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[[Category:SEDSAT-2 ADCS]]


This is the page for the [[SEDSAT-2]] Attitude Determination and Control team. 

==News==
Latest updates on the progress of the ADCS team:
<br>



===April 2008===

====Current state of subsystem====
Development of a prototype coil system is currently underway . Currently the team is working on the requirements for the coils themself, and the magnetometers used to sense the magnetic field around the earth. 
A model of the magnetic field is also under investigation. 

====Progress since Design Review I====
*New team. more regular meeting activity
*access to equipment to make prototype coils have been gained.
*new major design choices made.

====Time frame for completion====
We are currently hoping for a functional prototype of the main ADCS systems to be completed by IAC2008.

====Design Choices Made====
*Using a active magnetic system with 3 magnetic coils controlled by a MCU that gets input form a 3axis magnetometer and a model of the earths magnetic field.

*magnetic field model will be stored in a dedicated NV Flash Memory device. Flash memory is cheap, small in size and robust and is ideal for this type of application. Substantial storage capacity can be easily implemented and data storage should not be an issue.

*The coils will be made from Printed Circuit Board (PCB) material, this is easy to make, easy to test/prototype and easy to install behind the solar panels.

*ADCS will send attitude data to CDH via the onboard I²C bus. CDH will send the data back to earth as part of a house keeping packet. ADCS will also be able to receive simple commands from CDH, like start and stop.


====Preliminary Figures====
*Mass: ~ 170 to 200g
*Dimensions: mainboard: 100cm^3 (10x10x1cm) coils: (10x10x0.1cm) X3coils
*Operating Voltage: 5VDC or 3.3VDC
*Control/Data Interface: Philips [http://en.wikipedia.org/wiki/I²C I²C]
*Power Consumption: 200mW (average, more on startup, less after stabilization)

====Discussion====
*the processing power needs for the system is a bit unsure, hopefully we will be ok with an 8-bit MCU, worst case we have to move the processing down to earth
*what kind of secondary sensing system will be used? sun, earth, moon trackers?


===March 2008===
We are working heavily on the Coils. Hoping to have a working prototype for testing within a couple of weeks. First step is calculating all the variables, like the number of turns, thikness of wire, material etc. The design of the prototype will be traces printed on a PCB in a rounded square pattern. The idea is that the coils will be fast and directly behind the solar panels on 3 of the sides. The PCB will be aprox. 0.5 mm thick. The image is just to show the concept, on the real coils there would be more traces and they would be closer together.
<br>
[[Image:Coil.PNG]]
<br>

===February 2008===
Just making the Wiki site ready for more active use, also updated the "system diagram":

[[Image:Adcs_diagram.png]]

===January 2008===
The[-p ADCS team have decided on what system type we are going to go with. It is going to be an active magnetic system for attitude control, and an magnetometer system for determination. More info will come when I get the time.
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<br>
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==Interface Tables==
{{SEDSAT-2 Interface ADCS}}

<br>
== Team Members ==

*<b>Ryan Bourlier</b> (Leader) (USA) - rbourlie@purdue.edu <br />
 
*<b>Brad Appel</b> (USA) - bappel@purdue.com <br />
 
*<b>Brendan Muelle</b> (USA) <br />
*<b>Kelly Mann</b> (USA) <br />
*<b>Adam Kerner</b> (USA)<br />
<br>
<br>

==Older Links==

[[ADCS New beginning, nov 2007]]

[[ADCS Control algorithms]]

[[ADCS Research to date]]

[[SWOT analysis of uppt vrs magnetics]]

[[SWOT analysis of dalsa]]

[[SEDSAT-2 ADCS Design Notes 20071017]]





==Passive Systems==

===Passive Magnetic===

-Permanent Magnet and hysterisis rods

===Gravity gradient boom===

-Gravity gradient boom (this is a partial control system, and needs a determination system)



Provides gravity gradient stabilization on small spacecraft


- Accurate to within ±5 deg of nadir

- Used for “short” deployments (< 6m)

- High stiffness compared to tethers

- Bigger and heavier than a tether



There are 5 main boom types to consider:

- STEM Boom

- Elastic Memory Composite (EMC) Boom

- STACER Boom (SSTL)

- Coilable Booms

- Inflatable Boom

questions:

The accuracy seems to me quite high, do you happen to know about the time frame such accuracy will be achieved? looks like there has a lot of time to pass to achieve that.....?

About the initial orientation, how do you get the boom to start prezising in the right direction? (towards or away from nadir)

==Active Systems==

===Reaction Wheels===
===Momentum Wheels===
===Active Magnetic System===

Determination: Magnetometers

Control: Magnetic Coils

Detailed documentation: http://www.cubesat.auc.dk/, http://www.ncube.no/

====SWOT Analysis====


{| border="1"

|-

! Strenghts

! Weaknesses

|-

| > Often used by other CubeSats (well tested)<br /> > cheap<br /> > no moving parts
| > interaction with magnetometers<br /> > not innovative<br /> > not free
|-
! Opportunities 
! Threats
|-
| > None
| > None
|}
<br />

===Micro propulsion system===


see http://en.wikipedia.org/wiki/Pulsed_plasma_thruster for general information

Design Goals for µPPT by ARC Seibersdorf (we would get fly-ready prototypes for SEDSat):

 - Impulse bit: 10-20µNs, which would guarantee a pointing accuracy of <1 degree
 - Spec. impulse: 500-1000 s
 - Power: 0,5-1,5 W
 - Weight: < 30g

====SWOT Analysis====


{| border="1"

|-

! Strengths

! Weaknesses

|-

| > Innovative (I think the first use with CubSat)<br /> > Very Accurate (<1°)<br /> > Electr. Prop: Can almost never run out of propellant<br /> > non-toxic propellant (Teflon)<br /> > professional manufactured devices<br /> > free
| > High electr. Power Consumption (maybe up to 1,5 W per Thruster)<br /> > relatively heavy (<30g) -> only 6 thruster configuration to use
|-
! Opportunities 
! Threats
|-
| > Could also be used for Orbit Changes (in limits), with additional thruster(s)<br /> > PR for using an innovative new technology for CubeSat
| > Not available before Fall 2008<br /> > New Technology (first ones to test)
|}

==Attitude determination systems==

===magnetometers===

===accelerometers===

===Gyroscopes===

===Sun sensors===

===Horizon sensors===

Documentation: [[Image:OM6802WCW5R2 071204.pdf‎]]

====SWOT Analysis====


{| border="1"

|-

! Strengths

! Weaknesses

|-

| > Innovative (I think the first use with CubeSat)<br /> > Accurate<br /> > professional manufactured devices<br /> > free<br /> > light weight, small volume
| > Possibly High electr. Power Consumption depending on use<br /> > Have not determined precisely how they would be used
| > Complicated
|-
! Opportunities 
! Threats
|-
| > PR for using an innovative new technology for CubeSat
| > New Technology (first ones to test in space)<br /> >need to test them to determine how we will use them<br /> > need to negotiate in order to <br />obtain them without committing to using them.  <br />company representative currently out of office
|}
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ADCS design notes are filed in '''[[:Category:SEDSAT-2 ADCS]]'''.

'''Create new design note:''' [[SEDSAT-2 ADCS Design Notes {{CURRENTYEAR}}{{CURRENTMONTH}}{{CURRENTDAY2}}]]


[[Category:SEDSAT-2|ADCS]]
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