Copter slowly descends or climbs in loiter mode

ArduCopter Copter 3.1
1

I recently test the pixhawk in loiter mode, I find my hexa slowly descends or climbs in this mode until I switch to stabilize mode. I use
a. DJI F550 b. Pixhawk 2.4 c. ArduCopter V3.1.2(e2e3dd1) d. T14SG

My logs and pics has been attached below. I got my THR_MID value according to this page
http://copter.ardupilot.com/wiki/ac_throttlemid/
I disarm my hexa in stabilize mode, then adjust the throttle to keep the hexa hovering. As shown in
log and pic also attached. I changed my THR_MID to 500. Is this value correct?

Then I disarm my hexa in loiter mode, the GPS is good and HDOP is below 2. I push the throttle beyond 50% (about 60%), then my hexa climbs up, I pull the throtle to the middle position, but my hexa still climbs up slowly. I pull the throttle below 40%, hexa descents, I push the throtle to the middle position, it dose not stop, continuing to descent. I read the loiter mode and altitude hold mode separately from
http://copter.ardupilot.com/wiki/loiter-mode/
http://copter.ardupilot.com/wiki/altholdmode/#Controls

BarAlt(CTUN) WPAlt(I have not find this para…, but DAlt in CTUN), RelAlt(GPS) as show below

log and pic also attached. I want kwon

  1. Is there anything wrong in my operation?
  2. How can I keep the hexa a certain altitude when I put the throttle in middle position in loiter mode?

Thanks to anyone can give me advices!

2

ALT

[quote=“xiazibin”]I recently test the pixhawk in loiter mode, I find my hexa slowly descends or climbs in this mode until I switch to stabilize mode. I use
a. DJI F550 b. Pixhawk 2.4 c. ArduCopter V3.1.2(e2e3dd1) d. T14SG

My logs and pics has been attached below. I got my THR_MID value according to this page
http://copter.ardupilot.com/wiki/ac_throttlemid/
I disarm my hexa in stabilize mode, then adjust the throttle to keep the hexa hovering. As shown in
log and pic also attached. I changed my THR_MID to 500. Is this value correct?

Then I disarm my hexa in loiter mode, the GPS is good and HDOP is below 2. I push the throttle beyond 50% (about 60%), then my hexa climbs up, I pull the throtle to the middle position, but my hexa still climbs up slowly. I pull the throttle below 40%, hexa descents, I push the throtle to the middle position, it dose not stop, continuing to descent. I read the loiter mode and altitude hold mode separately from
http://copter.ardupilot.com/wiki/loiter-mode/
http://copter.ardupilot.com/wiki/altholdmode/#Controls

BarAlt(CTUN) WPAlt(I have not find this para…, but DAlt in CTUN), RelAlt(GPS) as show below

log and pic also attached. I want kwon

  1. Is there anything wrong in my operation?
  2. How can I keep the hexa a certain altitude when I put the throttle in middle position in loiter mode?

Thanks to anyone can give me advices![/quote]

3

I spent quite a while debugging a similar mode, and had found an that I had inadvertently checked that I had a SONAR when I did not.

I presume the code was looking for data from it when I was close to the ground, and that was messing the control loop code.

4

[quote=“interplanetary”]I spent quite a while debugging a similar mode, and had found an that I had inadvertently checked that I had a SONAR when I did not.

I presume the code was looking for data from it when I was close to the ground, and that was messing the control loop code.[/quote]
Yes!

You are correctly right!

Thanks for your help!