Switched reluctance motor position by resonant signal injection
First Claim
1. For a brushless commutated motor having a plurality of poles on a rotor and a plurality of phase windings on a stator, a system for controlling a switching frequency Fs of the power signal applied to each phase winding, the system comprising:
- at least one tank circuit comprising capacitive, resistive and inductive elements, wherein one of the phase windings of the motor is the inductive element;
a switch in series connection with the phase winding and in parallel connection with the capacitive and resistive elements of the tank circuit, the switch being responsive to a drive signal for providing the power signal to the phase winding at a switching frequency Fs ;
means for injecting into an input of the tank circuit a low-energy signal having a frequency F1 that is substantially greater than the switching frequency Fs of the power signal;
a detector responsive to an output of the tank circuit for monitoring the low-energy signal and detecting an event resulting from a change in the value of the inductance of the phase winding caused by a change in the relative position of the stator and rotor and generating a signal indicative thereof; and
a motor controller responsive to the signal from the detector for adjusting the timing of the drive signal in order to maintain a predetermined relationship between the signal from the detector and the power signal.
1 Assignment
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Accused Products
Abstract
A apparatus is provided for estimating the position of a rotor of a commutated brushless motor operating without a shaft position sensor. The apparatus includes a tank circuit that incorporates a phase winding of the motor. A low-power signal of a frequency F1 is injected into the tank circuit. The frequency F1 is much greater than the switching frequency Fs of the phase winding. Because the effective inductance (L) of the phase winding incorporated into the tank circuit changes in a cyclic manner in response to changes in the mechanical angle Θ of the rotor, the characteristic resonant frequency F0 of the tank circuit varies between maximum and minimum values. The effect of the variation of the resonant frequency F0 on the output characteristics of the tank circuit are used by a detection circuit to resolve the mechanical angle Θ of the rotor and, thereby, control the timing of the phase firing sequence. The two illustrated embodiments detect changes to the amplitude and phase, respectively, of the signal from the tank circuit in response to the changing inductance of the phase winding incorporated into the tank circuit.
80 Citations
27 Claims
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1. For a brushless commutated motor having a plurality of poles on a rotor and a plurality of phase windings on a stator, a system for controlling a switching frequency Fs of the power signal applied to each phase winding, the system comprising:
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at least one tank circuit comprising capacitive, resistive and inductive elements, wherein one of the phase windings of the motor is the inductive element; a switch in series connection with the phase winding and in parallel connection with the capacitive and resistive elements of the tank circuit, the switch being responsive to a drive signal for providing the power signal to the phase winding at a switching frequency Fs ; means for injecting into an input of the tank circuit a low-energy signal having a frequency F1 that is substantially greater than the switching frequency Fs of the power signal; a detector responsive to an output of the tank circuit for monitoring the low-energy signal and detecting an event resulting from a change in the value of the inductance of the phase winding caused by a change in the relative position of the stator and rotor and generating a signal indicative thereof; and a motor controller responsive to the signal from the detector for adjusting the timing of the drive signal in order to maintain a predetermined relationship between the signal from the detector and the power signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for controlling a switching frequency Fs of a power signal to each winding of a brushless commutated motor having a plurality of poles on a rotor and a plurality of phase windings on a stator, the system comprising:
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at least one tank circuit incorporating one of the phase windings of the motor and having a resonant frequency F0 that varies over a band of frequencies in response to cyclic changes in the effective value of the inductance of the phase winding between maximum and minimum values as the poles of the rotor change position with respect to the one phase winding; a switch in series connection with the phase winding and responsive to a drive signal for providing the power signal to the one phase winding at the switching frequency Fs ; means for injecting into an input of the tank circuit a low-energy signal having a frequency F1 that is substantially greater than the switching frequency Fs ; a detector responsive to an output of the tank circuit for detecting when the difference between the resonant frequency F0 and the frequency F1 of the injected low-energy signal is at a minimum and generating a signal indicative thereof; and a motor controller responsive to the signal from the detector for generating the drive signals to maintain a predetermined relationship between the switching frequency Fs and the signal from the detector. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A circuit for sensing the position of the poles of a rotor for a brushless commutated motor relative to the position of the poles of a stator for the motor, wherein the stator has a plurality of phase windings, the circuit comprising in combination:
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at least one tank circuit incorporating one of the phase windings and having a resonant frequency F0 that cyclically varies over a band of frequencies in response to cyclical changes in the effective value of the inductance of the one winding between maximum and minimum values caused by the poles of the rotor changing position with respect to the one phase winding; means for injecting into an input of the tank circuit a low-energy signal having a frequency F1 ; and a detector responsive to an output of the tank circuit for detecting when the difference between the resonant frequency F0 and the frequency F1 of the injected low-energy signal is at a minimum and generating a signal in response thereto that is indicative of the position of the rotor. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification