1. 2 nd SSS, July 2010, Christina Scholz Performance Analysis of an Attitude Control System for Solar Sails Using Sliding Masses Christina Scholz Daniele Romagnoli Bernd Dachwald

2. Slide 2 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

3. Slide 3 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

4. Slide 4 Simualtion Approach Objective Closed loop with controller Dynamics simulation reduced Assumptions Perfect reflecting sail Rigid body 2 nd SSS, July 2010, Christina Scholz

5. Slide 5 2 nd SSS, July 2010, Christina Scholz Equation of Motion With [Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy]

6. Slide 6 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

7. Slide 7 2 nd SSS, July 2010, Christina Scholz Control Approach The Controller Structure The Controller has two degrees-of-freedom

8. Slide 8 2 nd SSS, July 2010, Christina Scholz Equation of Motion Used for the Feed Forward Controler Design [Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy]

9. Slide 9 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

10. Slide 10 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 inertia matrix 1AU from Sun  4.563x10 -6 N/m² [Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy]

11. Slide 11 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

12. Slide 12 2 nd SSS, July 2010, Christina Scholz Discussion of the Results

13. Slide 13 2 nd SSS, July 2010, Christina Scholz Discussion of the Results

14. Slide 14 2 nd SSS, July 2010, Christina Scholz Discussion of the Results

15. Slide 15 2 nd SSS, July 2010, Christina Scholz Discussion of the Results ROLL PITCH YAW

16. Slide 16 2 nd SSS, July 2010, Christina Scholz Influence of the Offset Vector on the Near-Optimal Maneuvertime for a Single 35° Yaw Maneuver

17. Slide 17 2 nd SSS, July 2010, Christina Scholz Comparison of a Single 35° Reorientation With Different Disturbances Acting on the System

18. Slide 18 2 nd SSS, July 2010, Christina Scholz Comparison of the Position of the Sliding Masses for Different Single Maneuvers

19. Slide 19 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  orbit control simulation Exploration of possible couplings between thermal distributions and attitude dynamics

20. Slide 20 2 nd SSS, July 2010, Christina Scholz Please Contact Us for Further Information Christina Scholz: christina.scholz@dialup.fh-aachen.de Daniele Romagnoli: Daniele.Romagnoli@dlr.de Bernd Dachwald: dachwald@fh-aachen.de