NASA’s Flexible Range Exploration
Device - FRED(aka LER; aka SPR)
Bill Bluethmann
NASA/Johnson Space Center
ICRA 2010
May 3, 2010
Overview
• FRED Overview
• Chariot Chassis Overview
• Focus: The Chariot Active Suspension
Flexible Range Exploration Device
• Pressurized Mobile Habitat
consisting of:
– Small Pressurized Rover cabin
– Chariot chassis
• Crew explores in shirt sleeves
• Access to space through suit ports
– No airlock
– Direct access to suits from cabin
– EVA in 15 minutes vs. 4 hours on
Space Station
• Nominal operations: 2 crew for 3, 7
or 14 days
– 4 crew for up to 24 hours
– Field tested 3 days in 2008, 14 days
in 2009
Concept
Flexible Range Exploration Device
• Features:
– 2 person cockpit
– Redundant driving stations
– Separate crew areas with privacy
curtains
– Storage for up to 14 days
– Water system
– Waste control system
– Exercise devices
– Hatches with docking ports
– Aft driving station
– Aft enclosure for suit dust and thermal
protection
– Solar particle event protection
• Currently two (unpressurized) models in
1st generation series
Video – Field Testing Northern
Arizona, Sept 2009
Overview
• FRED Overview
• Chariot Chassis Overview
• Focus: The Chariot Active Suspension
Chariot Chassis
• Goal:
– Challenge the conventional
wisdom of crew rovers
• Approach:
– Develop system full of
features
– Prototype, prototype,
prototype
– Allow team the flexibility to
try new ideas and concepts
Chariot Chassis
• Six wheeled rover
• Each wheel module 3 degreesof-freedom
– Active suspension
– Steering with continuous turn
(crab drive)
– 2 speed transmission
• Lithium-Ion batteries
– 2x18 kW-hr
– Plug in electric vehicle
• Capable of being driven by onboard crew, teleoperation and
ground control
Chariot Chassis
• Designed as a modular chassis
carrying a variety of payloads
– Crew in pressurized suits, standing
up, Chariot style
– Configured as a flat deck for general
purpose payloads
– Small pressurized rover cabin
– Science and surveying instruments
– Supplementary power
• Currently two models in 1st
generation series
• Developed by Human Robotics
Systems Project and NASA’s ETDP
Office
Video – Field Testing Northern
Arizona, Sept 2009
Overview
• FRED Overview
• Chariot Chassis Overview
• Focus: Chariot Active Suspension
Vehicle Suspension System Review
• Passive
– Most consumer vehicles
– Trading comfort and performance
• Adaptive and Load Leveling
– Able to vary ride height, pitch and roll of vehicles
– Often using air springs or oleo-pneumatic
systems
• Semi Active
– Actively control damping rates
– Frequently high latency systems
Vehicle Suspension System Review
• Low Bandwidth Active
– Passive and active elements in series
– Frequency responses on order of 10 hz
– Chariot suspension falls in this
classification
• High Bandwidth Active
Bose Active Suspension
– Passive and active elements in parallel
– Frequency responses on order of 100 hz
U. Texas – CEM
Chariot Chassis Active Suspension
• Passive suspension in series with
active components
• Passive suspension is traditional
Absolute Position Sensors
Upper Arm
– Dual control arms
– Coil over shocks
Springs/Dampers
• Active suspension sets position of
the lower control arm
– Allowed each wheel module to be
raised/lowered
– The vehicle can operate with any
single wheel module lifted
• Sensing on motor, ball screw, control
arms
• Motor brake enables suspension to
be locked out
Active Yoke
Ball Screw
Rails
Lower Arm
RA Gear Reducer/Motor/Brake
Chariot Chassis Active Suspension:
Control System
• Position control mode
– Control ride height, roll and pitch
• Compliance control mode
– Extends range of passive springs through programmable
virtual springs
– Ground force is proportional to displacement from desired
position (Hooke’s law)
– Reduces impulses to chassis
– Allows vehicle to conform to terrain
– Performance limited by top speed of motor/gear set
• Fully tunable for various vehicle loading and
performance
• Plus multiple off-nominal modes
Applications of Active Suspension
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Lower chassis for crew ingress/egress
Raise chassis extra ground clearance
Redundancy
Leveling against gravity
– While driving
– At rest
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Improving ride comfort
Steering assist
Getting out soft soil
Docking
Site preparation/Bulldozing
Holding a constant force to a single wheel
Active Suspension Videos
Auto-leveling
Getting out of Soft Sand
Terrain at JSC Rockyard
Berm Building in Central Washington
Active Suspension Videos
Capability Sequence