RTL comes home at right altitude. FBW-A flies nice. so PID's ire not too bad.
When in AUTO, AP applies negative pitch, and would hit terrain.
WP altitude is 100 -"Verify Altitude" not checked in planner.
I see in the log that targetalt = 103 and targetaltd100=1,0285 (what is this value??)
Actual altitude is 73, and AP is still descending at -7 degree when going for first WP. - any idea of why ?
Are you using an airspeed sensor?
Try disabling that and see if it makes a difference. That would give us useful info to debug.
Also, make sure you don't have Absolute Altitude selected. You should be using Relative.
Thank you for the advice, I'll fly soon (with airspeed sensor disabled in setup) - and report the results.
BTW: regarding the situation of my first report: I did use relative altitude. - and the altimeter was not displaying wildly wrong altitude before flight. (maybe + a few meters.)
You were right. The plane flew the mission perfectly.
Even at the sharpest turn, 320degree at 40degree bank angle - it stayed within the altitude of the whole trip between 110-118m - VERY nice.
The are two major differences between yesterday's and todays flight:
today, very little wind, yesterday - strong wind.
yesterday I had APM connection using TCP (GSM) - today - I forgot my Android - and were not able to remote control my workstation, and connect.
Are you still confident that the bug is related to the airspeed ?
- should I get back ASAP and redo the flight with telemetry ?
Would you mind to take a look at http://code.google.com/p/ardupilot-mega/issues/detail?id=569
- lots of tlog data and other info that might help hunting this bug down. :)
Chris: thanks for help - I assume you had reasons to suspect airspeed related routines. Hope we see a fix soon.
What was the conclusion of this case? Did the negative pitch have something to do with the AS-sensor?
I had same kind of issues with RTL and I thought they were caused by the failed (not precise) initial GPS calibration of the altitude. The plane flew nicely when I made a warm reboot from the APM button after the power up initialization.
I also think the gyros should be calibrated so that the plane has about 1-3 degrees nose up attitude.
Please let me know if you have some other opinions.
if you follow the bug link, you'll see that airspeed sensor was to blame. (or - rather the code apm that uses airspeed) however - I've never seen it interfere with RTH.
But why the APM wants to fly down when AS-sensor is operating. Is the airspeed minimum speed set too high so that the APM tries get more speed by setting nose down or what?
no, it reduces the throttle to 0% , and then keeps nose down as speed increases up to cruise speed. This would not be a way to recover from/avoid stall.
-We don't even have a place to ever stall-speed.
-also - remember that it's fully capable to RTL with airspeed sensor enabled.
This bug affects only AUTO mode. if other paramters were wrong, RTL would fail too.