2 nd SSS , July 2010, Christina Scholz

2nd SSS , July 2010, Christina Scholz

Performance Analysis of an Attitude Control System for Solar Sails Using Sliding Masses

Christina ScholzDaniele RomagnoliBernd Dachwald

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


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

Simualtion Approach

ObjectiveClosed loop with controller

Dynamics simulation reduced

AssumptionsPerfect reflecting sail

Rigid body

2nd SSS, July 2010, Christina Scholz


Equation of Motion

With

[Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy]

TJJ

2

2

22 )(

ymIJ

zmIJ

zymIJ

rzzzz

ryyyy

rxxxx

mM

mMmmr 2

)(

controloffsetextern TTTT


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


Control ApproachThe Controller Structure

The Controller has two degrees-of-freedom


Equation of Motion Used for the Feed Forward Controler Design

)()( ,,,, xextxoffsetySzS

r

zyzzyyxxx TTzFyFmM

mIII

zextzoffsetxS

r

yxyyxxzzz TTyFmM

mIII ,,,)(

[Solar-Sail Attitude Control Design for a Sail Flight Validation Mission, by Wie, Murphy]

yextyoffsetxS

r

zxxxzzyyy TTzFmM

mIII ,,,)(


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


Simulation Results

Parameters of Test Case40x40m 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]

Ikgm²2171

21714340

2025320226653266


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


Discussion of the Results


Discussion of the Results

ROLL

PITCH

YAW


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

00,020,040,060,08

0,10,120,140,160,18

0,2

0 50 100 150 200 250 300 350

near-optimal maneuver time [min]

Off

se

t [m

]


Comparison of a Single 35° Reorientation With Different Disturbances Acting on the System


Comparison of the Position of the Sliding Masses for Different Single Maneuvers


ConclusionAn attitude controller for solar sails using sliding masses as control

elements developedSimulation for simplified dynamics and different disturbancesController allowes to perform two axes maneuvers simultaneously reducing maneuver time

Open PointsEstablishing a maneuver-time optimizationConsider flexible structuresDevelop coupled simulation of orbit and attitude orbit control

simulationExploration of possible couplings between thermal distributions and

attitude dynamics


Please Contact Us for Further Information

Christina Scholz:

[email protected]

Daniele Romagnoli:

[email protected]

Bernd Dachwald:

[email protected]

mailto:[email protected]



2 nd SSS , July 2010, Christina Scholz

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