This binocular head was designed by Sébastien Menot during a 4 month diploma project ended in February 1998. The goal was to build a eight Degrees Of Freedom (DOF) stereo platform embedded on a Koala (©K-TEAM): each eye has three DOF (pan, tilt & cyclotorsion) embarked on a 2 DOF neck (pan & tilt). This project is the continuation of the EPFL Vision Sphere already built by Sébastien Menot in 1997. The EPFL Vision Sphere was limited to a monocular view that restricts its ability of perceiving the depth. We, the Biovision & Robotics Group, are interested in perceiving the depth cues on an autonomous mobile robot. The constraints were the same : small size, power efficiency and high acceleration performance. Nonetheless, two new constraints were added : maximized the mobility and minimized the control algorithm complexity.
Design
The originality in the design of this platform is the smart parallel mechanism that control the elevation and azimuth of the camera. This mechanism is close to the Agile Eye built by the Robotics Laboratory of the Laval University. The main difference is that our parallel structure has only 2 DOF (+/- 90o) and the third DOF (cyclotorsion) is embarked on it (+/-90o). The result is a simplification in the coordinate transformation : the azimuth is directly obtained from the corresponding motor shaft encoder and the elevation is calculated by a fonction of the two motor shaft encoders. The neck is based on a serial pan-tilt mechanism (motor on motor) enabling an important mobility (+/-180o).
The pan & tilt motors for the eyes and the neck are all Maxon
motors. The cyclotorsion motors, the smallest in the system, are from
Minimotor. The two embedded cameras
are the same as the EPFL Vision
Sphere (i.e. V-1210 from Marshal
Electronics, Inc. ). All the mechanical parts have been worked out
in LAMI and with the collaboration
of EPFL Microtechnics and Electricity Workshop.
Results
At the end of the project, the EPFL Vision Sphere can be remotely controlled via a serial link from any computer. The control board is the same as previous work (EXT336 board) and simple PID control algorithm have been designed on it for all the eight DOF. This prototype still needs some improvements that will be done in a near future.
This project received three industrial awards :
© Sébastien
Menot 98 Last Modified : 8/9/98