Wow, I haven't updated since July!
Well, work continues at USC. The motion capture suit
project is entering testing and verification. Currently,
we are testing three sensors (1 for elbow tracking, 1 for
shoulder tracking, and 1 for reference.) A few months were
burned designing an algorithm that fused the sensor
information using floating point quaternions that could
update at 100 Hz on a 8 bit, 16Mhz Atmel Mega32 processor
with 32k of flash! I tried 2 algorithms from literature,
Linear Gauss-Newton Iteration and a Quaternion-based
Extended Kalman Filter. Both failed, the first because of
a terribly slow 4x4 matrix inversion and the second because
of size limitations. I scraped them and developed my own
linear filter that works pretty well, although we are still
tuning the parameters. Since this project is funded by
DARPA, all of the info will be public domain, which can be
VERY GOOD NEWS for anyone looking for a very small IMU with
3 axis gyro, 3 axis accelerometer, and 3 axis magnetometer
for about 260 dollars in parts! If you are intersted let
me know, I can always let you see what I got.
The humanoid is coming along. I have one arm and the body
rapid prototyped and mostly constructed. I am most likely
going to modify the servos so that I can just talk to them
over a serial line using Atmel's cool addressing function.
This way, I can get positional information back from the
servo, and also program cool little functions like going
slack when the joint hits something. I should have
pictures up soon, I am waiting on the rapid prototyping
company to send a piece that they had accidently left off
of the last order, then I will have both arms and the body
constructed. I feel this will give a better representation
of the project, so I am holding out to take the pictures.
It is cool though! Work continues on the head design to
make it interactive and appealing, yet not scary to
children or us for that matter. It is bigger than everyone
expected, which wasn't very big since we are using digital
servos. The arms are heavy enough to have to worry about
inertia, etc. I think the size helps to distinguish this
robot from the others that look like toys. I do want to
invest a little bit of time over the summer developing a
smaller version that may be purchased for at or under $3000
using rapid prototyping, or under $1000 for bulk plastic
orders. I'll have to see if there is any interest for this
though. Plus, you never know what is going to happen since
I'll be graduating in June. There may be some good news,
but I can't really talk about it now :-)