PANTS • THE CHRONICLES OF PARTICIPANTS • THE CHRONICLES O
Digilent provided us with the crucial items: a
Cerebot MX4cK board (Microchip 32-bit PIC);
Cerebot Nano board (Atmel eight-bit ATMega168
microcontroller); accelerometer Pmod; gyroscope Pmod;
and two 2. 4 GHz RF Pmods.
We used the Cerebot Nano as the control board on
the glove, which transmitted all of the information
obtained from the sensors on the glove to the Cerebot
MX4cK board. This was connected to a computer and
used for displaying the interpreted results.
So, how could we translate hand
gestures into readable letters? The idea
was to mount the accelerometer and
gyroscope — better known as an IMU
(Inertia Measuring Unit) — on the back of
the glove to obtain the hand's position,
and then read the position of each finger.
Sounds simple enough, right?
Obtaining the finger positioning was
easy enough. Initially, we wanted to use
resistive flex sensors that changed their
resistance according to the degree of the
bending of the sensors. However, the
time to complete the project was limited,
so waiting two or three weeks for the flex
sensors was too long (taking into account
that the contest was going to take place
in one week).
In our search for a solution, we found
that by just placing contactors (simple
buttons, in our case) on the tip of the
fingers, we could get pretty accurate
results. So, we decided to use these as a
temporary solution. Simple, right?
Well, when it got down to obtaining
angles (pitch and roll) from the IMU, it
got a whole lot trickier. Even though a
gyroscope is very precise, it tends to drift.
On the other hand, (no pun intended),
the accelerometer is a bit unstable, but it
doesn't drift. By using these two
combined and with the help of a Kalman
filter (which basically predicts with very
high accuracy the needed pitch and roll
angles), we obtained the hand's position.
Having all this worked out, it was easy to
interpret the results obtained from the
sensors and use them for whatever
The acquisition board with the Cerebot
Nano and the RF Pmod connected.
SERVO 12.2012 59