I. Introduction

Robotics has achieved its greatest success to date in the world of industrial manufacturing. Robots are the part of our life in fields like research, development, medicine, and defense. They have simplified our job to great extent and provided efficient, reliable and safe mode of working hands to human beings. Due to robotics, men are now able to perform distant operations. Mobile robots are robots with a mobile base which makes the robot move freely in the environment Mobile robots have become more common in commercial and industrial settings. Industrial and technical applications of mobile robots are continuously gaining in importance, in particular under considerations of reliability, accessibility or cost. One of the advanced mobile robots is the Line Follower.

A line follower is a robot that is capable of navigating in which it is designed to follow a

‘line’ or path already predetermined by the user. This line or path may be as simple as a

physical white line on the floor or as complex path marking schemes e.g. embedded lines,

magnetic markers and laser guide markers. In order to detect these specific markers or lines,

various sensing schemes can be employed. These schemes may vary from simple low cost line

sensing circuit to expansive vision systems. The choice of these schemes would be dependent

upon the sensing accuracy and flexibility required.

Basically, a line-following robot is a self-operating robot that detects and follows a line drawn on the floor. The path to be taken is indicated by a white line on a black surface. The control system used must sense the line and maneuver the robot to stay on course while constantly correcting the wrong moves using feedback mechanism, thus forming a simple yet effective closed- loop system. The basic operations of the line follower are as follows: Capture line position with optical sensors mounted at front end of the robot. Most are using several number of photo-reflectors, and some leading contestants are using an image sensor for image processing. The line sensing process requires high resolution and high robustness. Steear robot to track the line with any steearing mechanism. This is just a servo operation, any phase compensation will be required to stabilize tracking motion by applying digital PID filter or any other servo argolithm. Control speed according to the lane condition. Running speed is limited during passing a curve due to friction of the tire and the floor. This system can be of great use in large industries where goods are needed to transport along a predefined path, thereby increasing the productivity and efficiency of the industries and could be helpful in enhancing the research work in space technology.

The line follower uses interfaces for the sensors to make the behavior of the robot as versatile as possible. Two light detectors are mounted at the front of the robot. It uses the principle of reflected light, so it can differentiate the color, black and white. If the light falls on a white surface, it gets reflected but when it falls on black surface, it will completely get absorbed by the surface. The LDR (Light Dependent Resistance) acts as a sensor which senses the reflected light i.e. “transmitted light by LED”. If the sensor is placed on a white surface, the DC

motor is turned on while in black surface, it will be turned off and the robot will move accordingly. The table below shows how the robot senses its position on the line:

LEFT SENSOR RIGHT SENSOR POSITION

HIGH HIGH ON THE LINE

HIGH LOW OFF THE LINE, LEFT SIDE OF THE LINE

LOW HIGH OFF THE LINE, RIGHT SIDE OF THE LINE

Table 1

Basically, the line follower is divided into four sections: Input system, Processing system, Controlling System and the Output system.

Input system

The input system is nothing but eyes, which will observe or detect the things around and will send signal to the brain accordingly. Similarly, in line following robots we need to have such eyes to detect the surface and once the type of surface is detected, it should send the signal to the brain. Basically the input system comprises of sensors which will act as eyes and will sense the surface that comes in its vicinity. Sensor is part of the robot that functions convert physical quantities into electrical quantity (which distinguishes black and white). There are several types of sensors used in line follower robot, such as proximity, photodiode-infrared, phototransistor, LDR-LED, etc. The sensors should be capable of detecting black or white line. If the sensor on the light colored objects, the light will be reflected while if it is on the dark object, the light will be absorbed.

Processing System

Processing system is the brain which will take decisions depending on the input from the eyes. The processing system is usually comprised of either Comparator or Microcontroller. So, once after the surface is detected by the sensors (eyes), a signal is sent to the processing system (brain) which could be a comparator or microcontroller. Depending on this signal the processing system will take decisions whether the robot should move right or left.

• Controlling System

The controlling system is something that will help us to drive our robot in a systematic way. Basically controlling system is a group of electronic components like resistor, transistor, diodes, LED’s etc. which are connected in such a way that they will give us desired output. So

when the decision is taken by the processing system, it will send out signals to the controlling system and the controlling system in turn will control the motion of the robot at the output.

Output System

The output system usually consists of motors and wheels that will help my robot to move through black or white line. Motor will move in accordance with the logic generated by the comparator, so that the robot can follow the line.

Table 2 shows the advantages and disadvantages of a line follower.

ADVANTAGES DISADVANTAGES

• Robot movement is automatic.

• Fit and Forget system.

• Used for long distance applications.

• Defense applications.

• Used in home, industrial automation.

• Cost effective.

• Simplicity of building.

• Line following robot follows a black line

about 1 or 2 inches in width on a white

surface.

• Line tracing robots are simple robots with

an additional sensors placed on them.

• It always needs a path to run either white or

black since the IR rays should reflect

from the particular path.

• Slow speed and instability on different line

thickness or hard angles.

Table 2

Applications

Line followers are widely used in various fields of application. Some areas of use are listed below:

Industrial Applications: These robots can be used as automated equipment carriers in

industries replacing traditional conveyer belts. An example might be in a warehouse where

the robots follow 'tracks' to and from the shelves they stock and retrieve from. Line followers

can also be used to deliver mail within an office building and deliver medications in a

hospital. In this environment, these robots functions as materials carrier to deliver products

from one manufacturing point to another where rail, conveyor and gantry solutions are not

possible

Automobile applications: These robots can also be used as automatic cars running on

roads with embedded magnets. The technology has been suggested for running buses and

other mass transit systems, and may end up as part of autonomous cars navigating the

freeway.

Domestic applications: These can also be used at homes for domestic purposes like floor

cleaning etc.

Guidance applications: These can be used in public places like shopping malls, museums

etc to provide path guidance. The line follower can be used in guidance system for industrial

robots moving on shop floor.

Defense applications: A line follower robot can be used in military as spy kids or in many

other applications