Bunnie Huang
COLUMN
SPARK
y doctoral thesis advisor,
Dr. Tom Knight, imparted
upon me many valuable
pieces of wisdom. One
aphorism was “wrap
a computer around it”:
instead of making a system more perfect,
it’s often cheaper to use a computer to
compensate for the imperfections.
For example, instead of making
storage media absolutely perfect, it’s
cheaper to throw a rather sophisticated
processor into every hard drive or SSD
that can compensate for the natural
imperfections –
and the inevitable
degradation over
time – inherent in
physical storage
media. The laws
of nature conspire
against highly
ordered, perfect
systems, so it’s
cheaper and easier to accept the natural
state of things and simply compensate for
the bits that we find undesirable.
Motors are another everyday object
that are difficult to perfect, but essential
to everyday life. Subtle imbalances and
asymmetries of a motor’s construction
can lead to excess vibration and efficiency
loss. While solutions exist to ‘wrap a
computer’ around these problems, quite
often the computer and the motor are
two separate entities. However, in recent
years, Moore’s Law has progressed to the
point where microprocessors and sensors,
powerful enough to ‘close the loop’ around
a small brushless DC (BLDC) motor, can
be essentially hidden within the motor’sphysical size and power envelope. For
negligible extra power and mass, a small
computer can be wrapped around such
motors to make them behave closer to
ideal elements.
A good example of this principle in
practice is a motor recently launched
by a company called IQ Control
[hsmag.cc/PDfUpM]. The smart BLDC
motor incorporates a computer and
sensor suite that enables it to consume
20% less power, while delivering 5%
more torque. The internal computer
also delivers smoother rotation by
remembering the
unique torque
ripples inherent
in the motor,
and inverting
the ripple during
normal operation.
Drone enthusiasts
reading this issue
would also benefit
from the faster response time enabled
by the internal computer, allowing the
motor to reverse direction much faster
than conventional ESCs that rely solely
on back-EMF for feedback. The net result
is a more manoeuvrable drone, that can
do tricks and flips without losing as
much altitude.
One of the great things about computers
getting so cheap and small (like the
Raspberry Pi), is we can now use them to
improve imperfect things with minimal
overhead. Whenever I encounter a physical
engineering problem that’s chasing
perfection, I take a pause and consider- could I wrap a computer around it and
make it better for less?
Wrap a computer
around it
Or, how to build a better drone motor
Bunnie Huang
Andrew ‘Bunnie’ Huang is a
hacker by night, entrepreneur
by day, and writer by
procrastination. He’s a
co‑founder of Chibitronics,
troublemaker‑at‑large for the
MIT Media Lab, and a mentor
for HAX in Shenzhen.
M
The laws of nature
conspire against
highly ordered,
perfect systems@bunniestudios