Hi. - Happy new year.
Im new to copters but have been using arduplane for a while.
I have been setting up a new quadcopter and following Dave Cs guide. Its flying very nicely in all modes and I have done a few auto missions around my field.
Before the problem flight I had done exactly the same Flight Plan (route and heights) except at speed 2m/s.
For the second flight I set 6m/s and a halfway waypoint with speed change to 10/m/s. On the way back there was another speed change down to 2 m/s.
Height keeping on this last flight was not great but on the way back it just went into full climb reaching 227m before I rescued it. The green height bar on the flight data display is defiantly below.
It is not an error in the flight plan and the alt-error feed shows an increasing error.
I just cant see why it did this.
Any help appreciated. Logs attached.
Looking at your tlog, it shows your distance to home at 250000 or something silly like that? suggesting the home point was not set correctly or there was an error with GPS?. You need to look at the dataflash files or post them here, to get a better idea of what happened..
log file for that flight uploaded
I think the strange home dist is after the last W.P. when it goes into loiter. GPS must have been OK as route nav was ok.
Is there a guide to de-bugging with the log files? I can graph log data in the CLI but cant see much different from the tlogs.
Did a 60 waypoint grid flight this morning at constant height and speed - no probs. Not confident it wont go ballistic again though.
Doesn`t make any sense to me? maybe something to do with using sonar? I haven`t used it before as it isn`t really needed and seems to cause issues sometimes..
Another idea, what APM are you using?
Thanks for taking a look Dean. I have had quite a few flights today, getting ever more adventurous and the last one had a speed change 10m/s to 2 m/s like the problem flight but all seemed OK today. On occasions it did seem reluctant to descend though so I increased the IMAX alt hold from 3 to 4. (not really sure what Im doing but it seemed to improve things) As far as I can see there is no parameter for descent rate.
I dont really want to turn this issue into a general shout for copter help but, auto land sometimes doesn’t quite touchdown and then climbs to ‘home’ or descends too fast, sometimes with drift. Also ‘takeoff’ wont take off in auto unless I’m already hovering. Cant find any info on that.
By the way Dean, I dont have sonar, but was thinking it may help with the landing?
Looks like you have a professional set-up?
I thought you had sonar as it was showing in the log file you posted? check it is turned off in hardware options... If you are using an open board i.e apm 1 or 2 make sure the air pressure sensor is covered with some cotton wool or something so that the wind or prop wash doesn`t affect the altitude. the altitude parameters and throttle will affect auto landing, You can get the machine to auto takeoff but it requires messing around or at least the last time I tries on arducopter 2.5 or 6 it did? it is possible though but requires making an error to take off and then the I term corrects the error in flight.. Probably sounds a bit confusing?
Now I run a business for aerial photography and cinematography although I dont use Arducopter for it as the kit costs around 10k a machine, so reliability and accuracy is very important, the APM will get there one day, and although it improves fairly quickly with time it isnt there yet, but a great tool for learning how these things work and how to fly.. The expesive stuff that I fly can get a little boring, so I get out a KK board or an APM to keep my hand in :) I plan to get another copter soon to put an APM on and get up to date with progress.
Data files of a recent upset - probably prop downwash. The copter was on the bench for ages so its a big file. Crash is at about 95%
Opps, sorry you meant these ones.
I have looked at your logs and I have some feedback. This does look like the effect I was talking about but I suspect the real problem was your tuning of roll and pitch. This is the most aggressive tune I have seen so far.
Stab_P = 7.5 (This is massive, I would stick to 4.5 on all Stab P terms)
Rate_P = 0.17 (Large but might be ok)
Rate_I = 0.01 (too small, should be as large as Rate_P or bigger)
Rate_D = 0.004 (good number)
I think you have tuned this to a whisker away from stable and the copter started to oscillate as you descended. The roll and pitch input you gave in the last second seems to be the final straw and it let go.
I would suggest that you leave the Stab_P terms all the same at 4.5. I would also re tune the Rate P term with the Rate I term at 0.1. Then once you have finished tuning Rate P, I would make sure that Rate I is the same size or larger. You may also consider reducing the Rate P by 25% if you are tuning to near unstable.
After tuning I do a number of tests.
1. Full Roll input and let go of the sticks. (No motor oscillation should be heard)
2. Repeat 1 for Pitch and Yaw.
3. Repeat 1 and 2 in fast climb at 3/4 throttle.
4. Fast decent on near zero throttle for 5m followed by full throttle (all at about 30m+)
5. Fast forward flight followed by leveling and applying full yaw (all at about 30m+)
6. Fast shuttle runs with full Roll and Yaw input at each end. (all at.... you get it)
Warning: I break cheap Hobby King props on 6. (my tune lets me fly on half a prop)
During 4 and 5 I expect to get some wobble but nothing scary.
If you can do these things without any problems you probably have a very good tune. With large props you may still have a good tune but not have the power in the motors to cope with the more extreme maneuvers. The large prop problem should be seen in 6 as the copter falling out of turns and maybe bucking.
I am very sorry to see your crash. I hope this helps.
Big thanks for taking a look at that. Will give those settings a try in the morning.
Im not sure if the PIDs reported in the logs are only those from start-up, as I spent some time changing them with CH6 and thought my rate P was more like .15 or lower at the crash.
The stab P ended up that high simply because there was no observable wobble up to that point but will back it way off tomorrow. I assumed it went higher than normal due to slower high inertia props.
Also, I find the yaw sluggish compared to RC heli and my first attempts as adjusting yaw stuff didn’t seem to improve it.
Is there an idiots guide to using the log files to diagnose problems. I can see that graphs etc in the CLI bit but can’t get much useful info out of them.
Yaw is very sluggish on copters compared to helli's. No amount of tuning can fix that. There is a danger in trying to fix it though. Because yaw is not controlled by the thrust of the props but the drag or taque of the motor you need much bigger rpm changes to get even a slow yaw than you do to correct pitch and roll.
If you push Yaw too hard you can quickly find yourself in a position where the Yaw is dominating the motor commands. We have added limits on this to help prevent things like the rise on yaw problem and even flips when yaw shuts down two motors and doesn't leave any control authority for roll and pitch.
The only way to increase yaw authority is by tilting all your clock wise props in one direction and your counter clockwise props in the other. This then applies the propeller lifting force to the yaw.
As you know, Heli's have a prop that directly applies it's lift to yaw control. Tri's have a rotating rear prop that does the same but also provides lift.
Yaw sucks, I got used to it :)
I am glad I could help!
Oh, and the I don't know anything about an idiots guide. But basically look at the ATT column to start with. In stabilize mode you want to see your commanded Roll and Pitch the same as your measured. It can also show you how far you are overshooting.