Sensors and Sensing for Reactive Robots

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Sensors and Sensingfor Reactive Robots

• Alexander Stoytchev
• Mobile Robot Lab
• Georgia Tech

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Sensing Conceptual Level
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Sensor Classification

• Proprioception
• relative to internal frame of reference
• Exteroception
• measurements of the environment relative to
  robots frame of reference
• Exproprioception
• Measurement of the position of robot body or
  parts relative to the layout of the environment

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Proprioceptive Sensors

• Shaft Encoders
• Internal Navigation System (INS)
• Global Positioning System (GPS)
• Regular
• Differential GPS (stationary base moving robot)

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Proximity Sensors

• Sonar
• IR
• Bumpers
• Radar
• Laser Range Finders
• Time of Flight
• Phase-based

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Other Sensors

• Compass
• Accelerometers
• Inclinometers
• Gyroscopes
• Thermometers
• Microphones
• Cameras

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Sensor Properties

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

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Desired Sensor Properties

• Simple to operate and maintain
• Modular
• Redundant (physical logical redundancy)
• Fault Toloerant
• Cheap!

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Sensor Errors

• False Positive
• False Negative
• Sometimes not clear
• Cost of Errors

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Case Study Sonar

• Calculate distance based on the time of flight
• d ½ c t
• c c0 0.6 T
• c0 331 m/s T- temperature in degrees
  Celsius
• Frequency 50 KHz

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Sonar Cone Regions
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Problems with Sonars
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Sensing Conceptual Level
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Raw v.s. Logical Sensors

• Raw Sensor Data
• List of distances to obstacles
• Logical Sensor Data
• Egocentric polar/Carthesian coordinates
• Independent of physical sensor

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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

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Sensor Fusion
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Sensor Fission
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Sensor Fashion