Importance

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Abstract

A sensorless detector 25 uses a rotor angle finally detected by a sensor interpolation detector 24 as an estimated value (.theta. ) of the rotor angle of a motor 3 in a first control cycle upon changing from a rotor angle detecting process carried out by the sensor interpolation detector 24. In subsequent control cycles, the sensorless detector 25 uses estimated values (.theta. , .omega. ) of the rotor angle and a rotor angular velocity in a preceding control cycle as calculation parameters, updates the calculation parameters with an observer which sequentially updates the calculation parameters depending on a phase difference (.theta.-.theta. ) calculated in the preceding control cycle in order to eliminate the phase difference, for thereby calculating the estimated value (.theta. ) of the rotor angle of the motor 3 in the present control cycle.

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First Claim