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: 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

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
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

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
Terrain at JSC Rockyard
Berm Building in Central Washington

18. Active Suspension Videos
Capability Sequence