Hey gang, thought I would just start a thread on a retrofit I'm doing on a Fury Ion camera ship that I'm going to take into the Arducopter realm. I've got my 3DR hexa running pretty well but need to use the Ion for much larger camera work so it's time to rebuild. Just as a bit of background I've been flying traditional helis for just over a decade 6 years of which I've been a team Hirobo pilot.
Currently I've got an APM 2.5 with a ublox GPS integrated along with a 3DR radio. The Ion is running 700 Radix FAI blades and the stock flybar and paddles setup. I removed the paddle weights I was using for manual AP work. I'm using the stock Ion motor (Hacker C50-15XL) on ~20/1 ratio at ~ 1700 rpm.
I've currently got stabilize mode working fairly well. One point of note, when doing the mechanical setup I noticed that there's not a whole lot of rudder throw once the servo is setup with the stock PIDs. I changed the Rate PID to 1.25 to get the throw I thought was correct but that was NOT a good idea, had serious tail wag issues. For the experienced heli pilots, trust that the throw in flight will be close to right with the stock PIDs! I'm currently set at .350 P for yaw rate and dropped the roll/pitch stabilize values from .700 to .550 to get the airframe to settle into a reasonable hover.
More to come as I get a chance to test GPS hold.
Replies
Guys, still ran into the "wanting to run away" issues. I changed out my ublox for another one to test. then I did a bit of interesting testing I thought I'd share.
1) Setup and turned on the Ion (remember this is a trad heli) and sat it with the rotor head so that the blades were 45 degrees off the center line of the copter and the flybar was 45 off as well the other direction.
2) Let it sit for about 10 minutes with a clear view of the sky (I was actually on a roof top) had 8 -9 sats in steady state.
3) without the throttle connected, I armed the heli, put the collective up to about 50% and switched into loiter mode.
4) let the heli sit and watched the swash. I carefully move the heli about around the horizontal plane to verify that the swash was attempting to hold position, watching the ground station to verify GPS track was showing the right movement. All is good.
5) I then set the heli back down and left it for about 60 seconds, swash motionless and heli still thinks it in loiter holding a good position.
6) I then manually spun the main rotor. As soon as the main blade passed over the GPS sensor, I saw it jump on the ground station to a spot about 20m away (random direction.
I tried this 3 times with the same result (random direction changes tho.
In my mind, to say that the rotor disk isn't affecting the GPS accuracy is highly dependent on other factors, I've at least convinced myself that trad heli with this setup isn't going to do what I want with GPS. I've not tried moving the GPS sensor to anywhere else on the heli.
Since thismachine is older anyhow, I'm going to retire it and am building a monster octo to replace it. I'll start a build thread on that separately. Thanks for the help on this guys....
Uploading a log of the last testing where I was able to replicate the problem I tried watching several times with different graphing going but can't seem to find the source the problem. It seems like while armed and flying all of sudden the GPS thinks it's somewhere else. Any thoughts?
BTW I have the video TX off, only thing on was the 3DR radio so I could see what was happening while attempting to fly it.
2013-03-14 12-01-28.tlog
Rob = Guru.
Rob the PPM encoder update made a huge difference.
Next question since you've been spot on all the way:
I've noticed attempts to run away intermittently in position hold and associated with those instances the GPS position (trail of the individual flight) in MP shows a huge error in position ie it shows it having traveled 200 feet away when I've been hovering 20 ft in front of me the whole time. To correct I have to land, dis arm, re arm, and then take off and hover and it will usually be fine the second time around. I'm using the UBLOX GPS unit.
If I have this mounted above the APM and under the blade disk could that be part of the problem? There's not a whole lot of heli that is not under the blade disk so I'm a bit at a loss on where to mount it.
Any thoughts on what would cause a wide GPS error intermittently?
BTW if it is locked in, I've not noticed any big errors, it either starts funky or starts and position holds cleanly.
Any ideas?
Got 4 minutes (all I could stand in the cold) of GPS position hold in one spot in winds gusting from 8-15 mph. With just a little drift it did seem to hold position pretty well. I was managing the pitch and that ballooned with the wind gusts but it feels like it's coming on now. The firmware update to 2.9.1 and the gyro foam seemed to help a lot. I think I'm going to work loiter PIDS a bit and then work on altitude hold and full loiter testing. The ff values definitly helped with control authority. I do notice my tail seems to aggressively correct about 5 degrees or so periodically.
Is it safe to assume that's an yaw I term adjustment needed?
I've been watching the compass on the ground station and it seems to be pretty close to what I'd expect. I did turn off auto declination and manually input the settings which seemed to work better on this thing.
More to come.
Any ideas where I went wrong?
I got the Heli working ok in stabilize mode but the jitter seems to be coming from the apm unit output.
Great to hear. Good luck and let's see some pics when you're ready!
I'm based in Japan and I've run into a couple of Hirobo people at a UAV conference. They seem to be working on a full size competitor to the Yamaha RMAX...that's my understanding anyway.