Given the popularity of the 230/250 quads at the moment (blackout etc), I thought - wouldn't it be cool to have a rig that can do the ground skimming proximity stuff, but also with the normal "mod cons" of the APM?
Traditionally though, an APM would never fit. Until HK released the mini...so I built one.
I started with the Haldey-Bocks 230 frame, in Carbon Fibre. This was a mistake. I should have gone for the 250, because the fitting of the ESC's was a bitch of a job, especially with the thick 3DR power module hanging off it. And naturally, I forgot to solder in the XT for the video feed, so had to start again...
Anyway, this is the bare airframe:
So onto the fun part...
First, I fitted the camera, so I could make sure the clearances were good. I mounted it directly to the front CF plate to make sure I had as much room as possible behind it.
Second, I mounted the GPS antenna pole. This required a lot of trial and error, but eventually I found a position which worked.
Third, I fitted the APM mini in front of the post, and behind the camera. There is *just* enough room to do this. It is currently mounted with double 3M pads - I will review vibe damping after the first flight. Supposedly the blue balls do the "clean/dirty" thing, but is it enough to keep the APM within Z axis tolerances? Time will tell. These rcx are not the smoothest I have to say, and a propless spin up was really vibey.
I wired in the GPS, and the radio.
Then I mounted the 3DR telemetry radio to the roof. It is likely I will replace this with a minimOSD, and run a really simple OSD - volts, ground speed and home distance.
I then cable-tied the xt60 back on on itself on the PM - it was interfering with the props.
CoG is spot on, even though I thought it would be rearward.
Weight with tx will be 505 grams as you see it here. I have a wiring exercise to do (shorten and tidy), and to enclose the APM with some foam (for the Baro), and I hope that brings it down below the target 500 grams.
And that's it! It all fits together nicely. All the normal calibrations done - just compassmot to do (want to wait until I've got the camera and tx wired in first). Going for a really small 200mW 32ch 5.8. Will fit perfectly.
I didn't have time to get the thing in the air, but should able to get it in the air at the weekend. Can't wait to use DRIFT on this...:-)
Comments
Hi all,
I just thought you would like a small update. I have been working on why Arducopter isn't working as well on the mini quads as it should. The good news is I think I have cracked it and the improvements should be out with the next release candidate.
(release candidates are not formal releases because they may have bugs and are there for testers to crash with them to find the bugs so use at your own risk)
The problem I found is the cut off frequency for the input filtering to the PID D terms is too low for these very small quads. Randy and I have updated the code so these filters change with the MPU6k filter setting the parameters. I am very happy to report that the difference this has made on my QAV250 using the setting of 42 Hz is night and day!! It is now rock solid, just like the bigger quads, and autotunes!!! Although I now have a couple of improvements to make to autotune as well now we have solved this basic problem.
The other big step forward is there is now a expo setting for ACRO.
Further down the track I will probably add a detune setting that reduces the roll/pitch (and maybe yaw) pid scaling as throttle is increased to help remove those high throttle wobbles. This is needs some cartful thought before it is done so it won't be in the next release.
So let us know how you find the next release when you get it. As always I would suggest waiting for the formal release.
So I have been monitoring this thread, amongst other Mini Quad APM builds. I am in the middle of a re-design, currently running the MHQ Hovership Frame(flex is just too great and the arms will start vibrating terribly at about 85% throttle. I have overcome the oscillation issue though. I see most of you guys are talking about raising the Hz on the LPF, we need to be lowering it. I dropped mine to 10Hz and noticed an IMMENSE difference in the throttle burst oscillations. Balanced props made a big difference too. Let me know if this helps you guys. I would love to see some more APM mini quads in the air, best of both worlds; small, fast and autonomous!
@Sevet – Any updates with your oscillations? I see on the whitespy mini thread (regroups) several look like their running with proper tuning. I don't want to resort to the very basic CC3d for my mini : /
I believe now that the control inversion happened more than twice, it was just twice that I was LOS and notice what is actually happening, the other times I was FPVing and though I was loosing control because of the flips and orientation so I immediately moved to stabilized to gain better control, A friend of mine told me it happened to him on a KK but he is doing more crazy maneuvers than me, I only started acroing some weeks ago.
Here is the post with the log:
http://ardupilot.com/forum/viewtopic.php?f=80&t=9019
Hey Shay, where is the log on that control inversion you were describing?
Thanks for PID's and nice video:-)
Here are my PIDs with the LPF @98hz:
PARM, STB_RLL_P, 6.2
PARM, STB_PIT_P, 9.3
PARM, STB_YAW_P, 6
PARM, RATE_RLL_P, 0.07
PARM, RATE_RLL_I, 0.3
PARM, RATE_RLL_D, 0.008
PARM, RATE_RLL_IMAX, 1800
PARM, RATE_PIT_P, 0.2
PARM, RATE_PIT_I, 0.3
PARM, RATE_PIT_D, 0.015
PARM, RATE_PIT_IMAX, 1800
PARM, RATE_YAW_P, 0.2
PARM, RATE_YAW_I, 0.05
PARM, RATE_YAW_D, 0
PARM, RATE_YAW_IMAX, 800
For a moment I though it's 100% but still oscillating on throttle, had this on a different Mini with Naze, there is a setup there called TPA which basically lowers the PIDs on throttle, I put this as a request from DEV on the git, I would really like to raise my PIDs even more but then it oscillate sooner on throttle.
Here;s the latest:
https://www.youtube.com/watch?v=OLMctzO6V7M
Still oscilates, this is only on stabilized, watch after 3:00 before that it's more goofs...
Anyone can say why I can't finish Autotune?
I tried Acro on a Mini, Putting the acro_rp_rate on the max 10 still doesn't flip fast enough, I added expo to my RC to be able to controll it.
also after a few flips my pitch was reversed suddenly and I almost crashed, putting back to stabilized fixed my pitch, this happened twice on two different flights. i opened a thread on this with logs on the ardupilot forum and also tried to open a thread on the DEV drone discuss.
Agreed. I would really love this. Good luck as well!
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