Motion tracking*

or Motion flow – the ability to track motion direction and speed – in this particular case, to fill the gap between the point where integration / calibration errors in the accelerometer are too large and the point where GPS becomes useful.

Here’s my overview of what’s required.

Altimeter / Baromoter – needed for level flight beyond the time frame that integrated accelerometer readings can be trusted – interesting because these two sets of data come from separate reference frames, and will need moving to the same frame, and merged with a complementary filter.

Compass / Magnetomer – needed for orientation and another source of pitch, roll and yaw angles because the compass has 3 axis so you can detect reorentation of the quad wrt the static location of the earth’s magnetic core.

Motion tracking – needed to track distances / directions beyond the scope of the integrated acclerometer readings’ accuracy and the point where GPS is useful:

  • RaspiCam per frame video movement vectors is the raw data (units of pixels measuring rotation, direction and distance traveled per frame, but then this needs to be interpreted from pixel movement into real units requiring
  • details of the lens focal length – i.e. how physically large is landscape the video is capturing at a given height from the ground meaning we need
  • height above the ground measurement – barometer will do for level ground, ultrasonic proximity will do for sloping / uneven ground, GPS will have to do beyond the scope of the ultrasound
  • Angles of pitch and roll – what the compass can kindly provide.

This definitely is sounding like a project of it’s own right, but which can be done in lots of little increments, some of which can be applied directly by adding new sensors to Phoebe / Chloe, and others done independently using one of my raspberry pi’s already decked up with a RaspiCam.

I’m starting to get excited by this as it allows me to progress while I wait for someone to come up with a half decent design for the MPU9250 + barometer to site on Chlöe’s Beret**.

*See these bits and bobs for more details.

**Beret – Breadboard Replacement Technology – A non-conformist HAT, lacking EEPROM, CSI and DSI slots.  Chlöe took offence at me calling her a Mad Hatter!

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