Transcript Folie 1
Performance Analysis of an Attitude Control System for Solar Sails Using Sliding Masses
Christina Scholz Daniele Romagnoli Bernd Dachwald 2 nd SSS , July 2010, Christina Scholz
Overview
Motivation on the project Introduction on the simulation Description of the controllers Presentation on simulation results Conclusion and future research objectives Slide 2 2 nd SSS, July 2010, Christina Scholz
Motivation on the Project
Preliminary study for an attitude control system of solar sails (Gossamer Project DLR) Analyze the capabilities of the attitude control system for the most chalanging cases Testing the behaviour of the attitude control system by changing the design parameters Slide 3 2 nd SSS, July 2010, Christina Scholz
Simualtion Approach
Objective Closed loop with controller Dynamics simulation reduced Assumptions Perfect reflecting sail Rigid body Slide 4 2 nd SSS, July 2010, Christina Scholz
Equation of Motion
J
J
T
With
T
T extern
T offset
T control J J yy J xx zz
I
I yy xx
m r
(
y
2
m r z
2
z
2 )
I zz
m r y
2
m r
m
(
M M
2
m m
) [Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy] Slide 5 2 nd SSS, July 2010, Christina Scholz
Simulation Capabilities
One, two and three body axis maneuvers Offset torques due to the displaced center of pressure with respect to the center of the geometry A non-diagonal inertia matrix External torques Slide 6 2 nd SSS, July 2010, Christina Scholz
Control Approach The Controller Structure
The Controller has two degrees-of-freedom Slide 7 2 nd SSS, July 2010, Christina Scholz
Equation of Motion Used for the Feed Forward Controler Design
I xx
x
(
I yy
I zz
)
y
z
M m r
m
(
yF S
,
z
zF S
,
y
)
T offset
,
x
T ext
,
x I zz
z
(
I xx
I yy
)
x
y
M m r
m yF S
,
x
T offset
,
z
T ext
,
z I yy
y
(
I zz
I xx
)
x
z
M m r
m zF S
,
x
T offset
,
y
T ext
,
y
[Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy] Slide 8 2 nd SSS, July 2010, Christina Scholz
Tasks of the Controller Feed Forward Controller
Design and computation of the desired trajectory Handling of the torques due to the offsetvector
Feed Back Controller
Compensating torques due to disturbances Compensating simplifications in the model Compensating non-diagonal elements in the inertia matrix Compensating the change of the inertia principal elements Slide 9 2 nd SSS, July 2010, Christina Scholz
Simulation Results
Parameters of Test Case 40x40m square sail 1200m² sail surface 2 sliding masses of 1kg each 150kg satellite bus mass 4340 266 53 266 2171 202 53 202 2171 inertia matrix kgm² I 1AU from Sun 4.563x10
-6 N/m² [Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy] Slide 10 2 nd SSS, July 2010, Christina Scholz
Presentation of a Default Maneuver
Two axis maneuver 40 ° pitch 10 ° yaw Environmental torques 0 Nm about the roll axis 0 Nm about the pitch axis 0.00001 Nm about the yaw axis Offset vector 0 m in x-direction 0.1 m in y-direction 0.04 m in z-direction Slide 11 2 nd SSS, July 2010, Christina Scholz
Discussion of the Results
Slide 12 2 nd SSS, July 2010, Christina Scholz
Discussion of the Results
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Discussion of the Results
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Discussion of the Results
ROLL PITCH YAW Slide 15 2 nd SSS, July 2010, Christina Scholz
Influence of the Offset Vector on the Near-Optimal Maneuvertime for a Single 35
°
Yaw Maneuver Near-optimal time dependence for a variation Offset
0,2 0,18 0,16 0,14 0,12 0,1 0,08 0,06 0,04 0,02 0 -0,02 -0,04 -0,06 -0,08 -0,1 -0,12 -0,14 -0,16 -0,18 -0,2
0 50 100 150 200 250 300 near-optimal maneuver time [min] 350
Slide 16 2 nd SSS, July 2010, Christina Scholz
Comparison of a Single 35
°
Reorientation With Different Disturbances Acting on the System
Slide 17 2 nd SSS, July 2010, Christina Scholz
Comparison of the Position of the Sliding Masses for Different Single Maneuvers
Slide 18 2 nd SSS, July 2010, Christina Scholz
Conclusion
An attitude controller for solar sails using sliding masses as control elements developed Simulation for simplified dynamics and different disturbances Controller allowes to perform two axes maneuvers simultaneously reducing maneuver time
Open Points
Establishing a maneuver-time optimization Consider flexible structures Develop coupled simulation of orbit and attitude simulation orbit control Exploration of possible couplings between thermal distributions and attitude dynamics Slide 19 2 nd SSS, July 2010, Christina Scholz
Please Contact Us for Further Information
Christina Scholz: [email protected]
Daniele Romagnoli: [email protected]
Bernd Dachwald: [email protected]
Slide 20 2 nd SSS, July 2010, Christina Scholz