Single-slew manoeuvres for spin-stabilized spacecraft

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Single-slew manoeuvres for spin-stabilized spacecraft29th March 2011James BiggsGlasgowIn collaboration withNadjim Horri at the Surrey Space Centre6th International Workshop and Advanced SchoolSpaceflight Dynamics and Controlwww.strath.ac.uk/[email protected] and nano spacecraft seen as viable alternatives to larger spacecraft for certain missions e.g. Enable rapid space access.

29th March 20112James BiggsIntroduction

Motion Planning

Reduction method

Practicalcost function

Example

Conclusion

SSTL-150 UKube 1 Clydespace andStrathclyde University Use an arrow like this to mark current sectionAttitude ModesTwo vital mission phases:-

De-tumbling and stabilisation initial tip-off speeds (worst case scenario for Ukube -5rpm in every axis .) Tumbling motion must be stabilised or mission will fail. B dot control has been demonstrated.

Re-pointing and stabilisation reorient spacecraft to target specific point (e.g. point antenna to ground station, point solar cells towards sun for maximum power.) Accurate re-pointing is yet to be realised .

This presentation proposes a method for re-pointing.

29th March 20113James Biggs

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ConclusionUse an arrow like this to mark current sectionStabilizationTwo conventional methods:-

Spin stabilization passive, re-pointing required.Early satellites NASA Pioneer 10/11, Galileo Jupiter orbiter

Three axis-stabilization active control.Thrusters, reaction wheels on conventional spacecraft.

Spin stabilization is attractive for nano-spacecraft Enables temporary GNC switch off.

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Use an arrow like this to mark current sectionRe-pointing spin stabilized spacecraftPossibility:-

Spin down, perform an eigen-axis rotation, spin up.

Computationally easy to plan and track.

may not be feasible with small torques of micro/nano spacecraft in a specified time.

Requires better planning/design of reference trajectory.

29th March 20115James Biggs

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ConclusionUse an arrow like this to mark current section29th March 20116James Biggs

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ConclusionUse an arrow like this to mark current section29th March 20118James BiggsMotion Planning using optimal controlKinematic constraint:

Subject to the cost function:

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ConclusionUse an arrow like this to mark current section29th March 20119Insert Name as Header & Footer

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Sketch of proof Kinematic constraintIntroduction

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Sketch of proof Use a Lie group formulationIntroduction

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ConclusionUse an arrow like this to mark current section29th March 201112James BiggsSketch of proof - Construct the left-invariant Hamiltonian (Jurdjevic, V., Geometric Control Theory, 2002)

Introduction

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ConclusionUse an arrow like this to mark current section29th March 201113James BiggsSketch of proof - Construct the left-invariant Hamiltonian vector fields and solve:

Solve the differential equations:

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ConclusionUse an arrow like this to mark current section29th March 201114James BiggsSketch of proof.Lax Pair Integration:

Solve for a particular initial condition

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Practical cost function 1Minimise the final pointing direction:Introduction

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Use an arrow like this to mark current section29th March 201116James BiggsPractical cost function 2

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ConclusionMinimize J by optimizing available parameters:Minimize torque requirement amongst reduced kinematic motions:Use an arrow like this to mark current section29th March 201117James Biggsexample

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ConclusionSSTL-100 Use an arrow like this to mark current section29th March 201118James Biggsexample

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ConclusionSSTL-100 Use an arrow like this to mark current section29th March 201119Insert Name as Header & Footer

Control Torque History (Nm)Introduction

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ConclusionUse an arrow like this to mark current section29th March 201121James BiggsIntroduction

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Use an arrow like this to mark current sectionConclusion29th March 201122James BiggsTo realise nano-spacecraft as viable platforms for remote sensing precise attitude control is essential.

Poses research challenges low-computational methods for generating low-cost (zero fuel) motions.

The presented method reduces the kinematics to a subset of feasible motions that can be defined analytically.

Massive reduction in computation reduced to parameter optimization.

Can be extended to minimum time problems, three axis re-pointing i.e. No spinning constraint.

Introduction

Motion Planning

Reduction method


Example

Conclusion

Use an arrow like this to mark current sectionThank You for your attentionQuestions?23

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Single-slew manoeuvres for spin-stabilized spacecraft