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having some issues with a custom quadcopter

#1
i 3d printed a 10inch prop quadcopter and im having some issues with it wobbling really bad to the point i cant get more that a foot or 2 off the ground and it just wobbles really bad and tries to flip. im going threw everything and making sure everything's tight and re checking that my flight controller is in cog i know the motors are spinning right all connections are good but it just refuses to take off and get in the air and if it does get up it just wants to flip, ive tried tuning the pids a bit and if i raise the p and d gain it gets a bit better and i can get higher but it still just starts wobbling and wants to flip i have a 6 inch fpv racing quad i built with no issues flies great this one thou is giving me lots of problems
 

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JasonK

Elite member
#2
The size difference is going to require different PID loop settings then your race quad. if your sure your not getting any frame noise/etc, then the next step is to work on your PID loop settings.

Regarding mechanical issues/etc.
  • Do you have all matching ESCs?
  • What ESC protocol are you using?
  • Are you over propped? (IE do the motors have enough torque to be changing the speed of the props fast enough to react to the PID changes).
  • Have you checked your black box data?
 
#3
The size difference is going to require different PID loop settings then your race quad. if your sure your not getting any frame noise/etc, then the next step is to work on your PID loop settings.

Regarding mechanical issues/etc.
  • Do you have all matching ESCs?
  • What ESC protocol are you using?
  • Are you over propped? (IE do the motors have enough torque to be changing the speed of the props fast enough to react to the PID changes).
  • Have you checked your black box data?
i have blheli 32 35a esc all matching
im using dshot 600
the motors are 935kv came with 10 inch props recommended for 3s
i just started tuning so i haven't checked to much with the black box yet but from what i did check on the gyro the right front and back left were fighting each other might've been from the loose arms

im waiting on some parts to replace the bolts use for the arms since they move a little so im gonna take care of that before continuing
 
#4
Yea sounds like gains need to be adjusted... set the I gain to zero and P and D to twice what you initially had them at for the first go and report back on the behavior. Oscillations? P probably too high. 'Noisy' looking response? D probably too high.
 

PsyBorg

Wake up! Time to fly!
#5
3d printed frames are hard to get to fly right at 3 inches let alone 10. My guess is you are getting a TON of vibration in that frame. This is why 99% of multi rotor craft use carbon fiber. Even then on a 5 inch with poor quality fiber they wont fly right. I had a 5 inch frame that when I flicked it with my finger actually resonated like a bell when it was just a bare frame.

If it was me tuning I would shut off all the filtering and fancy bells and whistles in betaflight. then tune with just pids. that way you know what you are tuning and that you are the only thing making the changes. The reason I say turn off filters is because if they are set too high you end up with it toilet bowling then resonating to the point you lose control and it flys away.

You can raise P gains first. Set I gains to 35 for pitch and roll. I would start with D at 20 but don't take D over 35 - 40 other wise you take a huge risk smoking the motors. Raise P gains by 10. Test hover for 10 to 15 seconds. Land and check heat on motors. Raise another 10 if they are cool and don't make you pull your hand away instantly. At some point you should start seeing a change without heating up the motors.
 
#6
alright the new hardware got here and i can actually get off the ground now but auto level mode it does not like and flips out and when i land one or 2 of the motors rev up slowly i thin i have some interference or my fc is not isolated well or somethings not tuned well on my transmitter possibly because if i just let it idle its fine but if i go to take off it flips out in angle mode
 

PsyBorg

Wake up! Time to fly!
#9
Several things going on here. If the quad wont lift off evenly in auto level mode two things can be effecting it. First is throttle calibration. If the motors dont start to spin at the exact same time when first armed then that could show an imbalance between motor speeds. Second cause for poor auto level flight is the accelerometer calibration was not done or done on a not level surface.

Motors speeding up when landing or bumping something.. thats a sign that air mode is active. Air mode and auto level should never be used together.

If the motors are changing just sitting still that is normal operation. Auto level actually makes it happen faster and more severe. What is happening is once armed the controller assumes it is flying and will immediately start correcting to be level. when it makes a change to motor speed and nothing happens it makes another change and will continue to hunt correct motor speeds until the quad is level. Dont leave a quad idling on the ground with auto level on. In acro its not so bad but auto level it will hunt until it flips over on its own from over correction.

Either lift off or disarm and rearm to be able to get in the air faster before it starts to hunt again.

As for stock pids they are wishy washy and about the same effect of trying to pilot a wet noodle. Add in a 3d printed frame with long arms and your creating the problem you see now. Start by isolating your flight controller better from the rest of the frame silicone stand offs are for this particular reason vs just the silicone gummy inserts that come with most flight controllers for hard mounting to a carbon race / freestyle frame.

Once the resonance in the frame effects the flight controller it starts a correction loop that adds each cycle until the craft starts to "Toilet bowl" and either loop locks and flys away or crashes.


EDIT: Also make sure those props re perfectly balanced. That would also be a huge contributing factor that is not so common with 5 inch quads.
 
#10
i ended up getting it off the ground hovered for a bit about 4 to 5 feet up and it started wobbling bad hit the ground and shattered 2 arms im re printing the arms and i found a isolation plate that isolates the electronics from the body and there's another isolation plate just for the flight controller my main printer started acting up up on me so im calibrating my second printer to print them and ill try again
 

PsyBorg

Wake up! Time to fly!
#11
i ended up getting it off the ground hovered for a bit about 4 to 5 feet up and it started wobbling bad hit the ground and shattered 2 arms im re printing the arms and i found a isolation plate that isolates the electronics from the body and there's another isolation plate just for the flight controller my main printer started acting up up on me so im calibrating my second printer to print them and ill try again
Yes that wobble is the reason carbon fiber and hard materials like it are used. Frame resonance is a HUGE hurdle to get past and what your seeing is in direct relation. This is why 95% or more of multi rotor craft use carbon fiber frames and the bigger they get even that makes it harder to tame.
 
#13
Yes that wobble is the reason carbon fiber and hard materials like it are used. Frame resonance is a HUGE hurdle to get past and what your seeing is in direct relation. This is why 95% or more of multi rotor craft use carbon fiber frames and the bigger they get even that makes it harder to tame.
Right, frame resonance is an issue, but you should still be able to at least get a decent controlled hover. I've flown really floppy hovering platforms and achieved stable hover before. My guess is still gains either cranked way too high or too low.
 

LitterBug

Troll Spammer
#14
Right, frame resonance is an issue, but you should still be able to at least get a decent controlled hover. I've flown really floppy hovering platforms and achieved stable hover before. My guess is still gains either cranked way too high or too low.
The Yaw gyro has vibrations written all over it. Probably just needs to soft mount the FC for starters...
 

PsyBorg

Wake up! Time to fly!
#15
Right, frame resonance is an issue, but you should still be able to at least get a decent controlled hover. I've flown really floppy hovering platforms and achieved stable hover before. My guess is still gains either cranked way too high or too low.
Im not the one building the quad... why quote me? I addressed soft mounting, frame resonance AND tuning issues in above posts..

After actually looking at the black box I'm gonna roll with unbalanced props and hi yaw P gain.

I had a noisy frame that rang like a dinner bell when you flicked it with a finger. Messed around with pids up and down would not hover. Shut filters off and it would hover. I did best tune I could on it and it would still build resonance in stable acro hover until it loop locked the gyros and went into fly away.

Floppy frames are one thing they can flex and bend and an FC will compensate. A singing frame it can never recover from no matter how you tune as it will always cross or fall onto the frames natural resonance and will be eternally unsafe due to unpredictability.
 
#16
i have my flight controller soft mounted with anti vibration fixed screw mounts but its still getting vibes im swapping to 9045 tri props (was using 2 balde 1045) and using this to isolate the flight controller completely with 2 levels of soft mounting the gummy's on the fc plate mount and then anti vibration fixed screw mounts for the flight controller its self
 

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PsyBorg

Wake up! Time to fly!
#18
Was just continuing the conversation...chill my man
All good mate. Just figured you should be passin info on to the guy needing help is all. Personal experience makes the advice seem to sink in better. I been flying multi rotor over 6 years now + I have to deal with Bills Law all the time.. I have pretty much experienced all that the hobby can throw at me hehe.
 
#19
All good mate. Just figured you should be passin info on to the guy needing help is all. Personal experience makes the advice seem to sink in better. I been flying multi rotor over 6 years now + I have to deal with Bills Law all the time.. I have pretty much experienced all that the hobby can throw at me hehe.
ive been into rc for years mainly small planes and cars but ive always loved quadcopters i started messing around with building them last year around nov so the electronics part and wiring i got but tuning and tweaking im still fairly new so any and all criticism is welcome if i cant manage to get this 3d printed frame to work ill just grab a iflight 10 inch frame and go from there i just want a big quadcopter for my kid to watch fly around since the small ones are hard to see, and at the moment im waiting on props to get here and prints to finish and ill start tweaking again
 

PsyBorg

Wake up! Time to fly!
#20
ive been into rc for years mainly small planes and cars but ive always loved quadcopters i started messing around with building them last year around nov so the electronics part and wiring i got but tuning and tweaking im still fairly new so any and all criticism is welcome if i cant manage to get this 3d printed frame to work ill just grab a iflight 10 inch frame and go from there i just want a big quadcopter for my kid to watch fly around since the small ones are hard to see, and at the moment im waiting on props to get here and prints to finish and ill start tweaking again
Good luck mate. Just be sure you keep your children at safe distances. Spinny vegomatics of deaths are no joke. This is a "Minor" oopsie.

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