Brushless Motor Controller

simonl

Another recent post pointed me to the MikroKopter website (www.mikrokopter.com/ucwiki/en/BrushlessCtrl) which has some stuff about brushless motor controllers. Unfortunately I can't make much sense of it; I mean, the theory seems fine, but I have no idea how to put that into practice with the PChip as the controller.

Would anyone be willing to give me some pointers / a starting point?

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Cheers,

Simon

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www.norfolkhelicopterclub.co.uk
You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
BTW: I type as I'm thinking, so please don't take any offense at my writing style

Ale

simonl: I came to the same problem some while ago, and after some searching... decided to use a prebuilt controller. they cost some 10 to 20 €.
Brushless controllers are not that easy from the ground up, you need fairly powerful output mosfets and the controller i.e. a uC with appropriate soft.

Joerg

Hi
controlling brush less motors could be done easily with the Propeller chip! Could you post more details about the motor please.

Saluti Joerg

Graham Stabler

Can you suggest what problem you have with putting theory into practise?

Ale

Of course can be done, but you have to program it and make a board with the mosfets and all. That is why I suggested a prebuilt controller. You can start with that and when is all up and running you change the controllers with your own. Building the quadcopter is a roject in itself.
I had a couple of interesting links... but they are lost... I started witht the wikipedia age and some google search , there is soft on the net... somewhere.

This article is sort of useful:

http://www.eetasia.com/ARTICLES/2005SEP/C/2005SEP_REF_WK1.HTM

Both referenced ANs are more detailed with circuit and all, and software, well for pics. They speak of 16 kbytes of code... I thought was... simpler

have fun

Edit: In the mikrokopter page there is a brushless controller with schematic and source, and description.

Post Edited (Ale) : 1/4/2008 7:16:53 PM GMT

Sapieha

Hi All.

It is fine controler´s and motor´s on old CD player´s

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Nothing is impossible, there are only different degrees of difficulty.

Sapieha

Fred Hawkins

What is the design reasoning for four motors instead of three? Propeller clearance issues? Ease of construction?

Seems like a good place for this controller chip pdf link: http://allegromicro.com/en/Products/Part_Numbers/1442/1442.pdf

Post Edited (Fred Hawkins) : 1/5/2008 8:24:31 AM GMT

deSilva

Never used one, but BLDCs are more or less stepper motors

Paul Baker

Yes and no, stepper motors have detents which permit better holding power. Also the method of driving them is different, stepper motors do not require feedback for thier operation where as BLDC motors do. Lastly BLDC motors can operate much faster and have a better efficiency.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

deSilva

All processor fans contain BLDCs (they have to, brushes would drive the chips crazy) and thus a tiny motor controller

Fred Hawkins

Link back to previous bldc thread, with a pointer to a terrific pdf by Jianwen Shao. (In Paul Baker's post): http://forums.parallax.com/forums/default.aspx?f=25&m=157068

Nick Mueller

> What is the design reasoning for four motors instead of three? Propeller clearance issues? Ease of construction?

With four, it is possible to rotate along the vertical axis. Two rotors (sitting on a diagonal and running CCW) run slower, the other two (running CW) run faster and then you rotate, but keep the level. They normaly do have constant pitch, so that's the only way to do it.

Nick

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Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO

Joerg

To get back to the original question here a very simplified diagram of how a brusless tree phase
motor works. I have left the influence of back EMV and other effects.



You can drive such a motor in two ways:

- driven like a stepper motor in synchronous mode. Here you have take care to not over force the
unit other ways it gets stalled.

- driven like a normal DC motor, where electronic devices are acting like the collector. The position
of the rotor has to be known! There are two way for that:

-sensing the position with sensors built in the motor (i.e. hall sensors)

-sensing the coils current and doing switching in the zero crossing moment!

I hope that helps for doing a first step

Saluti Joerg

simonl

Hey all,

Many thanks for all your replies. I kinda fired this off just before leaving work on Friday and should've given it more thought before doing so

Loads of info' to digest!

Thanks especially to Joerg - I really like diagrams (words aren't so easy for me to digest!).

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Cheers,

Simon

---

www.norfolkhelicopterclub.co.uk
You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
BTW: I type as I'm thinking, so please don't take any offense at my writing style