Stereo Vision at

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Stereo Vision at

• Sasha Browning

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Overview

• Stereo Vision Basics
• NASA and Stereo Vision
• Rover Navigation
• Mars Rovers
• Spirit and Opportunity
• The Mars Scientific Laboratory
• Other Rover Applications
• Questions?

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Stereo Vision Basics

• Stereo vision is a method in visual perception
  that leads to the sense of depth from two
  slightly different projections of the same
  object.
• By comparing information of a scene from multiple
  camera angles, limited 3D information is
  extracted by examining relative perspectives.

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• Each eye/camera receives a different image of an
  object because the eyes/cameras are about 2
  inches apart.
• The two eyes/cameras focus on the same object, in
  doing so they converge.
• By taking two images of the same
• scene, from two slightly different
• locations and matching the
• corresponding location will give
• you the distance to the objects.

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Example
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Stereo Vision and Robotics

• Very useful in robotics because it is
• an efficient technique for determining range
  information from the environment.
• a passive sensor no interference with other
  sensor devices.
• easily integrated with other vision routines
  (for example tracking or object recognition).

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NASA and Stereo Vision
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• Rovers must be able to see its environment and
  respond to what it sees.
• Real-time stereoscopic machine vision is an
  advanced technology that is commonly used to
  detect obstacles and maneuver around them.

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Rover Navigation 101
http//marsrovers.nasa.gov/gallery/video/movies/me
r_rovernav_240.mov
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Mars Rovers

• Mars 2 Crashed on Martian surface 1971
• Mars 3 Failed upon landing 1997
• Sojourner rover Launched Dec 4, 1996
• On Mars July 4 Sept 27, 1997
• Spirit (MER-A) Launched June 10, 2003 On Mars
  Jan 4, 2004 Present
• Opportunity (MER-B) Launched July 7, 2003
• On Mars Jan 25, 2004 Present

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Some Mars Facts

• Marss solar day (sol) is about 2.7 longer than
  an Earth day.
• 1.027491 sols/day
• Average sol is 24 hours, 39 minutes, and 35.244
  seconds.

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Sojourner
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• Total of three cameras forward facing stereo
  system (2) and a rear color imaging system (1).
• Stereo system was used to avoid obstacles while
  an operator on Earth chose points of interest for
  the rover.

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Spirit (MER-A)
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Spirit (MER-A)

• Landed on the Martian surface Jan. 4, 2004.
• As of April 8, 2009 it had been operational for
  1800 sols.
• May 1, 2009, Spirit became stuck in sand trap
  called Troy, located in the Gusev crater, and
  is still stuck.
• Spirit Update
• http//jpl.nasa.gov/video/index.cfm?id877

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Opportunity (MER-B)
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• On April 26, 2005 (Sol 446) Opportunity dug
  itself into a sand dune, later named Purgatory
  Dune. Found that all 4 corner wheels were dug
  in more than a wheel radius.
• Finally on June 4, 2005 (Sol 484) all six wheels
  were on firmer ground.

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• http//www.jpl.nasa.gov/video/index.cfm?id795

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Future Rover

• In order to expand Mars research, NASA has plans
  to dispatch a bigger, nuclear powered rover
  called the Mars Science Laboratory (MSL).

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MSL Navigation

• 4 pairs of Hazard Avoidance Cameras (Hazcams)
  located on each corner.
• Uses visible light to capture 3-D imagery. With
  its 120 degree field of view it is able to map
  the terrain 10 feet in front of the rover.
• 2 pairs of Navigational Cameras (Navcams) located
  on the mast.
• Uses visible light to capture 3-D imagery and has
  a 45 degree field of view.

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Setbacks

• Images may need to be rather large to gather
  accurate data about the environment
• The larger the image, the more time required to
  process information.
• Robots arent made to move fast.
• They may not be able to detect their distance
  from obstacles.

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Various Rover Applications
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UrbieThe Urban Robot
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• Hes small, lightweight, and able to control
  himself.
• His set of stereoscopic cameras detect obstacles.
• He also has a pair of arms that are useful when
  climbing over obstacles and flipping himself over
  if he rolls onto his side/back.

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The ATHLETE Rover

• ATHLETE All-Terrain Hex-Legged
  Extra-Terrestrial Explorer

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• Capable of rolling and walking over various
  terrains similar to the moon.
• Goal is for the robot to assist in human or
  robotic missions on the moons surface.
• Future versions will be able to move faster than
  the MERs and travel over any terrain (e.g. sandy
  slopes, vertical rock faces).

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2 Is Better Than 1
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Why Not Both?

• Andrew Ng, a professor at Stanford, has developed
  a more accurate depth estimate method.
• He incorporates both monocular cues and
  stereo/triangulation cues. This allow for more
  accurate estimation for objects that are nearby
  and at a distance.

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Any Questions?