Extended speed range operation of permanent magnet brushless machines using optimal phase angle control in the voltage mode operation
First Claim
1. A voltage mode control method for extending speed range operation from a sinusoidally excited permanent magnet motor, comprising:
- determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;
reading a second set of parameters;
computing a first derived angle using said first set of parameters and said second set of parameters;
computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and
outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.
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Abstract
A voltage mode control method and apparatus for extending speed range operation from a sinusoidally excited permanent magnet motor is described. The method includes a determination of a maximum value from a first set of parameters with each parameter having a known maximum value as well as a reading of a second set of parameters. A computation of a first derived angle using the first set of parameters and the second set of parameters is then performed. A computation of amplitude of phase voltage and a second derived angle using the first derived angle follows. A resultant output comprising a set of derived command voltages for controlling a power circuit is created whereby the power circuit can achieve required torque levels with lower currents for power switches.
188 Citations
30 Claims
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1. A voltage mode control method for extending speed range operation from a sinusoidally excited permanent magnet motor, comprising:
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determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;
reading a second set of parameters;
computing a first derived angle using said first set of parameters and said second set of parameters;
computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and
outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
a set of tabled available torque having a maximum torque; and
a set of tabled mechanical speed having a maximum mechanical speed, whereby both said set of tabled available torque and said set of tabled mechanical speed are derived from a set of maximum allowed phase rms currents.
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3. The voltage mode control method of claim 1 wherein said second set of parameters comprises:
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a requisite torque; and
a sensed speed derived from a rotor of said sinusoidally excited permanent magnet motor.
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4. The voltage mode control method of claim 3 further comprising:
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determining whether said requisite torque is greater than said maximum torque; and
if said requisite torque is greater than said maximum torque, setting said requisite torque as said maximum torque.
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5. The voltage mode control method of claim 1 further comprising computing a requisite phase current.
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6. The voltage mode control method of claim 1 wherein:
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said reading of said second set of parameters comprises;
reading a speed value; and
reading a requisite torque value.
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7. The voltage mode control method of claim 1 wherein said first derived angle is computed by:
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where, α
=first derived angle,Np denotes the number of pole pairs, Ke denote back-emf constant of the electric machine, rms value, Eph,rms=Keω
m,ω
m is machine mechanical speed, in rad/s,Eph,rms is phase rms back-emf.
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8. The voltage mode control method of claim 1 further comprising:
computing a phase rms voltage given by;
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9. The voltage mode control method of claim 1 wherein:
- said second derived angle is computed by;
where,
- said second derived angle is computed by;
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10. The voltage mode control method of claim 1 wherein said set of derived command voltages comprises:
Va Vb and Vc with Va Vb and Vc denoted by;
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11. The voltage mode control method of claim 1 wherein said power circuit comprises an inverter.
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12. The voltage mode control method of claim 1 wherein said third set of parameters comprises rms phase current, rms voltage, phase impedance, and phase resistance.
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13. The voltage mode control method of claim 12 wherein said phase resistance is compensated for temperature variations by a method comprising:
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measuring the temperature of the phase windings; and
calculating the actual phase resistance by using the equation;
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14. A power steering assist system comprising:
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a steering wheel and column;
an electric motor comprising a motor controller, said electric motor adapted to impart rotational force to said steering column;
a power steering controller adapted to control said electric motor in a manner effective in providing power steering assist to an operator of said steering wheel; and
wherein said electric motor controller operates by the method of claim 1.
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15. A voltage mode control method for reducing torque ripple in an electric motor, comprising:
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providing a sinusoidally excited permanent magnet motor without current sensors;
determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;
reading a second set of parameters;
computing a first derived angle using said first set of parameters and said second set of parameters;
computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and
outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.
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16. A storage medium encoded with machine-readable computer program code for extending speed range operation from a sinusoidally excited permanent magnet motor, said storage medium including instructions for causing a computer to implement a method comprising:
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determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;
reading a second set of parameters;
computing a first derived angle using said first set of parameters and said second set of parameters;
computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and
outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
a set of tabled available torque having a maximum torque; and
a set of tabled mechanical speed having a maximum mechanical speed, whereby both said set of tabled available torque and said set of tabled available mechanical speed are derived from a set of maximum allowed phase rms currents.
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18. The storage medium of claim 16 wherein said second set of parameters comprises:
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a requisite torque; and
a sensed speed derived from a rotor of said sinusoidally excited permanent magnet motor.
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19. The storage medium of claim 18 further comprising instructions for causing a computer to implement the procedure of:
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determining whether said requisite torque is greater than said maximum torque; and
if said requisite torque is greater than said maximum torque, setting said requisite torque as said maximum torque.
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20. The storage medium of claim 16 further comprising instructions for causing a computer to implement the procedure of:
computing a requisite phase current.
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21. The storage medium of claim 16 wherein said reading of said second set of parameters comprises:
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reading a speed value; and
reading a requisite torque value.
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22. The storage medium of claim 16 wherein said first derived angle is computed by:
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where, α
=first derived angle,Np denotes the number of pole pairs, Ke denote back-emf constant of the electric machine, rms value, Eph,rms=Keω
m,ω
m is machine mechanical speed, in rad/s,Eph,rms is phase rms back-emf.
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23. The storage medium of claim 16 further comprising instructions for causing a computer to implement the procedure of:
computing a phase rms voltage given by;
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24. The storage medium of claim 16 wherein said second derived angle is computed by:
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where, α
=first derived angle.
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25. The storage medium of claim 16 wherein said set of derived command voltages comprising:
Va Vb and Vc with Va Vb and Vc denoted by;
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26. The storage medium of claim 16 wherein said power circuit comprises an inverter.
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27. The storage medium of claim 16 wherein said third set of parameters comprises rms phase current, rms voltage, phase impedance, and phase resistance.
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28. The storage medium of claim 27 wherein said phase resistance is compensated for temperature variations by a method comprising:
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measuring the temperature of the phase windings; and
calculating the actual phase resistance by using the equation;
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29. A power steering assist system comprising:
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a steering wheel and column;
an electric motor comprising a motor controller having a storage medium, said electric motor adapted to impart rotational force to said steering column;
a power steering controller adapted to control said electric motor in a manner effective in providing power steering assist to an operator of said steering wheel; and
wherein said storage medium operates said electric motor controller by the method of claim 16.
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30. A method of reducing torque ripple in an electric motor, comprising:
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providing a sinusoidally excited permanent magnet electric motor without current sensors;
providing a controller for controller said electric motor;
said controller having a storage medium encoded with machine-readable computer program code, said code comprising instructions for causing a computer to implement a procedure comprising;
determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;
reading a second set of parameters;
computing a first derived angle using said first set of parameters and said second set of parameters;
computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and
outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.
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Specification