A method of controlling a brushless permanent magnet motor

A rotor of a brushless permanent magnet motor experiences, during rotation of the rotor, a cogging torque that oscillates between a negative cogging torque that opposes the rotation of the rotor and a positive cogging toque that promotes the rotation of the rotor. A method of controlling the motor includes, determining a first period in which the rotor experiences the negative cogging torque; and controlling, during the first period, current to flow in a phase winding of the motor to drive rotation of the rotor against the negative cogging torque. The method further includes, determining a second period in which the rotor experiences a positive cogging torque; and controlling, during the second period, zero current, or a braking current to oppose the rotation of the rotor, to flow in the phase winding of the motor such that the rotation of the rotor is driven by the positive cogging torque.