ME474 Final Presentation

The City College of New YorkDepartment of Mechanical Engineering

Magnetic Hysteresis-based Passive Attitude Control for CUNYSat-1

Mechanical Engineering 47400 Senior Design ProjectProf. Charles B. Watkins

CCNY PicoWorksTeam LeaderDean James

Team MembersAldi Dilo

Javier FrancoMourad BennisDanishwer Khan

December 10, 2009

• Introduction• Problem Statement and Design Specifications• Design Concepts• Product Architecture• Configuration Design• Parametric Design• Final Design• Analysis & Testing• Prototype Applications• Recommendations• Conclusion• Acknowledgements

12/10/2009CCNY PicoWorks

2 Final Presentation

Introduction- CubeSat



History PurposeCalPoly’s

Role

Introduction- CUNYSat and CCNY PicoWorks

CUNYSat

• University-wide Research group

• Will construct CUNYSat-1, a CubeSat-compliant nanosatellite

CCNY PicoWorks

• CCNY ME Senior design team

• Charged with designing optimal ADCS.






Problem Statement and Design Specifications

• Problem Statement

– Upon separation from the launch vehicle, CUNYSat-1 will have random orientation and spin




• Design Objective

– Design an ADCS subsystem to control the orientation of CUNYSat-1 and to stabilize its spin




• Major Constraints

– 40 grams of the mass budget will be set aside for the ADCS

– Power consumption should be minimal

– Mechanical complexity should be avoided when possible

– Cost should be minimized where possible




• Product Design Specifications

– All components of the subsystem must be fully compliant with the latest version of the CubeSat Design Specifications

– The subsystem may weigh no more than 40 grams

– The subsystem must be able to stabilize the satellite






Design Concepts

Passive Concepts

Active Concepts

Evaluation matrices



Passive Design Concepts

Passive

Telescoping Boom

Wire Drum Deployer

Coilable Boom

Magnetic Hysteresis

• 12/10/2009CCNY PicoWorks


Active Design Concepts

Active

Reaction wheels

Momentumwheel

Torquer coilsControlled momentum

gyros

• 12/10/2009CCNY PicoWorks


Evaluation Matrix- Passive Stabilization

Concept Cost Ease of

Manufacture/

Acquirement

Mechanical

Complexity

Power

Consumption

Collision

Recovery

Total

Telescoping

Boom

0 - - - - - 0 -5

Wire Drum

Deployer

+ - - - - -3

Coilable

Boom

- - - - - - - -7

Hysteresis

Rod

+ + + + + + 6



Evaluation Matrix- Active Stabilization

Concept Cost Ease of

Manufacture/

Acquirement

Mechanical

Complexity

Power

Consumption

Weight Total

Reaction

Wheel

0 0 0 - 0 -1

Momentum

Wheel

+ 0 0 0 + 2

Torquer Coil - + + 0 + 3

Controlled

Momentum

Gyro

- + + + - -1






Product Architecture: Components

Item Description

Rod- dissipates oscillation energy in form of heat

Magnet- aligns satellite in same axis as that of the Earth magnetosphere's field lines

Bracket- secures magnetic materials to satellite, ensuring transmission of torque to satellite



Product Architecture:Functional Schematic



Product Architecture: Fundamental Interactions

Item Fundamental Interaction

Magnet Torque between itself and magnetosphere

Hysteresis rod Internal magnetic domain realigned to local flux lines

Brackets transmits torque to satellite



Product Architecture:Secondary Interactions

Item Secondary Interaction

Magnet may interfere with other electronic components on board the satellite

Hysteresis Rod Heat transferred to satellite

Bracket Inefficient design will result in excess weight






Configuration Design via CubeSim

Config. Design- Magnetic Materials Ratio vs. Stabilizing Time & Resolution

Magnet ratio(p/h) Transient time(min) Stab. Resolution(deg)

0.5

0.875

1

1.143

1.5

2

2.75

…

4

20

23

28

28

35

43

53

…

180

36.72

29.7

21.74

19.62

15.99

13.01

10.53

…

~2



Configuration Design:Constraints Imposed

Unit of constraint Results

Spatial •Can't use bottom of frame because of Flight computer board•Can't mount outside because of solar panels

Mass •Total subsystem mass of 40g

Precision •CUNYSat places more weight on final precision than initial transient time






Parametric DesignThe Issue of the Z- Axis

Due to spatial constraints mentioned before can't mount straight down inside or outside

Parametric Design:Evaluated Concepts

PCB boardPros: can fit three axes of materialwithin the satelliteCons: unsupported ends more susceptible to damage during launch

Log Cabin stacksPros: strong, minimal non-magnetic material, most of mass budget goes to functional componentsCons: Not enough volume to create spans of sufficient strength



Parametric Design:Final Concept






Construction-phase Modifications



Final Design

(exploded view)






Analysis and Testing

• Purpose

• Procedure

• Video

Helmholtz Coil Rotation Duration

• Purpose

• Procedure

• Table of Results

Machining Effects on Magnetic Material



Analysis & Testing:Helmholtz Coil Rotation Duration

Purpose:

to verify that magnetic hysteresis exerts a measurable stabilization effect at the mass calculated




Procedure

i. Suspend mock CubeSat from string

ii. Set variable parameters for test run

iii. Wind 7turns

iv. Release and start timer

v. Stop timer when CubeSat comes to complete rest




Test #1 Test #2 Test #3 Test #4 Test#5 Test #6 Test #7

Suspension material Shoelace Shoelace Shoelace Shoelace Shoelace Shoelace Shoelace

Turns 7 7 7 7 7 7 7

Elapsed time 4:37 6:20 5:22 6:28 6:50 7:38 4:34

MagnetsAttached? Yes Yes Yes Yes Yes Yes Yes

Hysteresis RodAttached? No No No No Yes Yes Yes

Coils Energized? No Yes No Yes No Yes Yes

Mounting Top Top Side Side Side Side Top

Suspension Length 5" 5" 5" 5" 5" 5" 5"



Analysis & Testing:Machining Effects on Magnetic Material

Purpose:

To verify water cooling as a viable method of negating demagnetizing effects of machining magnetized material




Procedure

i. Notch Alnico-5 bar

ii. Secure in vise and strike with hammer

iii. Measure and record magnetic field strength

iv. Secure in vise

v. Alternate between grinding and dousing with water

vi. Measure and record magnetic field strength




Before Grinding Post Grinding Delta

Flat surface 613 Gauss 590 Gauss -3.75%

Rough (Ground) Surface

-770 Gauss -717 Gauss -6.88%






Prototype Applications

• Future of CUNYSat-1

– Research and methods conducted by PicoWorks will be used to develop the ADCS system once CUNYSat-1 obtains a launch vehicle and orbital profile






Recommendations

• Omni directional antenna should be utilized

• Torquer coils should be utilized for greater pointing accuracy






Conclusion

• Procedure developed for design of passive ADCS

• Custom-built magnets should be ordered

• Helmholtz test should be conducted under more controlled conditions






Acknowledgements

• Dr. Charles Watkins

• Mechanical Engineering Department

• Dr. Shermane Austin

• Mr. Chen

• CalPoly CubeSat program

• SAE-CCNY



Documents

ME474 Final Presentation