Mars Rover
communications
and autonomy
Dr Anthony J H Simons (from NASA materials)
Rover and Lander
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Different Configurations
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Solo rover, or working with lander and/or orbiter?
Landing: arrest via rocket, parachute, or airbag?
Swarms: copters, biomorphs, penetrators
Different Control Strategies
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Signals direct to rover, or via orbiter, lander?
Base, orbiter, lander, rover distribution of control
Sensors: pressure, altimeter, laser, radar, vision
Control: experiment deployment, data uplink
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Example Missions
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NASA Pathfinder Sojourner
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July-September 1997
Lander base station plus small rover
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http://www.jpl.nasa.gov/news/fact_sheets/mpf.pdf
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NASA Mars Exploration Rovers
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January-April 2004 (but still active)
Two independent rovers Spirit and Opportunity landed at
different locations
http://www.jpl.nasa.gov/news/fact_sheets/mars03rovers.pdf
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NASA Pathfinder Sojourner
Antenna
Solar cells
Multi-wheel
drive
Steerable
front pair
Image © Neil English, Exploring Mars, Pole Star Publications Ltd.
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Pathfinder Sojourner Lander
Airbags to
cushion
landing
Exit track
for rover
Lander
bounces
(like ball)
Airbags
deflate and
shell opens
Lander has
uplink
Image © Neil English, Exploring Mars, Pole Star Publications Ltd.
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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NASA Spirit Rover (MER)
Stereo
imaging and
navigation
cameras
Direct-toEarth uplink
Multi-wheel
drive
Special
hazard
cameras
Strut for
long reach
Poseable
instrument
package
Image © Neil English, Exploring Mars, Pole Star Publications Ltd.
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Deep Space Communications
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Distance to Mars
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Signal times
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Closest to Earth: 54.5 million km
Furthest from Earth: 401.3 million km
Based on c = 299,793 km/s
~ 3.03 minutes (Earth/Mars closest)
~ 22.31 minutes (Earth/Mars farthest)
Consequences
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Base cannot react in real-time
Rover must act autonomously
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Mission Management
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Base station (Earth)
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Local station (Orbiter, Lander)
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Mission goals, priorities, master control
Master data uplink, processing science results
Local area planning, local priorities, alternate tasks
Global hazards, sandstorm warnings, rover safety
local data uplink, local processing, data reduction
Rover
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Navigation, terrain following, obstacle avoidance
Experiment selection, control, completion
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Hardware Issues
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Satellite uplink
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Microcontrollers
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Small processors to read sensors and drive devices
What memory, buses/ports, power rating, software?
Communications bus
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Need for Earth/Mars, Rover/Orbiter communications
What hardware, comms. protocols, power rating?
How many sensors, devices, moving parts to control?
Devices and sensors
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What devices/sensors? What registers to read/write?
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Navigation
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Global Positioning System (GPS)
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Tilt Sensors (Accelerometers)
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Could the Rover use this to find out its location?
How many Orbiters/registration signals?
How often/accurately measured? How important?
Compute velocity, position from known starting point using
internal acceleration sensors
Integrate acceleration over time for velocity, velocity over
time for distance – but how to correct drift errors?
Ultrasonic sensors
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Echo location system for computing distance from target
Use in Martian atmosphere for obstacle avoidance?
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Ultrasonic Sensors
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SRF08 ultrasonic sensor
On-chip microcontroller PIC
determines distance from
objects
Detects objects from 3cm –
6m
I2C bus communicates with
external TINI
TINI concentrates on highlevel control
Product image © Total Robots. SRF08 sensors available from Total Robots
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Instrument Packages
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Navigation
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Stereo navcams, hazcams, laser striper, ultrasound, inertial
compass (no magnetic field)
Science
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360 panoramic camera, HD cameras
Spectrometers: infrared/thermal emission (carbon,
minerals), Moessbauer (iron-bearing properties)
Rock abrasion tool
Microscope (spores, bacteria)
Wet science chemistry (lifesign reactions)
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Software Issues
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Multi-tier
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Reliability
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AI for high-level autonomous decisions
Stereo vision algorithms for navigation
Sensing, analysis and data compression
Triple-redundant voting system?
Cosmic ray damage: reboot and/or reconfigure?
Failsafe shutdown options
Communications
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Coordinate rover, lander, orbiter?
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Slide © NASA, 2004. See http://robotics.nasa.gov/
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Future Missions
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NASA Phoenix Scout
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NASA Mars Science Laboratory
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Launched in 2007, Polar Lander
Wet chemistry, water-finding, life?
Launch in 2009, 10*payload of MER
Skycrane rocket lander, nuclear power
Projected Biomorph Swarms
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Aerobot/rotorcraft, biomorph/micro-rovers and subsurface
penetrators
Work as cooperating swarm, resilient to failures
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NASA’s Phoenix Scout
Lander only
mission
Mission to
northern
polar region
Subsurface
water ice?
Wet water
chemistry
experiments
Image © Neil English, Exploring Mars, Pole Star Publications Ltd.
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NASA Mars Science Laboratory
Direct-toEarth uplink
Much larger
rover (*10)
Nuclear
powered
Image © Neil English, Exploring Mars, Pole Star Publications Ltd.
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Work by Ilan Kroo, Peter Kunz, Dept. of Aeronautics and Astronomy, Stanford University
Stanford: Mesicopter Swarm
Swarm
rotorcraft
Robust and
redundant
Cooperating
agents
Image © NASA/DoD Second Biomorphic Explorers Workshop, JPL 2000.
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Work by Ilan Kroo, Peter Kunz, Dept. of Aeronautics and Astronomy, Stanford University
Swarm Exploration
Image © NASA/DoD Second Biomorphic Explorers Workshop, JPL 2000.
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ANTS Mission
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Swarm Control
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Massively parallel system
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How to predict all possible interactions?
Cannot hope to test all behaviours
System must be correct by design
Tools for understanding, specifying swarms
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Individual-based modelling (FLAME tool)
models cellular automata
Formal method: X-Machines
specifies cellular automata
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Any
Questions?