BLDC speed controller recommendations for variable braking

Discussion in 'General Electronics Chat' started by allezgrand, Feb 11, 2018.

  1. allezgrand

    Thread Starter New Member

    Feb 11, 2018
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    Hi all,

    I’m looking for guidance in selecting an off-the-shelf electronic speed controller for a brushless DC motor.

    I’m looking for an ESC with forward, reverse, and variable braking which I can control using a microcontroller (virtually any hardwired input signal (PWM, PPM, 0-5V, etc.)).

    For braking, I’m looking for one of two options, or ideally, both:

    A) If you imagine a heavy car going downhill, I’d like to apply the brakes so that it moves at 5 mph, 10 mph, or 20 mph, depending on the signal the ESC receives.

    B) I’d like to be able to resist a fixed amount which I can vary. If you imagine a car going into a turn, you want to be able to brake a different amount depending on the track conditions and the point in the turn. For example, I want to be able to vary the resist from 10 Nm to 100 Nm. I’m guessing this would be common in the RC racing world, but I don’t know.

    For forward or reverse, I’d like to be able to set the RPM based on the PWM signal such that as the load varies, the motor speed does not. My understanding is that this is the way an ESC typically functions, correct?

    The motor I’m controlling will be using a 24V supply with a maximum load of 10A. It is 4 pole and equipped with a hall effect sensor. The range will be 120 to 480 RPM. Any help or direction you can offer is greatly appreciated!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Use of the term ESC usually implies the RC type motor/controller combo.
    Disconnecting the control from the motor and shorting the three motor leads leads to dynamic braking the level of which will depend on the rpm of the motor at the point braking is implemented, decreasing to zero at zero rpm.
    Max.
     
  3. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    I am thinking that in this case the "ESC" means Electronic Speed Controller, not "escapement", as was used in ancient RC equipment.
     
  4. allezgrand

    Thread Starter New Member

    Feb 11, 2018
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    Hi Max,
    This isn't an RC project, but there are a plethora of off-the-shelf electronic speed controllers in the RC world, so that's what I've seen the most of.

    I'd like to avoid a secondary system if possible and find an off the shelf option. I'd also like to be able to adjust it beyond simple dynamic braking. For example, if there is a controller which can apply constant power to 2 of the wires in variable amounts, that should provide a controllable, variable resistance, no? Does something like that exist?
     
  5. allezgrand

    Thread Starter New Member

    Feb 11, 2018
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    Yes, by ESC, I mean electronic speed controller. Sorry for confusion.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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  7. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    What you are asking for is a servo-drive package with both speed and torque control in more than one quadrant. They are available commercially but they are neither small, light, nor cheap. Probably Automation Direct can be useful, and they are a good supplier, also one of the less expensive suppliers. There are also such controllers made for electric motorcycles, which are smaller, more rugged, and also more expensive. What you are seeking is not something simple.
     
  8. allezgrand

    Thread Starter New Member

    Feb 11, 2018
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    MisterBill2, thanks. My guess it that to fulfill both option A and B would not be simple. Is dynamic braking, as Max suggested a simple option in an ESC?

    How does a typical, off the shelf ESC with braking capability work? Does it simply open a MOSFET between 2 phases, allowing full power through to slow the motor down rapidly? Or are there ones that can variably resist by advancing the phase angle in order to slow the motor rotation more gradually?

    Alternatively, are there ESC's with enough capability (maybe more than one channel?) that I could control them through upstream programming?
     
  9. allezgrand

    Thread Starter New Member

    Feb 11, 2018
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    To simplify, maybe I can just ask two questions:
    1) I'm well aware that there are ESC's out there with braking capabilities. Does anybody know what options there are for braking and how they are implemented within the controller (to help me understand the exact effect)?

    2) Does the control of a typical ESC (PWM of 1.0 ms to 2.0 ms at 50 Hz) tell the ESC to vary power (thus varying the RPM, but the actual RPM will depend on the load), or does it tell the ESC to vary RPM and to maintain a given RPM so long as the load is not greater than the motor is capable?
     
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