Transcript Senior Space Design Projects

Spacecraft Dynamics and Control
Chris Hall
Associate Professor
AeroSpace and Ocean Engineering
Virginia Polytechnic Institute and State University
Overview
• Aerospace and Ocean Engineering Dept
• Spacecraft Dynamics and Control Projects
– Rotating tethered interferometer
– Formation flying
– Distributed Spacecraft Attitude Control System
Simulator
– Base motion effects on magnetic bearings
– HokieSat
– HokieSat Attitude Determination and Control
Virginia Polytechnic Institute and
State University
•Founded as a Land Grant
College in 1872
•Offers 200 degree
programs to 25,000
students
•100 buildings on a 2600
acre campus in Blacksburg
•1500 full-time faculty
•$500M annual budget
•8 different colleges
Burruss Hall is the main
administration building
College of Engineering
• Twelve departments offer 15 degree
programs at B.S., M.S., and Ph.D. level
• Graduate program ranked 16th in the
nation by professional engineers and
recruiters
• ~30 different Research Centers, e.g.:
– Commercial Space Communications
– Intelligent Materials, Systems, and
Structures
– Multidisciplinary Analysis and Design
Center for Advanced Vehicles (MAD)
• More than 300 full-time faculty
• Annual research expenditure of more than
$60M
• 570 M.S. & 99 Ph.D. degrees awarded in
1998
Norris Hall is the main
Engineering building
Aerospace Engineering at Virginia Tech
• Aerospace and Ocean Engineering
Department Overview
• Space Design Projects
• Space Systems Research
• HokieSat!
Randolph Hall houses AOE,
as well as
Engineering Fundamentals,
Mechanical Engineering, and
Chemical Engineering
Aerospace and Ocean Engineering
• 19 Faculty in
–
–
–
–
aerodynamics and hydrodynamics
structural mechanics
dynamics and control
design
• Yearly graduation rate of approximately
– 50 Bachelor of Science
– 25 Master of Science
– 10 Doctor of Philosophy
• $3.5 million annual research funding
• Extensive research facilities
–
–
–
–
Innovative wind tunnels
Water tunnels
Full-scale flight simulator
Spacecraft simulator
National Ranking*
1. Massachusetts Institute of Technology
2. Stanford University (CA)
3. Georgia Institute of Technology
4. University of Michigan–Ann Arbor
5. California Institute of Technology
6. Purdue University–West Lafayette (IN)
7. University of Texas–Austin
8. University of Illinois–Urbana-Champaign
9. Princeton University (NJ)
10. Cornell University (NY)
11. Pennsylvania State University
12. Virginia Tech
*Aerospace Engineering Departments in U.S. News and World Report
Senior Design at VT
• All seniors complete one year of “capstone” design
– two semesters with 3 credit hours each semester
• Choose between Aircraft and Spacecraft
(Ocean Engineering students choose Ship Design)
• Students work in groups of 6 to 12 students
– typically include freshmen in second semester
• Access to “Senior Design Lab”
– PCs, Workstations, Printers, Plotters, Software
• Typically compete in national and international design
competitions
– In 1998, two 1st Place, one 2nd Place, one 3rd Place
Space Design Projects ‘99
• Single-Stage-to-Orbit Reusable Launch Vehicle Using
Rocket-Based Combined Cycle Technology
– 8 AE seniors + 2 Georgia Tech students
– took 1st Prize in AIAA Design Competition
• Virginia Tech Ionospheric Scintillation Measurement
Mission
– 9 AE seniors, 2 AE freshmen, 2 AE juniors, 20+ EE
juniors/seniors
– also called “HokieSat” - 1st VT-built spacecraft
– 15 kg “nanosatellite” will launch on shuttle in 2003
– funded by Air Force and NASA
• Leonardo — a small group of Earth-sensing satellites
flying in formation
– 8 AE seniors, 1 AE freshman
– supporting research sponsored by NASA Goddard
Space Design Projects ‘00
• Three tethered space systems projects
– two involve collaboration with Technical University
of Vienna
• tether system based on Space Station
• free-flying tether system
– one involves cooperation with Next Generation
Space Telescope program office at NASA Goddard
• Rotating tethered interferometer at L2
– eventually became research project funded by
NASA
• Continued work on HokieSat
Space Design Projects ‘01
• PowerSail
– Large deployable flexible solar array connected to
the host spacecraft by a flexible umbilical
– Sponsored by USAF, team traveled to Edwards AFB,
CA to present design
• SOTV – Solar Orbit Transfer Vehicle
– Solar thermal engine powers a reusable space tug
– Sponsored by USAF, collaboration with BWX
Technologies
• Venus Sample Return Mission
– AIAA Undergraduate Team Space Design
Competition
– Travel to Venus and return a 1 kg sample
VT-Zero G Reduced Gravity Experiment
• Four VT Juniors designed, built
experiment to fly on “Vomit
Comet”
• Effects of Microgravity on a
Human’s Ability to Control
Remote Vehicle
• Eliminate visual and vestibular
cues
• Goggles allow “pilot” to see 3D
environment with crosshairs and
illuminated targets
• Microgravity impedes inner ear
equilibrium processes
• Pilot uses joystick to navigate
between targets
Space Systems Research
• Formation Flying
– attitude and orbit dynamics and control
• Spacecraft Dynamics and Control
– with gimbaled momentum wheels (GMWs)
• Integrated Energy Storage and Attitude Control
– using high-speed flywheels as “batteries” and GMWs
• Optimal Continuous Thrust Orbit Transfer
– approximations for indirect methods
• Supported by Air Force, NASA, and NSF
• Graduated 31 M.S. students and 4 Ph.D. students
• Currently advising 7 M.S. students and 1 Ph.D. student
Control of a Rotating
Tethered Interferometer
• In Halo orbit about L2
• 3 infrared mirror satellites,
1 central collector
• 10 m to 1 km tethers
Stowed
configuration
Deployed
configuration
Formation Flying
• Ionospheric Observation Nanosatellite
Formation (ION-F)
– HokieSat will fly in formation with nanosatellites
being built by UW and USU
– Uses micro pulsed plasma thrusters
• Leonardo
– Earth-science remote sensing mission
– Six small satellites in large formation to study
radiative forcing of Earth atmosphere
Distributed Spacecraft Attitude
Control System Simulator
• Two spherical air
bearings, “floating” a
spacecraft-like system
• One stationary
“spacecraft”
• The three spacecraft
communicate via radio
modems, and “fly in
formation” with
integrated pointing
maneuvers
Base Motion Effects on
Magnetic Bearings
• Proposed applications
for magnetic bearings
involve use in moving
vehicles
• Most research literature
on magnetic bearings is
for static systems
• Base motion effects
have not yet been
thoroughly investigated
• Will “Fly” magnetic
bearing system as
payload on Spacecraft
Simulator
HokieSat
• Virginia Tech Ionospheric Scintillation
Measurement Mission (VTISMM)
AFRL Multiaka HokieSat
Satellite
Deployment
• Ionospheric Observation
System (MSDS)
Nanosatellite Formation (ION-F)
– Utah State University
– University of Washington
– Virginia Tech
• University Nanosatellite Program
– 2 stacks of 3 satellites
• Sponsors: AFRL, AFOSR,
DARPA, NASA GSFC, SDL
NASA Shuttle
Hitchhiker
Experiment
Launch
System (SHELS)
University
Nanosatellites
The ION-F Mission
• The Ionospheric Observation Nanosatellite Formation
mission addresses the following science topics:
• Evolution of ionospheric plasma structure, irregularities and
scintillations
• Spectral characteristics of ionospheric plasma waves
• Global latitudinal distribution of ionospheric plasma structures
and irregularities
• Accomplished using
• Plasma Impedance Probe (PIP)
• Global Positioning System (GPS)
• Uniqueness of measurements lies in the ability to vary
satellite separation
• Complement data collected with ground-based radar and
concurrent observations from other satellites
ION-F Mission
Configuration:
T0 = 0:00
USUSat
T1
= T Safe, All Systems Except
Recontact Hazards
= 20 minutes
MSDS released from
Dawgstar
Orbiter/SHELS
T0 =
om
MSDS is 20 minutes out
from Orbiter,timers
time-out
T2
= TSafe,
T3
= T SEP
Recontact Hazards
= T0 + 96 hours
Recontact hazard inhibits
removed aboard MSDS
= T0 + 96 hours,
Stack separation sign
releases both stacks
Recontact hazard inhibits
T4 = TSEP, Nanosat
T3 = T SEP removed aboard
= TSafe,
Safety
inhibits
removed
Recontact Hazards
Recontact Hazards
Nanosats
= T4SEP
= secs
TSEP, Nanosat
T3hours,
=systems
TSafe,
T1 = T Safe, All Systems Except
= T0 + 96
secs
T2
= T0 + 102 T4
hours, 4
for=all
MSDS
T0
+
96
hours
= 20 minutes
Recontact
Hazards
Recontact Hazards
without recontact
= T0 + 96 hours, 4 secs
= T0 + 102 hours, 4 secs
= T0 + 96 hours Stack separation signal
=
20
minutes
hazards.
Recontact hazard
inhibits
out = T
0:00MSDS is 20 minutesT1
T4 = T
T3 = T SEP
=T
T Safe,initiated
T1 =timers
MSDS
All Systems Except
0:00
3CS
ION-F
T2
T2
Intersatellite separation
Safe,
SEP, Nanosat
Safe, All Systems Except
removed aboard MSDS
releases both stacks
from Orbiter,timers
Recontact Hazards
Recontact Hazards
Recontact
hazard
inhibits
Stack
separation
signal
MSDS is 20 minutes out
time-out
= T0 + 96 hours, 4 secs
Intersatellite
separation
= T0
+ 102 hours, 4 secs
removed aboard MSDS
releases both stacks
from Orbiter,timers
= T0 + 96 hours
= 20 minutes
Recontact hazard inhibits
time-out
Safety inhibits
ted MSDS released from
removed
aboard removed
hazard inhibits
Stack separation signal
out Recontact Recontact
Safety inhibits removedMSDS is 20 minutesfor
Intersatellite separation
hazard inhibits
Nanosat systems
Nanosats
Orbiter/SHELS
removed
aboard
MSDS
releases both stacks
from
Orbiter,timers
for all MSDS systems
timers initiated
removed
aboard
without
recontact
time-out
Safety inhibits removed
without recontact
Nanosats
hazards.
for all MSDS systems
hazards.
Recontact hazard inhibits
without recontact
MSDS timers initiated
removed aboard
hazards.
Safety inhibits removed
Nanosats
Safety inhibits removed for all MSDS systems
without recontact
for Nanosat systems
hazards.
Safety
inhibits
removed
without recontact
for Nanosat systems
hazards.
without recontact
hazards.
Safety inhibits removed
S released from
biter/SHELS
Scenario:
HokieSat
for Nanosat systems
without recontact
hazards.
Multiple Satellite
Deployment
System
External Configuration
Crosslink Antenna
GPS Antenna
Solar Cells
LightBand
Pulsed
Plasma
Thrusters
Data Port
Camera
Science
Patches
Downlink
Antenna
Uplink
Antenna
Internal Configuration
Cameras
Torque
Coils (3)
Camera
Crosslink
Components
Power
Processing
Unit
Magnetometer
Pulsed Plasma
Thrusters (2)
Camera
Battery
Enclosure
Rate Gyros (3)
Downlink
Transmitter
Electronics
Enclosure
Overview of HokieSat’s DCS
Attitude Determination Hardware
• Three-axis magnetometer (TAM)
– Measures Earth’s magnetic field
• Four CCD Cameras
– Determine nadir vector from Earth
horizon
– Determine Sun vector
• Solar array Sun measurements
– Determine Sun vector
• Three single-axis rate gyros
– Measure body-fixed angular velocity
Attitude Control Hardware
• Three torque coils
– Generate magnetic moment (0.9 Am2)
– Orthogonally mounted
• Torque coil sizing
M  INAμnˆ
Number of turns
Hexagonal coil
80
Rectangular coil
133
Size
5.7" radius
7" x 9"
ADCS Hardware
Magnetometer
Camera
Torque
Coils
Camera
Rate
Gyros
Camera
Hardware Summary
• Mass: 2.7 lbs (1.2 kg)
• Power: 4.4 W (during control maneuvers)
Component Mass (g) Voltage (V) Power (W)
Torque Coils
570
3.3
0.45
Cameras
381
5.0
0.06
Magnetometer
69
15.0
0.30
Rate Gyro
232
5.0
3.60
Attitude Determination Algorithms
• Nadir, sun, and magnetic field vector sensors
• Rate gyros
• Multiple cases
– Rate gyros with >1 vector sensors
– Rate gyros with 1 vector sensor
– Rate gyros not available
• QUEST least-squares solution using vector
measurements
• Extended Kalman Filter incorporates rate
measurements
Attitude Control Synthesis Algorithm
• Develop equations of motion  nonlinear system
• Linearize about nadir-pointing  linear time-varying
system, periodic effects of magnetic field
• Average over one orbit  linear time-invariant system
• Determine candidate control torque gains using LQR
and LTI system
• Check stability of linear time variant system using
Floquet theory
• Check stability of nonlinear system using simulation
Magnetic Attitude Control
• Nonlinear equations of motion are
1 
1 
1


ˆ
ˆ
ω  I ω Iω  3ωcI o3Io3  I M B


q
1
q    q4 1ω
2   qT 
• Control input is based on linear feedback
~
M(t )  Kx(t )
where K is the gain matrix calculated from the
linear quadratic regulator
Magnetic Moment
• Magnetic moment is most effective when it is
perpendicular to magnetic field
~
MB
~
M  M:M 
B
• The mapped magnetic moment is the ideal
desired moment, and M is the moment of the
same magnitude that can feasibly be applied
Attitude Control Synthesis
Nonlinear
Equations
Linearize about
equilibrium
Linear
Time-Varying
Equations
Average periodic
magnetic field Linear Timeterms
Invariant
Equations
Stable Linear
Time-Invariant
Equations
Q
LQR
Floquet Theory
K
Stable Linear TimeVarying Equations
Nonlinear Simulation
to Check Stability
Conventional Control Results
Initial attitude error: ~14° from nadir pointing
0.6
0.4
q
bo
0.2
0
0.02
0.01
M1
M2
M3
0
-0.01
-0.2
-0.02
-0.4
-0.03
-0.6
-0.8
-1
0
0.03
2
q1
q2
q3
q4
0.8
Magnetic Moment vs Time
0.04
Magnetic Moment, A-m
1
Nonlinear, LQR Controller
with Gravity-Gradient Stability
-0.04
0.5
1
1.5
2
time, sec
2.5
3
3.5
4
x 10
-0.05
0
0.5
1
1.5
2
time, sec
2.5
3
3.5
4
x 10
Conventional Control Results
Reorienting an inverted spacecraft
bo
q vs Time for Inverted Case
1
0.8
q2
0.6
q4
q3
q
bo
0.2
0
-0.2
-0.4
-0.6
0.1
M1
M2
M
3
0
-0.1
-0.2
-0.3
-0.8
-1
0
0.2
Magnetic Moment, A-m2
0.4
Magnetic Moment vs Time
0.3
q1
0.5
1
1.5
2
time, sec
2.5
3
3.5
4
x 10
-0.4
0
0.5
1
1.5
2
time, sec
2.5
3
3.5
4
x 10
Conventional Control Results
Required magnetic moment is periodic with
period of approximately one day
Magnetic Moment vs Time
Magnetic Moment, A-m2
0.04
M1
M2
0.03
0.02
M3
0.01
0
-0.01
-0.02
-0.03
-0.04
-0.05
0
1
2
3
4
5
6
time, sec
7
8
9
10
5
x 10
Dynamic Testing
Modal Testing of Structure (Without Skins)
Mode 1
fn = 245 Hz
(vs 249 Hz
predicted)
Mode 2
fn = 272 Hz
(vs 263 Hz
predicted)
Acknowledgements
•Air Force Research Lab
•Air Force Office of Scientific
Research
•Botstiber Foundation
•Defense Advanced Research
Projects Agency
•Georgia Tech
•NASA Goddard Space Flight
Center
•NASA Wallops Flight Facility
Test Center
•National Science Foundation
•Technical University of Vienna
•University of Washington
•USRA
•Utah State University
•Virginia Tech