Method and apparatus for acoustic signal generation

1. A motor drive system for controlling operation of a multi-phase electric machine, comprising:

an inverter including a plurality of paired power transistors that are electrically connected to the electric machine, wherein the inverter is electrically connected to a DC power source via a high-voltage electrical power bus; and

a motor controller including a first controller and an acoustic signal generator, wherein the first controller is disposed to control the paired power transistors of the inverter to effect operation of the multi-phase electric machine;

wherein the first controller is disposed to determine an initial output voltage based upon a torque command;

wherein the acoustic signal generator is disposed to generate a sound injection voltage, including a sound pattern generator that is disposed to generate an instantaneous audio signal and a rotational transformation element that is disposed to generate the sound injection voltage based upon the instantaneous audio signal, and wherein the instantaneous audio signal is adjusted by a first gain factor associated with a torque-based gain derating and a second gain factor associated with a speed-based gain derating;

wherein the motor controller is disposed to combine the initial output voltage and the sound injection voltage; and

wherein the motor controller is disposed to generate commands to control the paired power transistors of the inverter, wherein the commands are determined based upon the initial output voltage and the sound injection voltage.

2. The motor drive system of claim 1 , wherein the motor controller is disposed to generate the commands to control the paired power transistors of the inverter in response to the torque command and based upon the sound injection voltage.

3. The motor drive system of claim 1 , wherein the motor controller is disposed to generate the commands to control the paired power transistors of the inverter in response to the torque command, a rotational speed of the electric machine, and a voltage level of the high-voltage electrical power bus and based upon the sound injection voltage.

4. The motor drive system of claim 1 ,

wherein the acoustic signal generator includes a sound pattern generator; and

wherein the acoustic signal generator is disposed to generate the sound injection voltage based upon an output from the sound pattern generator.

5. The motor drive system of claim 1 ,

wherein the first controller includes a current regulator disposed to generate current commands responsive to the torque command; and

wherein the acoustic signal generator includes a sound pattern generator that includes an arbitrary sound generator look-up table having frequency components that are greater than a maximum frequency associated with a bandwidth of the current regulator.

6. The motor drive system of claim 1 :

wherein the first controller includes a first converter and a current regulator;

wherein the first controller is configured to generate current commands in response to a torque command;

wherein the current regulator is configured to generate initial output voltage commands based upon the current commands;

wherein the acoustic signal generator includes an acoustic sound pattern generator;

wherein the acoustic signal generator is disposed to generate the sound injection voltage based upon an output from the acoustic sound pattern generator; and

wherein the sound injection voltage is combined with the initial output voltage commands; and

wherein the sound injection voltage combined with the initial output voltage commands are communicated to the first controller to generate PWM commands to control the paired power transistors of the inverter.

7. The motor drive system of claim 4 , wherein the sound pattern generator comprises an arbitrary sound generator look-up table including frequency components that are greater than a maximum frequency associated with a bandwidth of a current regulator that is associated with the first controller.

8. A method for controlling operation of an inverter that is electrically connected to a multi-phase electric machine, comprising:

determining, via a first controller, an initial output voltage based upon a torque command;

determining, via an acoustic signal generator, a sound injection voltage, including generating an instantaneous audio signal and a rotational transformation element that is disposed to generate the sound injection voltage based upon the instantaneous audio signal, wherein the instantaneous audio signal is adjusted by a first gain factor associated with a torque-based gain derating and a second gain factor associated with a speed-based gain derating;

combining the initial output voltage and the sound injection voltage; and

generating output voltage commands to control the inverter, wherein the output voltage commands are determined based upon the initial output voltage and the sound injection voltage.

9. The method of claim 8 , comprising generating the commands to control the inverter in response to the torque command and based upon the sound injection voltage.

10. The method of claim 8 , comprising generating the commands to control the inverter in response to the torque command, a rotational speed of the electric machine, and a voltage level of the high-voltage electrical power bus and based upon the sound injection voltage.

11. The method of claim 8 , comprising:

generating current commands responsive to the torque command; and

determining the sound injection voltage with frequency components that are greater than a maximum frequency associated with a bandwidth that is associated with the current commands responsive to the torque command.

12. The method of claim 8 , comprising:

generating the sound injection voltage based upon an output from the acoustic sound pattern generator; and

combining the sound injection voltage with the reference frame voltage commands; and

generating commands to control the paired power transistors of the inverter based upon the sound injection voltage combined with the reference frame voltage commands.

13. An acoustic signal generator for a motor controller that is disposed to control operation of a multi-phase electric machine, comprising:

a sound pattern generator configured to generate an instantaneous audio signal; and

a rotational transformation element configured to generate sound injection voltages based upon the instantaneous audio signal, wherein the instantaneous audio signal is adjusted by a first gain factor associated with a torque-based gain derating and a second gain factor associated with a speed-based gain derating,

wherein the sound injection voltages are input to the motor controller to control operation of the multi-phase electric machine.

14. The acoustic signal generator of claim 13 , wherein the rotational transformation is disposed to locate the sound injection voltage into the motor controller of the electric machine.

15. The acoustic signal generator of claim 14 , wherein the rotational transformation is expressed as:

[

V

di

V

qi

]

=

[

cos

⁢

⁢

γ

-

sin

⁢

⁢

γ

sin

⁢

⁢

γ

cos

⁢

⁢

γ

]

⁡

[

0

V

i

]

=

[

-

V

i

⁢

⁢

sin

⁢

⁢

γ

V

i

⁢

⁢

cos

⁢

⁢

γ

]

wherein:

γ represents a correct angular location to locate the sound injection voltage into the motor controller,

V di and V qi represent the sound injection voltages, and

V i represents voltage.