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Old Sep 20, 2012, 08:47 PM
CNC Machinist
Australia
Joined Jun 2009
211 Posts
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Hobbyking Multiwii lite V1 problems

Hi everyone, was hoping someone may be able to give me some advice. I've just recently built my third Quad and I have this time used one of the newly available HK multiwii boards. After much playing around with settings in the firmware and configuration options, I've managed to get my quad airborne, but I'm still having some random problems with the flight controller.
The quad takes off and hovers fine, and seems to be stable in forwards flight however, it will spontaneously drop from the sky in a mad rocking motion when higher throttle settings are applied (I.e pulling up from a drop). It sounds like vibration issues, but the same quad flies fine with my KK board attached and doesn't have these problems. I've tried dropping the PID values but I can't drop them enough to remove the problem and remain stable.
I've got the low pass filter set pretty low already (With the default setting I couldn't even get off the ground) so I'm currently on 20Hz, but I can't see why I should need to go any lower.

I haven't got a video of the problem, however If you need to see the problem I can get one.

Any help appreciated
Cheers, Daniel.
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Old Sep 20, 2012, 10:29 PM
Emress
sirbow2's Avatar
United States, SD, Rapid City
Joined Nov 2011
1,936 Posts
yeah high fast quick etc throttle can mess it up if your pids aren't right. try going to stock PID and then lower P until it doesnt oscillate. then tinker with I/D
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Old Sep 20, 2012, 10:50 PM
Registered User
Canada, ON, Alliston
Joined Sep 2009
178 Posts
Check your ESC's

check your ESC's, i had a similar problem with my latest quad, hover was perfect, start to put some power to it and became very unstable, i swapped out everything even tried another FC, figured it had to be vibrations or something small, then decided to swap ESC's, they were "weak", they would work for hover or very slow climb but anything after that and it became unstable, swapped them out for new ESC's and it flies like a dream with no other changes.

Quote:
Originally Posted by dmcke5 View Post
Hi everyone, was hoping someone may be able to give me some advice. I've just recently built my third Quad and I have this time used one of the newly available HK multiwii boards. After much playing around with settings in the firmware and configuration options, I've managed to get my quad airborne, but I'm still having some random problems with the flight controller.
The quad takes off and hovers fine, and seems to be stable in forwards flight however, it will spontaneously drop from the sky in a mad rocking motion when higher throttle settings are applied (I.e pulling up from a drop). It sounds like vibration issues, but the same quad flies fine with my KK board attached and doesn't have these problems. I've tried dropping the PID values but I can't drop them enough to remove the problem and remain stable.
I've got the low pass filter set pretty low already (With the default setting I couldn't even get off the ground) so I'm currently on 20Hz, but I can't see why I should need to go any lower.

I haven't got a video of the problem, however If you need to see the problem I can get one.

Any help appreciated
Cheers, Daniel.
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Old Sep 20, 2012, 11:30 PM
Registered User
Australia, QLD, Brisbane
Joined Nov 2011
949 Posts
If your ESCs are pulling too much power the battery voltage might collapse and the board resets at high throttle.
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Old Sep 21, 2012, 12:17 AM
CNC Machinist
Australia
Joined Jun 2009
211 Posts
Hi guys, thanks for the fast responses!
Still playing with it and haven't had much luck. Definitely not voltage dropping, as the board continues to run. My motors are pulling 2.5Amps each at full throttle on 6Amp Turnigy Plush esc's and a brand new 800Mah 2s 45c Lipo. I've just tried balancing the props and the problem is still there. I have my FC board mounted on silicon tube with screws from either side, so vibration at the controller itself shouldn't be an issue anyway. I read somewhere that there may be a very "Undocumented" problem regarding the low throttle setting in the firmware itself but I haven't been able to find much info on it. My speedies all arm properly and run up and down without a problem.
I'll try and give you a better description of what happens when it plays up. The quad will be flying very nicely(Very stable and no oscillations) I can flick it all over the place and the FC responds and corrects accordingly, and its generally very nice to fly. But then all of a sudden its like the FC gets confused and quickly turns the front right and rear left motor on and off constantly(I'm running X Quad btw) Which causes the quad to come falling down due to the loss of lift.

Lucky its a tough little thing, as it must have survived nearly 50 crashes so far without anything but broken props!

I've attached some photos just so you know what I'm talking about with the board mounting.
http://i302.photobucket.com/albums/n...ps9f0d3d04.jpg
http://i302.photobucket.com/albums/n...ps99265920.jpg

As always, Any suggestions would be great
Dan.
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Old Sep 21, 2012, 12:23 AM
Custom quad builder
tech69x's Avatar
United States, TX, Spring
Joined Apr 2012
2,364 Posts
Quote:
Originally Posted by dmcke5 View Post
Hi guys, thanks for the fast responses!
Still playing with it and haven't had much luck. Definitely not voltage dropping, as the board continues to run. My motors are pulling 2.5Amps each at full throttle on 6Amp Turnigy Plush esc's and a brand new 800Mah 2s 45c Lipo. I've just tried balancing the props and the problem is still there. I have my FC board mounted on silicon tube with screws from either side, so vibration at the controller itself shouldn't be an issue anyway. I read somewhere that there may be a very "Undocumented" problem regarding the low throttle setting in the firmware itself but I haven't been able to find much info on it. My speedies all arm properly and run up and down without a problem.
I'll try and give you a better description of what happens when it plays up. The quad will be flying very nicely(Very stable and no oscillations) I can flick it all over the place and the FC responds and corrects accordingly, and its generally very nice to fly. But then all of a sudden its like the FC gets confused and quickly turns the front right and rear left motor on and off constantly(I'm running X Quad btw) Which causes the quad to come falling down due to the loss of lift.

Lucky its a tough little thing, as it must have survived nearly 50 crashes so far without anything but broken props!

I've attached some photos just so you know what I'm talking about with the board mounting.
http://i302.photobucket.com/albums/n...ps9f0d3d04.jpg
http://i302.photobucket.com/albums/n...ps99265920.jpg

As always, Any suggestions would be great
Dan.
Your asking for trouble with the metal screws to hold the board in place
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Old Sep 21, 2012, 12:35 AM
CNC Machinist
Australia
Joined Jun 2009
211 Posts
Quote:
Originally Posted by tech69x View Post
Your asking for trouble with the metal screws to hold the board in place
Why's that? They are screwed into silicon which should be isolating a lot of vibration. Unless there's something I haven't thought off?
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Old Sep 21, 2012, 01:28 AM
CNC Machinist
Australia
Joined Jun 2009
211 Posts
Seems to be PID related after all. Bumped all of my P values down till the quad was barely controllable and then edged them up slowly and I now get through almost a full battery pack without a problem. Still not perfect sadly though My rudder doesn't stop turning as fast as I'd like when I let go of the stick now. Maybe I need to read up on the PID's so I understand them a bit better. Everywhere seems to give a different explanation.

Daniel
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Old Sep 21, 2012, 08:58 PM
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Dave66's Avatar
United States, NH
Joined Jul 2012
19 Posts
Quote:
Originally Posted by dmcke5 View Post
Seems to be PID related after all. Bumped all of my P values down till the quad was barely controllable and then edged them up slowly and I now get through almost a full battery pack without a problem.

Daniel
Couple of thoughts, have you tried to duplicate the problem while hooked up to the GUI and holding down the quad, you may see some elect interference at full throttle.
The silicon mounts may be too soft or flexible under high loads causing vibration problems, I know this seams odd but 1 guy had his board suspended with rubber bands and his board shook under high loads. Having to use or reset the low pass filters is usually correcting for a vibration problem. Maybe try remounting the board.
I'm not sure why but most people do not use 3 bladed props although some do with no problems. Something about turbulence while descending, maybe prop wash, not sure.
If your running 2.1 the problem is not the firmware. Are the board/sensors properly defined in config.h?
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Last edited by Dave66; Sep 21, 2012 at 09:19 PM. Reason: addition
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Old Sep 28, 2012, 09:27 PM
CNC Machinist
Australia
Joined Jun 2009
211 Posts
Pretty sure It's just all vibration. With the values down low enough(And a good balance of the props), the quad is flyable. For mounting boards in the past I've just used a bit of foam double sided tape, but I needed this board to sit up a little to allow the wires to run underneath it. I've seen plenty of commercial quads and Kits supplied with 3 bladed props, and haven't really heard anything bad about them. Turbulence while descending will always be a problem as far as I can tell it shouldn't matter if you have 2 or 3 bladed props...
Took a little while to get the sensors properly defined in config.h as the board itself doesn't yet have a pre-defined configuration, however I got that sorted out alright. The board just seems to be super sensitive to vibration compared to the KK boards that I'm used too.

Daniel
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Old Sep 28, 2012, 09:40 PM
Emress
sirbow2's Avatar
United States, SD, Rapid City
Joined Nov 2011
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prob because of proper code + sensors lol

maybe?
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Old Sep 29, 2012, 10:36 PM
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Dave66's Avatar
United States, NH
Joined Jul 2012
19 Posts
Quote:
Originally Posted by dmcke5 View Post
Pretty sure It's just all vibration. With the values down low enough(And a good balance of the props), the quad is flyable. For mounting boards in the past I've just used a bit of foam double sided tape, but I needed this board to sit up a little to allow the wires to run underneath it.l
From the Wiki Multiwii Troubleshooting page:
"The key to reducing vibration is to have a very stiff frame, and to couple the multiwii controller to it just the right amount. Frames made of aluminium, fibreglass and carbon fibre are generally much less prone to vibration than those made of injection moulded plastic or Lexan.

Coupling the multiwii to the frame is very important. The coupling needs to be sufficient for the gyro to be able to sense small movements of the frame, but not so strong that all of the vibrations created by the motors are transmitted to the gyro. Double sided foam tape is a very good way of achieving this, as are soft silicone grommets.

Too little coupling, such as when using rubber bands or springs, can result in the controller oscillating too much, and does not generally work well."

Sounds like you're on the right track with vibration being the problem. After some research I agree with you on the 3 blade props, sorry.
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Old Sep 29, 2012, 11:12 PM
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Perth Australia
Joined Feb 2010
507 Posts
sorry to be boring but ......is there a step by step guide for multiwii beginners ? i have searched .
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Old Oct 02, 2012, 08:36 PM
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Dave66's Avatar
United States, NH
Joined Jul 2012
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Quote:
Originally Posted by swervo View Post
sorry to be boring but ......is there a step by step guide for multiwii beginners ? i have searched .
Things change so quickly it's hard to keep anything current but you can start with this link:
http://www.multiwii.com/wiki/index.php?title=Main_Page

Any other questions are answered in the Multiwii Forum witch is much more organized then this one. Both forums have some pretty smart people and have bailed me out many times.
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