Minimization of motor torque ripple due to unbalanced conditions

A method of generating a set of minimized line-to-ground voltage commands for minimizing the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor in an automotive steering system, the method comprising:

• measuring the position of the motor;
• generating a set of modulation index terms;
• adding the measured position of the motor to a set of phase shift terms;
• calculating a trigonometric function of the summation of the measured position of the motor and the set of phase shift terms;
• multiplying the trigonometric function of the summation of the measured position of the motor and the set of phase shift terms by the set of modulation index terms, generating thereby a set of line-to-ground voltage commands;
• comparing the instantaneous values of the set of line-to-ground voltage commands;
• selecting the minimum value of the set of line-to-ground voltage commands;
• subtracting the minimum value of the set of line-to-ground voltage commands from the set of line-to-ground voltage commands providing thereby a set of minimized line-to-voltage commands.

A storage medium encoded with machine-readable computer program code for minimizing the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor in an automotive steering system, the computer code being executable whereby the computer code when run by a computer system will minimize the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor in an automotive steering system, the program code including instructions for causing the computer system to implement a method comprising:

• measuring the position of the motor;
• sampling the phase currents of the motor generating thereby at least one phase current;
• synchronizing the at least one phase current of the motor with the position of the motor;
• determining the imbalance in the magnitudes of the at least one phase current of the motor;
• generating a set of modulation index terms for reducing the imbalance in the magnitudes of the at least one phase current to ensure acceptable torque ripple characteristics over the operating velocity of the motor;
• and
• responsive to the set of modulation index terms, generating a set of minimized line-to-ground voltage commands.

A storage medium encoded with machine-readable computer program code for generating a set of minimized line-to-ground voltage commands for minimizing the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor in an automotive steering system, the computer code being executable whereby the computer code when run by a computer system will minimize line-to-ground voltage commands for minimizing the torque ripple produced by unbalanced phase currents in a sinusoidally excited motor in an automotive steering system, the program code including instructions for causing the computer system to implement a method comprising:

• measuring the position of the motor;
• generating a set of modulation index terms;
• adding the measured position of the motor to a set of phase shift terms;
• calculating a trigonometric function of the summation of the measured position of the motor and the set of phase shift terms;
• multiplying the trigonometric function of the summation of the measured position of the motor and the set of phase shift terms by the set of modulation index terms, generating thereby a set of line-to-ground voltage commands;
• comparing the instantaneous values of the set of line-to-ground voltage commands;
• selecting the minimum value of the set of line-to-ground voltage commands;
• subtracting the minimum value of the set of line-to-ground voltage commands from the set of line-to-ground voltage commands providing thereby a set of minimized line-to-voltage commands.