Ideas on how to improve video smoothness?

[pootman]

Hello All,

I just finished my first AP platform, a MK Octo. Here's my setup details:

--MK Stack (FC, NAVI, GPS, BLs)
--Avroto M2814-11S turning APC Slowfly 11x4.7 Props
--5/8" Diameter Aluminum Arms about 37" from motor to motor in length
--PhotoShipOne mkTR Professional Camera Mount

This machine is a blast to fly. I built it for personal use and for my daughter's school's film projects. I'm new to Multirotors and AP flying. I've shot a few videos as I played with the octo and all the videos have some shaking issues. I'm trying to figure out what I should target to improve my raw video quality. I figure I should get my raw images as smooth as possible prior to applying software stabilization. Here's a couple of recent videos.

Flying around my neighborhood
http://youtu.be/jVlf_g2rlHQ

Flying around my daughter's school
http://youtu.be/ZnLlf91NFnI

Sunset flight at our local (unofficial) RC flying site
http://youtu.be/tbLMp6FxjzM

I'm not sure where I should start first to try to smooth out the videos. My ideas are (not necessarily in this order):

--Change props?
--Change servos on the mkTR mount to nylon gear servos for less slop around center? (current servos ROLL HS-225MG, TILT HS-5485HB)

That's my only two ideas so far. Any ideas on how to improve my video quality? Or is the shakes normal and smoothness is achieved using software editing? Thanks all for your time and advice!

Lance

 

[Bartman]

there's a thread on MKTR mods that I started a few months ago. I believe some of the mods would still help the latest version. Whatever little room there is for things to move, you have to figure out a way to constrain the movement while keeping it from being rigid. It's a challenge but with each little change, do some sample video and see what works. it's a lot of trial and error.
bart

 

[BorisS]

Hi Pootman,

I wouldn't be concerned about changing servos or focusing on the camera gimbal. Start from the beginning to fine tune the setup. What I mean with that is hard mount your camera. Deactivate the servos so no stabilization signal comes from your FC and strap down the tilt and roll mechanics of your mount so its really solid. TMake a test flight with all variables in it. Hovering on one spot, Yaw left and right forward backwards etc. But one thing a time so afterwards you can analyse from your video material when witch wobbles vibrations happen.

Your videos differ in quality. The first one suffers from vibrations and the other ones are better on that.

Reasons for vibrations.

1. Props not balanced. ( how good do you balance them really 100%, or how long so you take to balance them. I sit up to 4 hours for my Octo with a new pair of props, depending on the product
2. Motors not balanced or some mechanical problem in them. Can they all be turned with the same ease by hand. When you look at them running on the ground do the propeller mounts stay a straight line or do they seems sloped bent.

It also seems to me that you could fine tune your gyro PID settings. Did you play with those already, I personally believe that the hard mount camera gimbal test is also very good approach to fine tune those.

It would also be interesting to see how you camera mount is mounted to the center-plate/Landing gear.

Regards

Boris

 

[DucktileMedia]

I have heard 2 people with custom builds that are using Avroto's say they have done everything they can and still have vibrations. I am on the waiting list for some of the short shaft Avrotos and cant believe that the motor would be to blame for this. But a few have stated that switching to AXI motors reduced this a bit. I wish I remember who this was that stated this. Again, how does such a precision motor get the blame for vibrations? I see most of this coming from props. In theory there is nothing else on a multi rotor that is capable of producing such a high frequency vibration. I don't think even a faulty signal or wiring in the flight control could make the craft twitch anywhere near the rate of motor vibrations. If assume if you took the props off your motors there would be very little shaking. There has to be a simple answer to this so we all dont have to go through the experimentation and trial and error for every different model and configuration.

 

[Gunter]

Personally I think a lot of those vibrations are caused by wind and flying technique. I have found in the last year of making videos, the way you fly it makes a huge difference. You have to literally just tickle the controls ever so gently in the direction you want to move. Also, avoid flying too fast, slowing down and then having to speed up again. Every time you push the stick forward, the nose wants to dive slightly, making the video bumpy. Best if you have a very gentle wind, and let the wind take the heli (obviously it has to be in the right direction!!)

Practice on a calm evening, try and fly nice and slowly putting as little stick movement in as possible. Aim the heli in the direction you want to go, give it some stick in that direction, let go and let it drift. Also try drifting in one direction and putting in some yaw to track a stationary object. Then you can film while you are practising to compare results at the end.

Good luck!

Gunter.

 

[Stacky]

As Boris mentioned motor and prop balancing will help a lot. The more care you take with motor and prop balancing the more you will see improvements. Once you have those things nailed the next improvements will come from flying style and once you get that nailed tweaking your camera gimbal will help.

Boris mentioned start from the beginning, thats great advice, work your way through systematically. It may be its mostly wind and flying technique but even before you concentrate on that get your motors and props as well balanced as possible.

Also if you want to be really pedantic you can also find the sweet spot for your motors with respect to the alignment of your props on the motors. Somewhere there is a thread showing some tests that show your motors and props combined have a sweet spot of least vibration with respect to the position of the props on the motor.

 

[RTRyder]

Are you using any expo in your TX? I have three flight modes setup on a switch with varying degrees of expo, the one I usually use when flying for video is 50% on both aileron and elevator control and 40% on Yaw. The "loosest" setting I have I use for practice flying and its 30% and 20%, makes a big difference in controlling the little abrupt motions.

Personally I find APC props to be the worst for causing vibrations and they are stupidly difficult to get the balance even close, I only use them if there's no other option. The Graupners I use aren't as efficient but they really are balanced from manufacturer, the most I've ever had to do to get one perfect was a tiny bit of sanding on the edge of the slightly heavier blade and that was it. As for balancing the motors, I don't bother, doesn't seen to yield much of a result for the amount of effort involved, but then again I generally only use good quality motors on the multis I use for APV.

My best setup for video is my Droidworx AD6 heavy lifter with Pulso motors, Graupner props, Full MK electronics, and Photohigher AV130 camera mount. Here's a short clip of raw video I did the first time out with the new AV130 I recently installed on it, the old one has been retired to backup status. I wasn't trying to be smooth, just flying around to see how close the setup was and how well the tilt and roll compensation worked. Camera is a GoPro HD with Sunex lens in the GoPro case on tripod foot hard mounted to the platform... http://www.youtube.com/watch?v=acr5-kLlfTo

Best things you can do is as Boris said verify the basics are right first, then setup a couple of flight modes with varying degrees of expo so you can switch between them to see the difference, and most importantly, practice, practice, practice, flying as much as possible and the smoothness will come. I try to get in at least 3 to 6 battery packs a day whether its on one of my little 12 quads or with the big Hexa makes no difference its the comfort level with the sticks that matters most.

Ken

 

[DucktileMedia]

I get nasty vibrations even in a perfect hover. And it does hover very well. I can visually see NO erratic movements at all. Plus the rate of change in direction from flying input would not give high frequency vibrations like an off balance prop would. Good to know about the APC's vs. Graupners. I would not have guessed the Graupners were inefficient though. I still blame everything on props/motors though.

 

[pootman]

Thanks for the ideas guys! *I'll definitely recheck my prop balance. *I did balance the props prior to installing them and I ran each motor (without props) to check for vibrations. Everything seemed normal with very low vibrations.

I did notice three main things durning my build that concerns me about possible vibration issues. *The first issue, and the main reason I focused on it on my earlier post, is that there is a noticeable center play on the roll servo. In other hobby applications, as long as gear strength isn't an issue, I've noticed that nylon geared servos have a lot tighter gear mesh and a lot less play around center.

The second issue is the aluminum arms and their tendency to have some harmonic vibrations when you flick them. Kinda like launching an eraser with a ruler held on a table type vibration. I've watched the arms durning motor start and spool up and they seem to stabilize as the RPM increases to hover power. But, I'm not sure if they vibrate durning flight loads or if they remain stable. Other than switching the arms to CF, I'm not sure what other solutions are available or if it's even needed.

The third issue is that one of my motors has a little more resistance then the rest when turned by hand. *I noticed this when I first received my motors. However, I've checked the AMP draw, RPM, and temps on that motor and BL and it's consistent with all the other motors. So far this motor really doesn't seem to be an issue at all.*

The other item rattling around in my head is prop choices. The APC slowfly props are quite flexible. Durning descents I've noticed the shakes are at it worst. I'm wondering if the props are the main cause. I also wonder if the props flex while hovering in level flight. In my videos, whenever I start to climb the video smooths out considerably when the props are under higher loads. *I'm curious about the other prop options that are available out there and the opinions from those that have used them.*

When I get back from work later this week I'll rebalance the props and check motor vibs. Those items are easy to check and the best part is it doesn't cost anything. I just hate dumping money toward troubleshooting an issue only to find that the last item checked was the only item that needed to be changed. I think I've rebuilt a few helis that way and it's financially frustrating.*

Thanks again guys for the input!

Lance

 

[DucktileMedia]

some interesting tests on vibrations and output.

http://www.rcgroups.com/forums/showthread.php?t=1388583#post18835696

http://www.vibrationmounts.com/video/index.htm

 

[burgor57]

This was all interesting reading. I am new to this - have a Droidworx AD6-HL to lift a uitable DSLR to aerial photography. I didn't know about balancing props and motors. Is there a thread anyone knows of that explains more about how to balance props and motors?

 

[Gunter]

This was all interesting reading. I am new to this - have a Droidworx AD6-HL to lift a uitable DSLR to aerial photography. I didn't know about balancing props and motors. Is there a thread anyone knows of that explains more about how to balance props and motors?

I recently bought new props for my Draganflyer. They are carbon fibre and cost £40 per prop Luckily I got then for a quarter of the price with a bit of wrangling Problem is that they were miles out of balance.

What I did is take the prop off the heli, get some thick fencing wire and balance the prop on that (wire goes through the spindle) When you do this, the prop should lie horizontal. If it dips one way or the other, one side of the blade is too heavy. When that happens, put a bit of sticky tape on the lighter side to balance it out. I have attached some photos below to show what I did.

The difference is huge. I will attach a quick video I have done showing unbalanced props and balanced. It seemed to cause very high frequency vibrations which isn't good, because video stabilisation won't get rid of these.

 

[BorisS]

pootman different props are not going to solve the situation. In the following video i am flying with APC 12 x 3,8 and the camera hard mounted to a AD 8. There are no vibs as far as i can see, maybe still small hick ups from my setting and lacking skills. You mentioning your booms and them being out of aluminum and harmonics etc. I also had that feeling the first time i looked at your build. But i didnt want to argument it since i dont know to much about materials and if carbon is really different when it come to passing on vibrations. Maybe someone else with more knowledge could comment on that. Like said dont focus on the camera mount or gimbal the servos play slope etc. Get the vibrations out of your frame and than you will see more clearly were the weaknesses are concerning your camera mount.

http://sprealinvest.at/phfrombehindwithstrapon/phfrombehindwithstrapon.html

 

[burgor57]

Makes a difference

that makes an obvious difference balancing the props. I will check mine asap. Ordered a Du-Bro prop balancer. Would have thought however that sticking bits of tape on the prop blade would reduce efficiency a little and could introduce some unwanted extra turbulance. The other method I have read is to carefully sand off a little from the opposite blade till the balance. I wonder if anyone has further insight into this?

 

[pootman]

Thanks again fellas for all the advice. I went through a week of trying some of the advice listed here and I finally made some head way. I started out with balancing the props again and really didn't see much of a difference. I then spent two days working on the gimbal. I locked everything down and noticed a huge improvement, but still just an occasional shutter. I then went through 8 roll/tilt servos combos. I found a combanation that pretty much reproduced the locked down gimbal video quality with an occasional shutter. It's much better than the constant shaking in the previous videos. I was at my wits end to fix the occasional shutter and I broke down and rebalanced the props once again. To my surprise, almost all the props were off balance. I thought that was a bit weird since I've balance plenty of props before. So I re-balanced them and went for another test flight. Argghhh!!!! Same occasional shutter. After scratching my head fir another day and a couple more servos combos with no improvement, I went back to balance the props yet again (4th time!!!). And guess what? They were almost all out of balance again!!! OK, now I'm questioning all my previous prop balancing endeavors. On a hunch, I rotated the props on the balancer shaft and found my problem. Evrytime I turn the prop 90 degrees on the balancer, I would get a different result. So my trusty 20 year old balancer is not balanced. I went to the hobby store and bought a new balancer and re-balanced my props (for the last time, I hope). Guess what? Occasional shutter is now gone. Yeah!!!! I still have shaky videos once in a while, but I think that's due to flying too aggressively. Here's a couple of videos, one in 1080p and the other in 720p at 60fps.

Thanks again everyone!!!

1080p
http://www.youtube.com/watch?v=Ge8dHo4kt5I&feature=youtube_gdata_player

720p @ 60fps
http://www.youtube.com/watch?v=lZbJrBP_miY&feature=youtube_gdata_player

Lance