ESC32 with T-Motor U8-Pro

Info and Discussion about the ESC32 hardware and software

Re: ESC32 with T-Motor U8-Pro

Postby aBUGSworstnightmare » Fri Sep 26, 2014 6:43 am

Hi Chris,
Your Motor is asking for 28A at 15.95V.

So you should set your max. to 29-30A.
I need to have a look at the current limiter results when I'm back home since my tablet will not open the file (for whatever reason).

Maybe you should start with a calibration current of 15A. You can try to increase it (if needed).

Boom diameter = Armdurchmessser = 18mm

Might be a little less; needs to be verified when the U8 is running properly.

this is a big prop --> you may need to increase start voltage and advance to make it start smoothly.

Joerg
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Re: ESC32 with T-Motor U8-Pro

Postby afernan » Fri Sep 26, 2014 11:54 am

Hi TheBone:

Your videos shows a problem on vibrations coupling (as Joerg anticipaded). Lack of torsional stiffness mainly, but also bending couplings.

This is you main and first issue to solve. I recommend you not to mix problems: so maybe you should attach the motor to a super-rigid test bench to isolate the ESC32 problems while tunning those. I´m pretty sure that both problems (vibrations and ESC32 tunning problems) are coupled.

Once you´re sure that ESC32 is tunned, you can mount the motors in the arm and test.

The idea is NOT to have a super rigid arm (see MicroKopter designs, so thin arms), but to separate as much as possible propeller excitation (rpm) from first natural frequency of the arms. Maybe you want to read this basics on that: http://autoquad.org/software-downloads/?did=127

Angel
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Re: ESC32 with T-Motor U8-Pro

Postby TheBone » Tue Sep 30, 2014 1:38 am

Hi Angel,

I read the paper and used the instructions to test it by myself. I'm not sure if I done everything right, cause my values are not really plausible.

Data:
Arm length: 1m
d0: 18mm
d1: 16mm
M: 473g
f: 6,1Hz
I = pi(d0^4 + di^4)/64

To get E, I tried to shift the formula to E.

f = sqr2((3EI/L³M))/2pi
f² = (3EI/L³M)/2pi²
f²*2pi² = 3EI / L³M
f²*2pi²*L³M = 3EI
(f²*2pi²*L³M)/(3I) = E
E = (f² * 2pi² * L³M) / (3 * I)
E = (6,1² * 2*pi² * 0,473) / (3 * 1936,006473)
E = 0,11963341

f = sqr2((3*0,11963341*1936,006473)/(0,473))/2pi
f = 6,1

Could you follow me? I hope so.
My Motor and Prop have at ~1560rpm around 26Hz.
Image
That's more than four times more than the frequency of the arm.

So I think, this should not be the problem. But what it is?

EDIT:

I've done an ESC Calibration test. The Results of the Current_Limiter_Test you can see attached.

The video you can watch below:


ESC32 config:
Image
Attachments
Frequency_Calculation.ods
Frequency Calculation
(251.32 KiB) Downloaded 257 times
CURRENTLIMITER_RESULT.TXT
Current Limiter Test
(2.25 KiB) Downloaded 207 times
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Re: ESC32 with T-Motor U8-Pro

Postby TheBone » Tue Sep 30, 2014 2:13 am

aBUGSworstnightmare wrote:Hi Chris,
Your Motor is asking for 28A at 15.95V.

So you should set your max. to 29-30A.
I need to have a look at the current limiter results when I'm back home since my tablet will not open the file (for whatever reason).

I've already done the enhancement of the max. A to 30A and in an other test to 40A, but I'm not happy with this results. Now I'm tried to use the "CL RPM" Startup Mode, but I'm not sure if it's an improvement of the starting condition.
aBUGSworstnightmare wrote:Maybe you should start with a calibration current of 15A. You can try to increase it (if needed).

I've done the calibrations with 15A and 20A. Both have nearly the same results.
aBUGSworstnightmare wrote:Boom diameter = Armdurchmessser = 18mm

Thank you. :)
aBUGSworstnightmare wrote:Might be a little less; needs to be verified when the U8 is running properly.
this is a big prop --> you may need to increase start voltage and advance to make it start smoothly.
Joerg

Start Voltage is at 2.0V. What value you would chose for advance?
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Re: ESC32 with T-Motor U8-Pro

Postby TheBone » Tue Sep 30, 2014 2:21 am

LPR wrote:Chris

You are using 5s lipos, right?

I don't know how high you could go with 5s lipos but I would guess around 30 amps. Changing timing from 15 to 20 or more might help smooth the motors some.

Larry


What do you mean with "How high you could go with 5s"?
I've 22,2V fully charged and 10Ah (at the moment). Max. continuous discharge is at about 100A. I would think that this is enough.
With timing you mean the value "Advance"? I think advance is 10 ED at std. settings. Are you sure that I improve this value to 20? I'll try it. :)
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Re: ESC32 with T-Motor U8-Pro

Postby aBUGSworstnightmare » Tue Sep 30, 2014 6:30 am

Hi,

your max duty for this calibration is 80% only!

I would:
- try different switching frequencies (start with 12kHz) to see if this makes an improvement. You can also go higher as 20kHz but you need to see how your motor reacts
- Advance is too low (from my point of view) --> increase in 1 increments
- increase start voltage to 2.5V (or even further)
- start align voltage needs to be increased

Try open loop first!

Joerg
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Re: ESC32 with T-Motor U8-Pro

Postby chschmid » Tue Sep 30, 2014 6:31 am

What do you mean with "How high you could go with 5s"?

Larry is talking about max Amps.

With timing you mean the value "Advance"? I think advance is 10 ED at std. settings. Are you sure that I improve this value to 20? I'll try it. :)

Try some timing (advance) higher than 15°for high pole motors. It could be that the best value is even higher than 20°. A higher advance gives usually a bit more power & torque, but it needs more juice and runs warmer. It is important to find the optimum value.

Cheers
Christof
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Re: ESC32 with T-Motor U8-Pro

Postby afernan » Tue Nov 25, 2014 2:55 pm

The configuration you have it´s a bit "extreme" (1m arms!). With that values you obtain a VERY low natural first frequency:

Hollow Cylindrical Cross Section
D inner 16 mm
D out 18 mm
mass tip 473 g
arm length 1000 mm
E 56000 N/mm2 (this is an average Young modulus for this CF tubes)
Ix = Iy = 1935 mm4
freq = 4Hz

In principle this should be OK with your 26Hz excitation (1560rpm). The problem of so low frequency (4Hz is that you will have also several resonances playing around with an important energy. If some of those resonances are close 26Hz, then there will be a problem.
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Re: ESC32 with T-Motor U8-Pro

Postby TheBone » Thu Jan 22, 2015 5:10 am

Hi @ all,

I hope you doesn't forget me. ^^
I gave it up with the v2 ESCs. In the meantime before the v3 ESCs will be released I planned to use some T-Motor ESC. I prefer the T60A and the AIR 40A. What would you think would be the best for my configuration respectively for the Tiger U8 Pro KV170?
Thank you for your answers in advance.

Greetings
TheBone
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Re: ESC32 with T-Motor U8-Pro

Postby kinderkram » Thu Jan 22, 2015 8:47 am

T-Motor recommends T30APRO or T40A but they only work up to 6s.
For lipos up to 12s you´ll need something like the Flame 80A.
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