Method and apparatus for controlling an electric assist motor
First Claim
1. An apparatus for controlling an electric motor comprising:
- a first switching device operatively coupled between one terminal of said electric motor and a first terminal of a source of electrical energy;
a second switching device operatively coupled between a second terminal of said electric motor and a second terminal of said source of electrical energy; and
control means for controlling energization of said electric motor, said control means including means for periodically switching both said first and second switching devices between ON and OFF conditions during a motor commutation period, the switching period of said first and second switching devices being less than the motor commutation period and each said first and second switching devices having more than one ON condition during the motor commutation period and only a portion of each of the ON conditions of the first and second switching devices overlap during the switching period, electrical current flows through said electric motor during each overlap portion of the ON conditions and power dissipation switching losses are shared by both said first and second switching devices, the amount of the ON condition overlap controlling current in said electric motor, said control means including means for controlling said ON condition overlap.
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Accused Products
Abstract
An apparatus for controlling an electric assist steering system (10) having an electric assist motor (26) operatively connected to a steerable member. Energization of the motor provides steering assist to the steering member. The apparatus includes a steering torque sensor (27) for sensing applied steering torque and providing a torque signal indicative thereof. A first switching device (72) is operative coupled between one terminal of the electric assist motor (26) and a first terminal of a source of electrical energy. A second switching device (98) is operative coupled between a second terminal of the electric assist motor and a second terminal of the source of electrical energy. A controller (76) periodically switches the first and second switching devices between ON and OFF conditions so that the ON condition of each the first and second switching devices is less than one-hundred percent of a period and a portion of the ON condition of the first and second switching devices overlap. Electrical current flows through the electric assist motor (26) during an overlap portion of ON conditions. The amount of the overlap controls current in the electric assist motor. The controller (76) controls the overlap in response to the sensed applied steering torque.
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Citations
40 Claims
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1. An apparatus for controlling an electric motor comprising:
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a first switching device operatively coupled between one terminal of said electric motor and a first terminal of a source of electrical energy; a second switching device operatively coupled between a second terminal of said electric motor and a second terminal of said source of electrical energy; and control means for controlling energization of said electric motor, said control means including means for periodically switching both said first and second switching devices between ON and OFF conditions during a motor commutation period, the switching period of said first and second switching devices being less than the motor commutation period and each said first and second switching devices having more than one ON condition during the motor commutation period and only a portion of each of the ON conditions of the first and second switching devices overlap during the switching period, electrical current flows through said electric motor during each overlap portion of the ON conditions and power dissipation switching losses are shared by both said first and second switching devices, the amount of the ON condition overlap controlling current in said electric motor, said control means including means for controlling said ON condition overlap. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for controlling a multiphase electric motor comprising:
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a first switching device operatively coupled between one terminal of a phase of said electric motor and a first terminal of a source of electrical energy; a second switching device operatively coupled between a second terminal of said phase of said electric motor and a second terminal of said source of electrical energy; and control means for controlling said electric motor including means for periodically switching said first and second switching devices between ON and OFF conditions so that no portion of the ON conditions of the first and second switching devices overlap and so that each of said first and second switching devices have more than one ON condition during a commutation period of said phase of said electric motor. - View Dependent Claims (10, 11, 12, 13)
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14. An apparatus for controlling an electric assist steering system having an electric assist motor operatively connected to a steerable member, energization of said motor providing steering assist to said steering member, said apparatus comprising:
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torque sensing means for sensing applied steering torque and providing a torque signal indicative thereof; a first switching device operatively coupled between one terminal of said electric assist motor and a first terminal of a source of electrical energy; a second switching device operatively coupled between a second terminal of said electric assist motor and a second terminal of said source of electrical energy; and control means for controlling energization of said electric assist motor, said control means including means for periodically switching said first and second switching devices between ON and OFF conditions during a motor commutation period, the switching period of said first and second switching devices being less than the motor commutation period and each said first and second switching devices having more than one ON condition during the motor commutation period and only a portion of each of the ON conditions of the first and second switching devices overlap during the switching period, electrical current flows through said electric assist motor during each overlap portion of the ON conditions and power dissipation switching losses are shared by the first and second switching devices, the amount of the ON condition overlap controlling current in said electric assist motor, said control means including means for controlling said ON condition overlap in response to said sensed applied steering torque. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A method for controlling an electric motor comprising the steps of:
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providing a first switching device operatively coupled between one terminal of said electric motor and a first terminal of a source of electrical energy; providing a second switching device operatively coupled between a second terminal of said electric motor and a second terminal of said source of electrical energy; and controlling energization of said electric motor by; (a) periodically switching said first and second switching devices between ON and OFF conditions during a motor commutation period so that the switching period of said first and second switching devices is less than the motor commutation period and each said first and second switching devices having more than one ON condition during the motor commutation period and only a portion of each of the ON conditions of the first and second switching devices overlap, electrical current flows through said electric motor during the overlap portion of the ON conditions, the amount of the overlap controlling current in said electric motor, and (b) controlling said overlap. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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30. A method for controlling a multiphase electric motor comprising the steps of:
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providing a first switching device operatively coupled between one terminal of a phase of said electric motor and a first terminal of a source of electrical energy; providing a second switching device operatively coupled between a second terminal of said phase of electric motor and a second terminal of said source of electrical energy; and controlling said electric motor by periodically switching said first and second switching devices between ON and OFF conditions so that no portion of the ON conditions of each said first and second switching devices overlap and so that each of said first and second switching devices have more than one ON condition during a commutation period of said phase of said electric motor. - View Dependent Claims (31, 32, 33, 34)
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35. A method controlling an electric assist steering system having an electric assist motor operatively connected to a steerable member, energization of said motor providing steering assist to said steering member, said method comprising the steps of:
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sensing applied steering torque and providing a torque signal indicative thereof; providing a first switching device operatively coupled between one terminal of said electric assist motor and a first terminal of a source of electrical energy; providing a second switching device operatively coupled between a second terminal of said electric assist motor and a second terminal of said source of electrical energy; and controlling energization of said electric assist motor, by; (a) switching said first and second switching devices between ON and OFF conditions during a motor commutation period, the switching period of said first and second switching devices being less than the motor commutation period and each of said first and second switching devices having more than one ON condition during the motor commutation period and only a portion of each of the ON conditions of the first and second switching devices overlap during the switching period, electrical current flows through said electric assist motor during each overlap portion of the ON conditions and power dissipation switching losses are shared by the first and second switching devices, the amount of the ON condition overlap controlling current in said electric assist motor, and (b) controlling said ON condition overlap in response to said sensed applied steering torque. - View Dependent Claims (36, 37, 38, 39, 40)
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Specification