Swapping motors, swapping problems

I’ve swapped the standard DJI motors + plastic blades back to the T-Motor + Carbon fiber blades; sure enough, no rocketting up into the sky, and once more I was able to complete a flight.  But…

all the old problems I had returned – excessive drift and yaw.

That suggests

  • the DJI motors are not powerful enough to manage the angular momentum of their heavier plastic blades
  • the T-motors are not all equal  – from the direction of the drift, I would guess the right-hand pair are damaged leading to drift and yaw.

So I have no choice but to buy new motors T-motors, and see what happens.  Hopefully that will sort things out and I can get back to real testing of my control software PIDs rather than diagnosing bizarre behaviour due to dodgy hardware.

So frustrating wasting my very limited testing time on something that turns out to be not my fault!

7 thoughts on “Swapping motors, swapping problems

    • No, partly because I didn’t think about it, partly because I couldn’t see any other possible cause – I was pretty confident I’d ruled out everything else.

    • Good thought – on the DJI motors, they are 10×4.5 DJI for 3S batteries so an exact match for my setup, although interestingly, I just checked and the 1045s are no longer available. DJI have released a new 10″ blade – a lighter, stiffer 10×3.8. Perhaps they found the same problem I’m having?

      The T-motors are used with 1150 (I think) carbon blades and there’s been no obvious problems with the motors struggling – probably because they’re carbon blades with more powerful 980Kv T-motors. But there is imbalance between the 4 motors – I’d suspected that might be the cause of the underlying yaw, and the drift from this morning is more circumstantial evidence of the same underlying problem.

      • Just to be safe (and rule out any other possible hardware causes) I’ve just bought some 1045 CF blades for the replacement T-motors as they seem to be affordable, and available in the UK

  1. How annoying!

    But what I don’t understand is that the PIDs should be able to take care of those imperfections/inequalities between the motors….?

    • They could, yes, if I had had the critical ones turned on – I only had the gyro feedback inner stability PID on – but not the one which ensures absolute horizontal flight. Gyros drift, and therefore so does the quad – you need the next absolute angle PID to kill the gyro drift, but I needed the test to be a match for the ones showing the manic climbing with zero drift from the DJI motors. It proved that point, but also probably proved the T-motors were duff because of completely consistent drift. I’ll soon find out if it’s money well spent.

      So the DJI has zero drift but manic climb suggesting motor overshoot; the T-motors has a much better takeoff but significant drift, suggesting no overshoot, but imbalanced motors. The last thing I need when tuning PIDs is hardware I can’t rely on!

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