Taking off like a rocket, near impossible to control

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MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Taking off like a rocket, near impossible to control

Post by MikeF74 »

I'm running an AIOP clone, and it's taking off like a rocket and is nearly impossible to control.

I have to have my Throttle Mid at .90 and Throttle Expo at .10 just to do anything with it, and it's still takes off fast and is so hard to control that I can't even begin to fine tune the PIDs. Does anybody have any suggestions?

I've balanced the props and minimized all vibrations. I've not balanced the motors, but they don't seem to have any excessive vibration. I've calibrated the ESCs and flashed to the latest firmware. I've spanned the radio inputs to 1000/2000 and sub trimmed to 1500.

Did I choose motors that were too powerful, or do you think there is just something wrong with my configurations (something obscure I might be missing)? I've been struggling with this off and on for two weeks now and finally busted up an arm, prop, and hard to replace motor mount. I'm at a loss. This thing climbs like a rocket with little stick, and the only way I can get it back down is to drop the throttle all the way and give it a blast once it's nearly on the deck (usually tumbles as it drops).

My build:
SK450 frame
AFRO 30A ESCs (SimonK)
HK Crius AIOP v2 clone running MW 2.3
10x4.5 Slow Fly props
Turnigy D2836/8 1100KV motors
3S 2700mAh battery
AUW: 1011g

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haydent
Posts: 583
Joined: Sun Jun 17, 2012 1:35 am
Location: NSW, AU

Re: Taking off like a rocket, near impossible to control

Post by haydent »

your setup appears like it should not do that.
hook it up to gui with props off, or motors disconnected, and arm, or arm with flight battery pack off, and check the throttle value at min throttle
and get back to us

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

It's not twitchy when revving the throttle on the bench, just in flight (in response to gyros I'm guessing).

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haydent
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Joined: Sun Jun 17, 2012 1:35 am
Location: NSW, AU

Re: Taking off like a rocket, near impossible to control

Post by haydent »

i guessing this is happening in acro mode ? ie no flight modes enabled like angle or baro
check you have the right gyro selected in config.h ?
with it plugged into gui i think there is way you an check your gyro working "correctly" by looking at corresponding graph for each gyro axis and rotating frame on that axis while watching graph response?

subaru4wd
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Joined: Sat Dec 08, 2012 2:16 am

Re: Taking off like a rocket, near impossible to control

Post by subaru4wd »

Does the quadcopter fall out of the sky like a rock when you reduce throttle? Or is it able to slowly descend?

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

haydent wrote:i guessing this is happening in acro mode ? ie no flight modes enabled like angle or baro
check you have the right gyro selected in config.h ?
with it plugged into gui i think there is way you an check your gyro working "correctly" by looking at corresponding graph for each gyro axis and rotating frame on that axis while watching graph response?
Yes, in acro. It's much worse with angle enabled. I'm no where near the point that I'd even attempt baro. I haven't plugged it into MultiWiiGUI in a while, not since it's been installed. I've been using an android app via bluetooth most of the time. But when I had it on my bench attached to the PC before installation, it responded appropriately to movements.

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

subaru4wd wrote:Does the quadcopter fall out of the sky like a rock when you reduce throttle? Or is it able to slowly descend?
It can't slowly descend, it just wants to climb. Well, it's really difficult to descend slowly. It ends up climbing away so fast that it's too difficult to thread the throttle just right to get it to descend at a decent rate, so I have to really just kill the throttle and then punch it when it's almost to the ground to prevent it from crashing. The second to last flight, I busted a prop. On the most recent flight I busted damn near everything on one arm -- only the motor survived. I'm waiting on new motor mounts to be delivered. I'll try to post a video once the new mounts arrive in a week or so -- I also need to go buy a hat so I can strap my mobius to it in order to get some video.

subaru4wd
Posts: 316
Joined: Sat Dec 08, 2012 2:16 am

Re: Taking off like a rocket, near impossible to control

Post by subaru4wd »

I suspect you have the MINTHROTTLE setting in config.h too high. Try reducing the value for Minthrottle to 1000.

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

I have it at 1065 or so, any lower and some of the motors fail to spin up when armed.

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haydent
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Joined: Sun Jun 17, 2012 1:35 am
Location: NSW, AU

Re: Taking off like a rocket, near impossible to control

Post by haydent »

and so if it spins up motors smoothly and slowly /gradually with props off on bench then it must be something sensor related.

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

My motor mounts won't be here until next week (and who knows when the weather will cooperate - we just had a bunch of snow).

Anyway, how many people find that they need to use the MPU6050 LPF filters? I'm thinking I might give those a try, thoughts?

MikeF74
Posts: 16
Joined: Fri Dec 13, 2013 5:38 pm

Re: Taking off like a rocket, near impossible to control

Post by MikeF74 »

Update: Things are a little better since I added the MPU6050_LPF_48 filter, but still not great. I might be able to finally start playing with the PIDs, but things are still a but wonk. I still need the extreme throttle expo set (as mentioned in an earlier post), but at least there isn't as much of a suspected sensor feedback loop that makes the craft want to continually rise. Occasionally it still jumps up a few feet when mostly hovering. I'll try to get a little video today. The 15mph wind with 25mph gusts aren't helping.

ttsalo
Posts: 7
Joined: Sun Jul 14, 2013 3:24 pm

Re: Taking off like a rocket, near impossible to control

Post by ttsalo »

I had somewhat similar problems with my quad (14x4.7 props, 1500 g AUW). For me the key turned out to be reducing the MAXTHROTTLE value (from default 1850 to 1650) so that the quad would hover at 50% throttle without expo. That completely changed the behaviour and made the quad reasonably controllable.

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