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Electronic Speed Controllers for R/C brushless motors...

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Patrick

Wed Feb 01 2012, 02:54AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ive started my new Embedded systems class this semester. id llike to be able to throttle up a 14.1 volt, 60 amp, 4 lbs static thrust ducted fan using STmicro's STM32L series devices. so my question is this, what type of waveform do ther ESC's produce? do they hold constant current across each of the two pole phases?

The BL motors ill use have three wires, phase/coil A, and phase/coil B, then a ground wire.
Specs, for the 80mm fan/duct:

Specs, for the BL motor (EFLM3032DFA):

here's an initial source:

And my batteries:

The normal Drone battery in the black hard case is 11.1V liPo, 1000mAh, and 105 grams, and 10C.
The second battery in orage shrink is 11.1V lipo, 2200mAh at 190 grams and 30C.
(Thats a 81% increase in mass, for more than doubling of power available!) and my drone still wheighs the same as a stock drone out of the box, even with the new heavier battery!

Ive done motor control on other apps, like my NC vertical mill, using the L298H power IC.
...

PDF here:
]l298.pdf[/file]

Another question: do the eflite and Novaks use current measurement? i know i did for my NC mill.

Id rather use CT's instead of resistors for current sensing, especially at 60 amps... id also like to use standard mosfet switches and gate drivers running off ARM Cortex microprocessor pins, instead of using the L298 or other special power IC's. I cant besure that hobby ESC's will be able to do whats needed for my research project.

Any help is appreciated...

Wolfram

Wed Feb 01 2012, 10:10AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Patrick wrote ...

what type of waveform do ther ESC's produce? do they hold constant current across each of the two pole phases?

The BL motors ill use have three wires, phase/coil A, and phase/coil B, then a ground wire.

Current across?

This is not right, BLDC motors are usually three-phase synchronous motors. There is a lot of info on how to drive them on the internet, you should do a lot more research before you try to do something like this. Here

are some documents I found after less than a minute on google.

Patrick

Wed Feb 01 2012, 12:51PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

"Across?" -> I meant into.

Also i need several weeks before ill have enough knowledge to make a first attempt. and yes the first source in your post i was fully aware of, but the second article you claim is much more useful.
And i see they're delta or wye connected internally... (oops)

it even shows the new SMT transsitors i like so much.

they also used FEMM 4.2 to do the magnetic graphics! just like i did for the e-fields in my probe.

im still looking at the power train graphs in the microchip docs...

this is a particularly useful pic. i was planning on using a gate drive ic (FAN7382, possibly) on each leg of the 3 element bridge. on my simple STM32L ill have 2 A/D converters, so ill have to analog multiplex the three locations to those 2 pins. the strobing of the lower leg FET prevents depeleting the Boot caps V (i think). in any case only one tranistor needs tobe pulsed to keep an average current into each winding, which decreases switching losses on the upper most FETs. Im hoping CT's will be able to handle the lowest PWM current sensing needs.

in UAV research and development, "OOPS!" and "why is it doing that ?! " really means -> $$$.

Patrick

Sun Feb 05 2012, 03:35AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

im trying to figure out how or if i can make a zero crossing detector for waveform generation, it may be easier and cheaper to buy another castle ESC, its just that i worry about the linearity for my PID loops.

or an IC like this one that has external ZCD lines availble, so i can use my own 3phase bridge FETS.

]22263a.pdf[/file]

Tetris

Sun Feb 05 2012, 04:17AM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

What are you going to use it for?

Patrick

Sun Feb 05 2012, 04:39AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

HighVoltageChick wrote ...

What are you going to use it for?

For a flying machine, in an autonomous application.

EDIT: based on "Wolfram's" (whoever that maybe ) links which proved most helpful, i think this Allegro IC, the A4960 will do the job.

]a4960-datasheet.pdf[/file]

haxor5354

Sun Feb 05 2012, 04:52PM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

what program do you study at college/university?

radiotech

Sun Feb 05 2012, 08:29PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

One question about this motor and the associated driver is the
relationship of the shaft RPM to the drive frequency. Is the motor
an induction motor or has it PM rotor?

Patrick

Mon Feb 06 2012, 01:25AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

haxor5354 wrote ...

what program do you study at college/university?

Electrical Engineering. Why do you ask?

radiotech wrote ...

One question about this motor and the associated driver is the
relationship of the shaft RPM to the drive frequency. Is the motor
an induction motor or has it PM rotor?

Some of my air motors are PM stator'ed others are PM rotor'ed, none have coils on both the rotor and stator.
my ducted fan is a 12 pole motor, the Power 10 is a also a 12 pole.

Instead of a quad-rotor im trying to build a bi-rotor... stabalized via PID or Kalman loops.

radiotech

Mon Feb 06 2012, 09:46AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Is there any gyroscope effects with the spinning mass of the rotor and fan
assembly that are considered in the machines you are modeling?

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