Long Version:
I decided to try loiter for the first time today on my DJI S800, it was okay for a few seconds and then a gust of wind hit and it was going all over the place. I flicked it back into stabilize and it was fine.
I tried loiter a second time, with similar results, however, this time after switching back to stabilize with the throttle very low (almost off) the helicopter ignored my inputs and continued to climb, then started oscillating. I eventually was able to get it to about a 3 feet above the ground and flicked throttle hold (instinctive reaction from my other helis, not a great idea on a multirotor), with only minor damage in the "crash" (went straight down on the landing gear, one arm broke from the stress, image attached)
Is it normal that for a few seconds after switching back to stabilize with the throttle a low position (~10%) the helicopter continued to climb? I am wondering if I am just over reacting to what felt like a loss of control (commanding it to move down and watching it fly up and away from me was not fun) and this lag time in control change is normal, or is something wrong with my setup? Could I reduce this loss of control by placing one of my modes as acro? I am much more familiar with a more direct form of control as in my regular single rotors (3D flight with BeastX or 3GX as FBL gyro) and the stabilize is still quite strange feeling to me.
Thanks all for any insight you may have, my experience on this platform is quite lacking still!
Short Version:
Switched from loiter to stabilize, decided to fly away from me and I wasn't able to regain full control for a few seconds, should I be worried or just repair and drop my gains?
btw, I'm guessing my P gain is too high if the heli is all over the place trying to loiter, is this a good assumption?
Replies
When you switch from loiter to stabilize, what level do you put your transmitter throttle at, right before going to stabilize ?
I'm quite familiar with the Z-vibration bug, but this does not sound to me like what happened to you.
Couple things:
Yes, there is a minor delay in the mode change. I think it's 1 second. It's done to "debounce" the switch. So, was your delay really a few seconds? Or did 1 second feel like an eternity as it often does in cases like this?
I'm guess the problem you had might have been the "Stability Patch Bug". This is usually caused by high PID tuning. What it looks like is the copter rapidly rocks back and forth in pitch or roll, and climbs a bit with each step. It is made worse in Stabilize mode. You can help stop the condition by going into Acro, and not fighting it. It may self stabilize if you leave it.
Hi Tom, unfortunately S800 is known to have major problems with the vibrations induced by the plastic arms (in the clone are still more), there are in fact kit to solve this problem, like this one:
Marco
Bad news about the arm - those S800 arm are not cheap!
This behaviour doesn't sound normal - even as an APM newb, I know that flicking from stablise to loiter and back works ok, and that loiter should be stable. My gains were too high as well, but I found that it affected stablise rather than loiter - my loiter has always been pretty good out the box.
Have you checked your vibration levels? That APM 'looks' secured directly to the frame without insulation. Is the APM getting enough juice? Is that GPS the right way up? I thought it was the other way round (I could be wrong!). Your 3DR is also in the middle of the frame - are you using MP for control? if so, you might want to extend the aerial outside of the aircraft.
Also, the climbing might be RTL; sometimes if RTL is triggered by a failsafe event, it needs to climb to a safe height before performing the actual descent. What your RTL settings, and can you detect if RTL has been triggered by a failsafe? (I don't know what to look for in the log, but I'd like to know myself!)
Edit: I hope that's not your flight pack in the pic there...no way will that have enough juice to power a S800! :-)
Edit 2: What are those XT60's doing? And are your powering the APM from an ESC/BEC?
Have you looked at the logs? Do you have any failsafe configured, as climbing might suggest its gone into RTL.