[EAS]Re: Modularity/Biomechanics

pjk pjk at design.eng.yale.edu
Fri Mar 2 03:33:54 EST 2001

Subject:   RE>Modularity/Biomechanics

Dear Colleagues -

Further to the earlier mailing about "Modularity", about the
partitioning of systems into smaller functional entities,
I meant to mention another book. 

While the book by M.J. French deals more with the man-made domain,
a recent book by Steven Vogel, "Cats' Paws and Catapults"
(Norton 1998), looks in much more detail at the biomechanical
world. To quote from the cover jacket

>    Our human technology has emerged from ten thousand years of
> design, trial and error. Nature's mechanical designs, the function
> of plants and animals, are billions of years older. Both
> "technologies" share the same physical environment--the same
> materials, atmosphere, and temperature range--and both are subject
> to the same gravitational pull. But they've turned out to be wildly
> dissimilar.
>    Human designers love right angles, but nature is typically
> round, curved, and its angles are more diverse. The wheel enables a
> huge amount of our technology, yet nature's only true wheels lie
> within tiny bacteria. Most of our water vessels sail buoyantly
> across water's surface, while nature typically swims submerged. Our
> hinges turn because hard parts slide around, whereas natural hinges
> (such as a rabbit's ear) turn by bending their flexible materials.
>    Steven Vogel examines the many questions that arise from these
> differences. "Cats' Paws and Catapults" ... introduces the reader
> to the field of biomechanics and explains how the nexus of physical
> law and historical accident determine the designs of both people
> and nature.

Vogel is James B. Duke Professor of Biology at Duke University and
a very congenial writer. His is one of many books I'm waiting to
have time to read at leisure. This may require retirement. The bits
I _have_ read are fascinating.

Lastly, the "Modularity" mailing prompted a response from Gregg
Favalora. Gregg is the '96 Yale EE graduate whose 3-D display
prototype won in the BF Goodrich Invention contest, and has
continued running in the Becton basement display case for over
4-1/2 years. The whole Yale Class of 2000 came and went while
currents continued to course through its Protoboard wires. I'm too
human not to pass on below my email exchange with Gregg (with his

All best,  --PJK

Date: 2/26/2001 1:58 AM
To: Gregg Favalora
From: pjk
        Reply to:   RE>>[EAS]Modularity

Gregg, I very much enjoyed your response. 

At the level of the circuits I taught you, modularity might
separate a preamp from a filter, a motor controller from a speed
ramp-up circuit. But mostly the modules I had in mind were at the
level of op amps, PLL chips, the organization within a larger FPGA,
a compactly implemented microcontroller system, etc.

_Within_ those circuits  I certainly advocated goals of
compactness, though mostly arising from taking the simplest
approach, less so from fusing functions or multiple purposes for

Anyway, yes, modularity is not so clearcut an ideal, but one that
deserves to get its share of prominence.

All best,  --Peter

Date: 2/25/2001 8:25 PM
To: pjk
From: Gregg Favalora

> My own very practical work in electronics design over more than 30
> years, has ingrained in me a modular approach, partitioning a
> larger whole into functional modules, each described by an
> input/output "cause & effect" behavior sufficiently resourceful,
> but also sufficiently ideal, to allow the efficient assembly of
> larger functions with such modular units. The "sufficiently ideal"
> part allows the descriptive framework of the larger modular
> assembly to be no more complex than that of an individual module.
> Nature does not "design" this way, she evolves very slowly. The
> result is a total fusion of function and form that we are right to
> admire aspiringly, but can seldom take as a direct lesson. A blade
> of grass is a totally integrated system of structure, fluid
> transport and chemical reactor.

Wow.  I really enjoyed this post.  Just purchased the book you

But I think you're being too modest here.  I've never seen your
"modular approach", possibly because you consider the circuits you
taught your students to be individual modules themselves.  I always
considered your circuits to have attained that fusion of function
and form -- or, a mixture of components which act as a whole.  That
is, each component is used in a way that is not "wasteful," and
they are used together in a compact minimalism that always inspired
me.  Take, for example, the motor control circuits that you wanted
us to design at the end of your 2nd course, or even that
introductory power meter.

I'm just writing because I think you're selling yourself short. 
Your students (I've heard them talking, and I'm one of them) come
to think that a good engineer uses fewer components than a novice
engineer -- and the big joke in the labs at night was always,
"Damn, Kindlmann could do this whole thing with one resistor.  Now,
where would he put that resistor?" If we went and built a circuit
out of modules, we knew you'd frown on it.

[And yes, I understand/agree that circuits destined to become
products need to be modular in some sense, so that they're
simulatable/buildable/testable.  But you sure showed us some nifty


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