Hi,
I have measured very good Zaccel vibrations with this mounting system. It consists of a suspended acrylic base plate (3mm thick) on which a silicon pad (6mm thick) is placed. The APM case is placed on it with a little pressure from a velcro band.
The O-rings go through holes on each corner of the acrylic plate and are attached to the black nylon spacers. In order to avoid that the o-rings would move up/down the nylon spacers, I used flat metal nuts to block the o-ring (it is screwed between the first 10mm spacer and the bigger 30mm spacer).
The acrylic plate is suspended about 2mm above the fiberglass mounting plate. In order to shield the EMI interferences that could come from the PDB/ESCs, I added special EMI tape on this bottom fiberglass plate.
I show below the obtained results with motors 100% throttle:
This AccelZ measurement in the logs show an average of maximum 0.5g deviation, which is I guess quite good!
Other pictures:
Hugues
Comments
Perhaps full throttle is not a good test. Is this accel Z graph a download from actual flying confditions or bench test? My quad hovers at 50% throttle and there is a lot of motor speed interaction happening and harmonic frequencies that you probably don't get at 100% throttle.
And I must add that the whole graph corresponds in the middle at Throttle 100% !
Update on my experiments, some more improvements versus my first setup, following Gary's advices:
I then get the following Zaccel graph:
Cu,
Hugues
Gary, I agree with mounting the Rx right on the APM. I assume you've seen my All-In-One blog post from June?
I'm now working on doing the same thing with a full-size FrSky D8R-SP Rx. Decased, and mounted to a daughterboard.
Too bad 3DR never went ahead with making an official daughterboard for this purpose. It would be really nice.
Thanks Gary!
I like the idea of dampening the entire Controller + Receiver, especially with rectangular boards like the APM. Combine that with high flex cables would be amazing.
Another question: should the signal wire from the controller to ESC be shielded with a ground wire or other method? Or will it be enough by itself?
http://fpvlab.com/forums/showthread.php?4251-Vibration-Dampening-am...
get attention to the dampers on the tip after engines =)
Hi Daniel,
I do briefly address the wire issue in the Vibration Control section of the Wiki and yes it is an issue.
Reducing wire gauge can help, but I would recommend some other methods that yield good results before resorting to that.
Use high flex wire which has more strands of copper and a more flexible insulator.
Use less wires, getting rid of unnecessary power and ground wires can reduce the number of wires by half.
Provide a unrestrained strain relief loop for all wires entering the flight control board.
If you want to go all out, you can go to a PPM-Sum receiver or mount the receiver on the same plate as the flight control board and then vibration isolate the whole thing.
These techniques can virtually eliminate interconnecting wires as a vibration entry path.
I think one of the biggest issues with the vibration is due to the cables. Think about it the ESC, Receiver, and sensor cables are very stiff. It can surely induce vibration even if you manage to dampen the controller. I'm going to experiment with using 26-30 gauge wiring to help isolate it further.
Good work, I may use some of these techniques to dampen my quad/hexa
@Brenton : Since firmware version 2.9.x the APM uses actively the accelerometer to pilot the quadcopter. In version 2.9.2 it will uses all three axes (accelX, accelY, accelZ). So yes, it is needed to limit the vibrations to have the best autpilot as possible.
I look at systems like this and can't help wondering what happens when one of your o-rings fails etc. I went down this road myself a long time ago, trying to isolate another type of board that was sensitive to vibes. In the end, the best solution was to balance the motors and props properly to get rid of the source of vibes, instead of fighting it with ever increasing levels of isolation and complexity.
Is the APM really so vibration sensitive as to warrant such a contraption?
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