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A Re-usable Software Architecture for Small Satellite AOCS Systems
Authors:• Associate professor Jan Dimon Bendtsen (
[email protected])• PhD. student Lars Alminde ([email protected])• PhD. student Karl Kaas Laursen ([email protected])
Affiliation:• Section for Automation and Control• Department of Electronic Systems• Aalborg University, Denmark
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 2
A Re-usable Software Architecture for Small Satellite AOCS Systems
Small Satellites with Involvement of Aalborg University
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 3
A Re-usable Software Architecture for Small Satellite AOCS Systems
Small Satellites with Involvement of Aalborg University
Agenda for Presentation
• Motivation of this work
• Hybrid Dynamical Systems
• SOPHY architectural overview
• AAUSAT-II Case Study
• Conclusions
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 4
A Re-usable Software Architecture for Small Satellite AOCS Systems
Motivational Case: AAU-Cubesat
• Launched in June 2003, 800km, SSO• First European cubesat to phone home• Total budget 200kEuro• Partial antenna deployment failure -> low signal levels• Operations moved to 8m dish• After 3 months batteries die (Li-Ion Polymer)
OBC COM
ACSCAMPCU
I2C-BUS
PARALLEL
DMA
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 5
A Re-usable Software Architecture for Small Satellite AOCS Systems
CDH – Services and Software Structure - AAU-Cubesat
PSU ACDS Camera
Supervisor
Log Service
Flight Plan
Beacon
Software services
Subsystem Control
Protocol
Modem/RF
ProtocolProtocol
Communications
HardwareAAU-Cubesat SW metrics:- 13 threads- 10k lines of code
I2C
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 6
A Re-usable Software Architecture for Small Satellite AOCS Systems
Motivation – Observations
Observations on architecture:• Distributed and networked architecture• Non-homogeneous execution platforms
Observation on the process:• Software is model based• Manually producing and verifying flight code takes a long
time• Later changes at the model level can incur significant change
in code
Ramifications on the project level:• Reduced time for testing• Design deficiencies discovered very late
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 7
A Re-usable Software Architecture for Small Satellite AOCS Systems
Motivation – Objectives for Sophy
DeclarativeControl Engine
ModelSpecification
ServiceSpecification
Measurements Control Signals
A Software platform that allows:
Level 1:• Provide a homogeneous execution platform• Handle distribution transparently• Turn specifications into executables• Be a tool throughout the whole process
Level 2:• Auto generate controllers from models• Auto generate observers from models
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 8
A Re-usable Software Architecture for Small Satellite AOCS Systems
Hybrid Dynamical Systems
Hybrid Systems:• A number of locations with different flow of
continuous variables• Transitions between locations:
• External events• State events, transition conditions
• Resets of the state-space during transitions• No unified formalism (see paper for details)
Suited to model:• Attitude/orbit determination and control• Fault detection and handling (FDIR)• Protocols• Supervisory control
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 9
A Re-usable Software Architecture for Small Satellite AOCS Systems
SOPHY – Simulation, Observation, and Planning in Hybrid SystemsXML descriptions of:• Hybrid System Components• Interconnection between
them
Plug-in support for:• Networks• Simulator/Controller/
Observer• Input/Output
Implementation:• Object Oriented• Java
• Garbage collection• Portability• Well tested APIs and
libraries
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 10
A Re-usable Software Architecture for Small Satellite AOCS Systems
XML File Representation
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 11
A Re-usable Software Architecture for Small Satellite AOCS Systems
Sophy – Deployment and Execution
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 12
A Re-usable Software Architecture for Small Satellite AOCS Systems
(Simple) Case Study
AAUSAT-II:• Launch is June 2007 from India• Student satellite• Gamma ray burst detector mission• Technology Evaluation
Attitude control system:• Magnetometer and sun-sensors• Magnetotorquers• Reaction wheels
Extensive simulation model in matlab exists
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 13
A Re-usable Software Architecture for Small Satellite AOCS Systems
Autonomous Attitude Capture
B-Dot LQR
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 14
A Re-usable Software Architecture for Small Satellite AOCS Systems
Case Study: Simulation Results
Lars Alminde – 26/9-2006 – Small Satellite Systems and Services – Chia Laguna, Sardinia 15
A Re-usable Software Architecture for Small Satellite AOCS Systems
Conclusions and Perspectives
Concluded:• Base architecture defined and implemented• On-line generation and execution of hybrid dynamical
systems• Matlab and general socket-based bindings for IO
On-going:• 3D visualization interface for outputs• Network Adapter for CAN-bus• Deployment on ARM-based On-board Computer• General continuous plant controller plug-in
Future:• Estimation plug-ins• Model builder GUI• Full scale deployment
