Quad Fame 52mm X 42mm need Gain Settings ?

[bob195558]

Hi,
I have built a 70mm Quad which is elongated by 10mm (4 inches).

I change from a MultiWii Flight Controller Board to the DJI Naza-M Lite Flight Controller with Ublox GPS and used the Gain settings for a F550.

These Gain settings are not right for this 10mm elongated 700 Quad.



What should the Gain settings be for this Quad ?



700 Quad Components:

Propellers: Rctimer 13"x 4 pitch Carbon Fiber

Motors: Rctimer BC3536/11 750KV Brushless

ESC's: AL-ZTW 40A

Flight Controller: DJI Naza-M Lite

Receiver: FrSky D8R-II plus

Battery: 4S 5500mAh Lipo 50C

Weight: 2550 g. or 72.3 oz. or 5.6 lbs.



Bob B.

 

[bob195558]

Here are some pics of the 700 Quad and the NASA Gain Settings.

When I moved the Rudder Stick just a little the Quad goes out of control and crashes.
It became a lawn ornament after only a little rudder stick movement.

 

[moonpie57108]

Double check your motor directions and props. The only time I have had your described problem is when I get the motors plugged in the wrong order and as the flight controller tries to correct it gets the exact opposite response which just increases the error correction the direction.

Gains should make it twitch or be sloppy, never seen it cause this. Yet.

Remove props and spool motors up one at a time if possible, use tape or a flag of sorts to verify direction and at the same time when you spool up motor 1, more sure that the correct motor is going.

 

[bob195558]

Hi moonpie57108,
Thank you for your reply, I will recheck and recalibrate everything before I try another test flight.
I was able to try test flying the 700 quad with the newer PID's at 230 values and when it lifted off up to about 3 feet was very unstable.
It was so very unstable as each of the four corners were taking turns dipping (rocking) about 5 inches up and down.
I was quickly decreasing throttle, trying to land it safely, when it suddenly flipped-over.
So I need to repair the GPS stand and check everything out before doing the next test flight.
I think I should recalibrate everything too, as it may not have been taken to be in proper calibration.

I have a 550 quad also using the NASA-M Lite F/C and it is flying very well using the default F550 Gain/PID setting: Pitch/Roll: 170, Yaw: 150 and Vertical: 140.

Bob B.

 

[moonpie57108]

Did it oscillate in the first flight at all? If adding gain caused new oscillation, I would probably back it down.

Also, when you said rudder stick caused loss of control, were you already in hover adding yaw input or just trying to throttle up?

Self level mode or Attitude?

Check your sensitivity maybe as well? Possible while fighting the oscillation there was too much stick input causing the flip? Same on yaw possibly with first loss of control?

I haven't used that FC, but if you can run without gps, leave it off for next test. Same with gimbal or anything else not needed for close hover. Worst case you will have to retune a little after adding weight but will help limit damage. Could also drop to a size smaller prop to increase your reaction time by reducing thrust if you have some 12" props. Not optimal but if a third crash is likely it could help reduce damage.

 

[bob195558]

Hi moonpie57108,
The first test flight did oscillate some as it was moving around a lot too.
It was difficult to keep it stable in flight.
When I am test flying, I am in Atti mode and not using GPS mode, as with this DJI NAZA-M Lite F/C it will not go into GPS mode unless the quad is 30 feet away from transmitter.
Like I have described above this is not a normal Quad frame size, as it is 4 inches longer then it is wide.
So it is a 550 quad size wide and 4 inches longer then the normal 550 quad size.
This may be the reason why it is so unstable.
I am hopeful by adjusting the PID's will be able to fix the problem.
In the first test flight adding just a little yaw (Rudder) input, it went out of control.
It happened very fast.
I will think about trying smaller propellers, I may have some I can use for test flying.
Thank you for your reply.

Bob B.

 

[moonpie57108]

Sounds like oscillation was worse on higher pids?

Is the frame capable of supporting the longer arms? Could be a vibration induced problem. Set the frame up on four motor boxes and apply a little pressure just to see how much give you have and compare it your 550.

The odd shape could cause some flight problems but not sure it would be this bad. If that was the case, you could look into custom mixing, adjust motor layout in flight controller for non-typical layouts. I have never found the need for this because it seems generally for locking in that last bit of feel.

I haven't built anything bigger than a 450, but I have run the same pids (different FC than you) on a 180 and 450 and while not a tight feel, both were stable.

 

[moonpie57108]

Any luck?

 

[bob195558]

Hi moonpie57108,
I have been busy with a 510 quad repairing a small crash and flying with it which also has the NASA-M Lite F/C.

I have been thinking about what to do with the 700 quad with the front motor arms being elongated 4 inch longer from the rear motor arms.
I have been thinking to modify the 4 motor arms by rotating (swiveling) them around more until they are equally spaced apart between each other.
This would correct elongated 4 inches which then I hope will stabilize when flying.

Bob B.