Unclassified Presentation

1. Unclassified Presentation Validation of Mission Critical Power and Control Systems for Lunar Settlement Julio C. G. Pimentel IEEE Dept. of Computer and Electrical Engineering Ste. Foy, Quebec, Canada Yosef Gavriel Tirat-Gefen IEEE, AIAA Castel Research Inc. www.castelresearch.com Fairfax, VA e-mail: yosefgavriel@computer.org & George Mason University Fairfax, VA

2. Overview • Motivation • Related Work • Mission Critical Systems • Power Systems for Lunar Settlement • Control Systems Validation • Solar Array Based Power System Example • Conclusion

3. Motivation • Major systems to be used in the Lunar settlement: • Power Generation • Life Support • Transport • Systems are subject to malfunction, faults, etc… • Need to Validate the systems for • Design errors • Degraded operation under fault • Sensitivity to design parameters • Validation cost should be affordable

4. Related Work • Jiang, Z., Liu, S. and Dougal, R. A., “Design and Testing of Spacecraft Power Systems Using VTB,” IEEE Transactions on Aerospace and Electronic Systems, Vol. 39, No. 3, July 2003, pp. 976-989. • Cho, B. H., and Lee, F. C. Y. “Modeling and analysis of spacecraft power systems,” IEEE Transactions on Power Electronics, Vol. 3, No. 1, Jan. 1988, pp. 44–54. • Colombo, G., Grasselli, U., Deluca, A., and Spizzichino, A., “Satellite power system simulation,” Acta Astronautica, Vol. 40, No. 1, 1997, pp. 41–49. • Rosero, J. A., Ortega, J. A., Aldabas, E. Romeral, L., “Moving Twords a More Electric Aircraft,” IEEE A&E Systems Magazine, March 2007, pp. 3-9. • Ganig6s, A., Carrasco, J. A., Blanes, J. M. and Sanchis, E., “Modeling the Sequential Switching Shunt Series Regulator,” IEEE Power Electronics Letters, Vol. 3, No. 1, March 2005, pp. 7-13. • Patel, M.R., Spacecraft Power Systems, CRC Press, 2004. • Billerbeck, W., and Lewis, G., Jr., “Spacecraft power system studies using Pspice,” 36th Intersociety Energy Conversion Engineering Conference, Vol. 1, 2001, 1–18. • Ganig6s, A., Carrasco, J. A., Rubiato, J., Avila, E. and Blanes, J. M., “System model of the sequential switching shunt series regulator for spacecraft regulated high power busses,” 351h Annual IEEE Power Electronics Specialists Conference, Aachen, Germany, 2004, pp. 2645-2650. • Pimentel, J. C. G., “Hardware Emulation for Real-Time Power System Simulation,” IEEE International Symposium on Industrial Electronics - ISIE’2006, July 9-12, Montreal, QC, Canada, 2006, pp. 1560-1565. • 13Spice Simulator, University of California at Berkeley, http://bwrc.eecs.berkeley.edu/Classes/IcBook/SPICE/, 2002. • XILINX ISE, FPGA Development Tool, Software Package, Ver. 8.1i, Xilinx Inc., San Jose, CA, 2006. • Matlab/Simulink, Flow Graph Simulation Tool, Software Package, Ver. 7.0.4, Mathworks Inc., Natick, MA, 2004. • Modelsim, HDL Simulation Tool, Software Package, Ver. 6.1, Mentor Graphics Inc., Winsonville, OR, 2005. • Easy5, Multi-Discipline Simulation Tool, MSC Software Corp., http://www.mscsoftware.com/, Santa Ana, CA, 2007

5. Critical Systems in a Lunar Settlement Distributed Control Systems (e.g. supervisory control) Power System Life Support (e.g. O2 and H2O processing and generation) Transport system (e.g. evacuation modules)

6. Validation and Verification • Simulation • Off-line • Real-time • Hardware in the loop • Formal methods • Design by assertion • May be coupled to simulation based methods

7. Simulation(Validate only what we know about) Simulation => more computationally efficient System Model (Implementation) Low-level Simulator Environmental Parameters Compare High-level Simulator System Model (high-level/ behavioral) Report of Bugs / Design Errors

8. Formal Method(automatically validate the whole design space) Formal Methods => Much less efficient what limits the size of the design it can handle System Model (Implementation) Report of Bugs / Design Errors Model Checker (Theorem Proofing) Environmental Parameters System Assertions

9. State of the Art • Simulation: • Widely used • Not able to detect/cover all possible faults • Time consuming (write/run many simulation cases) • Formal Methods: • Starting to be used for digital hardware design • Not fully understood for hybrid systems • Combinatory explosion

10. Mixed Approach System Model (Implementation) Report of Bugs / Design Errors Model Checker (Theorem Proofing) Environmental Parameters System Assertions Scenario co-simulation

11. Real-Time SimulationHardware in the Loop

12. Power - How Critical? • On Earth: • During a power failure, close to 90% of the economic/human activity will be affected • It is possible to wait a few hours or days for recover • On the Moon/Mars: • Close to 100% of all activities are interrupted • Communication may be disrupted • Life support activity is interrupted • Air supply may be depleted in a few hours • Settlers may die

13. Roadmap for Power Generation • Solar • Immediately available • Nuclear • Within 10 years of the start of the settlement • Mineral based • Not sure

14. Solar Based Power System Redundancy

15. HIL Real-Time SimulationGeneral Architecture

16. High Level Architecture

17. Examples of Modules

18. Examples of Modules

19. Programming Flow

20. Hardware Description LanguageComponent Modeling entity DiscPIController is generic (NBits:natural:=8; NBitsRadix:natural:=8; NBitsCoef:natural:=8; PIType:natura :=0; NCycles:natural:=1; A1:natural:=1; A2:natural:=1; Init:natural:=0; UpperBound:integer:=1; LowerBound: integer:=0 ); port (CLK: in STD_LOGIC; RST: in STD_LOGIC; EN: in std_logic; STC: in std_logic; Reg_output: in std_logic; Verr: in std_logic_vector (NBits-1 downto 0); Vcont: out std_logic_vector (NBits-1 downto 0); EOC: out std_logic );

21. Modeling a Power Switch

22. Mathematical Model

23. S4R System • S3R = Sequential Switching Shunt Regulator • S4R = Sequential Switching Shunt Series Regulator

24. Ladder Model

25. Experimental Real-Time Setup • The test environment consists of • an AMD XP2400+ microcomputer • a Digilent Inc. XUP Virtex II Pro Development FPGA Card with a 2VP30-7-FF896 Virtex II Pro FPGA. • The schematic of the simulation model was generated using Matlab/Simulink. • The VHDL simulation and the FPGA synthesis/implementation phases were realized using • Modelsim HDL simulator v6.1b from Mentor Graphics • and ISE Development System v8.1i from Xilinx respectively.

26. Simulink/Matlab Modelling

27. Power Cell Model

28. S4R Main Bus Results (Matlab)

29. Battery Bus Results (Matlab)

30. Bus Error (Matlab)

31. Real Time Results (FPGA)

32. Real Time Results (FPGA)

33. Discussion • The simulator uses low cost reconfigurable computing infrastructure (e.g. embedded processors and FPGAs). • It is capable of having simulation steps on the order of 0.4 microseconds. • It is suitable to represent typical modern aerospace power systems. • We realized the simulation of a sequential switching shunt series regulator (S4R) system

34. Future Work • Probabilistic Modeling • Capture of dynamic/transient faults • Couple simulator to a mixed formal method/simulation framework • Transition tool to a commercial product • Test other key modules (power and control) to be deployed in a lunar settlement • Add more modules for lunar settlement and aerospace applications to the VHDL library