1. Sensors and Sensing for Reactive Robots
Alexander Stoytchev
Mobile Robot Lab
Georgia Tech

2. Sensing: Conceptual Level

3. Sensor Classification
Proprioception
relative to internal frame of reference
Exteroception
measurements of the environment relative to robot’s frame of reference
Exproprioception
Measurement of the position of robot body or parts relative to the layout of the environment

4. Proprioceptive Sensors
Shaft Encoders
Internal Navigation System (INS)
Global Positioning System (GPS)
Regular
Differential GPS (stationary base + moving robot)

5. Proximity Sensors Sonar IR Bumpers Radar Laser Range Finders
Time of Flight
Phase-based

6. Other Sensors Compass Accelerometers Inclinometers Gyroscopes
Thermometers
Microphones
Cameras

7. Sensor Properties Field of view (FOV) Update rate
Accuracy/Repeatability/Resolution
Applicability to target domain
Power consumption
Hardware reliability
Size
Computational requirements
Interpretation reliability

8. Desired Sensor Properties
Simple to operate and maintain
Modular
Redundant (physical & logical redundancy)
Fault Toloerant
Cheap!

9. Sensor Errors False Positive False Negative Sometimes not clear
Cost of Errors

10. Case Study: Sonar Calculate distance based on the time of flight
d = ½ c t
c = c T
c0 = 331 m/s T- temperature in degrees Celsius
Frequency – 50 KHz

11. Sonar Cone Regions

12. Problems with Sonars

13. Sensing: Conceptual Level

14. Raw v.s. Logical Sensors Raw Sensor Data Logical Sensor Data
List of distances to obstacles
Logical Sensor Data
Egocentric polar/Carthesian coordinates
Independent of physical sensor

15. Passive v.s Active Sensors
Passive – the environment provides the medium for observation
Active – the sensor puts out an energy into the environment
!= Active Sensing - use an effector to better position a sensor for observation

16. Sensor Fusion

17. Sensor Fission

18. Sensor Fashion