autonomous fire extinguishing system.pdf

Autonomous Fire Extinguishing System 1A. Rehman, 1N. Masood, 1S. Arif, 1U. Shahbaz,

1National University of Sciences & Technology, Islamabad,Pakistan

[email protected], [email protected] [email protected], [email protected]

2F. Sarwar, 2K. Maqsood, 2M. Imran, & 2M. Pasha 2Department of Mechatronics Engineering,

Air University, Islamabad, Pakistan [email protected], [email protected],

[email protected], [email protected]

Abstract — Fires are very dangerous and detrimental to life, property, and the environment. They spread rapidly and indiscriminately obliterate all things in their path. Fighting fires entails undeniable danger to life and the majority of suppression systems used to control them is at a broad-spectrum or macro scale. We present the design, fabrication, and testing of an autonomous fire extinguishing system. This system provides a unique solution to the problem of fires and their destruction by targeting the initial ignition of the fire and suppressing it before it starts to increase in intensity and range. The presented system detects, targets, and extinguishes a fire within a working space by using heat sensors, a flow control system, servo motors, and a water extinguishing gun. The system scans its workspace through motors and uses thermopile arrays to detect heat concentration gradients in its range. After the detection of the fire, the system then locks on to the target by extrapolating its location. Efficiency of the system, suppression accuracy, response time, power consumption, and work space area are also documented and presented in this paper. Future considerations and recommendations are highlighted to advance the system’s design, efficiency, and scope. This is an indigenous solution to fire fighting in world and it is to make environment a healthier and safer place for the future.

Keywords- Automation; Flow Control System; Autonomous; Fire Extinguishing System; Fire Detection; Heat Sensors; Pyro Electric Thermopile Array; Nozzle Water Suppression; Servo Motors

I. INTRODUCTION Fire-fighting [1] has always been a very dangerous

profession. Fire fighters spend most of their careers putting their life on the line. Current fire-fighting techniques require that firefighters take high risks. Why not make a system which takes these risks instead and also the system that can be implemented in the sensitive areas like ware houses, factory and working places etc. These are the areas where one needs protection from fire immediately because life can’t be pushed into risk and as well as money [2].

A simple Fire Extinguisher is designed to control small fire because if a small fire not checked immediately then it will soon spread out of control and infect most big fire starts. It is important, therefore, that you equip your workplace with the proper fire extinguishers as part of your fire protection plan [3].

The fire extinguishing system is fully automatic and gives a unique solution to firefighting techniques [4]. This system only targets the area which is under fire and will not affect the surroundings areas. The implementation of this system will help us to save the important machinery and electronics lying

around in an industrial environment which are not under fire but can get spoiled due to excessive use of water by fire department [5].

Now-a-days there are many types of Portable fire

extinguishers and automatic fire suppression systems [6]. These existing systems help to extinguish the fire and perform good efficient work but it also damage the other expensive things which are not in the range of fire. These Systems only waste a considerable amount of suppressant but also do not target the fires’ source. This creates unnecessary and hazardous obstacles in the affected area for evacuation and relief of human life and well-being. Expensive and sensitive equipment in such cases are exposed to harmful suppressants that may impair their functionality or even render them useless [7]. The project present in this paper provides an efficient and intelligent solution to human safety as well as the property. This prototype is implemented in chemical, mechanical, and these kind of industries to save live and money.

II. METHODOLOGY The automated system used a thermal sensor to detect a fire and extinguish it with a blast of water. The sensor detects the fire at a point and the water pump motor extinguishes the fire. In this paper same techniques are used to extinguish the fire in the range of a sensor without any human interference [4]. The aim of this paper is to provide an efficient and intelligent solution to human safety. This prototype can be implemented in chemical and mechanical industries to save live and money. The project consists of a fire extinguishing nozzle, sensors, flow control system, motors, and controllers. Fire extinguishing nozzle is use to hit the desired target. Target detection will be detected by heat sensors that detect heat concentration within the range of extinguisher. For hitting the desired target, we will control the flow of the extinguisher. The motors are used to control the direction and motion of the system. After detecting the heat, controller will be able to allow the motion of a motor and control the flow of water to desired projectile [8].

III. MODELING & DESIGN

The mechanical structure, Fig.1, is made up of aluminum which is relatively lighter and having a reasonable strength as compared to steel, plastic or any other material. The model

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consists of a rod that is attached to the base over which disc assembly is attached. The disc assembly contains pair of discs attached by a rod in between them so that both of discs can be rotated simultaneously. On upper disc a sensor is attached and on lower disc the fire extinguishing nozzle is attached. Sensor and fire extinguishing nozzle rotate up and down by two separate servo motors whereas disc assembly rotates by the DC motor, attached on the lower disc. Gear is attached on the shaft of DC motor, which is meshed with the gear attached to the lower rod which helps to rotate the disc assembly. This prototype can be attached to portable robot or attached to the ceiling.

Figure 1: Mechanical Structure

A. DC Motor Control Position In Position control system, the output position Θ of an

actuator must have a linear response to an operators input command ‘Θd ‘ as shown in figure below .DC motor is used , except that a gear train is employed to reduce the speed of motor ‘ωm‘ as it moves the output inertial load ‘Θ’. The equations of motor torque and motor voltage [9] are given respectively:

Tm = KI (1) Em = k ωm (2)

Where Tm is motor torque and Em is motor voltage. The electronic amplifier or controller has inputs from the set point or desired position (with the gain of C) and from the feedback voltage ‘Ef ‘(which represents the actual position).

The amplifier’s equation of motor voltage is: Em = G (cθ-Ef) - R0 Im (3)

Where Em is motor amplified voltage. The feedback position sensor could be a rotary potentiometer similar to the volume control on the CD player. If a constant voltage is supplied across the potentiometer, then output voltage can be linearly proportion to the angular position of the output shaft ‘Θ’ with sensitivity of h.

This is the equation of feedback voltage which represents

the actual position: Ef = hθ (4) ωθ = Rs ωm (5) Tθ = (6) Where Ef is the feedback voltage of motor, ωθ is angular position and Tθ is angular torque. As the angular speed is a derivative of angular position ωθ = 휃̇. Neglecting the inertia of the gear train, and assuming some linear viscous damping B in the drive train and the inertia of load with a disturbance torque TL, so the torque balance equation becomes Tθ - Jθ̈ - B휃̇ - TL = 0 (7) By combining the proceeding (1) – (7) and solving for “θ” we get the following equation.

휃=( . )

(8)

B. Angle Calculation of Fire Extinguishing Nozzle The horizontal distance of target from sensor and fire

extinguishing nozzle is same. So the calculated values by using trigonometry angle of fire extinguishing nozzle from base with the error of ±10 are shown in Fig. 2.

Equation (9) – (13) show these calculations. Table I

summarizes the dimensions. 푏 = ( ) (9)

푏 = ( ) (10)

tan(휃 ) = (11)

tan(θ ) = = (12)

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θ = tan θ (13)

Figure 2: Angle Calculation

TABLE I. DIMENSIONS OF MECHANICAL STRUCTURE

C. DC & Servo Motors DC motor is used to create unidirectional rotation and when sensor detects any flame in its range the motor stops rotating but rotation should be much fast those sensors do not detect the flame. PWM is used to control the speed of DC motor. Initially it must rotate the motor to high acquire initial torque so that motor starts running and then slows down through PWM because when motor starts at slower speed, torque is not enough to rotate the motor. Two servo motors have been used for rotating sensor and fire extinguishing nozzle. The model of servos is Hi-Tech Zebra ZS-S1113. This servo can operate 180° when given a pulse signal ranging from 600 µsec to 2400 µsec

IV. EXPERIMENTAL SETUP For microcontroller programming BASCOM AVR 1.9.11.2

is used. This software is used because it has built-in libraries which made programming easy and comprehensive, Fig. 3 shows the microcontroller programming.

TPA81 sensor is used to detect the fire in the range of 2µm to 22µm which is the wavelength of radiant heat. The TPA81 is a thermopile array which gives temperature at eight different points at a view angle of 41° x 6° so the view angle of single point becomes 5.125° x 6° and the temperature that acquire from sensor is through TWI (two wire interface) or I2C bus.

Figure 3: Microcontroller Programming flow chat

As discussed that for acquiring temperature from TPA81 I2C bus is used. In TPA81 temperature is measured and save in 9 different registers which are as shown in Table II.

TABLE II. TPA81 TEMPERATURE ADDRESSING

Temperature can be acquired by reading these registers; these registers can only read and are not writeable. The standard PWM controlled servos are used for the position control of sensor from which can acquire 180o rotation. For position control of sensor it must write on register number 0 in sensor using I2C bus and values ranges from 0 to 31. This means 180o rotation is divided into 31 step and angle of each step become 5.806o.

As for sensor position control step angle is 5.806o so for each value which is send to sensor have its own angle which ranges from 0 to 31 for whole 180o rotation but it only need positions from 0o to 90o so angle according to given position sent to sensor is shown in Table III.

TABLE III. SENSOR POSITION CONTROL STEP

Value Given to Sensor Position (degrees) 0 0 1 5.80 2 11.61 3 17.41 4 23.22 5 29.03 6 34.83

Part Name Dimension

Lower rod (from base to lower disc) 304.8 mm

Distance between discs 152.4 mm

Diameter of discs 304.8 mm

Diameter of rod 50.8 mm

Thickness of discs 101.6 mm

Gear ratio 1 : 5

Register # Temperature which it saves 1 Ambient temperature

2 Temperature at pixel no. 1








DC motor speed control

Water pump flow control

Acquiring temperature

from sensor TPA81

Servo motors position control

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7 40.64 8 46.45 9 52.25

10 58.06 11 63.87 12 69.67 13 75.48 14 81.29 15 87.09

AVR ATMEGA16L has four PWM channels and for motor

speed control PWM channel number 1 is used. The above code will generate PWM of 70% duty cycle to give motor initial torque and then after one second motor will slow down to almost half of its speed by creating PWM of 52% duty cycle. The motor rated speed is 170 rpm and as it used gear for coupling the disc and rod on which disc rotates which have gear ratio of 1:5. By using gear motor speed reduces to 34 rpm. Initially it generated PWM of 70 % duty cycle which will reduce speed to 23.8rpm which gives the motor initial torque. Then after that it created PWM of 52% duty cycle which will reduce speed to 17.68 rpm. It used car wind screen pump to through water on the flame.

TABLE IV. SENSOR POSITION VALUE

Whenever flame is detected the DC motor will stop and servo motor for pump adjusts its position and then pump will be started to through water on flame. After the flame is extinguished the system will start searching

for next flame again. The signal which is generated through micro controller using PWM channels number 2. In code above the 180o rotation of servo motor is divided in to 40 steps according to values from 15 to 55. As 180o rotation is divided in to 40 steps which makes step angle to be 4.5o but for this task it need only positions from 0o to 90o and value for each step and its positions is given below in Table IV.

A. Programming Flow Chart

No

Yes

Yes No Yes No

Yes No

Figure 4a: Programming flow chat

Value given to sensor Position (degrees)

15 0 16 4.5 17 9 18 13.5 19 18 20 22.5 21 27 22 31.5 23 36 24 40.5 25 45 26 49.5 27 54 28 58.5 29 63 30 67.5 31 72 31 72 32 76.5 33 81 34 85.5 35 90

Start Pump

If Ind of Max Temp > 4

Increment Servo

Position

If Ind of Max Temp < 4

Decrement Servo

Position

Dc Motor

on

Start

Sensor Acquire Temp

Servo Motor

on

If Max Temp > Fire Temp

Track Flame

Stop DC Motor

If Ind of Max Temp = 4

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Figure 4b: Graph for calculation of angles for servo sensor and pump servo

Complete programming flow chat of the system and calculation of angles for both sensor and pump servos are shown in Fig. 4a and Fig. 4b respectively.

The range of sensor is only one meter which is the limitation of this paper and that range makes hypotenuse with the base where flame will be present. Maximum positions of servo that it used are only 13sectors and angle according to this will is given in Table above which is 75.48o and perpendicular distance of flame from base is 490mm.In the Fig. 5b red zones is workspace and green area is not in sensor range. So for 1 m range the distance from rod to flame is as follows. 푑 = √100 − 49 = 871.7푚푚 (14) And at the lowest distance which constrained sensor to detect the flame is as under: 푑1 = = 131.2푚푚 (15) Where: d = maximum distance at which sensor can detect flame d1 = minimum distance at which sensor can detect flame The graphical and schematic representation of the workspace and range is shown in Fig. 5a and Fig. 5b.

Figure 5a: Workspace Schematic

Figure 5b: Workspace Representation

V. CONCLUSION The technique used in this paper is at micro level, which

means it will affect only the area under the influence of the fire and will not spoil any surrounding areas or equipment. This system can be very beneficial and efficient in industries where sensitive machinery and electronics are critical for implementation and operation. After detecting the heat the total response time of sensor to sense the location of fire is 3 seconds and the total response time to extinguish the fire is 5 seconds. Once the target is locked it throws water until fire completely extinguished.

These enhancements can be made to the fire extinguishing system in future like range is one of the limitations in this work. The range of sensor is not more than 1 meter so sensor should be selected which have enough range for the industrial use. The number of points at which sensor gives temperature is only 8, so it can never target the middle point and can never gets 100% accuracy. As the servo is rotated at selected angles so by smooth controlling of servo it can get 100% accuracy in target. The Pressure of the water pump can also be controlled with respect to the distance of the target. The projectile of the water jet can also considered in creating a better equipped extinguishing procedure. These all steps decrease the response time of system in detecting and extinguishing flame.

REFERENCES [1] Maurice Jones, “Fire Protection Systems ”, Edition 1 Cengage

Learning, 08-Aug-2008 [2] Robert W. Klinof , “Introduction to Fire Protection”, April 12, 2006 [3] James C. Robertson, “Introduction to Fire Prevention”, Prentice hall,

01-Jan-2000 [4] Tao Chen, Hongyong Yuan*, Guofeng Su, Weicheng Fan Fire Safety

Journal 39 (2004) 297–307 [5] Dennis P. Nolan, “Fighting Pumping Systems at Industrial Facilities”,

Edition 1st and 2nd. [6] E. Cote,” Operation Of Fire Protection Systems”, National

Fire Protection Association, 2003. [7] Jones & Bartlett, “Fire Officer: Principles and Practice”, Second

Edition, 15-sep-2009. [8] W. Bolton, “Mechatronics: Electronic Control Systems in Mechanical

and Electrical Engineering”, Addison Wesley, New York, NY, 1999. [9] V.U.Bakshi, U.A.Bakshi, “Electrical Circuits And Machines”,

Technical Publications, 01-Jan-2007.

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