Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
1999-08-26
2001-06-12
Ip, Paul (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S132000, C318S434000, C318S721000
Reexamination Certificate
active
06246193
ABSTRACT:
FIELD OF INVENTION
The present invention generally relates to a method and apparatus for detecting the position of a rotor, and more particularly to a method and apparatus for detecting the position of a rotor without the use of an encoder.
BACKGROUND OF THE INVENTION
Traditional methods of rotor position estimation in a switched reluctance (SR) motor usually involve either: (1) injection of a signal into one of the phase windings during rotational movement, and identifying the resulting impedance using current sensors and/or flux sensors, or (2) bringing the rotor into alignment on a torque null position, then identifying impedance using the currents and fluxes inherent in the firing of the winding to determine impedance. These approaches have significant drawbacks. In this regard, a lookup table of impedance (inductance, core loss, resistance, capacitance, etc.) is used to find the starting position of the rotor. Moreover, movement may possibly be in a rotation direction opposite of that desired. Furthermore, a period of time must elapse for the position to stabilize before starting, depending upon the load friction and inertia, as well as any other connected load effects (e.g., damping).
One significant drawback to the foregoing methods is the need to use costly current sensors and/or flux sensors. Another drawback to these methods is that they are sensitive to the temperature of the motor and the applied line voltage.
It is recognized that tap voltages, as described in related U.S. patent application Ser. No. 09/257,867, now U.S. Pat. No. 6,150,778, and assigned to the assignee of the present application, may be utilized to determine rotor position. However, the system described in such patent application is best suited for determining rotor position after the rotor has begun spinning at a relatively high speed. It has been observed that the system is less suited for lower motor speeds, stopped or stalled motors, and during speed transients.
The present invention extends the concepts described in the prior patent application with regard to tap voltages signals, to provide an encoderless position detection method and apparatus which determines rotor position when the rotor is stationary.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method for detecting the position of a rotor relative to the position of a stator, in a salient pole machine having N phases. The method includes the steps of simultaneously energizing the N phases with a respective plurality of excitation voltages, to form one or more flux patterns representable by one or more flux vectors; and evaluating said one or more flux vectors to determine a rotor position.
According to another aspect of the present invention there is provided a system for detecting the position of a rotor relative to the position of a stator, in a salient pole machine having N phase windings. The system comprises switching means for simultaneously energizing said N phase windings with one or more respective excitation voltages, wherein each said N phase winding includes a plurality of coil sets; and evaluation means for evaluating one or more flux vectors resulting from said one or more respective excitation voltages, to determine rotor position.
According to another aspect of the present invention there is provided a method for detecting the position of a rotor relative to the position of a stator in a salient pole machine, without moving the rotor. This method includes the steps of: simultaneously energizing a first and second phase winding with a respective first and second excitation voltage, to form a first flux pattern representable by a first flux vector; simultaneously energizing the first and second phase winding with a respective third and fourth excitation voltage, to form a second flux pattern representable by a second flux vector; and evaluating said first and second flux vectors to determine a rotor position.
According to another aspect of the present invention there is provided a method for detecting the position of a rotor relative to the position of a stator in a salient pole machine, without moving the rotor. This method includes the steps of: simultaneously energizing a first and second phase winding with a respective first and second excitation voltage, wherein each said phase winding includes a plurality of coil sets; measuring a first pair of tap voltages respectively associated with a coil set of the first winding and a coil set of the second winding; simultaneously energizing the first and second phase winding with a respective third and fourth excitation voltage; measuring a second pair of tap voltages respectively associated with a coil set of the first winding and a coil set of the second winding; and determining the position of the rotor based upon said first and second pair of tap voltages.
According to another aspect of the present invention there is provided a system for detecting the position of a rotor relative to the position of a stator in a salient pole machine, without moving the rotor. The system comprising: switching means for simultaneously energizing a first and second phase winding with a respective first and second excitation voltage, wherein each said phase winding includes a plurality of coil sets; sampling means for measuring a first pair of tap voltages respectively associated with a coil set of the first winding and a coil set of the second winding; switching means for simultaneously energizing the first and second phase winding with a respective third and fourth excitation voltage; sampling means for measuring a second pair of tap voltages respectively associated with a coil set of the first winding and a coil set of the second winding; and means for determining a rotor position based upon said first and second pair of tap voltages.
According to another aspect of the present invention there is provided a system for detecting the position of a rotor relative to the position of a stator, comprising: first flux generation means for generating a first flux pattern representable by a first flux vector; second flux generation means for generating a second flux pattern representable by a second flux vector; and evaluation means for evaluating said first and second flux vectors to determine a rotor position.
An advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which is suitable for detecting rotor position with the rotor in a stationary condition (e.g., stall or start).
Another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which can determine rotor position of SR and non-SR motors having either regular or irregular pole configurations.
Another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which does not require the use of current sensors.
Another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which does not require the use of flux sensors.
Still another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which is not sensitive to the temperature of the motor.
Still another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which is not sensitive to the applied line voltage.
Yet another advantage of the present invention is the provision of an encoderless rotor position detection method and apparatus, which is suitable for detecting rotor position for a salient pole machine, including switched reluctance (SR) machines and synchronous machines.
Still other advantages of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description, accompanying drawings and appended claims.
REFERENCES:
patent: 4088934 (1978-05-01), D'Atre et al.
patent: 4088935 (1978-05-01), D'Atre et al.
patent
Arter & Hadden LLP
Ip Paul
Tridelta Industries, Inc.
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