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P2-BLDC-Motor-Control - Configuring the driver for your motor

We just had the occasion to add support for a new BLDC Motor. This page reminds us of steps needed to properly select a motor in our project code.

Project Maintenance

License

Motors Supported

The motors currently supported by this driver:

Category Value Description
MOTR_6_5_INCH -- 6.5" Motor-in-Wheel -- the Parallax Hoverboard-like motor
Hall Tics per Revolution 90 ticks
Degrees per hall tick 4 degrees
Ticks per hall-cycle 6 ticks FWD (CW): 1-3-2-6-4-5
REV (CCW): 1-5-4-6-2-3
Hall-cycles per Revolution 15 hall-cycles
Degrees per Hall-cycle 24 degrees
Magnets 30 poles
MOTR_DOCO_4KRPM -- docoEng.com 4k RPM 24v motor -- the new Parallax small motor
Hall Tics per Revolution 24 ticks
Degrees per hall tick 15 degrees
Ticks per hall-cycle 6 ticks FWD (CW): 1-5-4-6-2-3
REV (CCW): 1-3-2-6-4-5
Hall-cycles per Revolution 4 hall-cycles
Degrees per Hall-cycle 90 degrees
Magnets 8 poles

Select a motor, Select wheel size

  • Select an Enum constant value from the list of values
    • If you have the 6.5" In-wheel motor then use the MOTR_6_5_INCH enum value
    • If, instead, you have the DocoEng.com 4000 RPM, 24V smaller motor use the MOTR_DOCO_4KRPM enum value
  • In your project open the file isp_bldc_motor_userconfig.spin2 and set MOTOR_TYPE = {motorEnumValue} to the value you selected
  • Also in this same file, the DocoEng motor does not have a wheel attached. Until you add a wheel or gear to it you will need to set WHEEL_DIA_IN_INCH = 0.0. This will disable all distance based status as well as distance based methods (Since they are meaningless without an attached gear or wheel diameter.

The next time you compile the driver will now handle your new motor correctly.

That's all there is to selecting your motor for use with this driver.

Enjoy!

Motor Reference: Attainable RPM at Power

When characterizing the motors for this driver we search for the maximum attainable RPM at each power level and we set this as the limit for the motor at a given voltage. This way the driver can take a "Set power to 100%" request and "I'm driving the motor with a 12V supply" and can scale the request correctly for the power system.

This "limiting" of the reqeust at a given power level allows us to drive the motor at the highest RPM possible without the motor faulting. (That is without the driver being unable to keep the motor at the requested RPM value.)

NOTE(1): While there is a range of max rpm requests that all come up with the same achievable RPM at given power level we choose the lowest value (the value which gives the same RPM but at the lowest possible current draw that can achieve the RPM value.)

NOTE(2) these limits are all based on "no load" conditions. Which means under load the motor can fault. We are planning on adding a fall back so we can drive the motor as best we can while still handling a given load.

Motor Power (+V) RPM Max hall-tics / sec
MOTR_DOCO_4KRPM -- docoEng.com 4k RPM 24v motor --
  (+ is Fwd/CW, - is Rev/CCW )
PWR_6p0V 6.0V (Voltage too low)
PWR_7p4V 7.4V +1885/-1885 754
PWR_11p1V 11.1V +3645/-3645 1458
PWR_12p0V 12.0V +2242/-2242 897
PWR_14p8V 14.8V +2517/-2517 1007
PWR_18p5V 18.5V +2662/-2662 1065
PWR_22p2V 22.2V +3145/-3145 1258
PWR_24p0V 24.0V +2615/-2615 1046
PWR_25p9V 24.0V (N/A Motor rated for 24V!)
MOTR_6_5_INCH -- 6.5" Motor-in-Wheel --
PWR_6p0V 6.0V tba
PWR_7p4V 7.4V tba
PWR_11p1V 11.1V +165.3/-165.3 248
PWR_12p0V 12.0V +181.3/-181.3 272
PWR_14p8V 14.8V +224.0/-224.0 336
PWR_18p5V 18.5V +272.0/-272.0 408
PWR_22p2V 22.2V +320.0/-320.0 480
PWR_24p0V 24.0V tba

NOTE(3): With the v3.0.0 release of the driver, the top-end performance is much better. The 6.5" motor needs to be studies to see how these number have improved. Ad of this v3.0.0 release, this is upcoming work.

NOTE(4): This smaller motor is supposed to achieve 4,000 RPM, we've managed to get this motor up to 3,645 RPM pretty reliably but only at certain drive voltages. Just "why this is" will take time time understand...

If you like my work and/or this has helped you in some way then feel free to help me out for a couple of ☕'s or 🍕 slices!

coffee    -OR-    PatreonPatreon.com/IronSheep

Disclaimer and Legal

Parallax, Propeller Spin, and the Parallax and Propeller Hat logos are trademarks of Parallax Inc., dba Parallax Semiconductor

License

Licensed under the MIT License.

Follow these links for more information:

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