I have just bought the ArduPilot Mega 2560 Full Kit... plus the Triple Axis Magnetometer HMC5883L. I should have it built over the weekend.. then i'm off to a my mates machine shop, and i'll make the splitter plate for the lower frame onto which i am going to fit the Ardupilot. the magnetometer i'll put on the tail as suggested. I am going to use my X-cell Razor 600E. For those that dont know its around the 50 size nitro heli.
Do i need to buy any other sensors i.e. the Sonar... i can fly a helicopter all day long but this is my first time flying one with stabilisation so any tips would be gratefully appreciated.
If this works well then i am going to try and use it on my x-cell gasser. i can get up to 20 minute flights with this. But i think for the time being a battery 600 is the way to go.
i'll post some pictures when i have it all together.
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I have been flying with HXT900 servos with limited success. I think they are too jittery and too slow to work well with the flybarless head and the APM. What do you guys think? What servo's are you using? I am thinking about ordering something else.
Well, I just went out and hovered 2 packs out. It was absolutely BRILLIANT! Just superb. Keep in mind this is with no gyro, and with flybars, but I've got huge paddles on so it's quite responsive.
I had centered the servo and positioned the servo slider to place the tail rotor at zero pitch. This appears to have been the wrong thing to do. Soon as I got light the first time I had to feed in lots of right rudder. I started trimming it, and ended up almost maxing out my trim. I wasn't expecting this as I was flying in stabilize mode, and I expected it to operate like a heading hold gyro. It didn't seem to. I don't know if it would have kicked in at some point, but I basically had to hold it in place myself.
After the first pack, I moved the servo tray slider over to give it some pitch when the trim was at zero. On the second pack it was much better. I had to input a couple clicks of left rudder from center, and at that point it was rock solid. Again, I would have thought that with the trim centered, it would hold like a heading lock, but it didn't. With a couple clicks left, it was perfect and didn't move unless I told it. Well, I'd like to reserve some wiggle room in this statement for more testing. It might have moved a bit with some pitch pumps. I'll have to test more.
And that's all with my .03sec stupid fast servo which would help. And this is with whatever PID settings I had the first time out. I never touched it. No hunting either. My Flymentor always hunted. Stable stable stable.
The cyclic performance was pretty good too. It was dead calm, which helped. I needed a few clicks of trim which isn't surprising. It was easy to hover the 600 in a 5 foot box, or maybe 2 feet if I really concentrated. (the tail was distracting me a bit). I spent the first pack in an empty cul-de-sac in my neighborhood, with training gear on. For the second pack, I moved to the back yard. Here, I made the mistake of putting it in acro mode. When I took off, I think the training gear was stuck in the grass, something happened and I got into a violent oscillation. I'm guessing the rate PID isn't right. I set it down quick, flipped to stabilize again, and all was well.
I may be feeling a bit of effect of the flybar as sometimes there seemed to be deadband, then it suddenly responds with a bit of a jerk.
I basically spent the pack blowing the leaves around my yard with enough control that I could go exactly where I wanted. I'm not *that* experienced of a pilot either, so I was really impressed.
Overall, it was really impressive. Way more stable and confident feeling than the Flymentor was.
I have a few questions now but I'll write them down later.
Last night Randy and I had a long Skype call and worked through a few issues with the program and setup. Today I went through my setup again and I think I'm finally happy with how it's all working. Randy, I set it up with the pitch reversed (it had to, to get the swash moving in the correct direction), and the elevator NOT reversed. So it looks like the slider is going the wrong way, but the elevator servo moves in the correct direction with stick movement, or in response to pitching the airframe down.
I played with the rudder servo settings for a bit, and got them working pretty well I think. That is *without* a tail servo! I set it up in the basement again with no main blades, just the flybar and tail rotor. Set it down on a board of wood with shiny paper under it (ie: slippery). I got it working pretty well. I adjusted the PID loops. I found the Yaw Rate P term controls the response of the tail due to stick movement in Acro mode. And Stabilize Yaw Rate P term controls the response of the tail due to stick movement in Stabilize mode. I got them roughly dialed in and I'm happy with it.
So, I'll put my blades on and do the blade tracking. Then maybe fly it. We'll see.
Maybe I'll wear a helmet though. :p
@Robert,
I've looked into the reverse pitch problem you're seeing and I believe it's just an unintuitive radio screen in the APMP which is at fault. When I go into the APMP's setup screen, Radio Input tab, I also see that the green bar moves in the opposite direction to my pitch stick. So when I pull back/down, the bar moves up. When I push pitch forward/up the green bar goes down. I've reported this to Michael O and he may correct the display.
We've talked a little bit about control interactions, a mixing table, and Randy's circling loiter behavior and I just wanted to link in a bit of reading material for discussion.
http://www.rcheliwiki.com/Swashplate_timing_mix
http://www.rcheliwiki.com/Swashplate_timing
http://www.helifreak.com/showthread.php?t=338329
I find this discussion interesting as "TT" says that with a Vbar flybarless controller, the mixing is not necessary. I can see how this would help, as the Vbar controller can react to interaction. I still feel that a feed-forward control will make the response better.
I also remember something about how, regardless of gyroscopic precession, that when you push the cyclic forward, and the heli moves forward, it also drifts a little to the right. It's stuck in my brain from when I was learning to fly a Blade CP. I don't think it has to do with the gyroscopic effects, but more to do with the airflow through the disk. But I'm having trouble remembering the details or what the name of the effect is.
Good find Randy!
Thanks for all your work!
Randy, I was trying to look into the problem with the tail servo not reversing. I see the parameter in APMP is HS4_REV, but I can't find any reference to that in the Arducopter program. Any idea? Is that an APMP only variable and it's called something else in Arducopter?
I loaded the 2.0.49 version onto the APM and tested alt_hold on the workbench. Due to the noise of the baro (values are jumping by maybe +- 50cm or more, which I think is normal for a pressure sensor) you can see the swash moving up and down when the heli is sitting still on the workbench.
I wouldn't like to do a test flight with this setup, because I expect the heli to jump up or down several meters and worry I will loose control.
Anyone good experience with Alt_Hold on baro only? Any good tuning ideas? What about the altitude_mix function? What's the standard setup of this? 100% baro?
So, I just wanted to post a couple pictures of my install. I'm pretty happy with how it worked out. The APM fits nicely on the radio tray of my HK600GT. I'm using a machined aluminum tray which is available from HobbyKing. I drilled it and mounted the APM using servo rubber dampers screws and locknuts. The receiver is attached with velcro on the other side. I really like this because it's like a sled, the whole thing comes out as a unit with only a couple connections to undo. The provided 5mm servo wires were not long enough so I needed to use some short extensions. I don't really like this for obvious reasons so I'll order some 12mm extensions when I buy my Xbee next week. I glued a small piece of foam on top of the Barometric sensor.
I would prefer just to have the APM turned around facing forward, and I found the discussion thread where that is explained, just need to flip a couple signs in an array for the IMU sensors. The only issue with that would be access to the USB port and CLI switch might be difficult.
You'll also notice the header where I plug in the sonar sensor at the back. Note how I painted the plastic seperator just to indicate which way around the wires plug in. Black/red/yellow. Just makes it a bit easier.
A couple things about the heli. It's an HK600GT as I mentioned, running a Turnigy T600 880kv motor running on 2x4S(=8S) 5000mAh packs. Turnigy SuperBrain 100A ESC. Turnigy MG958 servos on the cyclic and HV-3S servo for the tail (the stupid fast one). I would like to get faster servos on the swash plate when I upgrade to flybarless.
Here's where I mounted the components on the tail. Previously I made a new stabilizer out of sheet plastic which I painted red for visibility. I don't like the "Skeletor" look of the stock carbon fiber pieces.
I'd like to put something over the GPS sensor, but I need to find the right thing...
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