Yesterday it was a cold and frosty morning, but more critically, sunny with only a light breeze:
So I managed to squeeze in another test flight, where the plan was to fly ‘H’ between 3 GPS wayspoint frisbee-markers from a takeoff in between all three. As you can see, reality deviated significantly from the plan.
I’d made a minor change to the code such that the maximum horizontal speed was 1 m/s reducing proportionally as ‘H’ got less than 5 meters from the target e.g at 3m from the target, the speed is set to 0.66cm/s. That worked well approaching the first red frisbee-marker after takeoff. However the next phase, although heading in the right direction between red and orange frisbee-markers, was very unstable and ultimately overshot the orange frisbee-marker, so I killed the flight. Here’s what the flight controller saw:
RTF TAKEOFF HOVER GPS: WHERE AM I? GPS TARGET 6m -69o GPS TARGET 6m -69o GPS TARGET 5m -70o GPS TARGET 4m -71o GPS TARGET 4m -73o GPS TARGET 3m -75o GPS TARGET 2m -78o GPS TARGET 2m -82o GPS TARGET 1m -86o GPS TARGET 1m -90o GPS TARGET 8m 85o GPS TARGET 8m 85o GPS TARGET 7m 85o GPS TARGET 6m 84o GPS TARGET 4m 86o GPS TARGET 2m 93o GPS TARGET 2m -117o Flight time 20.242111
The green text is from takeoff to the red frisbee-marker. The yellow section shows a good heading towards the second frisbee-marker. It started at the right speed of 1m/s while more than 5m away, but the red lines show velocity increasing to 2, 2 and 4 m/s as H got closer to the orange frisbee-marker. On the plus side, she knew she’d overshot the target and had been told to double back at the point I killed the flight -check the angles at the end of the red lines.
Time to go bug hunting – it’s hopefully just a stupid crass typo on my part. Luckily, the kids go back to school on Tuesday, and the weather forecast so far is looking good that morning:
I hope by Tuesday I’ll also have worked out how to get better video quality from the Mavic!
P.S. No crass bug found, so my second best guestimation is that the LiPo cooled to below optimal performance temperature; this has the same effect as seen, and I had set the heater elements on the lowest level. The plan for the next flight is identical to before, but with the heaters on high and with full logging enabled in case this also fails and I need to diagnose in detail the source of the problem from the lateral velocity targets.