[Skip all this and jump straight to the
earliest entry]
In the spring of 2001 or thereabouts, I was bored on a train ride going
to a convention, and my thoughts wandered toward trying to fathom the reasons
that many electric vehicles of the time were using AC induction drive motors.
There *had* to be something better, something more controllable at low speeds
and better suited for efficient regenerative braking -- perhaps a design
similar to the Hall-effect switched DC motors found in computer fans, but
with either a slip-ring fed rotor field winding or permanent magnets, and
smarter control. I figured the semiconductors and some switching smarts
could mount right inside the housing, and it would thus be possible to build
a very smooth, efficient and reliable plug-and-go traction motor whose only
connections would be main power and a PWM input lead. With enough poles,
losing one power transistor wouldn't be a showstopper -- the remainder
could simply continue powering the motor to limp home, just with a bit of
torque blip every time the bad phase came around.
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As the train's own diesel series-hybrid system pulled it onward through the
NJ pine barrens, I doodled out a sketch of a six-pole rotor spinning in a
seven-pole stator, and a set of MOSFETS to pulse-width-modulate varying
currents into the stator windings as the rotor turned and activated position
sensors. But I couldn't come up with the right way to switch windings at
first. To finally determine the switching order, I made a paper cutout of
the rotor so I could spin it relative to the stator and figure out which
coil[s] had to be on next and in which polarity, and drew out all the winding
waveforms in time. The result was basically a stepper controller gone
horribly wrong, but from that emerged a surprisingly simple pattern. It
was all a very silly way to pass the time, but took me one more step toward
an interest in modern motor control.
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I never really managed to figure out how to change directions, or how to
fiddle the switching vs. rotor position to recapture energy by regenerative
braking. I sort of lost interest/time at that point -- too many other
projects to deal with first. Something in the back of my brain told me
that the EV/hybrid people would eventually come around to using more
sensibly-controllable motor types, but it would take a few more years
because they were still out there losing away with off-the-shelf parts and
controllers -- cheap and available, maybe, but not really designed for the
purpose. In fact, by then the revolution had already started, but I wasn't
aware of it yet.
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Times sure can change, can't they.
I now own a Prius, after thinking for years that they were too small, too
weird/complex, too this, too that. In around February 2005 the concept
of replacing a somewhat unsatisfactory generic wagon with *some* sort of
hybrid began grabbing a larger chunk of my attention. I started poking
around on the net for info on what might be available, and soon discovered
the many Prius and other hybrid discussion groups. I spent almost a month
just finding and reading information, particularly the more technical sort,
and along with that my overall view on several aspects of vehicle ownership
and usage began to change.
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To help me escape from the brief delusion that the hybrid Highlander would
meet my needs, I did extensive testing of the Prius and got to go spin one
around in snowy parking lots for a while. The result? I bought it, under
the full realization that not only would this be transportation, it was about
to become a long-term project. By the time I took delivery, many ideas
for modifications were already in the pipeline. And after another month
or two, I had become a total mileage geek.
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This is an ongoing chronicle of that process, detailing the many hacks,
theoretical discussions, reverse-engineering, ivory-tower guesswork, and
entertaining events that have come since then and will continue to happen.
It's not just transportation, it's a rolling lab! It's the first time in many
years that I've actually had any enthusiasm about a *car*, which for me is
saying quite a bit. This is my learning experience, which seems like
something useful to share with those who have similar interests. All of
my mods are fully documented along the way, in the hope that they will be
useful to others.
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Through this I have become that very person I kept looking around for at the
local alternative-transportation festivals -- the one who could help answer
those questions about hybrid drivetrains, motor control, long-term reliability
issues, energy conversion and efficiency curves ... Now I can teach other
people about it, and help encourage acceptance of more efficient vehicles
and consumption-aware lifestyles.
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Use this index to start.
The sections are presented in REVERSE chronological order, so that occasional
revisits will show the newest stuff first. If you want to read it from the
beginning as it happened, start from the bottom at file 000 and work back up.
Enjoy!
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_H* 050522
[A tarball of these files *may* be available as allfiles.tgz -- no guarantees]