Robotix Tutorial 6
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Transcript of Robotix Tutorial 6
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TECHNOLOGY ROBOTICS SOCIETY
Indian Institute of Technology, Kharagpur
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A TUTORIAL ON ROBOTICSSensors
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Copyright © Robotix Team, IIT Kharagpur
Basic Parts Of Our Mobile Robot Locomotion system Power supply system Actuators Sensory devices for feedback Sensor Data processing unit Control system
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Sensors Analogous to human sensory organs
Eyes, ears, nose, tongue, skin Sensors help the robot knowing its
surroundings better Improves its actions and decision making
ability Provides feedback control
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LDR - Light Dependent Resistor Made of cadmium
sulphide Resistance between
two terminals vary depending on the intensity of light
Can be used to differentiate contrast colours
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LED – Light Emitting Diodes Used generally with LDRs
to make a complete sensor module.
Act as a source of light for the LDRs.
The main specification of LED are its current rating=20mA, typical cut in voltage=2V,voltage is around 4.5V.
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Thermistor Manufactured from the oxides of the
transition metals - manganese, cobalt, copper and nickel
Resistor depends on temperature Commonly available temperature
sensors are LM35,DS1621 thermistor.
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IR Photo Diode Detects presence of Infra
Red radiations Used for obstacle proximity
sensing IR Data Communication Used in combination with IR
LEDs
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Sensor Interfacing
Light Sensing Module using LED-LDR combination
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Sensor Interfacing
Bump Detector Module
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An Example - Line Follower A line follower is a robot
capable of tracking a line drawn on a surface
Optical sensors capture the line position at the front end of the robot
The robot is steered to keep it always over the line
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Block Layout of Line FollowerOptical Sensor Array
Steering Controller
Left Motor Right Motor
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Line Following AlgorithmStep1:Step1: All the sensors are assigned All the sensors are assigned some weight such assome weight such as
Sensor 1 = a1 = 3Sensor 1 = a1 = 3Sensor 2 = a2 = 2Sensor 2 = a2 = 2Sensor 3 = a3 = 1Sensor 3 = a3 = 1Sensor 4 = a4 = -1Sensor 4 = a4 = -1Sensor 5 = a5 = -2Sensor 5 = a5 = -2Sensor 6 = a6 = -3Sensor 6 = a6 = -3
Step2:Step2:Let b1 – b6 denote the state of each Let b1 – b6 denote the state of each
sensor. 0 for white line and 1 for black linesensor. 0 for white line and 1 for black lineStep3:Step3:
Line Position = Line Position = ΣΣaibiaibi
Step4:Step4:Vcm is fixed, Vcm is fixed,
predeterminedpredeterminedωωcm is cm is
proportional to Line proportional to Line positionposition
Step5:Step5:Vl = Vcm + (Vl = Vcm + (ωωcm / a)cm / a)Vr = Vcm – (Vr = Vcm – (ωωcm / a)cm / a)a : Separation between left/right a : Separation between left/right wheelswheels