JP2015142451A - Sensorless driving device of switched reluctance motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensorless driving device of a switched reluctance motor capable of accurately detecting a rotor position and efficiently rotating the rotor.SOLUTION: The sensorless driving device includes motor drivers 30 and 40 for rotating a rotor 10 by intermittently feeding a current to a plurality of electromagnets U1 to W2 for magnetizing the plurality of electromagnets U1 to W2, and generating magnetic force between a projection pole 11 of the rotor 10 and the plurality of electromagnets U1 to W2; a current sensor 50 for measuring the current flowing in the electromagnets U1 to W2; and a rotor angle detection unit 60 for detecting an angle of the rotor 10 on the basis of a ripple current flowing in a non-magnetization electromagnet among the plurality of electromagnets U1 to W2.

Description

  The present invention relates to a sensorless driving device for a switched reluctance motor, and more particularly to a sensorless driving device having a function of detecting the position of a rotor without using a sensor. The present invention also relates to a switched reluctance motor and a motor device including the sensorless driving device.

  The switched reluctance motor has a rotor made of a magnetic material having no permanent magnet, and is expected as a motor that can be manufactured at low cost. In this switched reluctance motor, an electric current is intermittently passed through the stator coil based on the position of the rotor, and the rotor is rotated by an attractive force acting between the salient pole of the rotor and the salient pole of the stator. FIG. 15 shows a schematic diagram of a switched reluctance motor. This figure shows a switched reluctance motor in which a 4-pole rotor 101 and a 6-pole stator 102 are combined. Current is passed through the coils 110 attached to the pair of opposed salient poles 105 to excite the salient poles 105 and generate torque for attracting the rotor 101.

  As the rotor 101 rotates, the distance between the salient pole 105 of the stator 102 and the salient pole of the rotor 101 changes, so that the magnetic resistance, that is, the reluctance changes. Torque is generated by this change in reluctance, and the rotor 101 is rotated using this torque. When the magnetic resistance changes, the inductance of the coil 110 also changes. Therefore, if this inductance change is detected, the position (angle) of the rotor 101 can be detected.

JP 2001-309691 A JP 2002-186283 A

  As conventional techniques for detecting the position of the rotor without providing another member such as a sensor, there are those disclosed in Patent Documents 1 and 2. These Patent Documents 1 and 2 disclose techniques for detecting the position of the rotor using an electromotive force in a non-excitation phase generated by magnetic flux from the excitation phase. According to the techniques described in these patent documents, the switched reluctance motor can be rotated without using another member such as a position detection sensor.

  In the case of using the above-described inductance change, actually, the magnetic circuit has strong nonlinearity, and information other than the rotor position information is mixed in the inductance. FIG. 16 is a diagram showing data obtained by measuring the inductance of the coil of the experimental motor. In the graph shown in FIG. 16, the vertical axis represents the inductance of the stator coil, and the horizontal axis represents the direct current flowing through the stator coil. The five curves show the relationship between the inductance and the direct current measured by changing the distance between the salient pole of the stator and the salient pole of the rotor (hereinafter referred to as the gap length). From these curves, it can be seen that the inductance changes according to the change in the gap length.

  However, it can be seen from FIG. 16 that the inductance is also changed by the direct current flowing through the coil. Therefore, it is not possible to distinguish whether the change in inductance is caused by the change in the gap length or the change in the coil current simply by performing the inductance measurement. In the case of an ideal magnetic circuit, the inductance does not change even if the coil current changes, but in reality, the inductance changes in this way due to the nonlinearity of the magnetic circuit. In a switched reluctance motor, the coil current is used up to the saturation region of the magnetic circuit, and the coil current varies greatly. Furthermore, high accuracy and high resolution are required for rotor position detection that determines the commutation timing of the switched reluctance motor. Considering a wide range of load fluctuations, individual differences during mass production, adjustments during production (measuring a large number of inductance curves for each individual), it has been difficult to put a sensorless switched reluctance motor into practical use with conventional techniques.

  Accordingly, an object of the present invention is to provide a sensorless drive device for a switched reluctance motor that can detect the rotor position with high accuracy and can efficiently rotate the rotor. Another object of the present invention is to provide a switched reluctance motor and a motor device including the sensorless driving device.

  In order to achieve the above-described object, one aspect of the present invention provides a switched device including a rotor having a plurality of salient poles made of a magnetic material and a stator having a plurality of electromagnets arranged so as to surround the rotor. A sensorless driving device for driving a reluctance, wherein an electric current is intermittently passed through the electromagnet to excite the electromagnet, thereby generating a magnetic force between the salient pole of the rotor and the electromagnet. A motor driver for rotating the rotor, a current sensor for measuring a current flowing through the electromagnet, and a rotor angle detection for detecting a rotor angle based on a magnitude of a ripple current flowing through a non-excited phase electromagnet among the plurality of electromagnets And a vessel.

The rotor angle detector may determine whether the rotor has reached a predetermined angle by determining whether the magnitude of the ripple current has reached a predetermined value.
The motor driver is characterized in that when the magnitude of the ripple current reaches the predetermined value, current flows through at least one of the plurality of electromagnets.

  The motor driver is a PWM driver, and the rotor angle detector extracts an AM modulation wave having the same frequency as the carrier frequency of the PWM driver from the ripple current flowing in the electromagnet of the non-excitation phase. An extractor; a demodulator that demodulates the AM modulated wave to generate a demodulated signal; and a comparator that compares the demodulated signal with a predetermined value; The current is passed through at least one of the plurality of electromagnets when the current reaches the value.

  The motor driver is a PWM driver, and the rotor angle detector extracts two AM modulated waves having the same frequency as the carrier frequency of the PWM driver from the ripple current flowing in two non-excited phase electromagnets. An AM modulated wave extractor; a demodulator that demodulates the two AM modulated waves and generates respective demodulated signals; and a comparator that calculates a difference between the demodulated signals, and the PWM driver includes the difference When the current reaches a predetermined value, a current is passed through at least one of the plurality of electromagnets.

The average value of the ripple current is close to 0.
The ripple current is a current when the duty ratio of the PWM driver is fixed.
The ripple current is a current when the duty ratio of the PWM driver is fixed, and the duty ratio is set to 0 when the comparator does not compare the demodulated signal with the predetermined value. To do.
The ripple current is a current when the duty ratio of the PWM driver is fixed, and the duty ratio is set to 0 when the comparator does not calculate the difference between the demodulated signals.

The rotor angle detector further includes a gain adjuster for adjusting a gain of the ripple current or the demodulated signal.
The AM modulated wave extractor is a band pass filter, and a center frequency of a pass band of the band pass filter is equal to the carrier frequency.
The demodulator is an envelope detection system that extracts a peak value of the AM modulated wave.
The demodulator is a synchronous detection system that demodulates an AM modulated wave using a reference wave synchronized with the carrier frequency.
The direction of the current flowing through the electromagnet is one direction.

According to another aspect of the present invention, there is provided a switched reluctance motor including a rotor having a plurality of salient poles made of a magnetic material, and a stator having a plurality of electromagnets arranged to surround the rotor, and the switched reluctance A motor device comprising the sensorless driving device for driving a motor.
Each of the plurality of salient poles has an asymmetric cross-sectional shape, and an upstream cross section of the salient pole in a rotation direction of the rotor is larger than a downstream cross section.
The rotor has a plurality of auxiliary poles respectively adjacent to the plurality of salient poles, and the plurality of auxiliary poles are shorter than the plurality of salient poles in the radial direction of the rotor, The plurality of auxiliary poles are alternately arranged along the circumferential direction of the rotor.
The auxiliary electrode has a ring shape.
A part of the auxiliary electrode has a thin ring shape.
The auxiliary electrode has a ring shape in which a notch is partially formed.

  Still another aspect of the present invention provides a sensorless device for driving a switched reluctance including a rotor having a plurality of salient poles made of a magnetic material and a stator having a plurality of electromagnets arranged so as to surround the rotor. A driving method is characterized in that a current flowing through the electromagnet is measured, and an angle of the rotor is detected based on a magnitude of a ripple current flowing through an electromagnet of a non-excitation phase among the plurality of electromagnets.

  According to the present invention, the rotor position is detected based on the change in the ripple current flowing in the electromagnet of the non-excitation phase that does not contribute to the torque generation of the rotor. Therefore, it is possible to accurately detect the rotor position without being affected by the nonlinearity of the magnetic circuit.

It is sectional drawing which shows a switched reluctance motor. It is a figure explaining the example of a connection of magnetic pole U1, U2, V1, V2, W1, W2. It is a figure which shows an example of the excitation timing of the magnetic pole of each phase. It is a schematic diagram which shows an example of a structure of the sensorless drive device for driving the switched reluctance motor shown in FIG. It is a figure which shows the detail of an example of the rotor angle detector of FIG. It is a figure which shows an example of the demodulated signal of U phase electric current, AM modulation wave, and AM modulation wave. It is a figure explaining a commutation timing. It is a figure which shows an example of the logic signal production | generation part which produces | generates a logic signal using the demodulation signal of two non-excitation phases. It is a figure which shows another structural example of a rotor. 10 is a graph showing a change in inductance of the stator coil when the rotor shown in FIG. 9 rotates. It is a figure which shows the example of the auxiliary pole which has a ring shape. It is a figure which shows another structural example of a rotor. It is a figure which shows another structural example of a rotor. It is a figure which shows another structural example of a rotor. It is the schematic of a general switched reluctance motor. It is a figure which shows the data which measured the inductance of the coil of the motor for experiment.

Hereinafter, an embodiment of a switched reluctance motor and its sensorless driving device will be described with reference to the drawings.
FIG. 1 is a sectional view showing a switched reluctance motor. A switched reluctance motor 1 shown in FIG. 1 is a three-phase switched reluctance motor including a 6-pole stator 2 and a 4-pole rotor 10. The stator 2 and the rotor 10 are made of a magnetic material such as a silicon steel plate. The rotor 10 has four salient poles 11, and the stator 2 has six salient poles 3. The stator 2 is disposed so as to surround the rotor 10. Coils (windings) 6 are attached to the salient poles 3 of the stator 2 to form magnetic poles U1, U2, V1, V2, W1, and W2, respectively. By passing a current through the coil 6, the magnetic poles U 1, U 2, V 1, V 2, W 1, W 2 become electromagnets, and these electromagnets generate a magnetic force that attracts the salient poles 11 of the rotor 10.

  FIG. 2 is a diagram illustrating a connection example of the magnetic poles U1, U2, V1, V2, W1, and W2. The coil 6 of the magnetic pole U1 and the coil 6 of the magnetic pole U2 are connected in series to form a U-phase electromagnet. By flowing the current iU to the U phase, the winding direction of the coil 6 is determined so that the magnetic pole U1 is an N pole and the magnetic pole U2 is an S pole. Similarly, the magnetic pole V1 and the magnetic pole V2, and the magnetic pole W1 and the magnetic pole W2 also form a V-phase electromagnet and a W-phase electromagnet, respectively.

  When the rotor 10 makes one rotation, the four salient poles 11 of the rotor 10 pass through each magnetic pole (for example, the magnetic pole U1) four times. That is, the rotor 10 rotates 360 degrees by passing current through the coil 6 of each phase four times and pulling the salient poles 11 of the rotor 10 by magnetic force. FIG. 3 shows an example of the excitation timing of the magnetic poles of each phase. In this example, the rotation angle (mechanical angle) of the rotor 10 when the magnetic pole U1 and one of the salient poles 11 of the rotor 10 are linearly closest to each other is 0 degree. When the U-phase electromagnets (magnetic poles U1, U2) are excited, the V-phase electromagnets (magnetic poles V1, V2) and the W-phase electromagnets (magnetic poles W1, W2) are not excited. Similarly, when the V-phase electromagnet is energized, the W-phase electromagnet and the U-phase electromagnet are non-excited, and when the W-phase electromagnet is energized, the U-phase electromagnet and the V-phase electromagnet are de-energized. The electromagnet is not excited.

  Although FIG. 1 shows a configuration of a three-phase motor having a 6-pole stator 2 and a 4-pole rotor 10, for example, a 12-pole stator and an 8-pole rotor each having 4 magnetic poles of U, V, and W phases. It's okay. Needless to say, the number of phases such as four phases can be changed.

  FIG. 4 is a schematic diagram showing an example of the configuration of the sensorless driving device 20 for driving the switched reluctance motor 1 shown in FIG. The motor device includes a switched reluctance motor 1 shown in FIG. 1 and a sensorless driving device 20 shown in FIG. The sensorless drive device 20 includes a target current generator 21, a PWM controller 30, a drive circuit 40, a current sensor 50, a rotor angle detector (commutation timing generator) 60, and a rotor angular speed determination unit 90.

The current sensor 50 is a current measuring device that measures three-phase (U-phase, V-phase, W-phase) current flowing from the drive circuit 40 to the switched reluctance motor 1. The PWM controller 30 controls the U-phase, V-phase, and W-phase PWM gate signals G _U and G _V of the drive circuit 40 so that the target currents i _U ^* , i _V ^* , and i _W ^* flow to the switched reluctance motor 1. , to generate the _{G W.} More specifically, the subtractor 31 subtracts the measured value of the current fed back from the current sensor 50 from the target current values i _U ^* , i _V ^* , i _W ^* and subtracts the signal obtained by the subtraction from the PID. Input to the compensator 32. The comparator 33 compares the signal moderately adjusted by the PID compensator 32 with the PWM carrier of the triangular wave, so that the U-phase, V-phase, and W-phase PWM gate signals G _U , G _V , G of the drive circuit 40 are obtained. _W is generated. The PWM carrier is not limited to a triangular wave, and may be a sawtooth wave, for example.

The drive circuit 40 includes a DC voltage generator 42 that generates the drive voltage V _DC and a plurality of switching elements 44 connected to the DC voltage generator 42. The switching elements 44 PWM gate signals _{G U,} G V, open and close in accordance with _{G W} (ON / OFF). The drive circuit 40 is connected to the switched reluctance motor 1. U-phase, V-phase, the W phase each coil 6, PWM gate signal is ON drive voltage _V DC, is _{-V DC} when the OFF is applied. In this way, a target current flows through the coil 6 of each phase, and the electromagnet is excited. The PWM controller 30 and the drive circuit 40 excite the electromagnet by intermittently passing current through the electromagnet of the stator 2, and rotate the rotor 10 by generating a magnetic force between the salient pole 11 of the rotor 10 and the electromagnet. Configure the motor driver. This type of motor driver is a PWM driver.

The rotor angle detector 60 generates logic signals P _U , P _V , and P _W based on the current value measured by the current sensor 50. The logic signals P _U , P _V , and P _W are signals that determine the timing of current flow through the electromagnets of each phase, and are composed of an ON signal and an OFF signal. The ON signal is a command signal for starting current supply to the electromagnets of each phase, and the OFF signal is a command signal for stopping current supply to the electromagnets of each phase. The current supply to the electromagnet of each phase and the stop of the current supply are repeated four times per one rotation of the rotor. More specifically, the logic signals P _U , P _V , and P _W are each composed of “1” and “0”, where “1” represents an ON signal, that is, the start of current supply, and “0” is OFF. It represents a stop of the signal, ie current supply. When the logic signal is 1, the electromagnet is excited, and when it is 0, the electromagnet is not excited.

  The rotor angle detector 60 further estimates the position of the rotor 10, that is, the rotation angle θ from the ON / OFF period of the logic signal or the demodulated signal (described later). For example, the rotor angle detector 60 estimates the rotation angle θ from the interval of the logic signal switching timing from the ON signal to the OFF signal (or from the OFF signal to the ON signal). The estimated rotation angle θ of the rotor 10 is sent to the rotor angular velocity determination unit 90. The rotor angular velocity determination unit 90 determines the angular velocity ω of the rotor 10 by calculating a temporal change in the rotation angle θ of the rotor 10.

The angular velocity ω of the rotor 10 is fed back to the target current generator 21. The target current generator 21 includes a subtracter 22, a PID compensator 23, and a multiplier 25. The subtractor 22 subtracts the angular velocity ω from the target angular velocity ω ^* to obtain a difference between the target angular velocity ω ^* and the angular velocity ω, and the PID compensator 23 generates a target current signal i ^* based on the difference. Furthermore, the multiplier 25, by multiplying the target current signal ^{i *} logic signals _{P U,} P V, the _{P W,} the target current value ^{_i U} _{*, i} V _*, to generate a _i ^{W *.}

According to such a sensorless driving device 20, when a load is applied to the rotor 10, the angular velocity ω becomes slower than the target angular velocity ω ^* , so that the target current signal i ^* increases. That is, the electromagnet of the stator 2 is excited according to the load of the rotor 10. As described above, the electromagnet of the stator 2 generates a magnetic force, that is, a torque so that the angular velocity ω follows the target angular velocity ω ^* .

  A ripple current synchronized with the frequency of the PWM carrier (referred to as carrier frequency) is superimposed on the current flowing through the coil 6 of each phase. This ripple current is generated by the PWM controller 30 and the drive circuit 40. The magnitude of the ripple current is inversely proportional to the inductance of the coil 6. That is, the ripple current decreases when the salient pole 11 of the rotor 10 approaches the salient pole 3 of the stator 2 and increases when the salient pole 11 of the rotor 10 leaves. Therefore, the rotation angle θ of the rotor 10 can be estimated by detecting the ripple current ripple. The rotor angle detector 60 detects the position of the rotor 10, that is, the rotation angle θ based on the magnitude (amplitude) of the ripple current.

  FIG. 5 shows details of an example of the rotor angle detector 60 shown in FIG. The rotor angle detector 60 includes a demodulator 70 and a logic signal generator 80. First, the demodulator 70 will be described. The demodulator 70 includes a band pass filter (AM modulated wave extractor) 71, an absolute value circuit 73, a notch filter 75, and a low pass filter 77. The band pass filter 71, the absolute value circuit 73, the notch filter 75, and the low pass filter 77 are connected in series in this order.

As described above, the ripple current synchronized with the carrier frequency is superimposed on the current flowing through the coil 6 of each phase. The current values i _U , i _V , i _W detected by the current sensor 50 are passed through a band pass filter 71 having the frequency of the PWM carrier as the center frequency of the pass band. Thereby, a sine wave signal whose amplitude varies according to the rotation angle of the rotor 10, that is, an AM modulated wave can be extracted. That is, when the salient pole 11 of the rotor 10 approaches the salient pole 3 of the stator 2, the peak value decreases, and when the salient pole 11 of the rotor 10 moves away from the salient pole 3 of the stator 2, the AM modulation wave increases. Can be extracted.

The AM modulated wave is then sent to the absolute value circuit 73. The absolute value circuit 73 turns the minus side component of the AM modulated wave back to the plus side. That is, the absolute value circuit 73 converts the minus side component of the AM modulated wave into a plus side component. By doing so, the AM modulated wave is composed only of the plus side component, and the frequency of the AM modulated wave becomes twice the frequency of the PWM carrier. The AM modulated wave having only the plus side component is passed through a notch filter 75 having a frequency that is twice the carrier frequency as the center frequency of the stop band, and only the peak value of the AM modulated wave is extracted by the notch filter 75. In order to remove the slight remaining carrier frequency noise, the AM modulated wave is passed through a low-pass filter 77 having a cutoff frequency set to about 1/10 of the carrier frequency. Thus AM modulated wave demodulated signal extracted from the ripple current by _{S U, S V,} obtaining _{S W.} If the noise is small, the low-pass filter 77 is unnecessary.

  FIG. 6 is a diagram illustrating an example of a U-phase current, an AM modulated wave, and a demodulated signal of the AM modulated wave. In an ideal state where there is no DC resistance or switching loss of the coil 6 of the stator 2, the average current output from the drive circuit 40 is constant when the PWM duty ratio is 50%. The drive circuit 40 operates so that the current increases when the duty ratio is greater than 50% and decreases when the duty ratio is less than 50%. Actually, since the DC resistance and switching loss of the coil 6 of the stator 2 exist, even when the duty ratio is fixed to 50%, the current does not become constant but tends to decrease.

  Due to the characteristics of the drive circuit 40, the current flows in only one direction. That is, a current always flows from the terminal U + in FIG. 2 to the coil 6 and returns to the terminal U−. Since a negative current cannot flow near zero current, the average value of the ripple current is near zero even when the magnetic pole of the stator 2 is in a non-excited state as shown in FIG. Therefore, when the magnetic poles of the stator 2 are not excited, the PWM duty ratio may be fixed around 50%. By fixing the duty ratio to a predetermined value, a stable ripple current can be obtained, and an AM modulated wave and demodulated signal with less noise can be obtained.

  The demodulator 70 described above is an envelope detection method that extracts the peak (peak value) of the AM modulated wave. Instead, the demodulator uses a reference wave synchronized with the carrier frequency of the PWM controller 30 to perform AM. A synchronous detection system that demodulates the modulated wave may be used.

  The peak value of the ripple current is usually inversely proportional to the inductance. However, at the start of excitation and at the end of excitation, the PWM duty ratio becomes 100% and 0%, respectively, and the PWM switching is stopped, so that no ripple current is generated. Further, during excitation, as the current increases, the stator 2 and the rotor 10 become magnetically saturated, and the inductance decreases. In this way, a nonlinear relationship is established between the inductance and the exciting current. In other words, stable inductance detection, that is, angle detection of the rotor 10 can be performed in the non-excited state. However, since the inductance changes with the excitation current in the excited state, accurate angle detection of the rotor 10 cannot be performed.

Therefore, in the present embodiment, the angle of the rotor 10 is detected using the demodulated signal generated from the ripple current flowing in the coil 6 in the non-excited phase, and the commutation timing of each phase is further determined. Next, the logic signal generation unit 80 will be described with reference to FIGS. 5 and 7. Here, only the U-phase commutation timing will be described to simplify the description. When the demodulated signal S _U is poles U1, U2 of the U-phase is energized, it can not be accurately detected due to the influence of the previously described non-linearity would otherwise always deenergized for simplicity in FIG. 7 It describes as. The same applies to the V phase and the W phase.

The U-phase inductance is greatest when the rotation angle θ of the rotor 10 is 0 degrees. Therefore, when the rotation angle of the rotor 10 theta is 0 degrees, the amplitude of the ripple current is reduced, also reduced demodulated signal S _U. When the rotation angle θ of the rotor 10 is 45 degrees, the inductance is minimized, so that the demodulated signal _SU is maximized. Thus, the demodulated signal S _U is repeated minimum, maximum every 45 degrees. The V-phase demodulated signal S _V is delayed 30 degrees from the U-phase demodulated signal S _U , and the W-phase demodulated signal S _W repeats the minimum and maximum 60 degrees from the U-phase demodulated signal S _U.

In order to accurately determine the excitation start and excitation stop timings of the U-phase magnetic poles U1 and U2, a non-excitation phase demodulated signal that is not affected by nonlinearity is used. In the example shown in FIG. 7, to compare the demodulated signal _{S V} and the threshold _P U ON the V-phase-energized, when the demodulated signal _{S V} reaches a threshold value _P U ON, the logic signal _{P U} is ON signal from the OFF signal Switch to Further, the non-excited W-phase demodulated signal _SW and the threshold value P _U OFF are compared, and when the demodulated signal P _W reaches the threshold value P _U OFF, the logic signal P _U is switched from the ON signal to the OFF signal. Thus, based on a change of the demodulation signal generated from the ripple current flowing through the coil 6 of the non-energized phase, the switching of the ON signal and the OFF signal of the logic signals P _U, that is, the timing of the excitation start and excitation stop poles It is determined. The same applies to the V-phase and W-phase logic signals P _V and P _W.

The logic signals P _U , P _V , and P _W are generated by the logic signal generation unit 80 shown in FIG. That is, each comparator 81 compares the demodulated signal of the non-excitation phase with a threshold value, and the adder 83 generates a logic signal composed of an ON signal and an OFF signal based on the comparison result between the demodulated signal and the threshold value.

ON signal and the OFF timing signal and switches logic signals P _U will vary depending on the rotation angle of the rotor 10 theta. Therefore, it is possible to calculate the rotation angle θ of the rotor 10 from the logic signals P _U. For example, when the rotation angle of the rotor 10 theta is 60 degrees, a logic signal _{P U} is by setting a threshold value _P U ON to switch to the ON signal from OFF signal, the logic signal _{P U} is switched to ON signal It can be determined that the rotation angle θ of the rotor 10 at the time is 60 degrees. Rotation angle calculator 85 provided in the logic signal generation unit 80 shown in FIG. 5 is constituted by a logic signal P _U to calculate the rotation angle θ of the rotor 10. While using FIG. 5, the logic signals P _U is calculating the rotation angle θ of the rotor 10, from the logic signal P _V or logic signal P _W may calculate the rotation angle θ of the rotor 10.

  If the rotation angle θ of the rotor 10 is known, the rotor angular velocity determination unit 90 uses a computing unit such as a CPU (Central Processing Unit) or DSP (Digital Signal Processing Unit) and a timer counter to determine the time of the rotation angle θ. Change, that is, the angular velocity ω can be calculated. The entire logic signal generation unit 80 may be constituted by a CPU or a DSP.

To further generate a good logic signals P _U accuracy, it may be used demodulated signals of two non-excited phase. For example, the logic signals _{P U} when pole U1, U2, V1, V2 is compared with the demodulated signal _{S U} and the demodulation signal _{S V} when de-energized, the difference between the _{S V} and _{S U} has reached the predetermined value Switch from OFF signal to ON signal. Further, the logic signal _{P U} when pole V1, V2, W1, W2 compares the demodulated signal _{S V} and the demodulation signal _{S W} when de-energized, the difference between _{P W} and _{P V} reaches a predetermined value Switch from ON signal to OFF signal. Demodulated signal S _U, S _V, the gain adjuster for amplifying the respective S _W provided, the rotor 10 rotation angle θ of each such ON signal or OFF signal of the logic signals P _U when a predetermined angle is switched The amplification degree of the demodulated signal may be adjusted.

Thus, by using the demodulated signals of the two non-excited phases, it is possible to cancel the influence of inductance characteristic changes due to individual differences, temperature changes, etc., and to realize commutation timing control with higher accuracy and excellent robustness. FIG. 8 shows an example of a logic signal generation unit 80 that generates a logic signal using two non-excitation phase demodulated signals. As shown in FIG. 8, the logic signal generation unit 80, the demodulated signal _{S U,} S V, and a gain adjuster G1~G10 for amplifying the respective _{S W.} The gain adjusters G1 to G10 are arranged in front of the comparator 81 and can finely adjust the switching timing of the ON signals and OFF signals of the respective logic signals P _U , P _V , and P _W. In the embodiment shown in FIG. 8, the comparator 81 calculates the difference between the two non-excitation phase demodulated signals S _V and S _U , and the rotation angle calculator 85 determines that the difference between the demodulated signals S _V and S _U is predetermined. When the value reaches (for example, 0), it is determined that the rotation angle θ of the rotor 10 has reached a predetermined angle.

Demodulated signal S _U, S _V, if stable change in the size of S _W is in any rotation angle theta, the demodulated signals S _U, S _V, only three gain adjuster corresponding to S _W respectively provided May be. The same effect can be obtained by adjusting the gain of the ripple current before demodulating by the demodulator 70.

  The demodulated signal of the non-excited phase is compared with the threshold value and other demodulated signals of the non-excited phase, and the switching timing of the ON signal and OFF signal of the logic signal is determined. Except for determining the ON / OFF switching timing of the logic signal, it is not necessary to accurately obtain the demodulated signal. For this reason, for example, when the demodulated signal is not compared with the threshold value or the demodulated signal of the other phase, the PWM duty ratio is completely set to 0%, the ripple current is completely zero, the copper loss, the iron loss, and the switching loss. May be reduced. If the angular velocity of the rotor 10 is stable, the logic signal becomes completely periodic, so that the time when the demodulated signal is required and the time when it is not required are clear. Therefore, the timing for setting the duty ratio to 0% can be accurately determined. When a change occurs in the angular velocity of the rotor 10, the control of the duty ratio 0% at the time of non-excitation may be stopped immediately and the duty ratio may be switched to about 50%.

The peak value of the ripple current is inversely proportional to the inductance of the electromagnet and proportional to the drive voltage _VDC . When the drive voltage _VDC varies, noise other than the rotor angle information is generated. In order to remove noise caused by the fluctuation of the drive voltage V _DC , the threshold values P _U ON, P _U OFF, P _V ON, P _V OFF, P _W ON, and P _W OFF are proportional to the drive voltage V _DC. It may be changed.

  FIG. 9 is a diagram illustrating another configuration example of the rotor 10. The rotor 10 has a plurality of auxiliary poles 12 in addition to the salient poles 11. The auxiliary pole 12 is shorter than the salient pole 11 in the radial direction of the rotor 10. The plurality of auxiliary poles 12 are respectively adjacent to the plurality of salient poles 11. The plurality of salient poles 11 and the plurality of auxiliary poles 12 are alternately arranged along the circumferential direction of the rotor 10.

  FIG. 10 is a graph showing a change in inductance of the stator coil 6 when the rotor 10 shown in FIG. 9 rotates. When the inductance reaches the maximum value, the energization to the coil 6 of the stator 2 is stopped. In FIG. 10, when the angle of the rotor 10 is 0 degree, the V-phase electromagnet is excited, and the U-phase and W-phase electromagnets are not excited. Similarly, when the angle of the rotor 10 is 30 degrees, the W-phase electromagnet is excited and the U-phase and V-phase electromagnets are not excited. When the angle of the rotor 10 is 60 degrees, the U-phase electromagnet is excited and the V-phase and W-phase electromagnets are not excited.

  A small peak of inductance due to the presence of the auxiliary pole 12 appears between the peaks of inductance. The auxiliary pole 12 provided between the two salient poles 11 adjacent to each other slightly increases the inductance, so that the demodulated signal can be easily compared with the demodulated signal of the threshold or other phases. For example, when the angle of the rotor 10 is 0 degree, the difference between the V-phase demodulated signal and the W-phase demodulated signal is calculated. The presence of the auxiliary pole 12 increases the difference between the V-phase demodulated signal and the W-phase demodulated signal, so that the difference can be further amplified to obtain a desired signal value. As a result, the timing for exciting the V-phase magnetic pole can be detected more accurately, and the influence of noise can be further reduced.

  However, when viewed from the excitation phase, the auxiliary pole 12 has a saliency. For this reason, the auxiliary pole 12 constitutes a magnetic circuit so as to prevent the torque generated at the salient pole 11 of the rotor 10 (generation of reverse torque). Therefore, the auxiliary pole 12 has a shape that magnetically saturates the magnetic path so that the saliency of the auxiliary pole 12 does not increase when a large torque is generated (when a large current flows through the electromagnet in the excitation phase). It is preferable. Examples of such shapes are shown in FIGS.

  FIG. 11 is a diagram illustrating an example of the auxiliary electrode 12 having a ring shape. A gap is formed at the center of the auxiliary pole 12, and the ring-shaped magnetic path of the auxiliary pole 12 is extremely narrow. As a result, when the current flowing through the coil 6 in the excitation phase increases to some extent, magnetic saturation occurs (no more magnetic flux passes through the auxiliary pole 12). Therefore, the reverse torque generated in the auxiliary pole 12 can be reduced. FIG. 12 is a diagram illustrating an example of the auxiliary electrode 12 in which a part of the ring shape is formed thin. FIG. 13 is a diagram illustrating an example of the auxiliary pole 12 in which a notch is formed in a part of the ring shape. The examples shown in FIGS. 12 and 13 can also easily cause magnetic saturation. Therefore, the reverse torque generated in the auxiliary pole 12 can be reduced.

  In the example shown in FIG. 14, the auxiliary electrode 12 is not provided. Instead, the salient pole 11 has an asymmetric cross-sectional shape. In the rotation direction of the rotor 10 (indicated by an arrow), the upstream cross section of the salient pole 11 is larger than the downstream cross section. In this example, since the auxiliary pole 12 as described above is not provided, it is difficult to generate a reverse torque that hinders the torque generated in the electromagnet of the excitation phase, while the inductance of the coil 6 in the non-excitation phase is reduced. Changes can be made.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 Switched reluctance motor 2 Stator 3 Salient pole 6 Coil 10 Rotor 11 Salient pole 20 Sensorless drive device 21 Target current generator 22 Subtractor 23 PID compensator 25 Multiplier 30 PWM controller 31 Subtractor 32 PID compensator 33 Comparator 40 Drive circuit 42 DC voltage generator 44 Switching element 50 Current sensor 60 Rotor angle detector (commutation timing generator)
70 Demodulator 71 Bandpass Filter (AM Modulated Wave Extractor)
73 Absolute value circuit 75 Notch filter 77 Low-pass filter 80 Logic signal generator 81 Comparator 83 Adder 85 Rotation angle calculator 90 Rotor angular velocity determination unit U1, U2, V1, V2, W1, W2 Magnetic pole (electromagnet)

Claims (23)

A sensorless driving device for driving a switched reluctance comprising a rotor having a plurality of salient poles made of a magnetic material and a stator having a plurality of electromagnets arranged so as to surround the rotor,
A motor driver for rotating the rotor by causing a current to flow intermittently through the electromagnet to excite the electromagnet and generating a magnetic force between the salient pole of the rotor and the electromagnet;
A current sensor for measuring a current flowing through the electromagnet;
A sensorless driving device comprising: a rotor angle detector that detects a rotor angle based on a magnitude of a ripple current flowing in an electromagnet of a non-excitation phase among the plurality of electromagnets.   The rotor angle detector determines whether the rotor has reached a predetermined angle by determining whether the magnitude of the ripple current has reached a predetermined value. Item 2. The sensorless drive device according to Item 1.   3. The sensorless drive according to claim 2, wherein when the magnitude of the ripple current reaches the predetermined value, the motor driver causes a current to flow through at least one of the plurality of electromagnets. 4. apparatus. The motor driver is a PWM driver,
The rotor angle detector is
An AM modulated wave extractor for extracting an AM modulated wave having the same frequency as the carrier frequency of the PWM driver from the ripple current flowing in the electromagnet of the non-excited phase;
A demodulator that demodulates the AM modulated wave and generates a demodulated signal;
A comparator that compares the demodulated signal with a predetermined value;
2. The sensorless driving device according to claim 1, wherein when the demodulated signal reaches the predetermined value, the PWM driver causes a current to flow through at least one of the plurality of electromagnets. The motor driver is a PWM driver,
The rotor angle detector is
An AM modulation wave extractor for extracting two AM modulation waves having the same frequency as the carrier frequency of the PWM driver from the ripple current flowing in the electromagnets of two non-excitation phases;
A demodulator that demodulates the two AM modulated waves and generates respective demodulated signals;
A comparator for calculating a difference between the demodulated signals,
The sensorless driving apparatus according to claim 1, wherein the PWM driver causes a current to flow through at least one of the plurality of electromagnets when the difference reaches a predetermined value.   The sensorless driving device according to claim 1, wherein the average value of the ripple current is in the vicinity of zero.   5. The sensorless driving device according to claim 3, wherein the ripple current is a current when the duty ratio of the PWM driver is fixed. The ripple current is a current when the duty ratio of the PWM driver is fixed,
5. The sensorless driving apparatus according to claim 4, wherein the duty ratio is set to 0 when the comparator does not compare the demodulated signal with the predetermined value. The ripple current is a current when the duty ratio of the PWM driver is fixed,
The sensorless driving apparatus according to claim 4, wherein the duty ratio is set to 0 when the comparator does not calculate the difference between the demodulated signals.   The sensorless driving device according to claim 4, wherein the rotor angle detector further includes a gain adjuster that adjusts a gain of the ripple current or the demodulated signal.   The sensorless driving device according to claim 4 or 5, wherein the AM modulation wave extractor is a band pass filter, and a center frequency of a pass band of the band pass filter is equal to the carrier frequency.   The sensorless driving apparatus according to claim 4 or 5, wherein the demodulator is an envelope detection method for extracting a peak value of the AM modulated wave.   6. The sensorless driving apparatus according to claim 4, wherein the demodulator is a synchronous detection system that demodulates an AM modulated wave using a reference wave synchronized with the carrier frequency.   The sensorless driving device according to any one of claims 1 to 13, wherein a direction of current flowing through the electromagnet is one direction. A switched reluctance motor comprising: a rotor having a plurality of salient poles made of a magnetic material; and a stator having a plurality of electromagnets arranged to surround the rotor;
A motor device comprising the sensorless driving device according to claim 1 for driving the switched reluctance motor.   The plurality of salient poles each have an asymmetric cross-sectional shape, and an upstream cross section of the salient pole in a rotation direction of the rotor is larger than a downstream cross section. Motor device. The rotor has a plurality of auxiliary poles respectively adjacent to the plurality of salient poles,
The plurality of auxiliary poles are shorter than the plurality of salient poles in the radial direction of the rotor,
The motor device according to claim 15, wherein the plurality of salient poles and the plurality of auxiliary poles are alternately arranged along a circumferential direction of the rotor.   The motor device according to claim 17, wherein the auxiliary pole has a ring shape.   The motor device according to claim 18, wherein a part of the auxiliary pole has a thin ring shape.   The motor device according to claim 18, wherein the auxiliary pole has a ring shape in which a notch is partially formed. A sensorless driving method for driving a switched reluctance comprising a rotor having a plurality of salient poles made of a magnetic material and a stator having a plurality of electromagnets arranged so as to surround the rotor,
Measure the current flowing through the electromagnet,
A sensorless driving method, wherein an angle of a rotor is detected based on a magnitude of a ripple current flowing in an electromagnet of a non-excitation phase among the plurality of electromagnets.   The sensorless drive according to claim 21, wherein it is determined whether the rotor has reached a predetermined angle by determining whether the magnitude of the ripple current has reached a predetermined value. Method.   23. The sensorless driving method according to claim 22, wherein when the magnitude of the ripple current reaches the predetermined value, a current is passed through at least one of the plurality of electromagnets.

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