T-motor P80 motors, Alpha 80A ESC

ArduCopter Copter 4.5
1

Hello,
Looking for some advice related to initial parameter set-up of a large HEXA X multi-copter using T-motor P80-100KV motors, Alpha 80A ESC and T-motor MF 3218 props.

I realize the Alpha ESC’s do not require calibration and the Throttle Range listed on the T-motor website is 1100-1940 so my assumption is the MOT-PWM_MIN, MOT_PWM_MAX could be updated with these values.

Using Mission Planner Helper I get the following initial parameters. Any comments related to these settings (and initial tuning in general) from others using similar set-ups / hardware would be much appreciated.

image

I have the T-motor Datalink and updated the Alpha ESC with the proper motor firmware. I could potentially use Datalink to capture real-time ESC data (e.g. RPM). Not sure how useful this is (in particular for the initial test flight), but if anyone has comments on this, it would be appreciated also.
thank you.

2

You are on the right track.

You may need MOT_THST_EXPO,0.60 if those Alpha ESCs try to do something with the “thrust linearization”
The 0.60 value is typical of those ESCs from what I’ve experienced, and the value of 0.78 is what you would use with almost any other ESC for those props.
The initial parameters calculator in MissionPlanner needs an update, I devised an updated formula for the calc of the expo given the prop size.

You will also be able to set these Harmonic Notch filter values as a starting point (also based roughly on prop size)

INS_HNTCH_ENABLE,1
INS_HNTCH_MODE,1
INS_HNTCH_REF,0.17
INS_HNTCH_FREQ,28
INS_HNTCH_BW,14
INS_HNTCH_FM_RAT,0.7
INS_LOG_BAT_MASK,1
INS_LOG_BAT_OPT,4

https://www.dropbox.com/s/w2ru1gmk7h7ga7m/Initial%20parameters.xlsx?dl=0

1 Like
3

Hi Shawn
Thank you for the reply and detailed information, it’s much appreciated.

One basic question related to the spreadsheet, in column A there are different versions of Arducopter listed with various parameter settings under each version. Do those parameter updates listed under each Arducopter firmware version only pertain to that particular version? For example there are many parameter settings listed under Arducopter 4.0 to 4.1 but if I’m using 4.5 do those parameters updates also pertain to 4.5. I’m assuming they do, but just wanted to confirm.

I understand your comment related to MOT_THST_EXPO as that appears pretty specific to the Alpha ESC.

Before the initial test flight would you suggest updating the Harmonic Notch filter parameters you listed, I’m guessing it’s probably wise considering the prop size.

thanks again, Steve

4

Yes, the 4.0+ parameters relate to 4.5 too. It’s only 3.6 and earlier that had some real diffrences.

Yes, you can safely set those Harmonic Notch Filter values before test flights.

5

Hi Shawn,
Was just working through the parameters in a bit more detail in preparation for a test flight. There is one parameter (ATC_ACCEL_P_MAX) that changes percentage wise more than other parameters as a function of the increase in prop side. The default value I believe is 110,000 but a prop size of 32 inches drops the value to 19100. Just wanted to confirm this is acceptable as some other parameters might change by a factor of 2, but this one is more significant.

Thanks again for the help, and the work you and others do to support this effort.
Steve

6

Yes that ATC_ACCEL_P_MAX is safe and used extensively.
When you do get airborne, run the VTOL Quicktune script.

Later if you run Autotune it will calc and set exact values for the ATC_ACCEL params that suit your aircraft.

7

Sounds good, thank you

8

Hi Shawn,
Sorry, a couple last questions if I may.

I noticed in the spreadsheet the comment that MOT_THST_EXPO of 0.6 has worked for the integrated ESC/motor series. My current set-up is not integrated – it’s separate ESC and motors. I know we’re working in the realm of many unknowns but wonder if you have any thoughts regarding EXPO for the non-integrated ESC’s/motors. I recently updated the ESC firmware to ensure all ESCs are using the most recent and same firmware.

Also been wondering a bit about the MOT_SPIN_MIN value to use for the initial test flight. It takes 5% throttle to spin the motors so I’ve set the MOT_SPIN_ARM to 7% and per ardupilot documentation the MOT_SPIN_MIN should then be set to 10%. However I’m a bit paranoid that value may be a bit low - any thoughts you have on that would be appreciated.

Thanks again.