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: Approach: 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 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 Passive and active elements in parallel Frequency responses on order of 100 hz Bose Active Suspension U. Texas – CEM

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

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 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

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

Active Suspension Videos Capability Sequence