Line Follower Robots – Controlling, Working Principle and Applications

A brief introduction to a robot:

A Robot is any machine which is completely automatic, i.e. it starts on its own, decides its own way of work and stops on its own. It is actually a replica of human being, which has been designed to ease human burden. It can be controlled pneumatically or using hydraulic ways or using the simple electronic control ways. The first industrial robot was Unimates built by George Devol and Joe Engelberger in the late 50’s and early 60’s.
Any robot is built on 3 basic laws defined by the Russian Science fiction author Isaac Asimov:

  • A robot should not harm the human being directly or indirectly.
  • A robot should obey human orders unless and until it violates the first law.
  • A robot should protect its own existence provided the 1st two laws are not violated.
A Fixed Robot
A Fixed Robot

Robots can be fixed robots or mobile robots. Mobile Robots are robots with a mobile base which makes the robot move freely in the environment. One of the advanced mobile robots is the Line Follower Robot. It is basically a robot which follows a particular path or trajectory and decides its own course of action which interacts with obstacle. The path can be a black line on the white floor (visible) or a magnetic field (invisible). Its applications start from basic domestic uses to industrial uses, etc. The present condition in industry is they are carrying the parcels or materials one place to another place using the crane system. Some times lifting of big weights at that time may cause the breakage of lifting materials and will be cause damage to the parcels also. The line following robots is commonly used for carry children through shopping malls, homes, entertainment places, industries. The use of line following robotic vehicle is transport the materials from one place to another place in the industries. This robot movement completely depends on the track. The robot can do any thing you set them to do. Like in factories all they have to do with making their products is make the robot.

A mobile robot
A mobile robot

Line follower robot

A line follower robot is a robot which follows a certain path controlled by a feed back mechanism.

Building a basic line follower robot:

Building a basic Line Follower Robot involves the following steps.

  • Designing the mechanical part or the body of the robot
  • Defining the kinematics of the robots
  • Designing the control of the robot
A Line Follower Robot
A Line Follower Robot 

The mechanical part or body of the robot can be designed using AutoCAD or Workspace. A basic Line follower robot can consist of a base at the two ends of which the wheels are mounted. A rectangular sheet of hard plastic can be used as the base. Further a rigid body like a cylinder can be added along with other shaped bodies inter connected with each other by joints, and each with its defined motion in particular direction.  The Line follower robot can be a wheeled mobile robot with a fixed base, a legged mobile robot with multiple rigid bodies interconnected by joints.

The next step involves defining the Kinematics of the robot. Kinematic analysis of the robot involves the description of its motion with respect to a fixed coordinate system. It is concerned mainly with the movement of the robot and with motion of each body in case of a legged robot. It generally involves the dynamics of the robot motion. The whole trajectory of the robot is set using the Kinematic analysis. This can be done using Workspace software.

The control of the robot is the most important aspect of its working.  Here the term control refers to the robot motion control, i.e. controlling the movement of the wheels. A basic line follower robot follows certain path and the motion of the robot along this path is controlled by controlling the rotation of wheels, which are placed on the shafts of the two motors. So, the basic control is achieved by controlling the motors.  The control circuitry involves the use of sensors to sense the path and the microcontroller or any other device to control the motor operation through the motor drivers, based on the sensor output.

2 Ways of controlling a line Follower Robot

  • Without using Microcontrollers
Block Diagram of the control System
Block Diagram of the control System 

It consists of an IR-LED and Photodiode arrangement for each motor which is controlled by the switching on and off of the transistor.

The IR LED on getting proper biasing emits Infra red light. This IR light is reflected in case of a white surface and the reflected IR light is incident on the photodiode. The resistance of the photodiode decreases, which leads to an increase in current through it and thus the voltage drop across it. The photodiode is connected to the base of the transistor and as a result of increased voltage across the photodiode, the transistor starts conducting and thus the motor connected to the collector of the transistor gets enough supply to start rotating. In case of a black color on the path encountered by one of the sensor arrangement, the IR light is not reflected and the photodiode offers more resistance, causing the transistor to stop conduction and eventually the motor stops rotating.

Thus the whole system can be controlled using a simple LED-Photodiode-Transistor arrangement.

  • With using Microcontrollers

Working principle:

The line fallowing robot is one of the self-operating robots. That detects and fallows a line drawn on the area. The line is indicated by white line on a block surface or block line on a white surface. This system must be sense by the line. This application is depends upon the sensors. Here we are using two sensors for path detection purpose. That is proximity sensor and IR sensor. The proximity sensor used for path detection and IR sensor used for obstacle detection. These sensors mounted at front end of the robot. The microcontroller is an intelligent device the whole circuit is controlled by the microcontroller.

Block Diagram of Line Following Robotic Vehicle with Microcontroller
Block Diagram of Line Following Robotic Vehicle with Microcontroller 

Different types of line controlled robotic vehicles:

There are two types of line controlled robotic vehicles

  • Mobile based line controlled robotic vehicle
  • RF based line controlled robotic vehicle

Applications of line follower robot:

  • Industrial Applications: These robots can be used as automated equipment carriers in industries replacing traditional conveyer belts.
  • Automobile applications: These robots can also be used as automatic cars running on roads with embedded magnets.
  • 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.


  • Robot movement is automatic
  • It is used for long distance applications
  • Simplicity of building
  • Fit and forget system
  • Used in home, industrial automations etc.

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