switch to loiter and it flies away!

[wildernessbob]

I have a CN-06 gps with the APM 2.5 fc, the first time i switched to loiter the quad dropped about 2'; then seemed to loiter fairly well, though a bit twitchy, then after about 30 sec, it took off up and to the right. now it does it every time and even if i try RTL. any thoughts?
wb

[firey1]

your prob not giving the gps enough time to get an accurate fix
recommended time is 3 mins on power up before flying for the best performance of the gps in any flight mode that requires GPS

Mike

[wildernessbob]

thanks Mike. i don';t know how long i had the fix before flying, but i';ll make sure to give it at least 3 min. next time. i';ll keep you posted.

[rickp]

Download your logs and look at the HDOP in the GPS message - that will give you some indication how good the fix is, and if that changes. You really want a sub 2.0 HDOP and sub 1.0 is very good.

[wildernessbob]

Thanks Rickp, I';ll have a look.
wb

[Toledodave]

Im sorry but i couldnt help but to laugh seeing your thread name!   Sorry to hear but funny!  Sounds like my luck!    I met a hunter in the woods one day! He said: (Hillbilly Voice) i pulled the trigger....and she was gone!  Not sure if he ever found his dog! Lol

[wildernessbob]

yuk yuk, thanks toledodave. sometimes when i';m dealing with this stuff i feel like a hillbilly.
wb

[Toledodave]

Bah...no worries myfriend. We all have our troubles. If it were that easy there would be no need for forums and never get too meet the intresting ppl around the world sharing the same intrests in life!  I was just trying to laugh with you. Ya got to keep the humor or the hobby turns into a job and thats no fun. I wish you luck and remember dont lose hope. The simplest things can cause havok in this hobby and ya just gotta shake it off get back on the saddle and ride on.

[FragglePete]

I have a CN-06 gps with the APM 2.5 fc, the first time i switched to loiter the quad dropped about 2'; then seemed to loiter fairly well, though a bit twitchy, then after about 30 sec, it took off up and to the right. now it does it every time and even if i try RTL. any thoughts?
wb

My APM does a drop as well whenever I put it into Loiter - got to the point now where I';m just scared to use it and I';ve had one crash a result of this. 

Pete

[Rocket_Col]

I had that problem. Sorted it by putting APM above lipo, loading latest firmware (3.0 i think) having my GPS as far up as the wires would let me, mounted it on a 1.5mm thick piece of aluminium on a CF rod. and did a manual compas calibration. was almost ready to put in bin as alt hold, loiter and RTL were well scary. followed pointers and advice from ppl on here. make sure the apm is isolated to keep vibration free (as much as you can) hope this helps

[ericb]

I wonder if this be of help....I know it';s the AIO, but it will be the same software :

Crius AIO Pro GPS Loiter fix

Eric

[wildernessbob]

Thanks guys, that helps to know i';m not alone and that there is a solution. i was concerned about the drop in alt when switching to loiter as well, but from the video it looks like thats just the way it is, but i all the other videos i';ve seen before building mine, they switch to loiter and it just stays there. real nice like. i';ve just upgraded to 3.0 and haven';t tested it yet, i';ll keep you posted.
wb

[rickp]

I wonder if this be of help....I know it';s the AIO, but it will be the same software :

Interesting - though I';m not yet convinced on the GPS being turned issue. You definitely need to wait longer than you';d think to get that first fix - 3mins is good (though if you have telemetry, seeing hdop drop below 2 is a good clue).
I';ll try and turn my model next time I change battery and see - I just can';t see how it makes any difference to the GPS as the aerials aren';t directional...

[rickp]

Thanks guys, that helps to know i';m not alone and that there is a solution. i was concerned about the drop in alt when switching to loiter as well, but from the video it looks like thats just the way it is, but i all the other videos i';ve seen before building mine, they switch to loiter and it just stays there. real nice like. i';ve just upgraded to 3.0 and haven';t tested it yet, i';ll keep you posted.
wb

On an APM running 3.0.1, you shouldn';t see a drop when you go into loiter or alt-hold. However, you probably need to get your THR_MID set correctly...

[wildernessbob]

this whole PID thing is eluding me. when i';m in the mission planner looking at the PID';s there are all sorts of them, and it seems that more than 1 say throttle or loiter or whatever, plus there is the iMAX thing too. how do i know which is which?
wb

[firey1]

One of the big issues when going to loiter or others is your throttle stick placement

It needs to be on the upper side of half or it will drop
they changed this in an earlier version   

[rickp]

this whole PID thing is eluding me. when i';m in the mission planner looking at the PID';s there are all sorts of them, and it seems that more than 1 say throttle or loiter or whatever, plus there is the iMAX thing too. how do i know which is which?
wb

Depends what you';re trying to achieve. On 3.0.1 the only PID i touch is the top one in this screen:



I hold the model down, and increase the throttle. If it oscillates quickly, then reduce the PID. So I setup ch6 to tune that parameter, and then I can reduce it whilst i';m holding the model down. Then you can feel if the model feels like it';d fly - does it try and level if you roll or pitch it? Does the cyclic stick give the right response? If so - I feel confidence enough to fly it and tune the rate p in the air.

Thats the only PID I touch - everything else is stock. If you';ve got a good CoG, I think thats all you neeed...

[wildernessbob]

i see, i';ve never looked at it. i do know that it hovers at about mid stick though. so, while i have you, it';s a real bugger to get this thing to hover nicely. i just touch the stick and up it goes, so i ever so slightly bring the stick down and it sinks, so i touch it up realy gently like and up it goes again. is this normal?

[wildernessbob]

COG is good. i read a very long post on how to set the PID';s and it told me to turn the I & D to 0 then play with the P then the D then the P again etc. i just got lost. does that P setting affect loiter as well as stable flight?
wb

[firey1]

i see, i';ve never looked at it. i do know that it hovers at about mid stick though. so, while i have you, it';s a real bugger to get this thing to hover nicely. i just touch the stick and up it goes, so i ever so slightly bring the stick down and it sinks, so i touch it up realy gently like and up it goes again. is this normal?

Put a bit of expo on your throttle so mid stick isnt so sensitive

[rickp]

COG is good. i read a very long post on how to set the PID';s and it told me to turn the I & D to 0 then play with the P then the D then the P again etc. i just got lost. does that P setting affect loiter as well as stable flight?
wb

The rate controller is the base of the control system. Prior to 3.0, tuning was a bit of a game - but its improved enormously in 3.0.

When you say the model goes up and down - are you in stabilise, or alt-hold? In stabilise, you may want to adjust your throttle on the tx to make it easier - you are manually flying the model after all. If its in alt-hold, then you should have a dead band around mid-sticks, and then find the model climbs/drops at a rate proportional to your distance from mid-sticks. If its not doing that, you may need to check your vibrations on the z axis...

[wildernessbob]

I am in stable mode. i';ll check the Z axis vibrations first i guess.
wb

[DarrenG]

I am in stable mode. i';ll check the Z axis vibrations first i guess.
wb

thats the first thing you must do.

[rickp]

I am in stable mode. i';ll check the Z axis vibrations first i guess.
wb

Have you set THR_MID? If not - how much throttle is needed to hover? Why not post a log of a test flight with IMU logging turned on....

[wildernessbob]

throttle is just over 50% i believe. i';ll have a closer look and try and get the logs posted. don';t know when i';ll get the chance though. watch this space!
wb