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Re: wind-up wearables

Shoe inserts seem to be the slickest method of providing infinite power
for wearables. The following is from a 1996 Thad Starner paper on
human-powered wearable computing:

http://www.almaden.ibm.com/journal/sj/mit/sectione/starner.txt

Piezoelectric shoe inserts. Consider the use of PVDF shoe inserts for 
recovering some of the  power in the process of walking. There are many
advantages to this tactic.

First, a 40-ply  pile would be only (28 micrometers)(40) = 1.1 mm thick
(without electrodes). In addition, the  natural flexing of the shoe when
walking provides the necessary deflection for generating  power from the
piezoelectric pile (see Figure 3). PVDF is easy to cut into an appropriate 
shape and is very durable.11,12 In fact, PVDF might be used as a direct
replacement for  normal shoe stiffeners. Thus, the inserts could be easily
put into shoes without moving parts  or seriously redesigning the shoe. 

A small woman's shoe has a footprint of approximately 116 cm2. Knowing
that the maximum effective force applied at the end of a user's step
increases the apparent mass by 30  percent, the user needs only 52 kg (115
lbs) of mass to deflect the PVDF plate a full 5 cm. Although the numbers
given in the last section were for a 15.2 cm by 15.2 cm triangular 
40-ply pile, the value can be used to approximate the amount of power an
appropriately shaped  piezoelectric insert could produce. Thus, scaling
the previous 1.5 W at 0.6 deflections per second to two steps per second, 
of electrical power could be generated by a 52 kg user at a brisk walking
pace.

-Chris Allen

ps  Future computers will use low-power optical microprocessors,
increasing the feasablility of alternative power sources.

On Mon, 1 Jun 1998, Boris wrote:

> 
> 
> Oak Davis wrote:
> 
> > Tim Gray wrote:
> > ----- SNIP -----
> > > I would love to cut my battery pack in 1/2 if I can find an
> > > alternativecharging system... (Solar panel hats are not socially
> > > acceptable yet  :-) and winding up the power system might get
> > > strange looks in the resturant...
> > ----- SNIP -----
> > >>From: Christopher Allen <>
> > >>Yes. From CMU's Metronaut page:
> > >>"Metronaut could alternatively be powered by a mechanical flywheel
> > >>converting kinetic energy to electrical energy."
> > ----- SNIP -----
> > >>On Thu, 28 May 1998  wrote:
> > >>http://www.cs.cmu.edu/afs/cs.cmu.edu/project/vuman/www/metronaut.html
> > >>On Thu, 28 May 1998  wrote:
> > >>> The Metronaut, presented by CMU at ISWC'97, was a wind-up wearable
> > >>> computer!
> 
> <snip>
> 
> > My point (finally) is that the wind up generator needed to provide power
> > to a wearable computer would be a lot larger than the batteries it
> > replaces and would require a lot of cranking. Even if the charging unit
> > did not have to be attached to the wearable all the time the user would
> > have to carry it around all the time because of the frequent need for a
> > recharge.
> 
> <snip>
> 
>  First an apology if this response doesn't get routed properly (first
> attempt).
> 
> I am not an engineer, but i wonder if using more of the body than just the
> hands might not ameliorate the tedium of hand crankinging?  For example as
> one walks ones arms and legs are swinging back and forth, could not some
> method be developed to use this motion to charge a bateery or capacitors?
> 
> Just a thought.
> 
> --
> Abraços,
> 
> B
> 

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