Getting more than I’d bargained for.

Both Phoebe and Zoe now rocket up to the sky at at least 3ms-1 when they should be climbing at 0.3ms-1.

The main relevant change is that both were flying with alpf 0 – 460Hz.  Reducing this to 2 (92Hz) with Phoebe yesterday got the vertical climb rate under some level of control, but the horizontal drift was back.  I’m assuming Zoe will show the improved behaviour at alpf 2 also.

Clearly there’s something in the accelerometer readings that’s integrating (after gravity is removed) to lower velocities than expected.  Then it dawned on me: sampling at 1kHz with the minimal low pass filter set to 0 means that >2g spikes could get picked up; with the range of the sensor set to ±2g, the value could overflow, resulting in the <0g values I’d been seeing.

A very quick test with Phoebe in a howling wind proved me right.  I tried it with Zoe and the result was better but a long way from perfect so more work required there, including fixing her broken arm before tomorrow’s engineering conference.  Oops!

3 thoughts on “Getting more than I’d bargained for.

  1. I was reading on your hassle with the elevation control – do you have a way of controlling the rotor speed? Because what I see is that you are getting only acceleration and no constant speed. The famous tp-fancontrol can be rewritten for those purposes.

    • like it detects sensors – if you have a sensor on your rotor – you can set a condition for it – the code is there – just needs tweaking.

      • Hi Yakob,

        Thanks for the suggestion – I do have elevation control, but I’m getting peaks in the accelerometer readings that are outside of the range when I swapped from soft platic props to hard CF ones; this then causes duff values, (gravity < 0!) and that's why the problem happens. Fixing it should be easy, there are several ways I can, so I'm just choosing which was to go.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.