Robot – North-facing Teddy with CM-900

Another experiment with the Robotis CM-900 and my Arduino ADK. This time it’s using a Pololu MinIMU-9 v2 and three Dynamixel AX-12A’s to try to keep the little teddy bear straight and facing North. Sometimes the sensors get a bit confused and the actuators follow to create interesting circle patterns. But overall it seems to be working ok.

Some things I learned;-)

• Don’t try to put a compass sensor too close to electric motors;-) When you think about it, it makes sense. But I needed a while to figure our why the sensors delivered different/strange values whenever I tried to turn the motors on.
• Also acceleration/deceleration would need some extra considerations to make the movements somewhat smoother.
• The ADK seems to be happy being supplied with power through the `reverse’ USB connection from the CM-900. I’m not so sure if that’s a supported feature, but it seems to work OK.
• Using human readable lines as the interface over the USB connection makes testing the pieces easy. But parsing them needs some effort. I had to modify a sscanf() function source for the CM-900 because the normal libc version would pull in to much and create a too large image to upload:-(

Here are some more images of the setup.  The two source projects are here: Robotis_Pan_Tilt and Robotis_Pan_Tilt_CM900

As always, have fun combining things;-)

— Marco