New GoPro-specific 2-axis gimbal for the F450...

[GGoodrum]

I finally got my new F450 built and setup with the new GoPro-specific 2-axis gimbal/mount that I've been working on with Andrey Kim (Askman...). Getting a 1st-rate, belt-driven GoPro gimbal has been a sort of holy grail quest for me, and now I have exactly what I've been looking for. I've gone through at least three platforms, from a VC-600-X8, to an XA Hexa and now to the most excellent F450. I've come close on a couple setups, but there was always one thing or another that was just not right. I also had a ton of vibration issues. Now, finally, I have a platform that is plenty powerful enough to carry the GoPro2, and has virtually zero prop-based vibrations. This new mount provides the last piece of the puzzle.

It has a 2:1 belt drive in each axis, which I believe is the optimum trade off between having smooth movement and fast responsiveness. We are using Hyperion DH16-SCD digital minis which have even higher resolution than the 10-bit Savox SH-1357 digital minis that are popular on some mounts. We program these to have a full 180-degrees of motion, and we "tune" the deadband to "fit" the Naza/WKM gimbal outputs. The result is smooth movement and extremely quick response, even running them on the 5V supplied by the Naza/WK-M PMU. These servos can be run on up to 7.4V, which increases the speed even more.

Below is a short video, showing how it works. This is after just doing a quick-and-dirty gimbal gains adjustment in the Assistant software. It's pretty close now, but could be tweaked a bit more. I'll eventually add a CC 10A programmable BEC, set to 7.4V, to drive the gimbal servos, and then I'll fine-tune the gains.

The mounting plate runs the length of the F450's bottom plate, and attaches to it with four vibration isolators. I've got a single 3s battery hanging off the back, which easily counter-balances the gimbal and camera. I plan, however, to use two packs, to get longer durations, so these will sit farther forward.

I was planning to use the stock DJI 30A ESCs, but when I ordered all the bits for this setup I screwed up and only ordered one ESC. So, I'm using four Maytechs instead.

In place of a dedicated set of landing gear, what I'm using instead are some 4" colored pool noodle sections. These come in two sizes now, with the smaller ones conveniently fitting inside the larger ones. I've found that lime green and pink are the best colors to be able to differentiate, to help figuring out orientation, even 250-300 feet up, just about directly in the sun. Anyway, withe gimbal basically being "inline", 4" is all that is needed to provide a full +/- 45-degree roll angle.

First test flight will be tomorrow. I'll post some video later.

-- Gary

 

[Droider]

Nice looks smooth as! What weight are you all up? How do you find the 3 blade props and what are they?

Dave

 

[GGoodrum]

Nice looks smooth as! What weight are you all up? How do you find the 3 blade props and what are they?

Dave

Thanks, Dave. The AUW is 3 lb 15 oz/1786g.

The props are GWS 9x5x3s, which are available lots of places. These take a bit long to balance, but the result is that they completely vibration free, and they are a ton quieter than the normal 10x5s that come with the F450 kits.

-- Gary

 

[kloner]

i can attest to that. they have a 10x6x3 and an 8x5x3 too

mine without a gimbal is 3lbs 9 oz, why is yours so light?

 

[GGoodrum]

i can attest to that. they have a 10x6x3 and an 8x5x3 too

mine without a gimbal is 3lbs 9 oz, why is yours so light?

Actually, I forgot. That measurement was without props. I just weighed it again, with props and a single 3s-5300 pack and it is 4lb 0.4oz/1826g.

-- Gary

 

[kloner]

still not bad. are you gonna run 3s or 4s? I'm switchin over to some suppo motors and try 3s with the 10x6x3. Really stoked on those props, they were the only thing i could get to actualy smooth out

Can't wait for the vids. Is there a way to make the gimbal act rate mode and follow the craft if it banks but just smooth it out or does it act more like a head hold and stay flat and level all the time?

 

[GGoodrum]

still not bad. are you gonna run 3s or 4s? I'm switchin over to some suppo motors and try 3s with the 10x6x3. Really stoked on those props, they were the only thing i could get to actualy smooth out

Can't wait for the vids. Is there a way to make the gimbal act rate mode and follow the craft if it banks but just smooth it out or does it act more like a head hold and stay flat and level all the time?

I did a quickie test flight a little while ago. I decided, after playing with the numbers in ecalc a bit, that this would be better on 4s, so I'm using two 4s-2600 packs in parallel. This upped the AUW slightly to 2030g/4lb 7.6 oz. I initially tried it in Manual mode, to see how much power is required to lift off and hover. It holds pretty close at around 50%. I then tried Attitude mode and it is quite smooth, taking off. I had the gains too high, and there was quite a bit of oscillation. I ended up with them down around 130%, which actually surprised me they needed to be that low. Anyway, I finally got it smoothed out, and the gains seem to be pretty well dialed in now. It descends nicely, with no wobbles.

I still have a bit of prop-related vibrations. I think this is because of the extra large diameter pool noodles I'm using on the "feet". Almost half of the 9x5x3 props are basically being blocked. I had put the "normal" noodle sections inside the larger diameter versions, which fit perfectly. On top of that, I didn't have one set attached very well, and it blew off. :frog: Anyway, tomorrow I will try the smaller noodles, and see if that helps. The vibes are not the normal high frequency variety, from out-of-balance props, so there's not a consistent amount of "jello" in the video. It is more random, which makes me think it is more of a "disturbed air"-type of issue. In any case, the mount/gimbal worked perfectly fine. So well that it makes it hard to sync the onboard video with the ground-based version.

You can see the gain-related oscillations in the first part of the video, as I played with various values. It was better towards the end. the other vibe issue isn't quite as noticeable, but there's definitely room for improvement. I haven't even played with the vibration isolation adjustments, just yet, and it is pretty close to being hard-mounted right now. I could probably tune them out, playing with these, but I'd much rather get the platform tuned better.

Anyway, this is just the very first flight.

-- Gary

 

[WillM]

Very interesting camera mount! Seems like it is right up my alley with what I plan to do with a Naza/Flamewheel !

Camera sync tip:

Easiest way to sync multiple cameras is to use a watch/clock/stop watch. Stop watch is best as it shows fractions of a second. After you hit the record buttons on both cameras, and just before starting your flight, aim both cameras at a running stop watch for a few seconds. Record a few seconds of video and keep the cameras rolling.

Back in the editing room, line up both clips at the exact same time as shown on the watch.

You'll be perfectly synced.

For really long videos, you may want to record a bit of the stop watch at the very beginning and the very end of the video.

Of course, edit the stop watch part out of your videos.

 

[digitalcam]

Gary, when I saw the size of the noodles right under the props, I thought, "I don't think that can be good". It's almost like you never get off the ground. You're always in bad air. Plus the force of the air hitting them, had to set up a lot of vibration that is getting transferred right back into the frame. -- (different topic) My Y-hex AUW is 7lbs 4oz. If I took the 11x4.7 apc props off and went with GWS 3 blade. Do you think I should go with 9x5 or 10x6 ?? -- thanks, JOHN

 

[kloner]

is that a bearing howling? sounds rough

i tried the 9x5x3 on 3s and it just had enough stick to hover on 3s and the pack had to be fresh or it didn't even stay aloft, 4s was a rocketship. just got the 10x6x3 today and there alot more like a 10x5 and 3s had it feeling good. gotta wait for light to see if it's still stable

 

[GGoodrum]

Very interesting camera mount! Seems like it is right up my alley with what I plan to do with a Naza/Flamewheel !

Camera sync tip:

Easiest way to sync multiple cameras is to use a watch/clock/stop watch. Stop watch is best as it shows fractions of a second. After you hit the record buttons on both cameras, and just before starting your flight, aim both cameras at a running stop watch for a few seconds. Record a few seconds of video and keep the cameras rolling.

Back in the editing room, line up both clips at the exact same time as shown on the watch.

You'll be perfectly synced.

For really long videos, you may want to record a bit of the stop watch at the very beginning and the very end of the video.

Of course, edit the stop watch part out of your videos.

Nice tip, thanks.

-- Gary

 

[GGoodrum]

Gary, when I saw the size of the noodles right under the props, I thought, "I don't think that can be good". It's almost like you never get off the ground. You're always in bad air. Plus the force of the air hitting them, had to set up a lot of vibration that is getting transferred right back into the frame. -- (different topic) My Y-hex AUW is 7lbs 4oz. If I took the 11x4.7 apc props off and went with GWS 3 blade. Do you think I should go with 9x5 or 10x6 ?? -- thanks, JOHN

My thought as well, regarding the oversized noodles. What made it worse, I think, is one of them blew off, so there was one that had "good air" and three that didn't.

I'd go with the 10x6x3s, if you are currently using 11" now.

-- Gary

 

[GGoodrum]

is that a bearing howling? sounds rough

i tried the 9x5x3 on 3s and it just had enough stick to hover on 3s and the pack had to be fresh or it didn't even stay aloft, 4s was a rocketship. just got the 10x6x3 today and there alot more like a 10x5 and 3s had it feeling good. gotta wait for light to see if it's still stable

No, it's actually not a bearing, but the servos in the gimbals "chattering", due to the vibrations. They aren't really that loud but the GoPro amplifies the sounds.

 

[GGoodrum]

Made a few changes today, and saw quite a bit of improvement. First, I removed the "outer" pool noodle layers, which helped quite a bit, just doing that. I then just had some "normal" jello, mainly because the props were not completely balanced anymore. I had had an incident, when trying manual mode where I "hopped" the landing, ending up partially in some bushes. When I couldn't get the disarm to work, I ended up doint a little "tree-trimming". This got those two props a bit out-of-balance. Anyway, I also discovered that power was a little on the sluggish side, with the 9x5x3s, so I went back to trying the 11x5 Graupners. This did the trick, and now the jello is gone. I was surprised to also learn that the Naza is much happier with this heavier (2kg...) weight, when using these props. Now the gains range is a lot wider between oscillations and wobbles on descent. I now have zero oscillations and zero wobbles.

What I still need to do is tweak the gimbal roll gains a bit, and then sort out the vibration isolators. In order to make sure I was seeing the worst case, for tuning out platform-related vibrations, I've basically hard-mounted the gimbal plate to the bottom F450 plate.

Anyway, progress...

-- Gary

 

[AddictiveRC]

Props are too big Gary.
Go with 9 x 5 graupners.
11 x 5's are too close together and there will lot's of distrubed airflow.
Also that mount is right in the front of the air flow of the props.
We had Problems with the jello effect using the XAircraft Camera Mount way up front like that.
Moved it under the frame away from the airflow and that solved our issue.
It would do much better under the frame.

 

[kloner]

this vid still had the noodles on it, was there another vid without? It's not too bad in atti to keep it in the sky,,,,,,, mines got white strip lights on the white arms and can see it way up there. atti pretty much keeps it there on it's own, just gotta fight the drift from the wind

How fast are the servos?

John, do the graupners have alot of bite? what kinda weight will the 9x5 lift?

 

[GGoodrum]

Props are too big Gary.
Go with 9 x 5 graupners.
11 x 5's are too close together and there will lot's of distrubed airflow.
Also that mount is right in the front of the air flow of the props.
We had Problems with the jello effect using the XAircraft Camera Mount way up front like that.
Moved it under the frame away from the airflow and that solved our issue.
It would do much better under the frame.

First of all, I don't agree that 9x5s are the answer. The 9x5x3 GWS 3-bladed version which lift-wise, are more like 10x4s, have a harder time lifting 2kg, in this setup. I think the 10x5 Graupners will work, however. The 11x5s are right in the zone, from a lift and disc loading perspective. The Naza, like most FC, don't like light disc loading. If it is too light you can never get to the point that it doesn't oscillate, while hovering, and then not wobble on descents. With these 11x5s, that's just not the case. I now have a very wide range where the gains can be set, without wobbling and without oscillations.

As for the mount positioning, another option is to turn the F450 lower plate 90 degrees, which will get the gimbal closer in, and farther away from the props. The way it is now is the worst case, installation-wise, which I wanted to test. But, there's really no jello in the video now, just some movements related to the roll gains not being spot-on. I was purposely not trying to fly smoothly either, as I was trying to make sure the gimbal was working properly. Also, I have the gimbal hard-mounted to the F450 lower plate, again, so I could see the worst case for platform vibrations, prop wash, etc. Next I will install the vibration isolation plate.

-- Gary

 

[GGoodrum]

this vid still had the noodles on it, was there another vid without? It's not too bad in atti to keep it in the sky,,,,,,, mines got white strip lights on the white arms and can see it way up there. atti pretty much keeps it there on it's own, just gotta fight the drift from the wind

I didn't remove the noodles completely. I have two sizes of pool noodles, one that is 2.75" in diameter, and one that is 4". It turns out the smaller ones fit inside the larger ones, so I gave that a try. When I had the disturbed air issue, I simply removed the larger 4" ones, and just kept the smaller 2.75" versions. In addition to the fact that these act in lieu of "regular" landing gear, they also provide orientation cues. I've used the colored LED strips, and while they do help with the orientation, I just can't distinguish them when the quad is up 200-300 feet on bright sunny days, which we have a lot of, but I can still see the noodles. I've found pink and green are the two colors that are easiest to distinguish.

How fast are the servos?

On 5V, which is what they are being run on now (via the Naza PU...), they are moderately fast, at around .12s. They can, however, be run on 7.4V, and at that voltage, the speed drops to .10s, which I've found to be plenty fast for gimbals with 2:1 reductions, or less. I have the tilt gains pretty much dialed in, but the roll gains are off a bit, in this last video. I actually had them pretty close, but then the numbers changed once I programmed the throws and dead band timing.

 

[GGoodrum]

Yesterday I used this setup to get some airborne shots of a $12m "tract" home, in Newport Beach. This was the first time I used the GoPro2 for still shots, and I have to say, I was pretty impressed, especially in low light. I had it set to record a pic every 2 seconds, and then I tried different heights and look-down angles. I was there for three hours, and ended up doing 5 separate flights, all on the same charge. I estimate my total time in the air was about 11-12 minutes, using two 4s-2600 packs. Anyway, I ended up taking 268 shots. Attached is one from the 2nd flight.

-- Gary

 

[digitalcam]

Nice Cabin

Gary,- good picture. Are you a Realtor or do you hire out for aerial shots for Realtors? My wife is, and when the snow goes away, I'm going to try to get some good shots of some of her commercial and waterfront listings. Don't know if it's how you do it, but I have the timer on my Tx set to start and stop when the throttle is above or below 10%. Also keep it in memory. Then when i do multiple take-off and land, shut it off and turn it on. It keeps a running total of just air time. Maybe that's how evryone does it?? No clubs or other flyers anywhere around me, so no one to compare to. -- JOHN