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Old Aug 03, 2010, 05:54 AM
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Idea
Specs for a custom quadrotor ESC

I know there are a few quads that have their own custom ESC (MK, X3D), but I'm not sure if even they have all the features that would be desirable from the perspective of quadrotor operation. (I was inspired to think about this from this thread: http://www.rcgroups.com/forums/showthread.php?t=958957)

Here's my wish list:

- Multiple choices of communication protocols - PWM, I2C, CAN, serial, etc.
- High command transfer rates to reduce latency
- High resolution for precise hover control
- More efficient switching for longer battery life
- Dynamic braking to better control prop deceleration and to possibly conserve battery (regenerative braking)
- Current or power limiting to prevent motor burn-up
- Control RPM directly - the ESC can calculate actual RPM in the process of electrical commutation
- RPM limiting to prevent prop damage

These could also be accomplished in the controller board or in the ESC

- Make thrust and torque output (i.e. what we really care about) proportional to the input command. This can be done by applying square root shaping to the usual voltage command (since both are proportional to the square of RPM). Or perhaps by controlling current instead of voltage (my understanding of typical ESC operation is that the input command gets translated into a PWM duty cycle on the motor windings, and hence the motor "sees" an average voltage proportional to the duty cycle. Also, I believe the current in the motor is proportional to the torque)
- Apply lead shaping to input commands to overcome the inherent rotor dynamics lag and improve overall response (assuming the motor can deal with rapid speed command changes)

Any other ideas?

- Roy
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Old Aug 03, 2010, 06:16 AM
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http://open-bldc.org/wiki/Open-BLDC
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Old Aug 03, 2010, 12:38 PM
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Quote:
Originally Posted by tori3 View Post
Thanks for the link tori3. I think I had come across it in the past. It looks like they have some things on their to-do list that are also on mine. The latest news is about a year old. Is this project still active?

- Roy
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Old Aug 03, 2010, 02:25 PM
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Not a clue, sorry.
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Old Aug 06, 2010, 11:12 AM
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Here's the impact of lead shaping on ESC performance, courtesy of lesnewell

http://www.rcgroups.com/forums/showp...&postcount=325

- Roy
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Old Sep 21, 2010, 06:13 PM
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Hey guys,

Yes Open-BLDC is still alive and kicking. The things are slowly falling into place. I am trying to keep the news more up to date now.

Cheers Esden
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Old Nov 19, 2010, 11:23 AM
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tutorial sets here
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