Phoebe now has a foam dome glued to her underside:
It serves a myriad of purposes:
- it means she can now self-level prior to take-off to reduce take-off drift further
- it provides the ability to do initial PID tuning without the use of the complex test rigs I’d used (step ladders, strings etc)
- it protects the arms from any stress of horizontal landings
- it reduces the risk of the props hitting the ground from non-horizontal (aborted test flight) landings
So in general, a very good thing; I did have to rewrite some of the startup code to allow for the self-levelling while the props were starting up, but in doing so, the code changes grew to the extent I reworked the flight plan code such that now it reads an easy-to-edit flight plan, rather than the plan being embedded in the code. This makes changing flight plans on the fly (as it were) much easier.
Lots of test flights later, she now levels herself while on the ground, takes-off to a few centimeters (ground effect gives her a little extra lift – at about 10cm the ground effect ceases leading to a stable hover). She then hovers for a short while (not drifting), then ups the power to gain height. It’s around this point the drift starts. Luckily one of the updates to the code I’ve made is to change ctrl-C to be a full-abort (it used to just move to the next flight step). This means I’ve been able to stop her immediately when things start going wrong, and the dome means she doesn’t get any damage as a result of her free-fall landing.