Title :

Bandwidth Improvement through Synchronized Switch Mode Control in Piezoelectric Energy Harvesting

Speaker :

Prof. Yi-Chung Shu

Institute of Applied Mechanics

National Taiwan University, Taiwan

Venue :

Room 215, William M. W. Mong Engineering Building, CUHK

Date :

Jul 2, 2010, Friday
2:30 PM - 3:30 PM

Abstract :

With advances in wireless technology and low-power electronics, energy harvesting from environmental resources has the potential to power mobile and wireless microsystems. Due to the ubiquitous presence of ambient vibrations, the use of piezoelectric materials for converting kinetic energy into electric power has recently witnessed a dramatic rise for power harvesting. Typically an energy scavenger is designed as a resonant oscillator for peak power extraction. As a frequency mismatch of only few percentages may result in a significant drop in power output, methods to adjust the resonance frequency to match the driving vibrations across a range of frequencies have been proposed recently by using resonance-tuning actuators. Alternatively, scavenger`s bandwidth can be improved through synchronized switch mode control. Indeed, a recently emerged energy harvesting circuit called `synchronized switch harvesting on inductor` (SSHI) has been proposed together with the standard DC technique for maximum power transfer to the load. It was originally used for power boosting in a weakly coupled electromechanical system. An improved analysis taking into the full electromechanical coupling response and vibration phase-shift effect shows that the scavenger`s bandwidth can be improved significantly in comparison to the standard technique. This talk introduces two SSHI techniques: Parallel- and Series-SSHI circuits and makes comparisons between these two. The result shows that the electrical response of an ideal Parallel-SSHI system is in conjugate with that of an ideal Series-SSHI system. Both avail against the standard technique in the case of medium coupling, since peak power is close to the ideal optimal power and the reduction in power is less sensitive to frequency deviation. However, the consideration of inevitable diode loss favors the Parallel-SSHI technique, since the frequency-insensitive feature is much more pronounced in Parallel-SSHI systems than in Series-SSHI systems. Finally, the analytic results are validated numerically and are found in good agreement with experimental observations.

Biography :

Prof. Yi-Chung Shu received the B.S. and M.S. degrees in Civil Engineering from National Taiwan University in 1990 and 1992, and the Ph.D. degree with major in Applied Mechanics and minor in Materials Science from the California Institute of Technology, USA, in 1998. He has been invited by Max-Planck Institute for Mathematics in the Sciences and by Isaac Newton Institute for Mathematical Sciences. Currently, he is a Professor of the Institute of Applied Mechanics, National Taiwan University, Taiwan. Prof. Shu`s research focus is mainly in the fields of mechanics, materials science and energy harvesting technology. He has served for different academic societies, conference organizers and speakers, and has been invited as a regular referee for over 27 international journals. Currently he is the Executive Editor of Journal of Mechanics.

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Enquiries: Ms. Winnie Wong or Prof. Wen J. Li, Department of Mechanical and Automation Engineering, CUHK at 2609 8337. *MAE Series (2009-10) is contained in the World-Wide Web home page at attp://www3.mae.cuhk.edu.hk/maeseminars.php#mae.