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Ultrasonic Sensors. for Planetary Exploration. What they are. Ultrasonic: Sound at a higher frequency than can be heard by humans (> 20000 Hz) Sensors use sound to sense objects that reflect sound AKA Sonar. How They Work. Piezo-electric mechanism Different Types: Modulated Waves

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ultrasonic sensors
Ultrasonic Sensors
  • for Planetary Exploration
what they are
What they are
  • Ultrasonic: Sound at a higher frequency than can be heard by humans (> 20000 Hz)
  • Sensors use sound to sense objects that reflect sound
  • AKA Sonar
how they work
How They Work
  • Piezo-electric mechanism
  • Different Types:
  • Modulated Waves
  • Echolocation
  • Frequency Sweeps
what they are good for
What They are Good For
  • Obstacle Avoidance
  • Navigation
  • Map Building
  • Underwater Exploration!
what are the advantages
What are the Advantages?
  • Can detect things that are hard to see Not affected by colour Less affected by target surfaces
  • Measures discrete distances to objects
what are the advantages1
What are the Advantages?
  • Resistance to many disturbances we talked about:
    • vibration
    • infrared radiation
    • ambient noise
    • EMI radiation
what are the issues
What are the Issues?

Target Angle

  • Examples of Angles from Migatron Sensors:
    • RPS-150: ±35°
    • RPS-400-6: ±6°
    • RPS-426: ±10°

θ

what are the issues1
What are the Issues?

Beam Spread

  • Examples of Max Spread from Migatron Sensors:
    • RPS-150: 58” at 72” away
    • RPS-400-6: 1.06” at 6” away
    • RPS-426: 14.5” at72” away

.25 m

.5m

.75 m

1 m

1.25m

1.5 m

what are the issues2
What are the Issues?
  • Don’t work in vacuum.
  • Poor sound travel on Mars, the moon
  • Time of Flight error

Time of Flight error

http://www.cs.brown.edu/people/tld/courses/cs148/02/sonar.html

assignment
Assignment
  • Your robot is mapping its environment with an ultrasonic sensor, and comes across a wall. Assume the beam spread is a cone with an angle of 20°, and the range is sufficient to sense the wall from its current position. The robot is 40° from pointing straight at the wall, and the shortest distance from the sensor to the wall is 0.75 meters.
  • What is the error between the desired distance measurement and the actual distance measured? Show your work.

20°

40°

0.75 m

what s new
What’s New?

Acoustic Doppler Current Profiler / Doppler Velocity Log

  • Underwater vehicles
  • Sound waves point downwards
  • Tracks water current
  • Doppler Velocity Log: Tracks position
what s new1
What’s New?

Acoustic Doppler Current Profiler / Doppler Velocity Log

  • Bluefin
    • MIT Autonomous Underwater Vehicle Lab spinoff
    • Scientific, Military, Industrial Applications
    • Uses Teledyne RDI Doppler Velocity Log

http://www.bluefinrobotics.com/

who develops them
Who Develops Them?
  • Sensor Development:
    • Migatron Corp, Hitechnic, Teledyne, Maxbotics
  • Low cost sensors for autonomous wheelchairs
    • Stott, Sanders, Tewkesbury, University of Portsmouth
  • Finding submerged mines
    • Toin University of Yokohama
who uses them
Who Uses Them?
  • Woods Hole Oceanographic Institution
  • Puma and Jaguar
  • Explore under Arctic ice
  • Search for hydrothermal vents
  • Multiple ultrasonic sensors onboard

http://www.whoi.edu/

who uses them1
Who Uses Them?

Woods Hole Oceanographic Institution

  • Kongsberg-Simrad EM300 Multibeam Echo Sounder
    • Creates 3D maps of the ocean floor
    • Mounted on bottom of ships

http://www.whoi.edu/

who uses them2
Who Uses Them?

CMU’s Red Team

  • H1lander and Sandstorm
    • In conjunction with lidar
    • Less accurate, longer range
    • Two different ranges

http://www.redteamracing.org

who uses them3
Who Uses Them?

Aurora Flight Sciences

  • PANOPTIS system
      • Micro Unmanned Air Vehicle
      • Combine optics flow and echolocation
      • Optics for large obstacles, ultrasonics for small
conclusion
Conclusion
  • Measures the reflection of sound
  • Detects things unseen by optical sensors
  • Used in all kinds of environments
    • Air, land, water
references
References
  • Sensors and Sensing: Ultrasonic Acoustic Sensing. Thomas Dean. Lecture notes for course titled “Building Intelligent Robots”. http://www.cs.brown.edu/people/tld/courses/cs148/02/sonar.html.
  • A. D. Hanford. “Computer Simulations of the Propagation of Sound on Mars,” 151st Acoustical Society of America Meeting, 2006
  • Science Clarified: Ultrasonics. http://www.scienceclarified.com/Ti-Vi/Ultrasonics.html
  • I. Scott, D. Sanders, G. Tewkesbury. “Low cost ultrasonic sensors for tele-operated vehicles,” Sensor Review, Volume 20, Number 3, 2000, pp. 227-234.
  • Migatron Corp. “Advantages of Ultrasonic Sensors,” http://www.migatron.com/understanding_ultrasonics.htm.
references1
References
  • Kunihiko Seo, Takashi Shirakawa, and Tsuneyoshi Sugimoto, “Ultrasonic exploration at extreme shallow underground in submerged soil.” J. Acoust. Soc. Am. 123, 3928 (2008)
  • Teledyne RDI DVLs for Unmanned Underwater Vehicles, http://www.rdinstruments.com/nav_app_auv.html
  • Woods Hole Oceanographic Institution, “Underwater Vehicles”, http://www.whoi.edu/page.do?pid=8123.
  • Bluefin Robotics, http://www.bluefinrobotics.com/index.htm
  • Aurora Flight Systems, http://informationsuperiority.blogspot.com/2008/10/enhancing-uav-guidance-by-integration.html
  • Red Team, http://www.redteamracing.org/
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