Help Vibration in video from Alexmos or xy8 / hoverfly...

[jfro]

My x8 / xy8 built with avroto 2814's, seems to be flying steady.

When I first flew a nex 5 size alexmos gimble with my gh2, my first 2 days of flying were outstanding.

For the last 2 months, I been chasing some slight to too much vibration in my video footage... Can't get back to as good as I got earlier.

Al sorts of issues/ changes and I'm struggling to figure this out. Spending way too much time trying to get this figured out.

Symptoms are mostly steady video (no vibration/shaking) when hoovering and on some slow movements. However, I get some small vibrations/jitters when sliding left or right on on occasion forward / backward.....

I have 2 gimbals as I bought a 2nd larger gimbal to carry a gh3 as I was having issues with the smaller gimbal. After way to many configuration changes, I found out it was a bad roll motor (iPower 2006). Motor has been replace but haven't tried the original gimbal again, but may try it even though it's a tight fit with my gh2.

I've tried mounting the gimbal numerous ways with different anti vibrations mounts. Some are better than others, but none as good as my original footage before bad motor reared it's ugly head.

I've checked / rechecked the the prop balance, vibration on each arm (all similar and pretty slight), and alignment of top/bottom motor on each arm... XY8 flies smooth as far as I can tell.

I've tried high low power settings on the Alexmos. I simple do not know if it's the xy8 or the gimbal at this point, although I suspect if may be the copter. I haven't messed with my gains for the hoverfly pro.

Besides the bad motor, I had two other issues that may have some bearing.
1. I had a hard sideways landing which broke the wires from the imu to the alexmos which I replaced. When I was chasing the bad roll motor, I also swapped out the imu and Alexmos (I have a 2nd unit) and still had the issue which at the time was a bad motor. I also replaced 1 landing leg and 1 arm that cracked.

2. When I got the 2nd gimbal, I also increased my lame flight times by flipping my bottom props. I had the print side down which turns out was inefficient (and wrong), but it still flew very smooth. Once props were oriented properly, flight times went up over 50% and the flying sound was less labored sounding. Batteries also ran cooler....


Copter now appears to be flying as it should. BUT I JUST CAN'T GET AS STEADY VIDEO AS I DID MY FIRST 2 FLIGHTS.....

I'd sure like some help/ suggestions.

 

[kloner]

if you grab one motor at a time and feel for any play whatsoever is there any? check it after a flight when it's warmed up

are you using a magnetic prop balancer?

 

[jfro]

if you grab one motor at a time and feel for any play whatsoever is there any? check it after a flight when it's warmed up

are you using a magnetic prop balancer?

Prop balancer is a DU-BRO. I'm balancing more carefully now then when I first started and had the good footage.

I just flew for 7 minutes under full load. All more seem tight except for 2 which, may have the slightest amount of play. Motors were not overly hot when I finished.... Hoovered around at 50-60 percent throttle for most of 7 minutes except for 1 small climb...

Tried flying with 2 fullsize 5000 mha batteries whereas before I was flying with 1 battery for MR and a much lighter/smaller one for the gimbal.

I also made a new/better screw/rubber mount for my camera. I have a vibration pad under the camera. Today, I didn't see the vibration so much, but I did see some back and forth stepping which I'm sure is the gimbal. Even though I set the voltage for the same coming my 2- 5000 mha batteries, it didn't feel as good when I hand held the xy8 and moved it around. Going to tweak the PID settings and try again. Small glimmer of hope.... esp if I can score a motor today. Big 3 day weekend that I was hoping to take the MR to. If camera shakes are still there, it's not flying.. Waste of time if video is no good IMO.

I have 1 extra 2814 motor and going to see about getting some new bearings. Might get lucky and score another 2814 locally today, but that's a crap shoot as it's hard to get hold of the guy other then internet buying.

Kloner, thanks for the suggestion on moving the motors after flight.

 

[gtranquilla]

Assumptions:
1) Your camera is perfectly balanced within the 2 axis gimbel system
2) Your two PID loops are correctly tuned on the bench

If the Alexmos 2 axis brushless gimble control follows the same concepts as does the open source Martinez BGC..... you still have to adjust the PWM - Pulse Width Modulation setting for each brushless motor.
If set too low, your brushless motors will lack the needed torque to reach the desired setpoint.
If set too high you will get camera jitter, the brushless motor(s) will hum and may get hot.

IMHO......
I tend to think of the PWM setting as the deadband setting (a narrow +- angular tolerance region where the motors are allowed to rest without constant and rapid correction). But I could still be wrong here with respect to brushless gimble control..... Finally... if you cannot entirely eliminate MR airframe vibration from your brushless gimble system.... your D - derivative setting in your PID loop tuning will be most prone to control instability.... back it off a bit and see if gimble performance improves while the MR is in flight.

Reference material:
http://www.csimn.com/CSI_pages/PIDforDummies.html

View attachment 12710



I stopped used magnetic prop balancers because the shaft became magnetized and introduced magnetic errors in prop balancing.... now using a qulity DuBro prop balancer with bearings.

Prop balancer is a DU-BRO. I'm balancing more carefully now then when I first started and had the good footage.

I just flew for 7 minutes under full load. All more seem tight except for 2 which, may have the slightest amount of play. Motors were not overly hot when I finished.... Hoovered around at 50-60 percent throttle for most of 7 minutes except for 1 small climb...

Tried flying with 2 fullsize 5000 mha batteries whereas before I was flying with 1 battery for MR and a much lighter/smaller one for the gimbal.

I also made a new/better screw/rubber mount for my camera. I have a vibration pad under the camera. Today, I didn't see the vibration so much, but I did see some back and forth stepping which I'm sure is the gimbal. Even though I set the voltage for the same coming my 2- 5000 mha batteries, it didn't feel as good when I hand held the xy8 and moved it around. Going to tweak the PID settings and try again. Small glimmer of hope.... esp if I can score a motor today. Big 3 day weekend that I was hoping to take the MR to. If camera shakes are still there, it's not flying.. Waste of time if video is no good IMO.

I have 1 extra 2814 motor and going to see about getting some new bearings. Might get lucky and score another 2814 locally today, but that's a crap shoot as it's hard to get hold of the guy other then internet buying.

Kloner, thanks for the suggestion on moving the motors after flight.

 

[jfro]

Assumptions:
1) Your camera is perfectly balanced within the 2 axis gimbel system
2) Your two PID loops are correctly tuned on the bench

If the Alexmos 2 axis brushless gimble control follows the same concepts as does the open source Martinez BGC..... you still have to adjust the PWM - Pulse Width Modulation setting for each brushless motor.
If set too low, your brushless motors will lack the needed torque to reach the desired setpoint.
If set too high you will get camera jitter, the brushless motor(s) will hum and may get hot.

IMHO......
I tend to think of the PWM setting as the deadband setting (a narrow +- angular tolerance region where the motors are allowed to rest without constant and rapid correction). But I could still be wrong here with respect to brushless gimble control..... Finally... if you cannot entirely eliminate MR airframe vibration from your brushless gimble system.... your D - derivative setting in your PID loop tuning will be most prone to control instability.... back it off a bit and see if gimble performance improves while the MR is in flight.

I believe I'm balanced pretty well, but perfect is a strong word. I'm as balanced or better than when I got good footage the first 2 times out 6-8 weeks ago. I used to own a steadicam pilot (it's now my MR), so I have an idea of what balance is and I'm not as balanced as I could get on my steadicam, but not bad either.

I have been all over the map on my pid settings. I'm using a belt driven system on my roll on the 2nd gimbal and I keep going downwards trying not to over power it.

After getting the real time graph to look good, I then grab my MR by the legs and roll it slowly left to right. I watch the upper edge of the pitch motor to see how steadi it is. I haven't been able to get it 100% vibration free yet, so still working on it. If I over power it, when pitching forward and rolling, I get obvious shudders....

I just took some of today's test footage and ran it through after effects. Looks very nice. Haven't been able to get the 2nd 2814 motor here locally, but did order 3 sets of bearing that will get here by Monday, so will replace them in the two motors next week.

I'd say 90% or more of my filming is steady, but it's just those friggin little left/right movements, little hitches as I call them from time to time that sucks. Did 1 test flight in 30+ mile winds yesterday and pretty calm winds today. Today's footage is a tad nicer. If I can get a moment, I may try to change the roll motor and see if that helps. I did have a similar hitch problem with a 2006 motor that I sent in and it was bad. I've read that there are some bad motors from time to time, so I think it's worth swapping as I do have an extra. In fact, I'm going to do that now before my last two tests.

I think with after effects cleaning up those hitches, I can get by with some weekend shooting that I had planned and make it till next week to replace the bearings. Movement on the two motors is pretty minimal and I really don't think they are the problem of my hitches.

 

[jfro]

It's not the roll motor. Changed it, same problem.

Local dealer who has 2814's never answered his email or phone. Called 3-4 times. So, no replacement motor.

Anyway, shelving my problem till monday or tuesday when new bearings get here. After replacing bearing, if still have problem, may try old brushless gimbal. Had success with it before bad roll motor. GH2 is a little tight on it, but it worked beautifully before. so it's worth a try.... If that's not it, maybe I should try another mounting technique. Guess, 3 tries isn't enough.....

Still open for suggestions.......