Patent ID: 7859215

Claim:
A controller for a motor provided with a resolver that outputs a cosine signal and a sine signal, the controller comprising: a reference signal generator that generates a reference excitation signal synchronized with a PWM (Pulse Width Modulation) period and that provides the reference excitation signal to the resolver; an A/D converter that performs A/D conversion of the cosine signal and the sine signal outputted from the resolver, the A/D conversion being synchronized with the PWM period; a first amplitude calculator that calculates an amplitude of the cosine signal of the resolver based on a twice-A/D converted cosine signal and that calculates an amplitude of the sine signal of the resolver based on a twice-A/D converted sine signal; a second amplitude calculator that calculates averages of the cosine signal and the sine signal of the resolver based on their past A/D converted values, and that calculates the amplitude of the cosine signal of the resolver from a difference between the cosine signal average and a latest A/D converted cosine signal, and that calculates the amplitude of the sine signal of the resolver from a difference between the sine signal average and a latest A/D converted sine signal; a synthesizer that synthesizes the cosine and sine signal amplitudes of the resolver obtained by the first amplitude calculator and the cosine and sine signal amplitudes of the resolver obtained by the second amplitude calculator; a rotational angle calculator that calculates a rotational angle of the motor based on the synthesized cosine and sine signal amplitudes of the resolver outputted by the synthesizer; a PWM controller that performs PWM control of motor winding current based on the rotational angle calculated by the rotational angle calculator.