We're bringing up a 3DR hex for use as an autonomous UAV. In a nutshell, the goal is to be able to tell it "Haul the camera out to location x, take video of the area, and RTL" with no human intervention.
We started with Arducopter 2.8.1. The first time we sent it off on an flight plan downloaded with Mission Planner, it performed flawlessly, until it returned to about 18 inches above the launch point. Then it suddenly slewed off in an apparently random direction, hit the ground at an angle, and cartwheeled.
We think that what happened is that, as the copter landed next to our two-story metal building, it lost sight of some satellites, and the GPS suddenly said "Oops, you need to be over there, not here", and crashed trying to get there.
I was hoping this might be fixed in 2.9.1, but I've discovered that a lot of people are complaining about unpleasant surprises during RTL. I also found out that the code has been dramatically restructured, so any fix I come up with for one version can't be ported to the other.
So I need to pick one.
I'd like to hear from people who've either used both for autonomous UAVs, or are familiar with the waypoint-navigating and other autonomous-relevant parts of Arducopter, about which would be the better choice for building a reliable system.
And, btw, the change we're looking at making is to start ignoring the GPS at some point during final descent, and rely on either inertial navigation or something like an optical flow sensor to maintain the horizontal positioning. That should protect us from unpleasant surprises when the sensor suddenly changes its mind about where we are.
Ran
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Ran,
I've flown some auto missions on 2.8.1 but most of them have been with 2.9.1b. I can tell you that 98% of the time we have had no significant problems with 2.9.1b.
But, there was a time when the GPS suddenly thought it was about 250m from where it actually was when it was going between waypoints and the quad responded accordingly (we have the 3DR MediaTek GPS). We haven't been able to replicate the problem so we're not sure what the exact problem was (we had about 10 sats at the point with HDOP of around 1).
2.9.1b has been pretty good to us so far, but I do know that a lot of people have had GPS problems with it.
Not sure if this helps but thought I should put in some 2 cents!
-Jake