Sensors

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Sensors
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Definition

• Sensor A device which provides information about
  the physical world.

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Transducers

• Convert of energy from one form to another.
• e.g. microphone and speakers convert between
  acoustic and electrical energy.
• Many transducers are bidirectional.
• Some sensors are transducers almost all involve
  transduction.

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What can be sensed?

• Direct Transduction e.g., electric and magnetic
  fields, mechanical strain, temperature,
  electromagnetic energy...
• Derived quantities e.g. distance, human
  presence, heading, air flow, molecular
  concentrations, air pressure, color...

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Common Animal Sensors
Sensor Phenomena
Eye Electromagnetic waves in some sub-spectrum
Ear Pressure waves between about 10 hz and 100kHz (animal-dependent)
Nose Concentration of airborne molecules
Tongue Concentration of dissolved molecules, etc.
Skin Pattern of pressure on animal's surface
Proprioceptive system Pattern of nerve impulses from muscles
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Unusual Animal Sensors

• Magnetoreceptor Sensing of earths magnetic
  field. Seen in newts, birds, rats and maybe
  humans.
• Electric field sensing Seen in a variety of
  fish.
• Cerci Cockroach airflow sensors
• Body as eye Brittlestar covered with optically
  perfect lenses

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Biological Rotation Sensor

• semicircular canals detect angular acceleration
• 3 canals one per plane
• inertia of fluid causes deflection of sensory
  element

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Robot design as creature design

• Animal sensory systems adapted to functional
  needs and environment.
• Robots can use non-biological sensors which suit
  them to their ecosystems
• e.g., neutron-sniffing robodog, UAV with weather
  radar, etc.

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Sensors for dead reckoning

• Typical sensor optical encoder
• One type found in standard computer mouse
• Quadrature encoding

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Sensors for orientation/heading

• Use orientation/heading
• Options gyroscope, geomagnetic sensors
• Issues gyro drift, B-field distortion

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Sensors for obstacle detection

• e.g., where are walls?
• Options ultrasonic TOF, lateral-effect
  photodiode (PSD)

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Sensors for detecting humans

• Options computer vision, pyroelectric sensor
• pyroelectric sensors detect far-IR radiation
• can also detect heat, fire
• standard alarm sensor (cheap)