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Topic: Controlling 4 brushless dc motors? (Read 1 time) previous topic - next topic

sfhrafi

HI,

For my project, I need to control 4 brush less dc motors where all of the motors are rated at 48V. I was thinking to use adafruit motor shield as they can be used for upto 4 bi-directional motors but the motor shield can take upto 5-36V. So I am not sure how should I do this. I have an Arduino Ethernet but I think I need to get an Arduino Uno for this. Any input will be greatly appreciated. Thanks

krazatchu

#1
Jun 20, 2012, 04:06 am Last Edit: Jun 20, 2012, 04:08 am by krazatchu Reason: 1
You can operate the 48v motors on 36v if the current is available, they will just run slower and cooler...
The Adafruit motor shield is for brush motors not brushless...

I strongly advise you to consider brushed which are a lot simpler to drive.
Driving a brushless requires commutation which in turn requires knowledge of the motor position, either through back EMF or Hall sensors...

As well, what level of control are you aiming for?
Position, constant velocity, constant torque?
Michael
----------------------
http://www.krazatchu.ca

sfhrafi

Thank you so much for your response.

I have to use a Maxon EC60 brushless motor. I need to control the torque with the motor. I also need to make it precise, so I need to use PID loop to do it. The no load current is 740mA.  I am attaching the data sheet here: http://test.maxonmotor.com/docsx/Download/catalog_2005/Pdf/05_165_e.pdf

I am so confused about designing the hardware. Especially, how to control all the 4 motors. Input will be appreciated

krazatchu

That's a big servo motor, 9.3 amps at 48 volts and 400 watts...

Not an easy task to run PID, an encoder read, as well as brushless commutation in real time on an Arduino...
As well, the PCB layout and motor driver will be critical at these power levels...

I've dabbled in brush motor servo drives which are tricky enough, I wouldn't even attempt brushless PID on an Arduino...
Starting from scratch without experience, I suspect your looking at least 6 months of learning and work...
I'd recommend an off the shelf driver for them, this one may work and is reasonably priced:
http://granitedevices.fi/index.php?q=servo-drive-vsd-e
Michael
----------------------
http://www.krazatchu.ca

Yankee

I agree with everything krazatchu says. Closed loop motor control is not an easy subject especially as applied to brushless motors. Once you get into the amperage range of your motor there are additional current control issues to think about as well. The Granite drives are very good industrial quality units. You might also look at these boards: http://jrkerr.com/boards.html. J.R. Kerr also offers preprogrammed chips and example circuits from which you can build your own drive. I have attached a PDF for one of these circuits that would probably do the job for you.

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