Control of sinusoidally driven brushless DC (BLDC) motors

摘要

In response to the determination or estimation of a back EMF zero crossing event for the phase, a time T1 is calculated, T1 being representative of the desired absolute maximum value of the phase current. Current samples are taken by the current sampling unit 104 symmetrically centred around T1. The values of the samples CS[1] to CS[10] are then input into the error function to calculate an error function value. The calculated error function value is input to the lead angle control unit 110 which calculates a value for lead_angle. The value of lead_angle is calculated to be the adjustment in phase angle of the driving voltage profile that will minimise the absolute value of the error function. In generating and adjusting the driving voltage profile the driving voltage generation unit 103 takes into account both lead_angle and the output of the position and speed estimation unit 108. The estimated motor speed may be used additionally in an outer speed control loop involving speed controller 111 to adjust the amplitude (AMP) of the effective driving voltage.