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NASA’s Flexible Range Exploration Device - FRED(aka LER; aka SPR)
Bill Bluethmann NASA/Johnson Space Center
ICRA 2010May 3, 2010
Overview
• FRED Overview • Chariot Chassis Overview• Focus: The Chariot Active Suspension
• 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
Flexible Range Exploration Device
Concept
• 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
Flexible Range Exploration Device
Video – Field Testing Northern Arizona, Sept 2009
Overview
• FRED Overview • Chariot Chassis Overview• Focus: The Chariot Active Suspension
• 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 degrees-of-
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 on-board crew, teleoperation and ground control
Chariot Chassis
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
• 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– Passive and active elements in parallel– Frequency responses on order of 100
hz
Vehicle Suspension System Review
Bose Active Suspension
U. Texas – CEM
Chariot Chassis Active Suspension
Springs/Dampers
Absolute Position Sensors
RA Gear Reducer/Motor/Brake
Ball Screw
Rails
Upper Arm
Lower Arm
Active Yoke
• Passive suspension in series with active components
• Passive suspension is traditional– Dual control arms– Coil over shocks
• 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
• 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
Chariot Chassis Active Suspension:Control System
• Lower chassis for crew ingress/egress• Raise chassis extra ground clearance• Redundancy• Leveling against gravity
– While driving– At rest
• Improving ride comfort• Steering assist• Getting out soft soil• Docking• Site preparation/Bulldozing• Holding a constant force to a single wheel
Applications of Active Suspension
Active Suspension Videos
Getting out of Soft SandAuto-leveling
Berm Building in Central WashingtonTerrain at JSC Rockyard
Active Suspension Videos
Capability Sequence