PROBLEM:
I am the pilot for a video production company, and they just had an F450 custom built. The first time I flew it, an arm broke off at the motor mount and it crashed to the ground breaking the GPS mount and 2 of the 12" props that came with it. I replaced all of the arms and did not disconnect any wires. I remounted things exactly the same. I zip-tied the GPS straight up and down and it consistently gives me an HDoP of 1.5 (mount broke at the base. Pole was fine) These last few times that I have flown it I have had a very peculiar problem.
I was testing the autopilot on a simple flight that had a circle WP and a loiter WP then another WP which triggered RTL. After the circles were completed the quadcopter seemed to be flying to its next WP but drifted down and bounced up off of the ground pretty hard. It seems like the throttle just wasn't enough. I then landed it and took off in loiter. I hovered 15 feet off the ground and after a minute it slowly came down and bounced back up. I put the throttle at full and it never responds.
I will attach the few log files that shows what happened. I have not had this long enough to familiarize myself with analyzing the logs. This is not good, very dangerous, and definitely not what I signed up for. Thank you for any help!
EQUIPMENT:
Pixhawk FC
RCxHobby 2814-700kv motors
Not sure what the ESCs are because they are black heat shrink wrapped (I was told they were upgraded)
3dr 915 mghz telemetry
Tarot 2d Gimbal
Turnigy 4000 mAh 4s Battery
3dr BEC Power controller
11 x 4.7 carbon fiber props
Ublox gps with built in compass
Turnigy 9x v2 TX and 8 channel Receiver
Replies
Hi Darren,
This is a funny one. Throttle goes to maximum but your current drops and voltage holds steady.
I wonder if your esc's didn't have their low battery slow down turned off.... You don't have RC out logged so I can't see if one esc went down or not. It also may be caused by an oscillation but I couldn't see any evidence of that in the logs.
As far as I can see the flight controller was doing everything it could to stay airborne but didn't have the power to do it any more.
You cannot/should not take off and land in loiter mode.......
Gustav, this is blatantly false!
Loiter is a mode that is designed to keep the copter in one place, altitude included.
You can "bump" it to a new position using the rc controller, but the onboard sensors will heavily dampen your inputs.
No good for the quick reactions required for TO and Landing.
Hi Gustav,
I am in a rather unique position to say exactly what Loiter was designed to do. This is because I am the one who designed both Loiter and Alt Hold.
Loiter is designed to approximate a docile stabilize in perfectly calm conditions. Alt Hold is a rate input altitude controller. As such they are very good at making fine adjustments during landing and takeoff. They both also transition very nicely into larger position adjustments.
On a well setup copter Loiter and Alt Hold are much much faster than a pilot at compensating for external disturbances.
When I am landing in extremely gusty and turbulent conditions, 30km/h winds + gusting and a rotor, I often switch to loiter to ensure a safe gentle landing. I often go out in these conditions to test loiter and auto modes.
So again, Loiter is fine for takeoff and landing provided the copter is set up well and has good GPS reception. In fact, it won't be long before more people take off in loiter or an autonomous mode than in Stabilize.
Well, thanks for putting me in my place :-)
I have a 3DR quad, APM 2.6 clone.
(I had a "real" Apm 2.6, until I installed the 3DR OSD.., long story, alcohol involved)
I've done the Auto Tune thing.
I come from RC background since 1980, fixed wing, and later Heli's.
And for me, there is a significant lag in response between Stab, and and every other semi, or full auto type mode.
My fault, "old dog, new trick" thing ?
No problem Gustav!!
I actually guessed based on what you said that you may have been using Arducopter for a long time.
I have been testing changes that will make Loiter just as sharp as Stabilize but they won't be out until the next release.
As for alcohol and copters. I understand. The first time I testing Autotune (I designed that too so I mean the first time autotune was ever tested) was the day I got home from hospital from a knee reconstruction and still had a fair bit of morphine in my system. Long story short is autotune made my copter much faster to react and I have two decent scars on my neck. I was very happy with the performance of autotune though :)