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The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-1
SkyworkerSkyworkerPreliminary Design ReviewPreliminary Design ReviewSkyworkerSkyworkerPreliminary Design ReviewPreliminary Design Review
Field Robotics Center
September 10, 1999
William “Red” WhittakerPeter StaritzChris Urmson
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-2
• Constellation of SSP satellites in GEO
• 1GW of energy to the ground via a microwave transmission antenna 1 km in diameter
• 150m wide and 10 to 15 kilometers in length
• Mass of 4800 MT (10X as massive as ISS)
• Assembled over 1 year, maintained for 30 years
• Need for robotic systems capable of Assembly, Inspection, and Maintenance (AIM) tasks
Space Solar Power (SSP) FacilitiesSpace Solar Power (SSP) FacilitiesSpace Solar Power (SSP) FacilitiesSpace Solar Power (SSP) Facilities
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-3
SSP Facility AIMSSP Facility AIMSSP Facility AIMSSP Facility AIM
• Solar array– Assembled through automated docking and deployment
• Microwave antenna– Requires completion of complicated assembly tasks
• Joining of deployable truss sections
• Attaching transmitter elements
• Coupling Power Management and Distribution (PMAD) system
• Entire facility will benefit from automated inspection and maintenance capabilities
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-4
Space Solar PowerSpace Solar Power
Automated Technology Roadmap Automated Technology Roadmap 2001-2005 2006-2010 2011-2015 2016-2020< 2000
Electrodynamic Propulsion Systems
FY99 FY00 FY01 FY02 FY03 FY04 FY05 FY06 FY07 FY08 FY09 FY10 FY11 FY12 FY13 FY14 FY15 FY16 FY17 FY18 FY19 FY20
LEGEND
R&D Result-Driven Decision Point
Major R&D Prm Milestone
Strategic Program Objective
Tether and Antenna Front Plane Maneuvering
Demonstration
single axis ED thruster
in uwave field
Autonomous Rendevous and Dock
Air-bearing precision
maneuvering
80% Reliable Fly-to-grapple and Robust Abort
Demo terminal guidance
sensing system
Trajectory planning and optimization
Robust control w/ attached
robot interaction
Force and Redundancy Control Strategies for Cooperative Systems
Learning/adapta-tion for unknown payloads&failure
90% Reliable Fly-to-grapple and Robust
Abort
Sensing/Perception
Stable Posture and gait
control w/ 4 cooperating
truss walkers
Perform mating tasks w/ 4 cooperating truss
walkers & flex. structure
Payload balancing w/ 6
cooperating truss walkers
Force-controlled free flyer payload
exchange
Joint failure compensation and increased
structural disturbance
Robust locomotion and free flyer interaction in dynamic
environment
Locate standard grabrail fixture under nominal conditions
Identify feducial mark scheme to simplify vision
Integrate high-bandwidth optical flow, range, and force to improve grasp reliability Develop compact flight
hardware implementation of high-rate vision
algorithmsDemonstrate
strategies to mitigate lighting effects
Borrowed from Automated Assembly, Maintenance, and Operations of a Space Solar Power System
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-5
Space Solar PowerSpace Solar Power
Automated Technology RoadmapAutomated Technology Roadmap2001-2005 2006-2010 2011-2015 2016-2020< 2000
FY99 FY00 FY01 FY02 FY03 FY04 FY05 FY06 FY07 FY08 FY09 FY10 FY11 FY12 FY13 FY14 FY15 FY16 FY17 FY18 FY19 FY20
LEGEND R&D Result-Driven Decision Point
Major R&D Pgm Milestone
Strategic Program Objective
Integrated Technology Demos
On-orbit walker/free flyer antenna assembly and repair demo
Autonomous grasp and
locomotion of antenna element
Multi. walker automated antenna assembly in neutral
buoyancy
Multi. walker/free-flyer antenna repair in neutral buoyancy
Prototype neutral
buoyancy truss walker
On-orbit multi. walker antenna assembly
demonstration
FY05 Decision on first flight
demo
Assembly and Maintenance Planning
Assembly activity planning for 4
cooperating truss walkers
Assembly activity planning for 4
cooperating truss walkers + free flyer
Simulation and visualization of
assembly activity
Demo automated Ground Segment
operations inc. power sales
Demo automated Space Segment operations inc.
maintenance flights Demonstrate 100% automation of space and
ground segment operations
Borrowed from Automated Assembly, Maintenance, and Operations of a Space Solar Power System
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-6
ObjectivesObjectivesObjectivesObjectives
• Demonstrate the viability of using robots for orbital construction
• Prove the validity of using structure walkers for orbital AIM
• Demonstrate SSP AIM relevant tasks using robotics
• Simulate prospective SSP AIM robots and tasks
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-7
Representative TasksRepresentative TasksRepresentative TasksRepresentative Tasks• Walk, turn, and transition across planes on a truss
structure
• Pick up and place a payload at arbitrary locations and orientations in space
• Carry a payload while walking, turning, and transitioning
• Conduct calibration and inspection tasks
• Connect power and communications cables
• Cooperatively carry massive or large payloads
• Perform tasks that require multiple robot collaboration
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-8
DemonstrationDemonstrationDemonstrationDemonstration
• Prototype Robot– Pick up and carry a model transmitting element the length of the
truss, turn while carrying, couple the element to the structure– Connect Power Management and Distribution (PMAD) to the
element– Perform a mock calibration
• Simulation– Large scale construction utilizing multiple robots– Coordinated installation of full scale transmitting elements– Demonstrate extended lifetime operations
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-9
Program PhilosophiesProgram PhilosophiesProgram PhilosophiesProgram Philosophies
• Design for Earth based demonstration, but always maintain a path to orbital application
• Accept a baseline environment (structure, tasks, etc..)
• Leverage heritage technologies when available
• Design and manufacture in house whenever possible
• Consider physical scalability of design
• Ensure robust software operation through incremental testing of components
• Maintain software scalability through Object Oriented Principles
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-10
Configuration - Key MetricsConfiguration - Key MetricsConfiguration - Key MetricsConfiguration - Key Metrics• Control Complexity
– The number of joints that must be actuated in synchrony
• Continuous Motion– System supports a gait in which the payload can maintain a constant
velocity
– How difficult it is to control that gait
• Cost– DOF, links, grippers, sensors, control complexity, gravity compensation
• Compatibility with gravity compensation– Possible to compensate with available resources, new system or
recycled heritage system
• Forces exerted / Forces experienced– Maximum forces and torques experience/exerted by the robot
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-11
Configuration - Key Metrics (Cont.)Configuration - Key Metrics (Cont.)Configuration - Key Metrics (Cont.)Configuration - Key Metrics (Cont.)
• Workspace– Effective working volume with one gripper attached to the structure
• Energy Consumption– The energy consumed by the machine to move a specified distance
and speed with a given payload
• DOF– Total number of joints– Number of different joint types
• Mass– DOF, links, grippers, sensors, constants
• Layout of available volume– Sufficient room for onboard components
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-12
ContendersContendersContendersContenders
DOF Grippers LinksM-type 12 3 4
N-type 11 3 4
S-type 12 4 7
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-13
N-typeN-typeN-typeN-type
• Key Features– Walking posture– Manipulating posture – Sufficient internal
volume to allow tetherless operation
– Fine motion / Transition Joint
• Inchworm Gait• Cable Mating
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-14
Configuration N-typeConfiguration N-typeConfiguration N-typeConfiguration N-type• Control Complexity
– At most 4 joints must operate in synchrony for standard gait
• Continuous Motion– System supports a continuous gait– Simplified gait, uncertainties in only one
dimension
• Cost– Lowest number of total components
affecting cost
• Compatibility with GC– Compatible with heritage system, only minor modifications
needed
• Forces Exerted / Forces Experienced– Normal stride exerts/experiences minimal torques
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-15
Configuration N-typeConfiguration N-typeConfiguration N-typeConfiguration N-type
• Workspace– N-type “unfolds” to become a 3 link
manipulator
• Energy Consumption– Continuous gait and fewer motors
needed for standard stride result in lower consumption
• DOF– 11 joints, 3 grippers
• Mass– ~35 kilograms
• Layout of available volume– Sufficient room for onboard
components
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-16
Gripper Design IssuesGripper Design IssuesGripper Design IssuesGripper Design Issues• Skyworker will move its own mass in
addition to a payload – Increased possibility of truss failure due
to point loads– Gripper faces will be extended and
shaped to match the structure (reducing point loads)
• Rotation about the longeron is a possibility– High coefficient of friction coatings
• Simple structure detection is necessary– Proximity sensors (capaciflectors)
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-17
JointsJointsJointsJoints
• 3 Joint types– 3 Axial revolute joints– 2 Offset revolute joint– 6 Inline revolute joints
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-18
Force AnalysisForce AnalysisForce AnalysisForce Analysis
Z2
X2
Y2
Z1
Y1 X1
Z0
X0
Y0
ZL
XL
Ft,2
Fn,2
Fy
Fx
Ft,1
Fn,1
Fn,L
Ft,L
Ry
Rx
T2
T1TT
Forces:-Payload Inertia-Arm’s Inertia
Given:-Payload Velocity-Payload acceleration
• Concept of “Walking lightly”
• Largest forces occur during a standard stride as opposed to during acceleration
• 2 forms of force analysis– Further analysis will
minimize the torque generated by the base joints
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-19
Maximum TorquesMaximum TorquesMaximum TorquesMaximum Torques
A
C
D
B
-4
-3
-2
-1
0
1
2
3
4
5
Torq
ue (N
m)
A B C DTorque (Nm) 4.12 .929 4.43 -3.57
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-20
Gravity CompensationGravity CompensationGravity CompensationGravity Compensation
• Allows for maneuvers not possible in normal gravity
• Passive compensation– Counterweight system– Transmission
• 10:1 ratio
– Active X-Y table– Heritage system
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-21
Power ElectronicsPower ElectronicsPower ElectronicsPower Electronics
• Tetherless operations
• 20 minute demonstration
• Less than 40 watt-hours of energy at a peak rate of 120W +/- 30%
• Mass Constraint 3kg (batteries/charger/converters)
• Volume Constraint
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-22
Battery RechargingBattery RechargingBattery RechargingBattery Recharging
• Onboard Charging Solution– Power obtained through special gripper– Contact with electrified terminal on demonstration structure– Inductively Coupled Charging a future possibility– All charging electronics/distribution onboard
• Battery Monitoring System– Automatically detects when charge is necessary– Returns to ‘Charging Station’ when needed– Disconnects and returns to work when fully recharged
The Next StepSPACE ROBOTICS INITIATIVE
Skyworker PDR 9/10/99-23
Battery TechnologiesBattery TechnologiesBattery TechnologiesBattery Technologies
• Batteries we considered:
• NiCd batteries selected for prototype, different battery technology may be used in space applications.
NiCd NiMH Li-IonEnergy/kg Fair Good ExcellentEnergy/cm3 Fair Good ExcellentCharge Rate High Moderate LowEase of Charging Easy Difficult DifficultMax. Discharge Rate Extremely High Moderate LowCost/W Low Moderate HighMass/W Low Moderate HighVolume/W Moderate Moderate High