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NASA’s Flexible Range Exploration Device - FRED(aka LER; aka SPR)

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.

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NASA’s Flexible Range Exploration Device - FRED(aka LER; aka SPR)

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  1. NASA’s Flexible Range Exploration Device - FRED(aka LER; aka SPR) Bill Bluethmann NASA/Johnson Space Center ICRA 2010 May 3, 2010

  2. Overview • FRED Overview • Chariot Chassis Overview • Focus: The Chariot Active Suspension

  3. 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

  4. 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

  5. Video – Field Testing Northern Arizona, Sept 2009

  6. Overview • FRED Overview • Chariot Chassis Overview • Focus: The Chariot Active Suspension

  7. 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

  8. 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

  9. 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

  10. Video – Field Testing Northern Arizona, Sept 2009

  11. Overview • FRED Overview • Chariot Chassis Overview • Focus: Chariot Active Suspension

  12. 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

  13. 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 Bose Active Suspension U. Texas – CEM

  14. Chariot Chassis Active Suspension Absolute Position Sensors Upper Arm Springs/Dampers • 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 Active Yoke Ball Screw Rails Lower Arm RA Gear Reducer/Motor/Brake

  15. 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

  16. Applications of Active Suspension • 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

  17. Active Suspension Videos Auto-leveling Getting out of Soft Sand Berm Building in Central Washington Terrain at JSC Rockyard

  18. Active Suspension Videos Capability Sequence

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