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Robotix Tutorial 6

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Robotix Tutorial 6

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

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