Control method for direct torsion of staircase waveform backemf brushless dc motor

The invention discloses a method for direct torque control of a stepped wave back electromotive force brushless direct current motor and belongs to a method for controlling a permanent magnetic synchronous motor. A torque adjusting signal KT, a stator magnetic linkage adjusting signal Kpsi and a stator magnetic linkage phase angle theta of the stepped wave back electromotive force brushless direct current motor are input into a switch state table to obtain a three-phase switch state of a three-phase full-bridge inverter. The three-phase switch state runs through the three-phase full-bridge inverter, produces certain basic vector to directly control actual stator magnetic linkage psi and actual torque T of the stepped wave back electromotive force brushless direct current motor. The method combines an idle load stator magnetic linkage track rule and three-phase synchronous conduction (no intermittent phase) of a sine wave permanent magnetic synchronous motor and the advantages of simple structure and high power density of a 120 degree square wave brushless direct current motor, improves the utilization rate of a permanent magnet (which is 1.3 times that of the120 degree square wave brushless direct current motor) and simplifies a motor body and a control system.