F450 log review

Good afternoon,

I have been battling to get this f450 to fly which I am using for research at my university and cannot figure it out for the life of me. I have gone through the basic setup and tuning wiki pages along with calibrating multiple times (ESC, accel., etc.). This is a f450 using a pixhawk and a 4s lipo. What happens is that it will fly very sporadically wobbling all over the place. I am flying in stabilization mode. It seems also that it does not respond well to the inputs from the transmitter aswell. Any input would be greatly appreciated. I have uploaded the log along with a parameter list for reference.

https://drive.google.com/drive/folders/1uow8NLzW_1gJZ02H-fjCHXg_vEpebq1v?usp=sharing

The F450’s can be surprisingly hard to get flying properly.

Try to work through all this in it’s entirety. Don’t just try changing a few settings and flying again, do everything here if possible.

If it’s not already, see if you can set your transmitter to spring-centered throttle. This is not essential but helps to avoid “I switched to stabilise mode and it fell like a rock”. If you can, or it already is spring-centered, then set this:
PILOT_THR_BHV,7

Your battery monitor is calibrated wrong or most likely your battery is sadly depleted, it’s going quite low in these small tests and will get permanently damaged. After changing all the settings I recommend below, if you get battery warnings or cant arm DO NOT change the battery related params, change the battery.

It’s hard to say with all that oscillation going on, but it might be underpowered too. We will find out more later.

There is bad vibrations and clipping, mostly you need to worry about Z axis. Dont fly again until you take actions to fix this. This could be flight controller anti-vibration foam, or you might need a mount with balls.
You could balance your props to clean up the X and Y axis too. With the cheap F450 kits some have found the motors need balancing too.


Tidy up any wiring or anything that might be loose and vibrating or flapping around in the prop wash. You want the X and Y vibes under 10 if possible, and Z axis vibes under 20 (or under 15 if possible).
Stay with Stabilise mode until you are sure the vibrations are fixed.
Later you will want AltHold and Loiter modes.

Update MissionPlanner, latest beta
Connect to MissionPlanner and go to the Setup and Initial Parameters, plug in your prop size and battery cells, select the optional battery failsafe settings too, accept everything it offers and save those parameters. (Don’t select the T-Motor Flame ESC settings)

Change these params, this should make a relatively safe starting point for a F450

ATC_ACCEL_P_MAX,85000
ATC_ACCEL_R_MAX,85000
ATC_ACCEL_Y_MAX,16000
ATC_ANG_PIT_P,12.0
ATC_ANG_RLL_P,12.0
ATC_ANG_YAW_P,6.0
ATC_INPUT_TC,0.20
ATC_RAT_PIT_D,0.006
ATC_RAT_PIT_I,0.11
ATC_RAT_PIT_P,0.11
ATC_RAT_RLL_D,0.006
ATC_RAT_RLL_I,0.11
ATC_RAT_RLL_P,0.11
ATC_RAT_YAW_I,0.08
ATC_RAT_YAW_P,0.8
AUTOTUNE_AXES,3
GPS_GNSS_MODE,65
INS_HNTCH_ENABLE,1
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,0
MOT_SPIN_ARM,0.10 ← check for reliable start up of all motors
MOT_SPIN_MIN,0.13

You can copy/paste these into a text file (notepad.exe) and save as a .param file, then load it via mission planner to avoid any typing errors. Obviously not my comment though, cut that out.

I would also set FENCE_ENABLE,1 and check the other fence params. This will force you to wait a while for a good 3D Fix before you can arm. You get used to it and is worth it to know you’ve got a good home point set.

After looking into vibrations and sorting that out as best as possible, and setting all the other params, do a hover test flight for a minute or two in Stabilise mode. Cautiously test the pitch and roll. If everything goes really well also try AltHold mode. Post the .bin log file from that flight and we’ll go over some more.

Alright,
I went ahead and put the flight controller on one of those mounts with the ball dampers on it instead of the foam pads. During flight it seamed more stable but had random twitches during flight. I changed the parameters that you had mentioned. The only thing I still need to do is verify the battery voltage monitoring. I had a bad battery I think so I switched it out with a new one. I tried to review the log myself and it looks like the z direction vibe got even worse… But I could be looking at this wrong.

https://drive.google.com/file/d/1bi2fS2HvzHfwv5dzT_pfE72gzZDSSTpY/view?usp=sharing

I appreciate all the help

Z axis vibrations are much worse. Luckily you only used Stabilise mode.
X and Y axis are not great either.
Have you got a photo of the flight controller and wiring, how it’s mounted?
Any wiring pulled too tight, or rubbing against the FC could be a contributor.

Check this post for how Greg was balancing props and motors on a similar aircraft to yours, in fact go over the whole discussion if you like :slight_smile: Apart from being 3 cell instead of 4 cell, everything is almost exactly the same. And it’s interesting how he sometimes got different vibration results on different days without making any changes. We’ve seen this in other threads too, probably temperature related.

Definitely put in all the battery voltage related parameters

That should be these:
BATT_ARM_VOLT,14.70
BATT_CRT_VOLT,14.00
BATT_LOW_VOLT,14.40
MOT_BAT_VOLT_MAX,16.80
MOT_BAT_VOLT_MIN,13.20
BATT_FS_CRT_ACT,1
BATT_FS_LOW_ACT,2

With those crazy vibrations it’s hard to know if the poor attitude control is because the PIDs are wildly wrong, or not. Probably soften the PIDs a bit anyway:
ATC_ANG_PIT_P,10
ATC_ANG_RLL_P,10
ATC_RAT_PIT_D,0.0055
ATC_RAT_RLL_D,0.0055

And keep doing tests until you have the vibrations under control, then show us that .bin log.

Ok, I am back… wish I had better news but slowly working through it. I went to a local shop that helped me pick out some new props. The old props were defiantly shot so I replaced them with some carbon props and they helped me balance them out. Next, we noticed that one of the motors had a fair amount of vertical play, so this motor was replaced. I took a log before and after replacing the motor and the vibrations drastically decreased. This could also be due to the new props. I had also replaced the mount for the pixhawk with 3m foam damping pads. I also had input all the parameters for my 10" prop. I went ahead and did another log before sunset and still notice that Z-direction vibrations are still considerable but lower than previously, along with x and y vibes. What seems to be happening is that during flight it gets these random bobbles and twitches making it very uncontrollable.

I have uploaded some photos for you guys of my setup along with the log in the google drive. Please tell me if you see anything new out of the ordinary…
https://drive.google.com/file/d/1a4R_yYfkDbzN0CyacWgPup_32ib8bKhY/view?usp=sharing