Numa



Numa is a 4 legged robot (quad) with 4 servos per leg (4DoF = 4 degree of freedom). Numa is the name of the second king of ancient Rome, and was a good excuse for the intended purple/black color scheme. Currently the colors are instead a black/yellow scheme. And no, I don't particularly care if a charming overweight guy "dancing" to Dragostea Din Tei comes to mind instead.

At RoboGames 2012, Numa placed third! Reliability was a major factor.

There's a lack of exciting footage of Numa outside the below Mech Warfare vid. More film, mostly from testing, can be found on my Youtube channel.

Hardware specs of Numa

 * 4DoF per leg


 * 16 AX-12A servos in the legs, 2 AX-12A servos for the camera/gun turret


 * Axon MCU


 * Tristate buffer allows Axon to control the Dynamixel servos.


 * Can use either Xbee communication, or serial port communication


 * 11.1 V LiPo battery for servos, camera, xBee and guns; 7.4 V LiPo battery for Axon and scoring system


 * Trendnet TV-IP110W wireless G camera for remote operation


 * Carbon fiber chassis plates, side panels, and leg brackets


 * Dyed Bioloid frame kit pieces for other parts of legs.


 * Delrin 'pan' bearing for turret


 * Aluminum and delrin 4-bar linkage turret 'tilt' mechanism


 * Polycarbonate hemisphere from one of those dome ceiling cameras


 * Pololu dual motor driver for controlling power to guns


 * Two AEG gearboxes for guns


 * Two 3D-printed gun hopups, and other assorted 3D printed parts


 * Two aluminum barrels removed from Crosman Mini Airsoft guns
 * 2012 Mech Warfare scoring system (note: powered by 7.4 V LiPo battery)

Initial gaits (sequences of servo positions that result in walking, turning, etc.) were generated with Mathematica. Real-time calculations for omnidirectional walking have being implemented. The bot is coded in C, using WebbotLib with the WinAVR compiler.

Postmortem (2012)
Numa was reliable at Robogames, but otherwise minimally noteworthy. In particular, Numa was quite slow. This is due to writing my own IK implementation, and probably due to non-ideal leg design.

During testing, 4 or 5 servos were killed in the legs. This was avoided at Robogames, and the two probable contributing factors to this are (1) adding a crouch pose where the coxa servos' torque is disabled and legs rest against frames; and (2) not sending position commands constantly to the servos when not moving (theoretically avoids overheating resulting from servos trying to make very small position corrections every time a position is given).