1. A Re-usable Software Architecture for Small Satellite AOCS Systems Authors: Associate professor Jan Dimon Bendtsen (dimon@control.aau.dk)dimon@control.aau.dk PhD. student Lars Alminde (alminde@control.aau.dk)alminde@control.aau.dk PhD. student Karl Kaas Laursen (karl@control.aau.dk)karl@control.aau.dk Affiliation: Section for Automation and Control Department of Electronic Systems Aalborg University, Denmark

2. 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

3. 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

4. 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) OBCCOM ACSCAMPCU I2C-BUS PARALLEL DMA

5. 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 Supervi sor Log Service Flight Plan Beacon Software services Subsystem Control Protocol Modem/ RF Protocol Communications Hardware AAU-Cubesat SW metrics: - 13 threads - 10k lines of code I2C

6. 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

7. 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 Declarative Control Engine Model Specification Service Specification 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

8. 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

9. 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 Systems XML 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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