Plan C = 3rd time lucky?

OK, so I’ve ordered another set of blades, due on Wednesday, so between now and then, I need to implement plan C – as Oscar mentions in his comment in the previous post, I should really have done some live testing with just one dimension free: essentially that means (when testing pitch PID gains for example),

  • tying both left arms to a heavy object, do the same with the right arms (different heavy object), such that the quad is dangling in free space and can only pitch.
  • starting up the quad to hover, and then if it’s stable, nudge the front end and check it returns to stable horizontal hover
  • tweak the gains as necessary
  • repeat for roll

I’d seen several videos of this being done online (can’t remember where sorry), but they looked like such a faff, I thought I’d do it via gut-feel / hand-holding.  Serves me right!

The other thing I need to do before this single dimention test is to add the code which, based upon command line parameters for the drone can either

  • calibrate the MPU6050 offsets and save then to file
  • do not calibrate MPU6050 offsets and instead read them from file or abort if no file found

I knew I’d need to do it sometime, as it’s needed for take-off from non-horizontal ground – I suspect dangling between two chairs counts as that!

Then there’s the final bit of faff on arrival of the blades: although they claim to be balanced, testing them with a magnetic balancer (near zero friction) always shows this can be refined further with time, patience and some P1000 wet or dry sandpaper.

Here’s goes, wish me luck!

P.S. I’ve just found some Graupner 10 x 5 propss which I’d used in some very early live flights indoors (the ones that hit furniture), and despite the unsuccessful test, only one blade has any damage (a tiny chip on the train edge of the blade); the rest are immaculate.  Even better, they are already balanced.  This means I can start testing once I’ve made the code changes; I’ve already identified the string and chairs I’ll be using!  Only downside now is the kids are on summer holiday, so timeslots for live testing are much reduced.

P.P.S. Between the two crashes I’ve had, I’ve just dug around and found a not-too-damaged set of 4 of the carbon fiber 11 x 5 blades, which means I don’t need to wait for the new blades nor use the Graupners, and nor now do I need to do the coding, as I’ve just finished it.  I’ve even identified the “heavy” objects as two garden chairs, so my only remaining problem is finding a time-slot when the kids aren’t around!

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