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.
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.
hmm..jitter could come from at least two places. Either the controllers are changing their mind a lot about what the output to the servos should be, or perhaps the servos aren't happy with the update rate.
I've always found that the servos hum a bit when connected to the APM..much more than when connected to a normal radio but it's never caused me any problems in flight.
Could you try reducing the RC_SPEED parameter at least to see if the jitter goes away. I think it's 125 by default for the heli and you can find it in the mission planner by clicking Configuratino, Standard Params, Adv Parameter List.
Paul, can you look in your parameters, and see if AHRS_GPS_GAIN is set to 1, or 0? If it's 1, that is likely the problem. In that case, try arming the copter, and see if the jittering stops. Please report back.
Another possibility, when you say jitters, do you mean that when sitting still, they are moving? Or do you mean that when you move the stick, the movement is not as smooth as you'd expect? If that is the case, I think it's "just the way it is", the APM isn't updating the servos as fast as an Rx direct does. Either that, or we've lost some precision somewhere, because I've noticed it too.
Hey thanks for the Response!
For the jitter, the behavior I am noticing is that while sitting on the bench, motionless with TX on and heli ready to run minus ESC batteries connected (running opto isolated on 10s), the swash only servos (just those three) are moving back and forth very slightly and rapidly, you can very faintly see the swash buggering side to side if you watch it closely. The movement is very small and rapid, almost as if the servo isn't finding center. I checked all three into the RX directly bypassing the APM and each sits perfectly even under load when direct connected to receiver. I'll check the AHRs config when I can get back down in the basement tonight and report back. I'll also check the memory tracking you mention below and try to get screen shots. Thanks again for the help!!!
Ok, I'm 99% sure that this is caused by AHRS_GPS_GAIN being 1.
The only problem is that the default wasn't set to 1 until after 2.8.1 went out. So it's weird you'd see this unless you are flying from GIT code?
Ok, then that's weird.
If you look in the HUD on MP, is the artificial horizon moving when this is happening?
Is the jitter you are talking about *really* small?
No it's not (first thing I was looking for) which is even weirder (is that a word?).
I pulled the board, checked the solder connections, and decided to add another spacer (plastic) below the rubber ones I'm using to screw the board down to the carbon plate I'm using to mount it. It's four screws into plastic standoffs, in a stacked config, I'll try and shoot a pic shortly.
Whats weird is that I took all the mounting stuff off, and placed the board temporarily on a piece of plastic spaced 1 inch off the carbon mounting board, no change.
When I added some 3mm spacers and the original rubber grommets and remounted to try again, the jitter was not gone but noticably less. I'm starting to wonder if I'm getting some weird ground plane/resonance noise from using a CF mounting plate below the APM? There's plenty of space in both scenarios below the board and no shorting connections to the CF plate (been through that dance before with std RC electronics).
It's truly weird. I'll try and get after it again tonight and see what else I can come up with.
I also graphed the three servo outputs using the above suggested graph technique, it didn't seem to show any movement, (not rapid) but every so often there'd be a 1 -2 point jump (infrequently) in the PWM output numbers.
I'm becoming convinced there's noise being induced somewhere on the output leads for the APM....
I'm wondering if I shouldn't just bite the bullet and machine up an acetal/delrin mounting plate for this thing and take the CF out of the picture completely to eliminate that possibility.
BTW I'm using a CCPro BEC set at 5.4volts and checked the power output with a voltmeter (scope wasn't working) it didn't seem to budge or fidget under any light load (usually you see flickering on the numbers and the LCD scale moves).
No, you shouldn't need to do that. I have the APM mounted right on top of CF on my 450, no problem. (no, not touching...)
Another idea, do you have telemetry running? Xbee or 3DR Radio?
I used to have a problem with the Xbee and my rudder servo. The servo moved in time with the Xbee transmit pulses.
Check for that.
Good idea, I'm using the 3DR radio and it's ziptie mounted to the carbon swing arm for the camera boom. I'll try moving it around and see if that changes it.