Inverse Kinematics: Part 1

Pen was put to paper today (and yesterday) to start to understand exactly how Hexy moved. Because I'm well aware just how little maths can fit into my brain at any one time, I decided to reduce the scope of the problem considerably from a whole robot to just part of one leg. This means that instead of having equations of motion/ position that have 18 degrees of freedom, I only have two.

[WARNING: maths in post]
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Early Update

Managed to get Hexy up and running on Sunday. Build took a little over 4 hours including some breaks. No major problems; built one leg part inside out and had to reverse part of the body to get the screws to bite.

Monday saw some failed attempts at making the Bluetooth work. Started to hack through the ~10,000 images that were taken by the pair of DSLR cameras that recorded the build. Had a challenge from my colleagues in the office to have it set up doing the Thriller dance at the end of the week, so spent the evening learning PoMoCo with a little python.

Tuesday has been spent designing a stand for practice moves, plus yet more hacking of images from the time lapse. Might see if I can get either Bluetooth going, or work towards some Saturday Night Fever dance moves...

Creative exercise

Once Hexy is up and running, I have had a thought to make a parody movie trailer akin to Arachnophobia or Eight Legged Freaks. Possible title Six Legged Freak?

Smart Phone Controller

Cunning idea might be to use the accelerometer of a phone top control the Hexy's body rotation. In a static standing position, use inverse-kinematics to replicate the angle with respect to vertical of the Hexy's body to mimic measurements taken from phone.

Targets for Next Week

Week off work booked. What am I going to do with my time? What do I think I can get done? What's going to be a stretch? What's going to happen later?

Targets to complete:

  1. Build the Hexy kit.
  2. Get PoMoCo working and move Hexy about with USB control (Ubuntu lappy).
  3. Get Bluetooth control working from my lappy (Ubuntu).
  4. Get feedback from the ultrasonic distance sensor/ move the head.
  5. Publish construction video.
  6. Take some photos and get them published.
  7. Make stand for Hexy to sit on so that legs can move freely.

Stretch goals:

  1. Make kinematic model of Hexy.
  2. Communicate with Hexy via Bluetooth from Android handset, perform basic moves.
  3. Get ultrasonic distance readings reported back to Android handset.
  4. Do some Inverse Kinematics (on paper or otherwise).
  5. Something, something, something Android app...