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I am designing a customized miniature drone for research and would like to embed the ESC for BLDC motor directly on board to save space and weight. I have searched a lot for ESC design online and can understand the basics to the point that I think I can implement a trapezoidal commutation algorithm using microcontrollers.

As I understand it, it only takes a periodically changing signal (with PWM modulation) in sync with the Back-EMF to control the motor. But there are a number of dedicated control firmware like BLHeli out there which are rather complicated, and there are also ICs like MCT8316A from TI that can do the commutation/control for me. Furthermore, it seems that almost all stand-alone ESCs are using MCUs with BLHeli firmware + gate driver + FETs design instead of ICs with everything included.

So my question is, what's the difference between:

  1. A simple commutation algorithm executing on my own controller.
  2. Stand-alone ESCs with MCUs with BLHeli firmware.
  3. ICs with the control algorithm built-in.

Are there any fundamental differences between these three solutions? What's the difference between them in the aspect of power efficiency? Why don't people use ICs with everything built-in in stand-alone ESCs?

Thanks a lot!

Some additional information:

In my application, the main concern is power efficiency and the simplicity of hardware/software, and higher prices can be tolerated.

The motor I would be using is similar to this motor and draws <5A current.

A quick follow-up question: I see there are ICs and algorithms for FOC control that provides higher power efficiency. But are they suitable for high-speed operating multi-pole motors used in drones?

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  • \$\begingroup\$ "Why don't people use ICs with everything built-in in stand-alone ESCs?" Because you have much less control of your end product. Does that IC even work with the pulse-length signals for radio-control models? It says PWM, but the "PWM" used in radio-control models is not actually PWM. \$\endgroup\$
    – DKNguyen
    Apr 24 at 3:00
  • \$\begingroup\$ @DKNguyen Thanks for your response! I know that there are different protocols to communicate with ESCs in drones (which are not supported in ICs), but in my case, I can write my own program to control/communicate with ICs, so this is not a problem. So are you suggesting that if I can properly control/communicate with both, stand-alone ESCs and ICs can both achieve my goal? \$\endgroup\$
    – Wjx
    Apr 24 at 3:05
  • \$\begingroup\$ Only if the IC does what you want it to do. If you later find out that it doesn't support something you want or you want to change or optimize something that is not supported then you are out of luck. The other obvious thing is that this IC only supports 8A. I initially thought it was a gate driver but it includes the power FETs. So if your motor needs 40A, obviously this IC (or any single IC solution is out of the question). \$\endgroup\$
    – DKNguyen
    Apr 24 at 3:07
  • \$\begingroup\$ @DKNguyen Furthermore, are you suggesting that the BLHeli firmware is more about working with all sorts of control protocols used in drones than complicated dark magic about commutation? \$\endgroup\$
    – Wjx
    Apr 24 at 3:08
  • \$\begingroup\$ Motors can also have peculiarities. For example, low pole, or high pole, or specific motors with specific loads might have issues commutating or starting up for whatever reason. And if you're dealing with such a motor using such an IC you are slave to only what the IC provides you. If you need to tune a setting that isn't provided you're stuck. And if something about the algorithm itself needs to be changed you're also stuck. \$\endgroup\$
    – DKNguyen
    Apr 24 at 3:09

1 Answer 1

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So my question is, what's the difference between:

A simple commutation algorithm executing on my own controller.

Impracticable. It won't work well, if at all.

Stand-alone ESCs with MCUs with BLHeli firmware.

A proven solution. Their design has been perfected over many years, and will be a good match your motor. Another advantage of stand-alone ESCs is that they are easy to replace if they burn out.

ICs with the control algorithm built-in.

'All in one' ICs suitable for high power brushless motors have only become available recently. Some may work OK with the right 'tuning', but that would be your responsibility (expect a lot of trial and error, a lot of crashes, and burned ICs).

The MCT8316A requires 4.5 V minimum, which might be a problem depending on what battery you want to use.

A quick follow-up question: I see there are ICs and algorithms for FOC control that provides higher power efficiency. But are they suitable for high-speed operating multi-pole motors used in drones?

Drone motors are usually designed for trapezoid drive, and don't need precise control at low speed. What they do need is fast acceleration, high power output and high peak current handling. The tiny motor you are looking at also needs high operating speed, which is easier to achieve with 6 step commutation.

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