2. Analog vs Digital  Digital on/off voltage Analog variable voltage

3. Environment Robot What do we want to know? Position Velocity Color Position Velocity Topography Temperature Size/shape Acceleration Orientation

4. Sensors  Sonar  Accelerometer  Gyroscope  Encoder  Camera  Potentiometer  Compass  Laser

5. Potentiometers  Variable resistance  Voltage divider  Linear or rotary

6. Accelerometer and Gyroscope  Measure deflection of micro-mass  Variation in output voltage V α a and V α ω  Resolution V/gcounts/V=> counts/g V/°/scounts/V => counts/°

7. Analog to Digital  Computers sample analog signals Voltage of sample corresponds to digital number

8. Using Accel/Gyro Info  Sampling Period = ΔT  Angular Velocity x Time => Angle Change  Acceleration x Time => Velocity Change  Velocity x Time => Position Change

9. Sonar sound navigation and ranging  Point Source Emitter and receiver Calculate distance  Reflected Signal Calculate distance to an object

10. Sonar Shortfalls  Object interference  Radial Distance  How can we overcome it? - Rotating sensors - Multiple sensors

11. Sonar with Multiple Sensors  Sensor Interference  Solutions: - Different frequency sensors - Double-Pulse Coding

12. Controlling Sonar  Sonar board configuration  Give command/pulse signal  Start counter  Receive response – stop counter  Calculate distance

13. Mapping with Sonar  Distance represents a 3D surface ○ 2D if you make good assumptions  Digital representation (map) Shaded cells MAY contain an object

14. Rotary Encoders  Diode light passes through slits in disk  Photocell gives high voltage

15. Encoders with Direction  2 Channels with slight offset A or B will be read first

16. Absolute Encoder  Standard Binary Encoding Contact 1Contact 2Contact 3Angle 1offoffoff0° to 45° 2offoffon45° to 90° 3offonoff90° to 135° 4offonon135° to 180° 5onoffoff180° to 225° 6onoffon225° to 270° 7ononoff270° to 315° 8ononon315° to 360°

17. Compass  Direction relative to defined direction  Analog output

18. Bringing it Together  Many sensors interfacing with microcontroller