raspberrypi.org/magpi The Official Raspberry Pi Projects Book 49
hardware is a very different
process.” One difficulty encountered
was in interfacing Dynamixel servos
with the Acrobotics components
that make up the robot arm. “This
gave me the opportunity to use 3D
printing to build components to
solve this problem.”
Another challenge was making
the arm movements precise. “In
a perfect system, the movement
of the arm could be modelled by
a simple math equation, but due
to inaccuracies in measurements,
and unexpected real-world effects,
this simple math equation model
broke down. It did well, but not well
enough to consistently grab the
piece every time.” Joey solved the
issue by collecting a dataset of arm
movements to see where the model
was having problems. “The results
worked well and the arm can move
very accurately now.”
The Raspberry Turk took Joey
around five months to build
and the process has been fully
documented on his site. “I knew I
wanted to open-source the robot
and describe the build process
on a website from the beginning.
I started this so I could use material
I had learnt in a real project, but
documenting the build process gave
me the opportunity to help others
learn, too.”
Asked how difficult would it be
for other makers to replicate, Joey
replies: “If you’re comfortable withsome electronics, programming,
math, and some simple handiwork,
this project would be a big
challenge, but is definitely doable.RASPBERRY TURK Projects
Below The
arm’s Dynamixel
AX‑12A servos are
controlled by the
Pi via an ArbotiX‑M
Robocontroller>STEP-01
Make a table
The Turk is built into a small 3×3 ft
(91×91 cm) table. A box on one side
houses all the electronics, while the
robotic arm is mounted on top.>STEP-02
View the board
To evaluate the positions of the pieces,
a top-mounted Pi Camera Module
captures a view of the board which is then
perspective-transformed using OpenCV.>STEP-03
Move the arm
The arm’s motion is controlled by the
rotation of two servos attached to
gears at the base of each link. Another
servo controls the gripper mechanism.BUILD A CHESS ROBOT
The code I wrote for mine is freely
available. The website explains
how everything works in detail and
I am happy to answer questions
for anyone who wants to take on
the challenge. Several people have
already reached out, telling me
that they are working on building
their own!”
While the Turk hasn’t been
showcased in public at the time of
writing, Joey says the response of
those who have seen it has been
interesting. “Reactions are usually
positive, but then they quickly
change to shock when they realise
the robot isn’t just playing them,
it’s beating them – badly!Another challenge was making
the arm movements precise