Hi
I was trying to see vibrations on my quadcopter using log files. I tried to use mission planner to analyze logs, but all I see is flat lines for AccX, AccY, AccZ even at maximum zoom level. I have attached the log file. If someone can give me some insights into it, It will be very helpful.
Regards,
Pritam
Replies
Yes, despite my intuition the foam was adding to vibrations. Attached is the log file where vibrations have halved after removing the foam. Looks like I fell for premature and misinformed optimization. Thanks again. I have uploaded photographs. the photograph of the APM is without foam, just dual sided tape. the motors have just four screws on the bottom side.
2014-11-20 23-21-36.bin
IMG_20141120_233955966.jpg
IMG_20141120_234032434.jpg
not your fault. there are loud foam advocates, none of which quietly present hard data like you just showed. Now if you can decrease vibs by a factor of 10, you are good to go. Cala just did that using the same approach.
thanks for the photos. your copter looks OK. my only suggestions to try:
- the four screws attaching the motors should be plenty as long as they tighten
- are there only two screws attaching each motor masts to the electronics platform (impacts mostly z)?
- anything you can to to get rid of weight will help. the lower throttle it takes to lift the craft, the lower the vibs.
- spin up each motor individually to a low RPM. Look for wobble/shake at low RPM. If you see any, the motor/prop is out of balance (impacts mostly x/y; you can't see the shake at high RPM).
- if the APM doesn't feel attached enough, use a little hot glue (any glue will help).
Under the IMU records, column 6-8, all of the accel data is there.
Do a flight where all you do is hover as best that you can for 1 minute. Then post the log file. That is a good place to start. Right now, it is hard to see what's happening.
Does it make a difference if quad hovers in stabilize, althold or acro mode. which one will be better for getting the most realistic results.
when you do a 1 minute hover so we can see what's happening when we toss the data into Hover Analysis, do it in the mode that allows you to control the craft the easiest. for me, a sucky pilot, it's stabilize mode. if your alt hold or loiter modes have pretty good PID tuning, you can use those. just pick the mode that results in the least jerky hover. as Graham pointed out, from a data point of view it doesn't matter.
I reset the LOG_BITMASK. I have set it to defaults + IMU. Took a 1 minute log. When I opened the log file in mission planner, it said too much bad data - failing. It still opened the file. But the graphs are either quite smooth or have huge spikes. Don't understand this. I didn't fly the copter hard at all. I just flew it in stabilize mode then a little bit of altitude hold and a little bit of roll movement and finally land.
BTW the quad flies fine. But I won't know better because this is the only quad I have. I just wanted to know how much vibrations the copter has and whether I am missing something due to vibrations.
2014-11-11 22-47-20 1.log
The file appears to be corrupted. It has records identified as IMU records that aren't.
Can you reload the firmware onto the APM and try again?
Before you do that though, when you hovered,
- could you physically see any vibration at the APM?
- What is between the motors and APM (follow the vibration route and describe it)? Motors to screws to motor mounts to motor mast to ...
previously I was running 3.1, but then I thought if I am flashing again, lets try 3.2.
With 3.2 I am getting proper log data. I see vibration graphs and they don't look too bad.
I can't physically see vibrations at APM. I followed the route between motors and APM. The motor arms had some vibrations but after that the centre plate had very fine vibrations only.
I have attached the new log file, I think i am getting a maximum deviation of about 0.4.
2014-11-16 16-44-34.bin
If that is your latest log file, it doesn't look good--a factor of 10X to 20X too high.
thanks for the correction, I looked at the graph again in APM planner. Its much more readable than mission planner graph and I see your point. My deviation is coming out about 2.0+ while it should be less than 0.2. Time to look for better dampner.
Right now, i was just using foam that came in the motor casing. I guess thats not very great for vibrations dampening.
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