1. Requirement-Driven Magnetic Beamforming for MIMO Wireless Power Transfer Optimization Guodong Cao, Hao Zhou, Hangkai Zhang, Jun Xu, Panlong Yang, and Xiang-Yang Li School of Computer Science, USTC

2. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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3. Wireless Power Transmission (WPT)
Inductive coupling (IC)
Magnetic resonant coupling (MRC)
The self-inductance and capacitor are tuned at each TX/RX so that
their impacts cancel each other at the resonant frequency
Hao Zhou　　　　　　　　　　

4. MRC-WPT SISO / SIMO MISO MIMO Qi 1.2 Rezence Magnetic mimo
[Dina et.al. Mobicom 2014]
MIMO
MultiSpot
[Dina et.al. Mobicom 2015]
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5. Application scenario
Requirement-aware MIMO MRC-WPT
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6. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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7. System architecture Assumption Magnetic resonance at each TX/RX
Mutual inductances are available through MIMO channel estimation method
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8. Circuit equations
Current equation
Voltage equation
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9. Matrix expression H : RX current transform matrix
B : TX voltage transform matrix
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10. Weighted sum-power maximization (WSPMax)
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11. Weighted sum-power maximization (WSPMax)
Power budget constraint
Peak current constraint
Peak voltage constraint
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12. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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13. Basic idea
WSPMax
DUAL-W
W-LR
W-LR-E
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14. Solution for W-LR-E problem (1/3)
Lagrangian multiplier method
Seek the stationary points to function :
Matrix expression:
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15. Solution for W-LR-E problem (2/3)
TX current canditates : eigenvector of matrix Y
with
For the s-th TX current candiate
Result of W-LR-E: with
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16. Solution for W-LR-E problem (3/3)
Optimal solution of W-LR-E
Optimal solution of W-LR
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17. Further discussion without peak current/voltage constraints
Theoretical bound of the WSPMax problem
For given weight factor matrix W
Adjusting mutual inductances
Tuning the TX/RX resistances
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18. Further discussion without peak current/voltage constraints
Power transfer efficiency maximization problem
The problem can be solved without coordination from the RXs
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19. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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20. Experimental scenario
5TXs and 4RXs
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21. Performance evaluation
Two TXs
Five TXs
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22. Converge evaluation
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23. Requirement-driven evaluation
Influence of the weight factors
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24. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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25. Prototype testbed
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26. Circuit diagram
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27. Verification over prototype testbed
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28. Another version of the prototype
Larger size of TX coils
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29. Outline Background Problem formulation Problem solution Evaluation
Prototype implementation
Conclusion
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30. Conclusion WSPMax problem in the MIMO MRC-WPT system
Lagrangian relaxation based algorithm
Solution to the relaxed problem
Obtain the eigenvector of a constructed matrix Y
WSPMax without peak current/voltage constraints
A close-form theoretical bound of the WSPMax problem
Power transfer efficiency maximization problem could be solved through a TX-only method
Prototype testbed
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31. Thanks!
Thanks
Hao Zhou