A Novel Modified Digital PWM Control Technique to Reduce Speed Ripples in BLDC Motors

With all the recent advancement in the domain of permanent magnet brushless dc (BLDC) motor control, many of the advanced and low cost control schemes are proposed. Despite of having multiple constructions based inherent advantages like reduced maintenance cost, high torque to weight ratio and others, BLDC motors still find sparse commercial applications. Conventionally used induction and dc machines have low initial cost and also are rugged. If maintenance cost, efficiency and volume are solely considered BLDC motors is undoubtedly the most preferable option. However, the extra cost involved with the compulsory power electronic converter to drive the motor makes the industries reluctant towards BLDC motor applications. Digital pulse width modulation (DPWM) technique was introduced to eliminate the usage of costly processors involved for the switching control of the converter. Digital PWM control is a simple approach and also can be implemented in reduced cost application specific integrated circuits (ASIC). The main disadvantage of digital PWM is the speed and torque ripples generated due to fixed duty cycles of the converter. This paper introduces a new modified digital PWM technique to eliminate the speed ripples in BLDC motor. The controller is designed in simulation environment and the same is also validated.