Replies to This Discussion

Permalink Reply by Andrew Jenkins on May 31, 2011 at 6:58pm

Yes I would say that would be a problem I always sit my quad on fairly level ground on the skids then attach the battery connector then do not touch it until it has booted completly.

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Permalink Reply by Sebastian Gralla on June 1, 2011 at 6:51am

just to clarify, your quad has not to be level on power up, it should just not move ;)

 

and you're correct, only gyros are calibrated on startup

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Permalink Reply by Greg Fletcher on May 31, 2011 at 9:08pm

This problem sounds like a gyro zero/temp problem to me. IMU chips out there in the sun and wind on most copters. I looked at the shematic and found a temperature analog channel. I thout it had temp comp, but wasn't sure. I then looked at the IMU code and I'm not sure but I think there might bee a problem with the <_sensor_compensation(uint8_t channel, int temperature)>,  and specificaly this

<const float   AP_IMU_Oilpan::_gyro_temp_curve[3][3] = {
    {1658,0,0},            // Values to use if no temp compensation data available
    {1658,0,0},            // Based on average values for 20 sample boards
    {1658,0,0}
};>

Maybe I just don't get it ?  Shouldn't those zeros be some values?

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DeveloperPermalink Reply by jasonshort on May 31, 2011 at 9:29pm

As far as I remember, Doug said that you would need to do a freezer to oven calibration and create a polynomial curve to represent temp comp. What your seeing is a generic shortcut.

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Permalink Reply by Oliver on May 31, 2011 at 11:09pm

while at the topic. In STABILIZE mode I do see mine permanently drift backwards without stick input at a pretty fast rate if i don't give it forward stick to counteract. as RC trim is not an option I was wondering what affects this and how to troubleshoot ?

 

I leveled it very carefully in setup as well and kept it super steady during startup calibration. what else could effect that behavior? It also persists between erases and factory resets and shows the same "backwards" drift consistently every time.

 

Otherwise 2.0.20 works great now!

 

Would be grateful for any hints.

 

 

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Permalink Reply by Kristian on June 1, 2011 at 12:13am

Why is RC trim not an option? If the quad is not in balance or you have a arm/motor pointing slightly in wrong direction etc., you will have to use some RC trim to avoid drift.

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Permalink Reply by Sebastian Gralla on June 1, 2011 at 6:54am

no, don't use RC trims

did you calibrate your accelerometers? you didn't mention...

if yes, tilt your quad slightly forward and calibrate them again

 

your quad has not to be leveled on startup, just still

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ModeratorPermalink Reply by John Church on June 1, 2011 at 7:41am

Oliver,

After you hold forward for a few seconds, does the quad want to fly backward with even more force than just after taking off?

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Permalink Reply by Oliver on June 1, 2011 at 7:51pm

John, No, it's a steady drift.

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Permalink Reply by Oliver on June 1, 2011 at 12:49am

Wouldn't it interact with other modes like SIMPLE mode for example, where the front is not always the quad heading ?

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Permalink Reply by Kristian on June 1, 2011 at 1:55am

It seems strange to me that temperature differences is causing this problem. Because:

1. There is no problem when running Ardupirates

2. The quad is flying level. After flying back and forward just a couple of times, the center is way off. We are talking about seconds from level flight to incontrollable. Sometimes I have to emergency land because I'm not able to give enough rudder to get the quad level.

 

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Permalink Reply by Oliver on June 1, 2011 at 3:01am

I don't see that behavior. I assume you are talking about STABILIZE mode ?

My backwards drift is constant and does not change. If I keep giving forward stick, I can fly quite stable.

 

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