Tau Labs Mounting of OP CC boards
- Thread starter Droider
- Start date
Gary Mortimer
Member
Did any one mention the vibration technology rolled out for platform testing by the OpenPilot project? Cutting edge stuff....
I had one but I kept chipping my teeth.
I had one but I kept chipping my teeth.
hahahaha on that note I have an app on my ipad that measures vibrations. Its been really handy in giving me a baseline reading while I test things out and work out what works best at reducing vibration and what doesnt. Its available for iphone as well. Its called the iVibrometer. Its never chipped my teeth...
matwelli
Member
Dankers you may know this answer: FredericG did a vibration analysis firmware for MK. Has he done anything like that for OP/CC or is it not possible due to hardware filtering. I was really hoping for a vibration gadget in the GCS.
Link here: http://www.mikrokopter.de/ucwiki/en/VibrationTest
//You guys really shouldn't be putting tools in your mouths. You don't know where they have been.
Link here: http://www.mikrokopter.de/ucwiki/en/VibrationTest
//You guys really shouldn't be putting tools in your mouths. You don't know where they have been.
The tool could be ported to OP; I have been thinking about that. I already have a python implementation of the OP UavTalk. In addition some support should be added to the CC code itself.
Should not be too much work, but I will not have time the coming months I'm afraid.
Frederic
Should not be too much work, but I will not have time the coming months I'm afraid.
Frederic
Hi Frederic and welcome to the forum. You did that vibration tool many months ago. Do you still find that it is useful or is it easier to just go old school and manually balance?
I do believe that the old school balancing is only part of the story. OMM on RCGroups has discovered that the vibrations are highly influenced by how the prop is positioned on the motor. In my tests I came to the same conclusions. It is believed that this is caused by the motors itself that are also unbalanced and that the prop unbalance can counter-act or enhance the unbalance. Props and motors should be balanced together. I used an MK and OMM used a dedicated setup for this.
The problem is that each time your prop hits something, you should re-balance. I have found that mounting motors on dampers is very good at fighting vibrations.
Frederic
peabody124
Member
What kind of dampers?
Droider
Drone Enthusiast
First of all, Welcome Frederic to MRF.. Guessing another OP guy but you could let us know a bit more about yourself before just jumping in to a thread with a statement like that...
DAMPERS ON MOTORS... ehh...
You need to explain a bit more
Again welcome and dont forget to just post a quick one in the DroidWorx frame give-away thread... u got to be in it to win it!
Dave
DAMPERS ON MOTORS... ehh...
You need to explain a bit more
Again welcome and dont forget to just post a quick one in the DroidWorx frame give-away thread... u got to be in it to win it!
Dave
I'll jump in here with my "theory only" views. The notion of mounting the motors on dampers (usually rubber or silicone grommets) seems on the one hand to be madness but on the other there might be some sense to it. After all, my car's engine is mounted on rubber blocks. But it can't be denied that the torque reaction of a rubber-mounted outrunner is going to "expend energy" winding itself up against the mounts before it transmits any force to the airframe. And when you reduce throttle it's going to "unwind" in a hurry. Theoretically the result should be awful. Best analogy I can think of is spraying oil on your car's brake disks to reduce squeaking - yes, it'll stop the squeak, but...
And yet... this seems to work for some people. I'm guessing that the AP-heads that want to minimise vibrations don't care that the "handling" is altered somewhat. I'd also reckon that very careful selection/design of the mounting components (and precise control of the pre-loading you apply) will make the difference between success and failure.
Does anyone know the range of frequencies we're dealing with?
And yet... this seems to work for some people. I'm guessing that the AP-heads that want to minimise vibrations don't care that the "handling" is altered somewhat. I'd also reckon that very careful selection/design of the mounting components (and precise control of the pre-loading you apply) will make the difference between success and failure.
Does anyone know the range of frequencies we're dealing with?
peabody124
Member
You can work out how bad it would be fairly easily. Just going through some back of the envelope calculations (please correct me if I missed any details), let's say your damping is really soft and the motor can rotate 45 degrees on the mount.
Assume the motor goes from 4000 rpm (24000 deg / s) and (this is very liberal) can accelerate to 4500 rpm (27000 deg/s) in 100 ms. In that 100 ms the blade would rotate an extra ~150 degrees (assuming constant acceleration, but let's ignore that). If you assume the torque were constant and the "spring" of the mount responded instantly you basically slip 45 degrees of that into the mount and lose ~30% of the response.
So basically you want something that dampens vibration while having very few degrees of rotation per unit of torque.
Assume the motor goes from 4000 rpm (24000 deg / s) and (this is very liberal) can accelerate to 4500 rpm (27000 deg/s) in 100 ms. In that 100 ms the blade would rotate an extra ~150 degrees (assuming constant acceleration, but let's ignore that). If you assume the torque were constant and the "spring" of the mount responded instantly you basically slip 45 degrees of that into the mount and lose ~30% of the response.
So basically you want something that dampens vibration while having very few degrees of rotation per unit of torque.
I use dampers like this: https://www.mikrocontroller.com/ind...id=394&zenid=ef269f9164d2dcec4cff5dcb4792d876
I use 4 per motor and this results in relatively rigid link
Vibrations are a difficult problem. Some people have very little problems with them others have lots of problems. I think it all depends on many factors, motors, props, weight, construction and material of the frame, what camera you use. I think it is important to fight vibrations at the source and at other places. because of all the different factors, I don't think there is a magic formula that will work for everybody. Just my 2 cent.
Frederic
I use 4 per motor and this results in relatively rigid link
Vibrations are a difficult problem. Some people have very little problems with them others have lots of problems. I think it all depends on many factors, motors, props, weight, construction and material of the frame, what camera you use. I think it is important to fight vibrations at the source and at other places. because of all the different factors, I don't think there is a magic formula that will work for everybody. Just my 2 cent.
Frederic
I fly RC stuff since I was a kid (30 years ago). I got interested in aerial photography almost 10 years ago, later in FPV. Started with MK 3 years ago but got very annoyed with the MK designers attitude. I started helping OP a bit more than a year ago. I did a few thinks for OP here and there, but no big chunks and unfortunately I do not have too much timeFirst of all, Welcome Frederic to MRF.. Guessing another OP guy but you could let us know a bit more about yourself before just jumping in to a thread with a statement like that...
DAMPERS ON MOTORS... ehh...
You need to explain a bit more
Again welcome and dont forget to just post a quick one in the DroidWorx frame give-away thread... u got to be in it to win it!
Dave
www.rc-flight.be
Frederic