Presentation on control systems for line follower robot

PRESENTATION ON CONTROL SYSTEMS FOR
LINE FOLLOWER ROBOT

DEFINITION OF CONTROL SYSTEM:
A CONTROL SYSTEM IS A SYSTEM OF DEVICES OR SET OF DEVICES, THAT MANAGES,
COMMANDS, DIRECTS OR REGULATES THE BEHAVIOR OF OTHER DEVICES OR SYSTEMS TO
ACHIEVE DESIRED RESULTS.
THE MAIN FEATURE OF A CONTROL SYSTEM IS THAT THERE SHOULD BE A CLEAR
MATHEMATICAL RELATIONSHIP BETWEEN INPUT AND OUTPUT OF THE SYSTEM.

LINE FOLLOWER ROBOT:
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 THROUGH MICROCONTROLLER.

LINE FOLLOWER ROBOT STRUCTURE:
THIS ROBOT CAN BE DIVIDED INTO SEVERAL PARTS:
• SENSORS
• ADC (ANALOG TO DIGITAL CONVERTER) AND SENSOR
CIRCUIT
• PROCESSOR (ATMEGA 328 MICROCONTROLLER)
• MOTOR DRIVER
• ACTUATORS (MOTORS AND WHEELS)
• CHASSIS AND BODY STRUCTURE

IMPLEMENTING THE IR SENSOR LOGIC
THE IR SENSOR CONSISTS OF AN INDIVIDUAL IR LED AND AN IR PHOTODIODE. THE IR LIGHT
EMITTED BY THE LED STRIKES THE SURFACE AND IS REFLECTED BACK TO THE IR PHOTODIODE. THE
PHOTODIODE THEN GENERATE AN OUTPUT VOLTAGE PROPORTIONAL TO THE REFLECTANCE LEVEL
OF THE SURFACE.

PID CONTROL
PID (PROPORTIONAL, INTEGRAL AND DERIVATIVE ) IS ONE OF THE MOST COMMON CONTROL
SCHEMES AROUND. MOST INDUSTRIAL CONTROL LOOPS USE SOME FLAVOR OF PID CONTROL.
PID ACTS AS A SIMPLE SPRING. A SPRING HAS AN ORIGINAL LENGTH, WHICH
WHEN DISTURBED BY EXPANSION OR CONTRACTION, TENDS TO REGAIN ITS
ORIGINAL LENGTH IN THE SHORTEST POSSIBLE TIME.
PID ALGORITHM IN A SYSTEM HAS A SET-VALUE OF A PARTICULAR PHYSICAL QUANTITY TO BE
CONTROLLED, CALLED A ‘SET POINT’, WHICH WHEN ALTERED DUE TO SOME REASON, THE SYSTEM
CONTROLS THE OTHER NECESSARY FEATURES IN IT, TO GET BACK TO THE ORIGINAL SET POINT IN THE
SHORTEST TIME POSSIBLE. PID CONTROLLERS ARE USED WHEREVER THERE IS A NEED TO CONTROL A
PHYSICAL QUANTITY AND TO MAKE IT EQUAL TO A SPECIFIED VALUE.

HOW DOES PID WORK?
• CALCULATES THE ERROR, OR DEVIATION FROM THE SET POINT
• MEASURE THE CURRENT VALUE BY SENSOR
TO GET BACK TO THE SET POINT, THIS ‘ERROR’ SHOULD BE MINIMIZED, AND SHOULD IDEALLY BE MADE
EQUAL TO ZERO.
IDEALLY, THERE SHOULD BE ZERO LAG IN THE RESPONSE OF THE SYSTEM TO THE CHANGE IN ITS SET
POINT.

IMPLEMENTING PID
i) ERROR TERM (E): EQUAL TO THE DIFFERENCE BETWEEN THE SET POINT AND THE CURRENT VALUE . ERROR = SETPOINT – CURRENT
VALUE THIS IS EQUAL TO THE DIFFERENCE BETWEEN THE SET POINT AND THE CURRENT VALUE OF THE QUANTITY BEING CONTROLLED.
ii) PROPORTIONAL TERM (P): THIS TERM IS PROPORTIONAL TO THE ERROR. P = ERROR PROPORTION TERM IS WHAT DETERMINES THE
CONTROL LOOP RISE TIME OR HOW QUICKLY IT WILL REACH THE SET POINT.
iii) INTEGRAL TERM (I): THIS TERM IS THE SUM OF ALL THE PREVIOUS ERROR VALUES. I = I + ERROR THIS VALUE IS RESPONSIBLE FOR THE QUICKNESS
OF RESPONSE OF THE SYSTEM TO THE CHANGE FROM THE SET POINT. USUALLY, SMALL ROBOTS DOESN'T USE THE INTEGRAL TERM BECAUSE WE ARE NOT CONCERNED ABOUT
STEADY STATE ERROR AND IT CAN COMPLICATE THE "LOOP TUNING".
iv) DERIVATIVE TERM (D): THIS TERM IS THE DIFFERENCE BETWEEN THE INSTANTANEOUS ERROR FROM THE SET POINT, AND THE ERROR FROM THE PREVIOUS
INSTANT. D = ERROR – PREVIOUSERROR THE DERIVATIVE TERM IS USED TO REDUCE THE OVERSHOOT OR HOW MUCH THE SYSTEM SHOULD "OVER
CORRECT".

PID FOR LINE FOLLOWING ROBOT
PID_VALUE = (KP*P) + (KI*I) + (KD*D)
•KP IS THE CONSTANT USED TO VARY THE MAGNITUDE OF THE
CHANGE REQUIRED TO ACHIEVE THE SET POINT.
•KI IS THE THE CONSTANT USED TO VARY THE RATE AT WHICH THE
CHANGE SHOULD BE BROUGHT IN THE PHYSICAL QUANTITY TO ACHIEVE
THE SET POINT.
•KD IS THE CONSTANT USED TO VARY THE STABILITY OF THE SYSTEM.
void calculatePID()
{
P = error;
I = I + error;
D = error-previousError;
PIDvalue = (Kp*P) + (Ki*I) + (Kd*D);
previousError = error; }

APPLICATIONS OF LINE FOLLOWER ROBOT:
APPLICATION ADVANTAGES DISADVANTAGES
•Industrial automated
equipment carriers.
The robot must be capable
of following a line.
LFR can move on a fixed track
or path.
•Automated cars.
Insensitive to environment
factors like noise and
lightning.
It requires power supply.
•Tour guides in
museums
and other similar
applications.
It should be capable of
taking various degrees of
turns.
Lack of speed control makes the
robot unstable at times.
•Deliver the mail
within the office building
The color of the line must
not be a factor as long as it
is
darker than the
surroundings.
Choice of line is made in the
hardware abstraction and
cannot
be changed by software.

Presentation on control systems for line follower robot

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Presentation on control systems for line follower robot