Motor controller
The motor controller drives an electric motor including a rotor as a field magnet and stator coils of U-phase, V-phase and W-phase. The motor controller includes an exploration voltage application unit for applying an exploration voltage to the stator coils of U-phase, V-phase and W-phase such that a voltage vector expressed by the voltage applied to the stator coils rotates in a predetermined cycle with maintaining a constant magnitude, an electric current detection unit for detecting an electric current flowing through the electric motor during the period in which the exploration voltage is applied by the exploration voltage application unit, and a rotor rotation angle estimation unit for estimating a rotation angle of the rotor based on a phase of the voltage vector when a magnitude of the electric current detected by the electric current detection unit takes a local maximum value.
1. A motor controller for driving an electric motor including a rotor as a field magnet and stator coils of U-phase, V-phase and W-phase, the motor controller comprising:
an exploration voltage application unit for applying an exploration voltage to the stator coils of U-phase, V-phase and W-phase such that a voltage vector expressed by the voltage applied to the stator coils rotates in a predetermined cycle with maintaining a constant magnitude,
an electric current detection unit for detecting an electric current flowing through the electric motor during the period in which the exploration voltage is applied by the exploration voltage application unit, and
a rotor rotation angle estimation unit for estimating a rotation angle of the rotor based on a phase of the voltage vector when a magnitude of the electric current detected by the electric current detection unit takes a local maximum value.
2. A motor controller as set forth in claim 1 , wherein the rotor rotation angle estimation unit includes a counting unit for conducting a counting operation synchronized with application of the exploration voltage by the exploration voltage application unit, and generating a counter value that expresses the phase of the voltage vector, and
wherein the rotor rotation angle estimation unit outputs, as rotation angle information for expressing the rotation angle of the rotor, the counter value of the counting unit when the magnitude of the electric current detected by the electric current detection unit takes a local maximum value.
3. A motor controller as set forth in claim 2 , wherein the counting unit conducts the counting operation in a cycle T/n in which a rotation cycle T of the voltage vector is divided into n equal sections.
4. A motor controller as set forth in claim 1 , wherein the motor controller further includes a rotation control signal generation unit for generating a control signal that is applied to the stator coils in order to rotate the rotor based on a rotation angle of the rotor estimated by the rotor rotation angle estimation unit.