Variable Rail Voltage Control of a Brushless DC (BLDC) Motor

Report No. ARL-TR-6308
Authors: Yuan Chen, Joseph Conroy, and William Nothwang
Date/Pages: January 2013; 30 pages
Abstract: A brushless DC (BLDC) motor achieves higher energy efficiency and endures less wear and tear than a traditional brushed DC motor due to the lack of friction between current coils and motor brushes; it requires additional control logic, however, often implemented using a microcontroller, to perform motor commutation. Standard drive circuitry consists of a rail voltage applied to a three-phase inverter and a pulse width modulated (PWM) signal applied to MOSFET gates in accordance with the commutation pattern. Typically, motor speed control is achieved by varying the pulse width applied to the gates while maintaining a fixed rail voltage. We implemented a proportional-integral (PI) feedback system to control motor speed while varying rail voltage. Using this PI controller, we examined the relationship between steady-state power consumption and rail voltage for a fixed reference, as well as the effect of variable rail voltage on transient controller response and total transient power consumption.
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2013