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Extreme Environment Robots: Mars Exploration Rovers


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Title: Extreme Environment Robots: Mars Exploration Rovers

Extreme Environment Robots Mars Exploration
  • Maria G. Bualat
  • March 15, 2005

My Background
  • B.S.E.E., Stanford University, 1987
  • Started working for NASA on graduation
  • M.S.E.E. Emphasis Controls, Santa Clara
    University, 1992
  • Have been working in robotics since 1995
  • Project manager for the K9 rover project since
  • Areas of interest rover navigation, computer
    vision, human/robot interfaces

Mars is an Extreme Environment
  • Extreme temperature changes (20C to -120C)
  • Rough, rocky terrain
  • No global positioning system
  • Communications time delay
  • Narrow communications bandwidth
  • Dust

Why is Mars interesting?
  • Most Earth-like planet
  • Once had/may still have liquid water and thus
  • NASAs Mars exploration strategy
  • Follow the water
  • Water is key because almost everywhere we find
    water on Earth, we find life.

Mars Rovers Past, Present, Future
Sojourner Specs
  • 13 cm (5 in) wheel diameter
  • Rocker-bogey chassis
  • Top speed .6 m/min (.02 mph)
  • .22 m2 solar panel providing peak of 16 W
  • With batteries, peak available power of 30 W
  • Normal driving power requirement is 10 W
  • 80C85 CPU, at 100 KIPS
  • 176K of PROM and 576K of RAM

Sojourner Instruments
  • Navigational
  • Front viewing stereo pair of cameras
  • Laser striping system
  • Gyro
  • Corrections made using lander imager
  • Scientific
  • Alpha Proton X-Ray Spectrometer (APXS)

Pathfinder Mission Highlights
  • Launched December 4, 1996
  • 7-month cruise to Mars with 4 trajectory-correctio
    n maneuvers
  • Landed 957 a.m. PDT July 4, 1997
  • Bounced at least 15 times up to 12 m high
  • Sojourner driven down the ramp on Sol 2
  • Primary mission 8 sols
  • Total mission 83 sols
  • Sojourner traversed 100m around the lander
  • Pathfinder returned over 16,000 lander images and
    550 rover images
  • Sojourner performed 16 chemical analyses of rocks
    and soil

Spirit Opportunity Specs
  • Brains
  • CPU PowerPC RAD6000 (200 MIPS)
  • 128 MB DRAM, 256 MB Flash
  • Brawn
  • 1.2 meters high
  • 180 kilograms
  • Top speed 5 cm/s (.1 mph)
  • Capable of 100 m/sol
  • Lifetime
  • Primary mission 90 sols
  • Spirit is currently on Sol 167
  • Other
  • Solar panels 140W (4 hrs) on Sol 1
  • 2 batteries
  • 100W required to drive
  • Communication via orbiter and direct-to-earth

MER Science Instruments
  • Pancam
  • High resolution imagery
  • Mini-Thermal Emission Spectrometer (Mini-TES)
  • Mineralogical and temperature information
  • Rock Abrasion Tool (RAT)
  • Remove surface dust and weathering
  • Microscopic Imager
  • APXS
  • Moessbauer Spectrometer
  • Determine the properties of iron bearing materials

MER Navigational Instruments
  • Mast-mounted Navcam
  • Front and Rear Hazcam
  • Sun sensor
  • Used to determine global bearing (no compasses on
  • Sun filter on pancam
  • Inertial Measurement Unit (IMU)

MER Landing System
  • EDL an adaptation of the Mars Pathfinder method
  • Aeroshell and parachute decelerate lander through
    the Martian atmosphere
  • Retro-rockets fired to slow landers speed of
    descent, airbags inflated to cushion lander at
    surface impact
  • Lander bounces along Martian surface until it
    rolls to a stop
  • Airbags deflated and retracted, and lander petals
    and rover egress aids are deployed
  • Rover deploys its solar arrays, and places system
    in a safe state

MER Mission Highlights
  • Spirit landed in Gusev Crater on January 3, 2004,
    835 p.m. PST
  • Opportunity landed on Meridiani Planum on January
    24, 2004, 905 p.m. PST
  • Opportunity discovered evidence of past standing
    water on Mars
  • Spirit and Opportunity successfully completed
    their prime missions in April and are continuing
    exploration on an extended mission
  • Spirit has traversed over 2 miles and is starting
    its exploration of the Columbia Hills
  • Opportunity has entered Endurance crater

Next Rover Mission MSL
  • MSL Mars Science Laboratory
  • 2009 launch
  • Study habitablility
  • 687 sol primary mission (1 Mars year)
  • 1 metric ton robot
  • 10x MER payload
  • Nuclear powered
  • 6 km range
  • Powered skycrane landing

MSL Skycrane Landing System
  • Rocket system hovers 5 m above the surface
  • Rover lowers down on a bridle
  • Once the wheels touch the ground, bridle is cut
  • Rockets fly off and crash elsewhere

Human Exploration
  • Robots will act as aides for humans exploring
    other planets
  • Rover roles for exploration with humans
  • Scouts
  • Videographers
  • Assistants (scientific, construction, site
  • Pack mules
  • Rescuers

Mars Rover Prototypes (K9)
  • Prototype of Mars rovers
  • Used as a testbed for software and autonomy
  • Size
  • Scicam height 1.6m
  • 70 kg
  • Computing
  • 1.2 GHz Pentium M laptop
  • Linux operating system
  • Software written in C
  • Power
  • Li-Ion batteries
  • Subsystems can be powered on/off

K9 Instrumentation (Science)
  • High resolution color cameras
  • Same resolution as human fovea
  • 5 degree-of-freedom (DOF) arm
  • Waist, shoulder, elbow, twist, and wrist
  • Near-Infrared spectrometer
  • Enables detection of carbonates
  • Camera HAnd lens MicroscoPe (CHAMP)
  • Zooms from 7mm to infinity

K9 Instrumentation (Navigation)
  • Mast-mounted navigation cameras (navcams)
  • Body-mounted hazard avoidance cameras (hazcams),
    front and rear
  • Inertial Measurement Unit
  • Compass/Inclinometer
  • Encoders on motors
  • Potentiometers on joints

K9 Software
  • CLARAty Rover Software Architecture
  • Jointly developed with Jet Propulsion Laboratory
    (JPL), Carnegie Mellon University (CMU),
    University of Minnesota
  • Modular with many generic parts
  • Two layers Functional Decision
  • Functional device controllers, lower-level
    autonomy and behaviors
  • Decision higher level reasoning (AI, planning

Mission Scenario
  • Placement from a distance on MER takes up to 3
  • Single Cycle Instrument Placement
  • Increased autonomy makes science more efficient
    and more robust
  • Provides safer and more accurate target approach
  • Provides options in case of non-optimal
    performance (contingencies)

Navigation Obstacle Avoidance
  • Morphin Navigator
  • Developed by CMU
  • Performs traversablility analysis
  • Generates a 2D traversability array
  • Stereo point mapped to cells
  • Points within cells are fit to a plane
  • Traversability calculated based on slope, quality
    of the plane fit (roughness), and step height

Navigation Path Planning, Mapping
  • D Global Cost Function
  • Integrates traversability analysis data into a
    global map
  • Calculates optimal paths
  • Visual Odometry
  • uses motion of objects between successive images
    to determine the rovers position
  • Simultaneous Localization and Mapping (SLAM)
  • Maps landmarks around the robot
  • Uses landmarks to determine the rovers position

Tracking Mesh Registration
  • Uses stereo vision to create 3D models of the
    target (meshes)
  • Initial estimate of alignment is given by rover
  • Meshes are register to each other to recover the
    target location relative to the new rover
  • From up to 10m away, system uses mast-mounted
    cameras to allow pointing
  • As rover nears target, target is handed off the
  • Mesh registration is used for target handoff
    between stereo pairs

Instrument Placement
  • Build 3D model of target
  • uses stereo vision
  • Register model using mesh registration
  • tells the rover where the target is w.r.t. itself
  • Find goal point
  • Find closest safe point
  • looks at the surface of the rock to avoid sharp
  • Plan arm motion
  • uses 3D models and kinematics to detect possible
  • Place instrument

Contingency Planning
  • Seed plan generated with maximum expected
  • Plan evaluated to determine where it might fail
    given uncertainties
  • Branch point chosen
  • Alternative (contingency) plan constructed for
    the branch and incorporated into primary plan
  • Plan is reevaluated and additional branches added
    as needed

Robust Execution
  • CRL - Contingent Rover Language
  • CX - Conditional Executive
  • Flexible, condition-based execution
  • temporal conditions (absolute, relative)
  • resource conditions
  • state-based conditions
  • conditions on any node (high- or low-level)
  • Hierarchical structure
  • task executable action
  • block sequence of nodes
  • branch choice point

Fault Diagnosis
  • Expect the unexpected
  • Natural terrains create uncertainty
  • Systems break
  • Fault Diagnosis
  • The system and the environment are modeled
  • Measured results compared to predicted (expected)
  • Model used to reason about what caused the fault
  • Must distinguish between faults and interaction
    with environment

Field Testing
  • Rover testing in Mars analogs
  • Test technologies in realistic environments
  • Demonstrate and validate new technologies
  • Simulate operational conditions on Mars
  • Rugged terrain
  • Geographically interesting
  • Communications delay
  • Lessens the likelihood of tuning an algorithm to
    home conditions

Scorpion Robot
  • Biologically-inspired robotics
  • Excellent mobility in rocky terrain
  • Small, light-weight
  • Could be carried by a larger robot

Antarctic Traverse
  • Robotically traverse the Antarctic continent
  • Completely autonomous system
  • Looks out for hazards such as crevasses
  • Performs science along the way
  • Meteorites
  • Microscopic life

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