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BOOSTXL-DRV8301: Position control of a low inductance BLDC motor

Part Number: BOOSTXL-DRV8301
Other Parts Discussed in Thread: LAUNCHXL-F28069M,

Hello, I have a tiny BLDC motor with 6 poles, a stator inductance of 30 uH, and series resistance of 0.8 ohms. It is an outrunner typically used in drones.

I am using the LAUNCHXL-F28069M evaluation board together with the BOOSTXL-DRV8301 driver.

Instaspin lab 02c was used to characterize the motor, and motor parameters were close to the ones measured experimentally.

05c was used to try to automatically identify motor inertia and friction parameters, but failed.

Then, using default inertia (0.014) and friction (0.030) values lab 13b was used to try to control the motor in position, in closed loop by using a magnetic rotary encoder, but either the shield goes in fault or starts sending a lot of current to the motor, which sometimes moves in a quite jerky way or never moves.

100 uH and 200 uH series inductors were added but no improvements were noticed.

Current sensing resistors were changed from 10mohms to 100mohms in order to further amplify phase currents (giving a full scale of 3.3A), I also tried changing PWM frequency up to 80 kHz and using the provided excel sheet to compute the parameters to be defined in the user.h file, changing power supply voltage from 24V to 12V but no improvements noticed.

Is it possible, in your opinion to control such a small motor in position with this hardware? Am I doing something wrong?

Best regards,

Stefano