HMArnold
Second Officer
Flight distance : 24012 ft
United States
Offline
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Doug,
That's a sad story, and other than words of solace the only thing I can say is that I have a Phantom 2 Vision Plus, and when I first bought it, I thought it was the most amazing device I had ever seen for both maneuverability and stability.
I liked it so much I wanted to get into the agricultural imaging business and purchased an S1000+ setup with gangster white-walls... A2, Lightbridge, IOSD Mk II, Datalink 900, and a Zenmuse Z15 gimbal.
After getting everything set up and seeing it fly, I thought the Phantom was old potatoes in terms of stability.
Maybe it's the 8 rotors, maybe it's the increased radius of the rotors, maybe it's the increased lift to weight ratio - I don't know, but its is a very stable flying device.
There is much less normal wobble than on a Phantom, with much less wandering with everything in neutral.
The only wobble I have ever noticed is when I'm at altitude and ready to come down, a full down throttle causes a wobble, but I have always figured that the motors and IMU like up better than down, so when I see the wobble, I just set the throttle to a little less down, and everything evens back to normal.
Everything else flight-wise has always been great. Distances, hovering, spinning, high winds, using the IOC "HOME" mode if I get so far away I loose the Lightbridge image on the monitor, etc.
A DJI forum acquaintance of mine, Gary Francis, has an instability at certain distances from the home point when he's flying in POI, but as I understand, no loss of control yet, and only in POI.
There are many things I wish I could change with the A2, like the fact that if you are headed home and ever accidently have both the throttle and pitch joysticks in the down position, you have just shut down the system and it's a dead weight coming down. For me it was only about 20 feet up, but it was over cement and I ruined a Z15 gimbal and caused so much damage to the S1000+ that I just bought a new body and moved over everything else.
Was that at least partial pilot error? Probably
Do I wish that something inside the A2 said "don't accept a shutdown command until you're either within 1 meter of the altitude your took off at or the motors are in idle with absolutely no movement in any of the 3 directions (landed)" - Yes
My plan is to get the Z15 repaired and to over time fix the crashed body, then buy a second A2 to give me a flyable platform without video feedback.
If your platform is totally inoperative you might never get the chance, but the first things I would look at would be the A2 System definition that says where the IMU is mounted in relation to the platform , and center of gravity. It sounds like what happened to you is a harmonic oscillation that the A2 couldn't overcome, and the only way I can think of that causing a wobble that increases would be a motor failure, which you probably would have noticed if you were looking at it, or center of gravity problem that caused the A2 to try compensating for one motor, then when that didn't move the platform in the correct direction, go back the other way, but a little stronger. Then noticing that pitch/roll problem, re-compensate back to the first motor, but even stronger. I can see where this harmonic oscillation could build to a point where the A2 could no longer react fast enough and over she goes.
Keep in mind that the center of gravity is affected by both battery and camera placement, so even if you were in balance sitting on a table before you mounted the camera, the added weight off-center would cause the A2 to over compensate to make pitch/roll corrections.
Also, the smaller the radius between the rotors and the fewer the rotors, the more pronounced a center of gravity problem would be.
If you still have the craft, and haven't taken it apart, see if holding each pair of opposite arms makes it hang perfectly straight.
I wish I could do more to help
Maybe we could start a "$2500 Zemnuse Boneyard" club of some kind.
Anything else I can do to help, let me know. |
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