Technical test of my new MR frame and gimbal

[R_Lefebvre]

Finally have something flying and working well. I took it for it's first real test on Sunday, and this is what I got:

When I looked at the footage, I was pretty happy with that. There's a tiny bit of jitter which I think is simply AlexMos tuning. And the horizon is horribly out of level sometimes, which is a problem with AlexMos, particularly when flying dynamically. But I was really impressed that I didn't get any wind buffeting at speeds up to 60 km/h. And the lens hood was on.

Has anybody else been able to fly like that? I have mostly seen hovering, and not much flying around with significant cameras on a multirotor with a stabilized gimbal?

 

[PeteDee]

Have a look at footage from the TBS Discovery Pro, Simple BGC but that is with a GoPro.

Pete

 

[R_Lefebvre]

Yeah, I've seen plenty of those videos. But I'm more interested in "significant" cameras. This is a Nex5. Youtube obviously murders it with compression so it might not be obvious. Though it's obvious this footage doesn't have fisheye. I do have to work on some of the settings. I just threw the camera on in full auto mode, and it was dusk. This was just my first real test.

It's also a compact Octo, so redundancy, etc. Just a completely different class of machine here.

The TBS DP is a nice machine though, I'll admit that. Wouldn't mind one for alternate uses.

 

[ovdt]

R_Lefebvre, I think the footoge you got is quite smooth.

Which FC are you using? Can you tell more about your setup? Thanks.

 

[kloner]

you have balance issues (horizon shifts with g-force from turns) and the bumping looks like vibration induced something. These cheap imu's hate vibration

the nex isn't much a significant camera in a month when hero4 comes out

Discos can carry 3 axis gimbals

 

[R_Lefebvre]

R_Lefebvre, I think the footoge you got is quite smooth.

Which FC are you using? Can you tell more about your setup? Thanks.

Thanks. It's Arducopter on APM. BLG is Alexmos.

Kloner, honest question, how is balance related to horizon drift? I don't really get that. I've had real trouble trying to figure out the Alexmos system. It's weird.

The bumping in that corner, not vibration, my frame has pretty much zero vibration. I think that is because the roll axis Z-CG isn't quite right. This typically isn't adjustable, but should be due to manufacturing tollerances. The pitch axis is good in X and Z, but the Roll axis is off a bit in Z. This in turn makes it's Y axis tricky to tune. I have to work on that.

But the drifting, I don't get at all.

We'll see how good the Hero 4 is. Maybe it'll blow my mind, but I'm skeptical.

 

[DennyR]

Rob
The horizon drift is caused be the Calibration not being set up right. Alex has the procedure on his web site.
Cross axis interference.....

 

[DennyR]

you have balance issues (horizon shifts with g-force from turns) and the bumping looks like vibration induced something. These cheap imu's hate vibration

the nex isn't much a significant camera in a month when hero4 comes out

Discos can carry 3 axis gimbals

Cloner
One month?
I have converted my 2 axis gimbals to 3 with a simple heading lock gyro and a fast servo. It is working fine.

 

[R_Lefebvre]

Rob
The horizon drift is caused be the Calibration not being set up right. Alex has the procedure on his web site.
Cross axis interference.....

I've gone through all that. Either the instructions suck so bad that I can't figure it out, or the AHRS is crap. I think it's the latter. Every video I've seen where the gimbal is being dynamically moved, the horizon goes off. If anybody has evidence to the contrary, I'd love to see it. Most videos show people hovering, or moving slowly. I'm banking and yanking at 60 km/h.

I did the 6 axis calibration exactly as described. Did it many times since the official instructions were not clear, but finally figured it out. Sort of. Maybe. How would we know? The GUI gives us zero feedback.

Here's a couple TBS DP's with off-level horizons too:
http://www.youtube.com/watch?v=CKqsGK8p_H4
http://www.youtube.com/watch?v=xQOpWRIqweE
http://www.youtube.com/watch?v=eIYfn3zxa0A
http://www.youtube.com/watch?v=H9aJjMWJunc&feature=youtu.be

Maybe even Trappy gets it? Interesting his videos rarely show panning shots where you can see the horizon. Except for here and... ah, the world is tilting! Actually, if you watch from that point on, there are a couple shots which have this exact problem.

http://youtu.be/2W3CB4bi_ts?t=2m46s

Interesting thread here. Seems many people have the exact same problem with TBS DP, and nobody has an answer. Not even Trappy who basically says (paraphrasing) "nothing is perfect, and you'll have to edit it out".

http://fpvlab.com/forums/showthread.php?17304-The-TBS-DISCOVERY-PRO-brushless-gimbal-quadcopter&p=336280&highlight=horizon#post336280

Not really wanting to compare to TBS DP again, these machines are in completely different classes, but it's the only other machine I'm seeing flying like this. And they have the exact same problem, even good old Trappy.

I think it comes down to the fact that, it's absolutely irrefutable, that an AHRS cannot work properly without GPS guidance and a compass. There's no way around that.

I have converted my 2 axis gimbals to 3 with a simple heading lock gyro and a fast servo. It is working fine.

Now that's an interesting point that I have been thinking about. There's really no burning need for the pan axis to be on a brushless motor. Assuming the copter has relatively good yaw stability (and most are excellent) you don't need a super fast system. I've thought a servo would work just fine here. And certainly it simplifies the mechanics.

Anyway, I just wanted to share what I've got here. I'm pretty happy with the performance of my system. It's not a bathroom mirror test, or a simple hover test. I took the lens hood off and went out again last night, even better at speed. I'm not having any problems with dampers or "head banging" either. I have the lowest level of vibration of any airframe running Arducopter, but no pitch or roll bounce either on the camera, and that's without even bothering to balance props or even thing about that stuff.

Now I just need to find some interesting subjects to shoot.

 

[PeteDee]

Yeah, I've seen plenty of those videos. But I'm more interested in "significant" cameras. This is a Nex5. Youtube obviously murders it with compression so it might not be obvious. Though it's obvious this footage doesn't have fisheye. I do have to work on some of the settings. I just threw the camera on in full auto mode, and it was dusk. This was just my first real test.

It's also a compact Octo, so redundancy, etc. Just a completely different class of machine here.

The TBS DP is a nice machine though, I'll admit that. Wouldn't mind one for alternate uses.

I was making the comment more about the limitations of the Simple BGC control system, if you want to do videoing with "significant" cameras then you probably have to spend significant cash to get the better result rather than the cheap SBGC setup.

I also note that the shifting horizon problem is accentuated on video using the GoPro because of the fisheye effect from the GoPro.

Cheers

Pete

 

[tombrown1]

You need to mess with the gyro trust numbers in advanced settings. We've had this same problem. If you do lots of fast flying with quick changes of direction you want a higher number. Try 100 for 2 minutes, land, then try 50, land, then try 150, you may even try 200 - that's what we're flying now. Then fine tune.

Good luck

 

[kloner]

that can help but in my experiences with these wacked out thins is balance is everything. if you cant let go of the camera in any position and it stays then your in a battle with yourself. alot of times an off up and down balance creates a downward self leveling when looking at balance, let go, cam falls back to flat and folks don't take it seriously. You got something like that going? a slightly higher I can help make it recover faster so it's less noticeable.

just spent the last 6 months r&d ing different brushless gimbal designs/controllers, the stuff aint normal, it'll drive a guy to drinking

 

[R_Lefebvre]

So how did that Hero 4 turn out?