Heavy Lift Quad copter Issues (MTOW ~ 150 KG)

ArduCopter Copter 4.6
1

Hello users,

Greetings….

We have assembled a quad copter of wheel base 99 inch , we are using : Hobbywing X11 max motor esc combo (60 KV motor, 18s), 48x17.5 inch propeller, CUAV X7+ flight controller, Hobby wing data link v2 (for giving esc telemetry data to flight controller via UART port, we have set ESC_HW_POLES parameter to 40), 18S Li-Po battery for powering the quad copter . We have done a test flight with gentle hover and slight roll pitch and yaw movement in Alti hold mode. For some time we had given loiter mode to the drone. The weight of the quad copter is approximately 52 kg. The flight log for this test flight is attached.

From the flight log we have observed the following:

1. In X, Y and Z axes , the maximum vibration is going upto 26.8 , 30.08 and 48.49 respectively (Which is not safe for flying , we need to do tuning)

2. Since we are using the Hobbywing X11 Max motor ESC combo along with 48x17.5 inch propeller, from the data sheet we have got for hovering the RPM should be around 1700.

3. But from the flight log we have got the average RPM of individual motors around 400. A huge difference from the expected one.

4. We have got the graph under FTN : NF1, NF2, NF3 and NF4 , all are coming on an average around 7 Hz(400/60 = 6.7 Hz). Which should be (1700/60 = 28.33 Hz approx).

5. From the ardupilot filter review tool we have got spikes around 30Hz, 60Hz , 120 Hz, 180Hz (Harmonically related). i.e the 30 Hz may be motor rotational frequency. 60 Hz may be due to we are using 2 blade propeller. Why the peak is coming at 120 Hz and 180Hz ? Also some peaks are are coming at 200hz and 231 Hz.

6. So, from these observations and please have a look at the log attached, please suggest how to move forward with this quad copter. RPM and desired harmonic notch frequency is not coming correct, what might be the issue? Please have a look at the PID and suggest us what values should be good for this quad copter. And vibration values are also not good , so what we should do to minimize the vibration to a safer level (below 15 in each axis).

                                                                                                      Thank you

5
51086×739 155 KB

4
41107×776 204 KB

3
31431×738 149 KB

2
21380×736 135 KB

1
11300×657 99.8 KB

6
61600×1200 792 KB

2

Use the AMC vehicle template Hoverit X11+.

It is very similar to your vehicle and it will get you started nicely.

Rename that nice vehicle picture into “vehicle.jpeg” and add it to the AMC vehicle directory.

If the measured RPM is off by a factor of 4.228 then upload this lua script to the
FC:

esc_telem:set_rpm_scale(0, 4.228)
esc_telem:set_rpm_scale(1, 4.228)
esc_telem:set_rpm_scale(2, 4.228)
esc_telem:set_rpm_scale(3, 4.228)
gcs:send_text(0,"LUA set RPM scale to 4.228")
3

AMC 4.3.3 has been released with two small improvements to the Hoverit X11+ template.