Instability problem
I have been flying a custom-framed aluminum Arducopter on the Ardupirates code. I took a break for a couple of months and then recently started up again. I decided to switch to the AC2 path, so I updated the firmware with the most recent version of the code using the Mission Planner. I then went through the setup and test procedure described in the wiki, setup the motors, setup the radio, turned on and tested the sonar, and so on. I setup my mode switch to start in "Simple" mode. Thus far in the setup and testing, everything seemed OK.
But when I attempt to take off, the quad is extremely unstable. As I increase the power on the throttle, even before it gets off the ground, I see it rocking rapidly, with small amplitude but high frequency. When I juice the power to take off, it goes up a few inches or feet depending on how much power I give it, but is extremely unstable, rapidly whipping and tilting back and forth in increasingly large motions, as if it's desperately trying to get control but loosing it, and then flips and crashes. This same behavior happened consistently three times before I decided I had a definite problem and I needed to diagnose it.
I've seen various bad flight conditions (backward props, lose motor connections, broken props, etc.), but I've never seen this rapid oscillation and wild instability before.
Does anyone have any suggestions?
Tags: arducopter, flip, instability, quad
Replies to This Discussion
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3D RoboticsPermalink Reply by Chris Anderson on -
That sounds like's it's probably due to one the following (commonly found when people convert from Ardupirates and aren't aware of the differences). If I had to guess, I'd predict that it's #1 below.
1) Is your APM facing forward? (between the arms for X or towards the front arm for +)
2) Have you configured correctly for X or +?
3) Have you run the "motors" test in the CLI to make sure you've got all the motors hooked up right and props spinning the right directions? It's the same as before, but always worth testing again.
4) Have you held the quad in your hand with motors are 1/4 throttle and tested whether stick movements tilt it in the right way?
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Permalink Reply by Robert Beatty on -
Thanks, Chris.
1) Sorry. I should have provided more info. I'm flying a + configuration.
2) I thought I selected + during the configuration, but I'll double check that again.
3) I will run the motors test again.
4) I will try this test also.
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Permalink Reply by Robert Beatty on
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On #4, I just did a test holding the quad above my head while a friend handled the controls. The quad responded to throttle with lots of wind power and upward thrust. When we moved the roll stick left/right, it responded appropriately, but when we applied pitch forward and back, the quad rolled rather than pitched. Also, when we tried to yaw, the quad tilted quite a bit (where I would expect yaw to be a flat rotational movement, not a tilt).
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Permalink Reply by Robert Beatty on
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I also wanted to mention that I'm using a Futaba transmitter and it's in Airplane (Acro) mode.
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3D RoboticsPermalink Reply by Chris Anderson on -
Did you load the right firmware (quad)?
Have you run the motors test in the CLI?
Shown settings in the CLI to confirm that you're in "+" mode?
It's a setup problem of one sort or another.
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Permalink Reply by Robert Beatty on
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Chris, you were right. It was number 2 on your list. I had it configured for x instead of +. Once I changed that in the CLI, it flies very, very stable. Excellent. I'm flying again! :)
Thank you for your excellent advice. I'm sorry I made such a dumb mistake. I'm appreciative of you pointing me in the right direction to find it.
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