Patent ID: 7400101
Filing Date: 2008-07-15
Classification: H02P

Abstract:
1. A method for detecting a rotor angle of a DC brushless motor in a motor controller that controls the energization of the motor by deciding a drive voltage to be applied to an armature of the motor for each predetermined control cycle so as to minimize the difference between a phase current passing through the armature of the DC brushless motor and a desired current, comprising: a first step for superposing a periodic signal that causes the total sum of output voltages in a predetermined period including two or more control cycles to become zero over the drive voltage; a second step for calculating a first-order difference in phase current of the motor between adjoining control cycles in the predetermined period, while maintaining the drive voltage during the predetermined period at a constant level; a third step for calculating a sine reference value and a cosine reference value on the basis of the double angle of a rotor angle of the motor, using the first-order difference calculated in the second step; and a fourth step for calculating the rotor angle of the motor on the basis of the sine reference value and the cosine reference value calculated in the third step.