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Permalink Reply by Eddie Furey on August 28, 2012 at 3:55am

I'm going to guess that the answer lies in the size of a 'notch'.

A control channel has roughly 1000 steps, ranging from 1000 to 2000. The upper and lower limits vary with each controller, but 1000 is a rough average. Roughly in the middle is the mid-point that is (roughly) 1500. I'm guessing that one 'notch' of your throttle trim changes your throttle midpoint by more than 1 step.

Copter guys feel free to jump in here, I have a plane so I'm partly just guessing

In any case, APM should keep your copter level when your throttle is set at it's mid point. It doesn't really matter if the midpoint is 1470 or 1550, as long as the APM software knows where you think it is.

Go to the mission planner, have a look at the value for your throttle channel in the Radio Calibration tab. Then find the parameters section and set your channel 2 mid point to the same value as you saw in the radio config panel.

I looked up the ArduCopter wiki and the copter doesn't seem to have the same raw parameters tab that ArduPlane has, so I hope this helps some how. :)

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Permalink Reply by Rick Eis on August 31, 2012 at 8:48am

So what is the magnetometer, atmospheric pressure, gps and sonar for in this case?  I thought if we take our hands off the sticks, the quad would get to an elevation and hold itself there.  And I thought if one had sonar, the elevation would be held even tighter at the lower elevations?  What am am I missing?  

In this thread below there are all kinds of fixes discussed for this issue, including removing the notches from our transmitter controls.

http://diydrones.com/forum/topics/adjust-the-sensitivity-of-throttl...

I don't understand ?  I would have thought in my "one notch down" situation, if I had my hands off the stick, that the copter would go down to the elevation that "notch" represented and "hold" itself.  And I thought that between the gps z coord, the barometric pressure, the magnetometer and the sonar (at lower elevations) that the copter would be able to hold itself.  

What am I missing?  What does the APM2 do with all this information when we get our hands off the stick?  What signal takes precedents....the gps, the barometer or the "one notch down" situation? 

Thanks in advance for your thoughts  :)

Rick

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DeveloperPermalink Reply by leonardthall on August 31, 2012 at 9:05am

Hi Rick,

I found the throttle very sensitive in Stabilize mode too and the way I addressed it was to adjust the center point of my throttle throw to be at hover then added expo. It was like night and day for me.

I also asked about the throttle control loops in my blog here.

http://diydrones.com/profiles/blogs/why-are-the-throttle-pid-s-like...

I think you want Alt Hold.

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Permalink Reply by Rick Eis on September 1, 2012 at 12:00pm

Leonard,

Wow...yes...just getting rid of the notches was day and night for me.  I have an older Hitec without many bells and whistles, but all I did was put a little tape on the throttle notches. With all my experience wrestling between notches, once they were removed I felt like a pro :)  Thanks so much.

Yes, I'm wondering if you could walk me through the diagrams.  I really would like to understand them.

I also took the time to put in a six position switch  - so now I can experiment a little more with the other modes.

Thanks again,

Rick

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Permalink Reply by Erik on September 1, 2012 at 12:32pm

Leonard et al,

I have been flying RC helicopters on and off for many years and now I have been bitten by the copter bug...

One lesson that I have learned is to remove the throttle ratchet inside the TX box. I think all heli flyers do that as a standrad practice.

It is a small metal ratchet (excuse my wording if it is not the correct one, english is not my native language) that sits in the throttle mechanism inside the TX box, very easy to remove or displace. Once done you have a very smooth throttle stick without notches.

It is the same with quadro-hexa-copters, it has to be removed. Throttle movements around hover position is just a fraction of a millimeter to keep a stable altitude when in a mode that is not stabilized/ alt hold.

Erik

 

 

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