parasitic power collection in shoe mounted device. nwew

7/29/2019 Parasitic Power Collection in Shoe Mounted Device. NWEW

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PARASITIC POWER COLLECTION

IN SHOE MOUNTED DEVICE

Presented by,

Abitha Babu.

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INTRODUCTION

Power can be captured parasitically from normal

human-body motion.

Generated power can be used in personal electronic

application .Foot is chosen as best site for power capture.

Bending of ball of foot and the strike of heel.

Dissipated energy with the foot action can be usefully

retrieved .

Three different system are built to capture power.

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BACKGROUND INFORMATION AND

MOTIVATIONProliferation of wearable devices.

Need of portable power source.

Inconvenience of past methods.

Need for a better option.

Generation of power parasitically.

Comparatively lower power.

Power requirement of modern electronicequipment is very low.

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Idea of harvesting power from human motion

not new.

Deliberate human motion was involved.

Goal is to inconspicuously derive power from

human motion.

In past there have been several attempts that

was not very successful.

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DESIGNS AND

JUSTIFICATIONS

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PLACEMENT OF DEVICES

Device to capture power is implanted in sole ofthe shoe.

Two ways to generate power from human body.

From wasted energy and by adding resistance.

Energy is wasted as heat in joints or due togeneral metabolism.

Unsuitable as parasitic power.

Converter used to draw energy can causediscomfort.

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Largest usable source of waste energy is that

dissipated into ground and shoe during walking.Waste energy can be converted into electrical

energy.

Piezoelectric device is used .

A person can generate upto 67W(68 kg person

at 2 steps per sec. and 5cm deflection).

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HEEL STRIKE AND BENDING OF

THE SOLEStrike of heel against the ground and bending

of the sole are the two most potential actions.

Strike of heel is regarded as force impulse thatcan cause deceleration.

Shoe sole widens the force impulse.

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In addition to direct force applied by the ball

of the foot , the sole also experiences aninduced stress from bending action.

Stress can be used directly to pull an inserted

PVDF or PZT laminate which will generatevoltage.

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HEEL STRIKE SYSTEM

Two systems are developed to take advantage

of the heel strike action.

piezoelectric system inserted in the sole of the

heel of the shoe .

Mechanical system that attaches to the outside

of shoe by means of straps.

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PZT Unimorph

To tap power generated by pressure during heelstrike.

A piezoceramic material is modified to be

flexible and is bonded to a curved piece ofspring steel .

It is basically PZT ( lead zirconate titanate )strip.

PZT can be pushed flat, hence should be placedon a rigid support.

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Fig.a.Diagram of PZt unimorph

Working in the sole of a shoeFig.b.Picture of PZT unimorph

under test

Figure . PZT unimorph

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Electromagnetic generator

Energy is extracted by coupling downward force

to standared electromagnetic generator.

Hand crank generators are used.

Generator is attached to sides of shoe.

Electromagnetic system have much higher

conversion efficiency than piezoelectric system.

Although inelegant it serves as a a useful

comparison with piezoelectric system.

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Figure .c.picture of electromechanical generator attached to shoe during tests

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PVDF staveA semicrystalline homopolymer.

Laminated in a bimorph design around 1mm

plastic substrate.

-crystalline phase is responsible for thepiezoelectric properties of PVDF.

Hexagonal geometry was choosen to maximiseboth stress and are since power increases withboth.

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SOLE BENDING SYSTEM


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Figure. PVDF stave

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OUTPUT OF DEVICESTo measure power output three devices are

attached to a test resistor .

Two piezoelectric was deflected at 7mm.

Generator went through a 3cm range of

motion.

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PVDF produces an output of 0.6mV.

PZT unimorph produces an output of 5mV.

When excited at 2HZ frequency produce 1.8vrmsacross 10 resistor which corresponds to an outputpower of 250mV.

APPLICATIONPVDF

Low PVDF power output can be used in application

where little power is needed or in low duty cycleapplications(0.6mv) .

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PVDF is least noticeable and unobstrusive touser if laminated to sole correctly.

Used in laboratory demonstrations.PZT

Power output is higher than PVDF(5mv).

Can drive more intensive applications.Main drawback is its curved shape.

Generator

produces enough energy to power almost anyhand held piece of electronic device(250mv).

Main drawback is weight and chunkiness.

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CONCLUSION

Devices must generate enough power .

Almost 1-5mW power is produced by the

prototype design.

Improvements can be made to derive more

power.

Parasitic power should be innocuous to user.

PVDF is the most innocuous.

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REFERENCES

Internet thesis by

CLYDE JAKE KENDELL

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THANK YOU.

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parasitic power collection in shoe mounted device. nwew

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