Rotation angle estimation device, motor control device, and rotation angle estimation method

摘要

The rotation angle of a rotor when driven by applying pulse voltages to multi-phase armature windings of an electric motor is estimated without using a sensor. Pulse voltages with shifted phases are respectively applied to the multi-phase armature windings to rotate the rotor, neutral point potential differences, i.e. the potential differences between the actual neutral points of the armature windings and the virtual neutral points formed as equivalent circuits of the armature windings, are sequentially detected, cross points at which the size relationships between a predetermined threshold value and the detected neutral point potential differences are inverted are detected while the rotor is in a state of rotating as a result of sequentially applying the pulse voltages having a prescribed phase difference to each of the armature windings, and the rotation angle of the rotor is estimated on the basis of the intervals from the timings at which the cross points are detected, to the next cross points. In the estimation of the rotation angle of the rotor, a non-usage range in which the cross points are not used to estimate the rotation angle is set.