I’m having an issue with my octocopter not taking off…
It’s fitted with a pixhawk autopilot running ArduCopter 3.2.1.
My problem is that the motors won’t gain enough RPM to actually take off. The max RPM at full throttle is around 4000, but if I bypass the Pixhawk and plug one of the motors directly into the receiver, it spools up to about 6000 RPM nicely.
While running the motors through the Pixhawk, the RPM is very “shaky” or “twitchy”. This also disappears if I run it through a receiver.
I tried to fiddle with a lot of parameters (using Mission Planner 1.3.19), and the only thing that seems to work is if I set the RC3_MAX to 3000-4000 pvm. Default after a succesfull radio-calibration is 1934 pvm.
I don’t think this is the right way to do it, 4000 pvm is way off scale. And the RPM is still twitchy.
log files are ok, they are an ascii version of the bin file, its tlogs that are hard to use…for me at least.
nsnetrich, have yo performed an radio cal and esc cal?
Your RCouts are all over the place oscillating. Are you sure the motors are wired in the correct position and spin in the correct direction. It doesn’t look like its correct to me.
Your throttle in from the radio only gets up to 1934, coule be closer to 2000, but with a radio cal I think it should cope with that. Some of your RCOUT get up to 1875 but are jumping up and down from min to this max or lower for some channels. again close to 2000 is typically the max.
@nsnetrich,
Here is an Auto Analysis of your .bin file:
Size (kb) 1228.2001953125
No of lines 17169
Duration -1 day, 23:29:06
Vehicletype ArduCopter
Firmware Version V3.2
Firmware Hash c8e0f3e1
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = FAIL - Truncated Log? Ends while armed at altitude 18.52m
Test: Compass = GOOD - No MAG data, unable to test mag_field interference
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERRs found: FS_BATT GPS_GLITCH GPS
Test: GPS = FAIL - GPS glitch errors found (1)
Min satellites: 0, Max HDop: 1.66
Test: IMU Mismatch = NA -
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = WARN - VCC min/max diff 0.332v, should be <0.3v
Thanks for the analysis, but I’m not sure what to make of it… If I make an auto analysis in mission planner on the same log, the brownout test just says good…
Size (kb) 675.6181640625
No of lines 9543
Duration 0:00:42
Vehicletype ArduCopter
Firmware Version V3.2.1
Firmware Hash 36b405fb
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = GOOD -
Test: Compass = WARN - Moderate change in mag_field (34.31%)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = FAIL - ERR found: GPS_GLITCH
Test: GPS = FAIL - GPS glitch errors found (1)
Min satellites: 6, Max HDop: 2.51
Test: IMU Mismatch = GOOD - (Mismatch: 0.29, WARN: 0.75, FAIL: 1.50)
Test: Parameters = GOOD -
Test: PM = WARN - 3 slow loop lines found, max 9.18% on line 6231
Test: Pitch/Roll = GOOD -
Test: Thrust = FAIL - Avg climb rate -11.27 cm/s for throttle avg 944
Test: VCC = GOOD -
Hi,
Did you connect the ground wires of your ESCs to the servo rail of Pixhawk? That could explain crazy signals if you only connected the signal wires.
I think TC ran the wrong file by mistake. the firmware version is different to yours, and as yours didn’t take off so it shouldn’t fail the brown out test…even if it did brown out…but pretty sure it didn’t brown out.
your z accel vibes seem a bit high too…not sure that would cause it though, that is normally bad altitude hold issues…but bear it in mind for when you get it flying. your accel Y seems very very large, but x not. How is your flight controller mounted? odd that x and y are not more similar. again not sure if that would cause it but needs investigating.
I see you aren’t using ekf, does it do it if you enable ekf?
The Pixhawk is mounted on some rubber-things to minimize vibration and it sits there quite “loose”. The whole copter vibrates/shakes when the RPM increases, probably due to the oscillation, and this could maybe explain the x- y- and z-vibes, or?
I’ll try to enable efk and test again as soon as possible but since I’m in Europe, it wont be until tomorrow…
I don’t think the vibes are dues to the oscillations, the frequency of the vibes is way higher. Try EKF to see if it responds the same way, and maybe try mounting in a different way, also check nothing tapping the flight controller like a cable or something, and check cables aren’t tugging it or something.
So, I figured out that my GPS antenna was somehow shaking the Pixhawk, so I dismounted it and held on to the thing to stop the vibrations. The RPM went from twitchy to smooth instantly, and the oscillations disappeared somewhat. I’m not getting it above 4000 RPM though… Attached the log so you can see for yourself. Also enabled EKF but I don’t think it helped…
Your motor outputs indicate is trying to flip back and left, does it appear to be trying to lift that way. With the levels indicated it should have flipped, but it hasn’t the power to do that. Is it level where you are doing this? Are the motors on the front and right working harder than the others in reality? Have you gone an accel cal? (that might be why it appears to be lifting on one side if accel cal is bad)
How did you do the esc cal? Pass thru mode (all motors spinning at same time) or direct connection to the receiver (one motor at a time)? You said the motor RPM was higher when direct to the rx. Is it higher if all but one are connected to the flight controller? If it is it might indicate a power issue.
if you clibrated direct to the RX then there maye be some difference for some reason between what the RX is sending and the pixhawk
You don’t have voltage or current logged from a power module so its hard to tell if its a power issue.
I only tried to test the drone with one propeller attached at motor 6 (bottom left). It is level and I did calibrate the accelerometer. The motors are adjusting fine if I touch or move the Pixhawk.
I calibrated the ESC’s with all motors spinning at the same time through the Pixhawk, and after the calibration it just transmits the signal from the receiver without any adjusting, and here all the motors spin up to max RPM, so I dont think it’s a power issue…
