1. An Introduction to Robotic Navigation ECE 450 Introduction to Robotics

2. Navigational Methods Dead-Reckoning Landmark-Based Navigation Map-Based Navigation 2

3. A Matter of Scale Global –Getting between end-points Local –The immediate area about the robot Personal –Monitoring the robot and anything in contact 3 http://www.doc.ic.ac.uk/~nd/surprise_97/journal/vol4/jmd/

4. Frame of Reference Absolute –Reference is to a fixed stationary point that whose position is known Relative –Reference is to a stationary point whose absolute position is not known 4

5. Global Positioning System (GPS) 24 operating satellites that transmit one-way signals that give the current GPS satellite position and time. The control segment consists of worldwide monitor and control The user segment consists of the GPS receiver equipment to calculate the user’s three- dimensional position and time. 5 USGlobalSat 20 Channel EM-406a SiRFIII GPS Engine Board with Patch Antenna From http://en.wikipedia.org/wiki/GPS

6. Rotary Shaft Encoders Mechanical –Low Cost, Low Resolution –Generate output by making / breaking a circuit –Example: volume control on a car radio Optical –Low to High Cost, Low to High Resolution –Generate output using infrared light and phototransistor –Example: Panel control in precision applications Magnetic –Medium to High Cost, Medium Resolution –Generate output by detecting changes in magnetic flux fields –Example: used most often in adverse environments Fiber Optic –High Cost, Medium to High Resolution –Generate output via a laser and phototransistor –Example: Where extremely flammable gasses are present Capacitive –Low Cost, Low to High Resolution –Generates output via changes in capacitance using high frequency reference signal –Example: Digital calipers 6

7. Rotary Shaft Encoders Optical Encoders Incremental –Tachometer encoder –Phase-quadrature encoder Absolute 7

8. Rotary Shaft Encoders Capacitive Encoder on Expansion Board 8

9. Linear & Rotational Speed Sensors Doppler Sensor –Based on Doppler shift in frequency –Lower frequencies easier to detect –Usually pointed 45º to ground to sense movement Accelerometer –Provide velocity rate –Poor signal-to-noise ratio at lower accelerations –One, Two and Three axis accelerometers Gyroscope –Provide angular rates –Need to be mounted on a very stable platform 9 HiTec's HG-R01 Robot Gyro $50

10. Active Beacons (Line-of-Sight) Radio Ultrasonic Reflective 10 Hagisonic StarGazer Robot Localization System

11. Ranging Sensors Types –Sonar –Laser –Light Methods for Determining Range –Time-Of-Flight –Phase-Shift Measurements –Triangulation 11

12. Measures distance in range from 20 to 80cm. Designed to interface to small micro-controllers. It’s relatively insensitive to the color and texture of the object at which it is pointed. Low current consumption at stand-by mode (Approximately 3  A). Actual Sensor Size GP2D02 SENSOR Triangulation Range Sensor GP2D02 SENSOR 12

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14. IR LED Transmits a bundled beam to the object plane. Reflected beam is receive by the photo detector. The angle of the received beam depends on distance of the object plane. Two Different Object Planes Distance Measurement by Triangulation 14

15. N-conductive substrate layer is an isolation layer P-conductive layer is embedded in isolation layer from IR irradiated Contact of the p-layer is made on left and right side Structure of a position sensitive photo diode(PSD) Structure of Photo Diode 15

16. Diodes in the Op-Amp’s feedback give a logarithmic behavior to the I-to-V conversion circuit. Collector current, Ic, in each Op-amp is identical to the I1 and I2. Third Op-Amp processes the difference of the two output voltages from previous Op- Amps. Vo =V T. ln(I 1 /I 2 ) Circuit for position sensitive Current-to-voltage conversion Circuit Diagram of a PSD 16

17. Spot irradiation in the center of the p-layer, both currents I1, I2 will have same value. Spot irradiation goes to the right, the I1 will decrease and I2 will increase by the same amount. The difference between the I1 and I2 will give the location of a spot irradiation on PSD. How Does A PSD Measures Distance? 17

18. Distance Chart 18

19. When interfacing with any type of hardware, timing is an issue. V in and V out are control measurements. V in drops to low for minimum 70ms. IR LED transmits 16 pulses towards the object. Mean value of 16 measurements reduces possible errors. Timing Diagram for Measurement and data handling Timing 19

20. Navigation Dead Reckoning Two typical methodologies –Odometers Advantages: –Good short-term accuracy –Inexpensive –High sampling rates Disadvantages –Systemic Errors »Unequal Wheel Diameters »Misalignment of wheels »Finite encoder resolution –Non-systemic Errors »Uneven floors »Bumps »Wheel slippage –Inertial Navigation Requires gyroscopically stabilized sensor platform Uses 3-axis accelerometer and integrates for velocity & position INS on aircraft cost from about $5,000 to $200,000. 20

21. Navigation Landmark-Based Natural Landmarks –Typically uses a vision system –Matches observed features to known landmarks Artificial Landmarks –Vision system can more easily detect Known pattern High contrast with background Line Navigation –Can use many types of sensors Electromagnetism, reflections, optical sensing… –Used for many years in buildings, restricts movement 21

22. Navigation Map Based Map Building –Feature extraction from raw data –Fusion of data from various sensors –Auto generation of an abstract model of the environment Map Matching –Most challenging due to different angles of observation –Feature extraction –Determining correspondence to model features Advantages –Uses existing structures to derive position –Can generate an updated map for other uses –Allows robot to learn about new environment Disadvantages –Must have enough stationary & distinguishable features –Sensor map must be accurate –Significant amount of sensing and processing 22