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Tuesday, 8 April 2014

Adding a 4dof arm to my Autonomous Rover - Now I have to learn Inverse Kinematics
My wife has said for the past several months, that she would only be impressed with my "toy" when it was able to bring her a glass of wine... 
Sounds like a challenge to me...

So I set about acquiring, assembling, and getting  a  4dof (degree of freedom) arm  attached.  It is neither powered nor operational today, but I am in the process of understanding the art of Inverse Kinematics.

Note: I had initially called this a 5dof arm, thinking the open/close action of the grip was a degree of freedom. I stand corrected.

While at rest, the arm is tucked up and out of the way.  It rests mechanically upon itself so I can remove power.   It is not very clear in this image, but the arm at rest does not block either the front Sharp IR Sensor nor the OSLRF range finder.

 I am currently reaching out to my friends at LetsMakeRobots to understand what sensors I need to make this both a reliable and useful robotic arm.

Consensus is:
  1. Electrical current sensor on the 5v rail feeding the servos to ensure that we do not damage them with weight.
  2. Tactile Pressure Sensor or Flex Sensor  on the fingers to grip the glass.
  3. Accelerometer so we don't spill the wine.
  4. And of course rubber grips.

The Raspberry Pi Camera is able to see and webcast the entire range of motion of the arm. I *assume* that at some point in time OpenCV can help guide the manipulator.

Please let me know if you know of any good resources I should be looking at, or any "must have" sensory feedback I must include.

I will be updating this post over the next few weeks as this gets hooked up and active.


Wikipedia:  Inverse Kinematics
Wikipedia: Degrees of Freedom
LearnAboutRobots: Robot Inverse Kinematics 
Society of Robots: Robot Arm Tutorial
Robotic Arm Inverse Kinematics on Arduino (with sample code)
CMU.EDU: Mathematics of Inverse Kinematics