Electric power steering system for a vehicle
First Claim
1. A system (1) being powered by a battery which delivers a voltage V, and (2) for operation in a vehicle, comprising:
- a) a two-phase electric motor having i) a stator of the synchronous type and ii) two stator phases;
b) a field-oriented controller for controlling voltages applied to the phases, wherein i) full battery voltage is available for application across each phase; and
ii) all phase voltages are independently controllable.
1 Assignment
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Accused Products
Abstract
A control system for an electric motor. Field Oriented Control, FOC, uses a digital control system, and attempts to maintain the rotating stator magnetic field ninety degrees ahead of the rotor field, in order to maximize torque. However, if a three-phase motor is used, which is very common, large amounts of computation are required, to convert from a three-phase coordinate system to an orthogonal coordinate system. The invention replaces the three-phase motor with a two-phase motor, which has been found to impose certain additional costs, but also provides benefits.
16 Citations
36 Claims
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1. A system (1) being powered by a battery which delivers a voltage V, and (2) for operation in a vehicle, comprising:
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a) a two-phase electric motor having i) a stator of the synchronous type and ii) two stator phases;
b) a field-oriented controller for controlling voltages applied to the phases, wherein i) full battery voltage is available for application across each phase; and
ii) all phase voltages are independently controllable. - View Dependent Claims (2, 3, 4, 5, 33, 34)
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6. A method for operation in a vehicle being powered by a battery which delivers a voltage V, comprising:
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a) maintaining a two-phase electric motor having i) a stator of the synchronous type and ii) two stator phases;
b) maintaining a field-oriented controller for controlling voltages applied to the phases, which i) applies full battery voltage across each phase; and
ii) provides independently controllable voltages to all phases. - View Dependent Claims (7, 8, 9, 10, 35, 36)
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11. A system (1) for operation in a vehicle having a power steering system, and (2) being powered by a battery which delivers a voltage V, comprising:
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a) a two-phase electric motor having i) a stator of the synchronous type and ii) two stator phases;
b) a field-oriented controller for controlling voltages applied to the phases, wherein i) full battery voltage is available for application across each phase; and
ii) all phase voltages are independently controllable, wherein pulse-width modulation, PWM, is used to control magnitude of current in each phase, the PWM applied to one phase need not be synchronized with the PWM applied to the other phase, and voltage V is available for application to each phase.
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12. A method (1) for operation in a vehicle having a power steering system, and (2) being powered by a battery which delivers a voltage V, comprising:
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a) providing a two-phase electric motor having i) a stator of the synchronous type and ii) two stator phases;
b) providing a field-oriented controller for controlling voltages applied to the phases, wherein i) full battery voltage is available for application across each phase; and
ii) all phase voltages are independently controllable, wherein pulse-width modulation, PWM, is used to control magnitude of current in each phase, the PWM applied to one phase need not be synchronized with the PWM applied to the other phase, and voltage V is available for application to each phase. - View Dependent Claims (18, 20, 22)
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13. In an electric motor which has stator coils which produce a rotating stator field vector, and which is controlled by a control system implementing Field Oriented Control, a method comprising:
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a) deriving data concerning behavior of the coils; and
b) based on the data, computing position of the stator field vector, without translating from an N-phase reference frame of the stator to an orthogonal reference frame, wherein N is greater than two. - View Dependent Claims (14, 15, 16)
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17. For an electric motor which has stator coils which produce a rotating stator field vector, and which is controlled by a control system implementing Field Oriented Control, a system comprising:
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a) means for deriving data concerning behavior of the coils; and
b) means for receiving the data and computing position of the stator field vector, without translating from an N-phase reference frame of the stator to an orthogonal reference frame, wherein N is greater than two. - View Dependent Claims (19, 21)
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23. A system comprising:
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a) a motor comprising a two-phase stator of the synchronous type; and
b) a control system which implements Field Oriented Control wherein the only coordinate transformations undertaken are (1) from a stationary system to a rotating system and (2) from the rotating system to the stationary system. - View Dependent Claims (24)
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25. A method comprising:
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a) providing a motor comprising a two-phase stator of the synchronous type; and
b) providing a control system which implements Field Oriented Control wherein the only coordinate transformations undertaken are (1) from a stationary system to a rotating system and (2) from the rotating system to the stationary system. - View Dependent Claims (26)
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27. A method, comprising:
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a) in a vehicle, maintaining an electric motor having a stator of the synchronous type;
b) generating currents in coils of the stator, said currents producing a rotating stator field vector; and
c) obtaining an expression for orthogonal components of the stator field, without computing said components. - View Dependent Claims (28)
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29. A system, providing:
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a) a power supply delivering a voltage V;
b) a motor having phase coils in a synchronous-type stator; and
c) a system for providing Field Oriented Control to the motor, wherein power in each phase coil equals V multiplied by the current in the phase. - View Dependent Claims (30)
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31. A system, comprising:
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a) a vehicle;
b) a power source-power receiver pair comprising i) an electrical power source in the vehicle, and ii) a mechanical device to be powered, the power source-power receiver having the characteristic that, when a 3-phase electric motor and Field Oriented Control implemented in a DSP are used to convert power from the source to the receiver, a computer program having N lines of code is required, and c) means for converting power from the source to the receiver which requires 0.75 N, or fewer, lines of code. - View Dependent Claims (32)
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Specification