Electronically commutated electric motor with harmonic compensation
The invention relates to an electronically commutated electric motor with a stator and a rotor, which is designed as a permanent magnet rotor in particular. The electric motor also has a control unit which is connected to the stator. The control unit is designed to generate control signals for energizing the stator coils of the stator in order to generate a rotational magnetic field. The electric motor is designed to at least partly compensate for a torque ripple of a torque generated by the rotor. According to the invention, the electric motor has a rotor position sensor and a current sensor. The current sensor is designed to detect currents flowing in the stator coils and to generate a current signal which represents the currents. The control unit preferably has a processing unit which is designed to ascertain harmonics of the electromotive force dependent on the current signal, a voltage applied to the stator coils, and a rotor position signal generated by the rotor position sensor and to generate a control signal which compensates for the effect of the harmonics. The control unit, in particular the processing unit, is designed to superimpose the compensating control signal with the control signal so as to completely or at least partly compensate for the effect of the harmonics and thus the torque ripple.
1. An electronically commutated electric motor having a stator and a rotor, the electric motor comprising:
a control unit connected to the stator, and configured to generate control signals for supplying stator coils of the stator with current for generating a rotating magnetic field, and wherein the electric motor is configured to at least partially compensate for a torque ripple of a torque generated by the rotor,
a rotor position sensor; and
a current sensor,
wherein the current sensor is configured to detect currents flowing in the stator coils and to generate a current signal representing the currents flowing in the stator coils,
wherein the control unit comprises a processing unit, wherein the processing unit is configured to ascertain harmonics of an electromotive force and to generate a compensating control signal which compensates for the effect of the harmonics as a function of the current signal and a voltage supplied to the stator coils and a rotor position signal generated by the rotor position sensor, and wherein the processing unit is further configured to overlap the compensating control signal with the control signal, so that it is possible to compensate at least partially or completely for the effect of the harmonics and thus the torque ripple.
2. The electric motor as claimed in claim 1 , wherein the processing unit further comprises a root least squared estimator configured to ascertain the harmonics, by a least-squares method.
3. The electronically commutated electric motor as claimed in claim 1 , wherein the processing unit is configured to control the stator by a flatness-based control as a function of the compensating control signal.
4. The electronically commutated electric motor as claimed in claim 2 , wherein the control unit is configured to generate a voltage for supplying the stator coils as a function of the compensating control signal.
5. The electronically commutated electric motor as claimed in claim 2 , wherein the processing unit is configured to generate a torque signal representing a compensating torque as a function of the harmonics ascertained by the root least squared estimator, and to generate the compensating control signal as a function of the compensating torque signal.
6. The electronically commutated electric motor as claimed in claim 1 , wherein the processing unit further comprises an electrical model of the electric motor, wherein the electrical model represents a manipulated variable for the voltage to be supplied to the stator coils as a function of the inductance of the stator coils, and an ascertained magnetic flux, wherein the magnetic flux includes the harmonics to be compensated for, and wherein the processing unit is configured to generate the compensating control signal as a function of the manipulated variable.
7. The electric motor as claimed in claim 6 , wherein the magnetic flux represents the harmonics in the form of a Fourier series.
8. An electrical power steering system for a vehicle, the system comprising:
an electric motor, the electric motor including
stator;
a rotor;
a control unit connected to the stator and configured to generate control signals for supplying stator coils of the stator with current for generating a rotating magnetic field, a rotor position sensor; and
a current sensor configured to detect currents flowing in the stator coils and to generate a current signal representing the currents flowing in the stator coils,
wherein the control unit comprises a processing unit configured to ascertain harmonics of an electromotive force and to generate a compensating control signal which compensates for the effect of the harmonics as a function of the current signal and a voltage supplied to the stator coils and a rotor position signal generated by the rotor position sensor, and wherein the processing unit is further configured to overlap the compensating control signal with the control signal, so that it is possible to compensate at least partially or completely for the effect of the harmonics and thus the torque ripple, and
wherein the power steering system is configured to generate a steering torque which aids steering by means of the electric motor.
9. A brake booster for a vehicle including an electric motor, having a stator and a rotor, wherein the electric motor comprises a control unit connected to the stator, wherein the control unit is configured to generate control signals for supplying stator coils of the stator with current for generating a rotating magnetic field, and wherein the electric motor is configured to at least partially compensate for a torque ripple of a torque generated by the rotor,
wherein the electric motor includes a rotor position sensor and a current sensor, wherein the current sensor is configured to detect currents flowing in the stator coils and to generate a current signal representing the currents flowing in the stator coils,
wherein the control unit comprises a processing unit, wherein the processing unit is configured to ascertain harmonics of an electromotive force and to generate a compensating control signal which compensates for the effect of the harmonics as a function of the current signal and a voltage supplied to the stator coils and a rotor position signal generated by the rotor position sensor, and wherein the processing unit is further configured to overlap the compensating control signal with the control signal, so that it is possible to compensate at least partially or completely for the effect of the harmonics and thus the torque ripple, and
wherein the brake booster is configured to generate a braking force which aids braking by means of the electric motor.
10. An electric bicycle including an electric motor, the electric motoring including
a stator;
a rotor,
a control unit connected to the stator and configured to generate control signals for supplying stator coils of the stator with current for generating a rotating magnetic field;
a rotor position sensor; and
a current sensor,
wherein the current sensor is configured to detect currents flowing in the stator coils and to generate a current signal representing the currents flowing in the stator coils,
wherein the control unit includes a processing unit configured to ascertain harmonics of an electromotive force and to generate a compensating control signal which compensates for the effect of the harmonics as a function of the current signal and a voltage supplied to the stator coils and a rotor position signal generated by the rotor position sensor, and wherein the processing unit is further configured to overlap the compensating control signal with the control signal, so that it is possible to compensate at least partially or completely for the effect of the harmonics and thus the torque ripple, and
wherein the electric motor is a drive motor of the electric bicycle.