Seminar Topic- Adaptive Piezoelectric energy harvesting circuit

    The need for a wireless electrical power supply has spurred an interest in piezoelectric energy harvesting, or the extraction of electrical energy using a vibrating piezoelectric device. Examples of applications that would benefit from such a supply are a capacitively tuned vibration absorber ,a foot-powered radio” tag and a Pico Radio .A vibrating piezoelectric device differs from a typical electrical power source in that its internal impedance is capacitive rather than inductive in nature, and that it may be driven by mechanical vibrating amplitude and frequency. While there have been previous approaches to harvesting energy generated by a piezoelectric device there has not been an attempt to develop an adaptive circuit that maximizes power transfer from the piezoelectric device.

INTRODUCTION

 The objective of the research described herein was to develop an approach that maximizes the power transferred from a vibrating piezoelectric transducer to an electromechanical battery. The paper initially presents a simple model of piezoelectric transducer. An ac-dc rectifier is added and the model is used to determine the point of optimal power flow for the piezoelectric element. The paper then introduces an adaptive approach to achieving the optimal power flow through the use of a switch-mode dc-dc converter. This approach is similar to the so-called maximum power point trackers used to maximize power from solar cells. Finally, the paper presents experimental results that validate the technique

APPLICATION

SHOE-POWERED RF TAG SYSTEM

 To demonstrate the feasibility and utility of scavenged shoe power, we developed a simple application circuit. The design is a self-powered, active radio frequency (RF) tag that transmits a short-range, 12-bit wireless identification (ID) code while the bearer walks. This system has immediate application in a smart environment, in which multiple users transmit their identities to the local surroundings. The IDs, for example, can enable a central server to make dynamic, near-real-time decisions to personalize the environment or route appropriate information to mobile users. Most previous work in this area relied on battery-powered infrared (IR) badges.9 Our RF-based design, however, requires no line of sight to the reader and therefore can be mounted in a shoe, operating without a battery under the power of a piezoelectric insert. Figure 11 shows a functional prototype pair of self-powered RFID sneakers.

CONCLUSIONS

 This paper presents an adaptive approach to harvesting electrical energy from a mechanically excited piezoelectric element. The dc-dc converter with an adaptive control algorithm harvested energy at over four times the rate of direct charging without a converter. Furthermore, this rate is expected to continue to improve at higher excitation levels.

 The flexibility of the controller allows the energy harvesting circuit to be used on any vibrating structure, regardless of excitation frequency, provided a piezoelectric element can be attached. Also, external parameters such as device placement, level of mechanical vibrations or type of piezoelectric devices will not affect controller operation. The control algorithm can also be applied to other dc-dc converter topologies.

This would allow the development of optimized designs based upon the expected excitation or the electronic load that is to be powered. Future work will focus on the design of an optimized system design using standalone control circuitry. 

REFERENCES

• Geffrey k. Ottman, IEEE,”Transactions on power electronics”, vol.17, no 5, pp 669-676, September 2002.
• C. Davis and G. Lesieutre. ”An actively tuned solid-state vibration absorber using capacitive shunting of piezoelectric stiffness” J. Sound vibration, Vol 232, no. 3, pp.601-617, May 2000.
• N .Shenck and J.A.Paradiso,”Energy scavenging with shoe-mounted piezoelectrics”, IEEE Micro, Vol 21, pp30-42, May-June 2001
• N.Mohan, T. Undeland, and W. Robbins, Power electronics: Converters, Applications and Design, New York, Wiley, 1998
• P.Smalser,”Power transfer of Piezoelectric generated energy”, U.S.Patent, 5703474, 2001.
• Web sites visited : www.IEEE.org

Submitted By 

HARISH.M
Department of Electrical and Electronics Engineering

MES College of Engineering

Kuttippuram