within approximately  
0.45ꢀseconds. This behaviour confirms the correct execution of the software-based acceleration routine and  
validates the choice of a simple open-loop ramping strategy for this low-speed, high-torque application. The  
absence of feedback control ( PID) is acceptable given the robot’s low maximum velocity (0.030ꢀm/s) and the  
unstructured indoor environment where smooth, predictable motion is more important than precise speed  
regulation.  
Limitations of the Study  
The following limitations are identified:  
Power Supply Constraint: The weight of the rechargeable 12ꢀV battery prevented the robot from  
moving when the battery was mounted. Consequently, during final validation, the robot was powered via  
an external AC-to-DC adapter plugged into a wall socket, reducing its untethered operational capability.  
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Sensor Power Fluctuations: The large number of sensors (six flame sensors and four ultrasonic sensors)  
drew considerable current, causing unexpected fluctuations in sensor readings and requiring careful  
power distribution.  
Prototype Scale Only: The robot was built as a small-scale prototype using a high-density polymer  
chassis. For real-world applications, a scaled-up version with appropriate safety factors would be  
required.  
Limited Fire Class Targeting: Although the robot was designed for Class B fires, tests were also  
conducted on Class A (paper) fires. However, the dry-powder extinguisher is not optimized for all fire  
classes, and the system was not tested on Class C (electrical) or Class K (cooking oil) fires.  
No Autonomous Extinguisher Refill or Replacement: The robot cannot replace or refill the  
dry-powder extinguisher on its own. Once the agent is depleted, a human operator must intervene.  
CONCLUSION  
This study designed, fabricated, and evaluated an autonomous fire-extinguishing robot capable of detecting Class  
B flammable-liquid fires, navigating around obstacles, and deploying a 1 kg dry-powder extinguishing agent  
without human intervention. The prototype was validated across five repeated trials and demonstrated consistent  
performance within the scope of the laboratory test environment. Key quantified outcomes are: flame detection  
across a calibrated range of 10–90 cm with an inverse-square ADC response (R² = 0.97); linear PWM  
acceleration from 0 to 0.030 m/s in approximately 0.45 s; effective obstacle avoidance using front/left/right  
ultrasonic sensors at thresholds of 25 cm (front) and 20 cm (sides); and a servo-controlled nozzle sweep (50–  
130°, 1.6 s cycle) covering 113.1 cm². Mean fire detection time was 2.1 ± 0.3 s and mean extinguishing time  
was 11.8 ± 0.8 s across the five trials, with a 100% suppression success rate. Steady-state power consumption  
analysis confirms that untethered operation via an appropriately sized and mounted battery is technically feasible  
in a scaled-up iteration. The system’s concurrent integration of Class B-rated suppression, tri-directional infrared  
sensing, and autonomous obstacle avoidance on a low-cost Arduino Mega 2560 platform advances upon prior  
Arduino-based robots limited to Class A fires or dependent on remote control. It must be acknowledged that  
testing was conducted exclusively under controlled small-scale laboratory conditions; substantial further  
development, including chassis scaling, onboard battery integration, and extended field trials under varied  
environmental conditions, is required before the platform could be considered for real-world deployment. This  
work nonetheless establishes the functional feasibility of the design concept and provides a reproducible,  
accessible platform for further investigation.  
Recommendations for Future Study  
The following recommendations are proposed:  
Scale Up the Robot Design: Increase the chassis size and use stronger, high-torque motors to carry both  
the battery and the extinguisher simultaneously, enabling true untethered operation.  
Incorporate Onboard Battery with Proper Weight Distribution: Redesign the chassis to allow the  
12ꢀV rechargeable battery to be mounted low and centrally, improving stability and eliminating the need  
for an external power adapter.  
Use Higher-Range Flame Sensors: Replace the current flame sensors with models that offer a wider  
detection range (>90ꢀcm) and better angular resolution, allowing earlier fire detection and more precise  
localisation.  
Implement Autonomous Extinguisher Replacement: Design a magazine or docking mechanism that  
allows the robot to automatically replace an empty extinguisher cylinder with a full one, enabling  
continuous operation during large fires.  
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Add Data Logging and Telemetry: Equip the robot with an SD card module or wireless communication  
(e.g., Bluetooth, Wi-Fi) to record operational data (detection distance, extinguishing time, obstacle  
encounters) for post-mission analysis and performance optimization.  
Develop Closed-Loop Speed Control: Incorporate encoders on the drive motors to implement PID  
(Proportional-Integral-Derivative) control, maintaining constant speed under varying loads (e.g., when  
extinguisher agent is depleted).  
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