Electric motor phase control system
First Claim
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1. An apparatus comprising:
- a controller configured toidentify a start time for a signal based on a back electromotive force present in an electric motor during operation of the electric motor, wherein the start time is for a position of a rotor relative to a group of coils; and
send the signal to the group of coils using the start time identified, wherein an effect of the back electromotive force on the signal is reduced;
wherein the signal is a current in the electric motor and has a waveform and the controller is configured toidentify a first area under the waveform,identify a second area under a commanded waveform resulting from a commanded current for the electric motor, andchange the start time based on a difference between the first area and the second area; and
wherein the controller is configured to advance the start time to an earlier start time if the first area is less than the second area by a selected amount.
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Abstract
A method and apparatus for controlling an electric motor. A controller is configured to identify a start time for a signal based on a back electromotive force present in an electric motor during operation of the electric motor. The start time is for a position of a rotor relative to a group of coils. The controller is further configured to send the signal to the group of coils using the start time identified. An effect of the back electromotive force on the signal is reduced.
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Citations
16 Claims
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1. An apparatus comprising:
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a controller configured to identify a start time for a signal based on a back electromotive force present in an electric motor during operation of the electric motor, wherein the start time is for a position of a rotor relative to a group of coils; and send the signal to the group of coils using the start time identified, wherein an effect of the back electromotive force on the signal is reduced; wherein the signal is a current in the electric motor and has a waveform and the controller is configured to identify a first area under the waveform, identify a second area under a commanded waveform resulting from a commanded current for the electric motor, and change the start time based on a difference between the first area and the second area; and wherein the controller is configured to advance the start time to an earlier start time if the first area is less than the second area by a selected amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electric motor system comprising:
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an electric motor having a rotor and a group of coils; a sensor system configured to generate information about a back electromotive force in the electric motor during operation of the electric motor; and a controller configured to receive the information from the sensor system; identify a start time for a current based on the back electromotive force present in the electric motor during operation of the electric motor using the information from the sensor system, wherein the start time is for a position of the rotor relative to the group of coils; and send the current to the group of coils using the start time identified, wherein an effect of the back electromotive force on a signal is reduced; wherein the current in the electric motor has a waveform and the controller is configured to identify a first area under the waveform, identify a second area under a commanded waveform resulting from a commanded current for the electric motor, and change the start time based on a difference between the first area and the second area.
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11. A method for controlling an electric motor, the method comprising:
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identifying a start time for a signal based on a back electromotive force present in the electric motor during operation of the electric motor, wherein the start time is for a position of a rotor relative to a group of coils in the electric motor, and wherein the signal is a current in the electric motor and has a waveform; identifying a first area under the waveform; identifying a second area under a commanded waveform resulting from a commanded current for the electric motor; changing the start time based on a difference between the first area and the second area; and sending the signal to the group of coils using the start time identified, wherein an effect of the back electromotive force on the signal is reduced. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification