JP2018186697A - Brushless motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor control device capable of correcting a rotor position detected by a position sensor with high accuracy.SOLUTION: A correction angle calculation unit 80 performs Fourier transformation of a signal of an induction voltage generated at a coil of a non-energization phase in a motor 52 to extract a waveform of the induction voltage. On the basis of a phase difference between a waveform of a signal that indicates a change in magnetic field of the rotor in the motor 52, which is outputted from a position sensor 12, and a waveform of the induction voltage, the correction angle calculation unit 80 corrects the signal outputted from the position sensor 12, and calculates a position of a magnetic pole of the rotor from the corrected signal. An output command unit 64 performs control to make a drive unit 70 generate a voltage that changes depending on the calculated position of the magnetic pole of the rotor and to apply the voltage to the coil of the motor 52.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a brushless motor control device.

  A brushless motor, which is a type of synchronous motor, has a rotor (rotor) composed of permanent magnets in a rotating magnetic field generated as a result of applying a voltage to a coil of a stator (stator) that is an electromagnet provided around the rotor. The rotor is rotated by following. In order to rotate the rotor smoothly, it is necessary to apply a voltage to the coil of the stator at a timing corresponding to the position of the magnetic pole of the rotor.

  For example, the position of the magnetic pole of the rotor is detected by a sensor using a Hall element (Hall sensor, Hall IC) or an absolute angle sensor using MR (magnetoresistance effect element). These sensors output an electrical signal corresponding to the magnetic field strength of the sensor magnet provided corresponding to the magnetic field of the rotor or the magnetic pole of the rotor. As the rotor rotates, the intensity of the magnetic field of the rotor or sensor magnet detected by the above sensor (hereinafter referred to as “position sensor”) repeats gradually increasing and decreasing, so the voltage change of the electrical signal output from the position sensor is: Presents a sinusoidal shape.

  In a brushless motor, a sinusoidal electric signal output from a position sensor is converted into a rectangular wave signal 110 as shown in FIG. 8A by a circuit such as a comparator, and the rectangular wave signal 110 is changed from a low level to a high level. Switching to level (hereinafter referred to as “rising edge”) and switching from high level to low level (hereinafter referred to as “falling edge”) are detected as timings at which the magnetic pole position of the rotor changes. Zero cross detection is performed, and the phase of the voltage applied to the coil is determined based on the timing.

  The position detection of the rotor using the position sensor is based on the premise that the position sensor is mounted at an optimal position for detecting the magnetic field of the rotor. However, the position sensor may be mounted at a position different from the original position during production of the brushless motor. In such a case, there is a possibility that the position of the rotor cannot be accurately detected.

  The position of the rotor of the brushless motor can be detected based on the induced voltage generated in the coil of the non-conduction phase in addition to the position sensor as described above. In Patent Document 1, the sinusoidal induced voltage signal 112 shown in FIG. 8B is converted into a rectangular wave signal 114 shown in FIG. An invention of a brushless motor control device that corrects an error in magnetic field detection caused by a position sensor mounting position by comparing 114 with a signal 110 based on a signal detected by a Hall IC is disclosed.

For example, FIG. 8 shows a case of a 4-pole 6-slot motor, and if the time T is a time when the rotor is actually rotated 360 degrees (mechanical angle 360 degrees), the time T is a time when the electrical angle is rotated 720 degrees. . In FIG. 8, since the signal 110 has a time difference t with respect to the signal 114, the correction angle (electrical angle) of the signal 110 is expressed by the following equation (1).
Correction angle = −720 × t / T (1)

JP 2009-240041 A

  However, in recent years, there is a tendency that the rotation speed of the brushless motor that is a control target is increased. In such a brushless motor with a high rotation speed, the electromotive force coefficient is smaller than that of a brushless motor with a low rotation speed, so that the detected induced voltage is likely to have a small amplitude like the signal 116 shown in FIG. Further, the influence of the offset error 118 of the comparator shown in FIG. 8B cannot be overlooked. The comparator may be composed of an operational amplifier and a plurality of resistors, but is generated when the current of the operational amplifier input section flows through the resistor in the circuit. As shown in FIG. It becomes difficult to converge to a value of 1.

  Since the amplitude of the induced voltage is small and the reference voltage does not converge, the zero cross detection error d shown in FIG. 8C is generated. As a result, in the brushless motor control device described in Patent Document 1, the position sensor There was a problem that it was difficult to correct the detected rotor position.

  The present invention has been made in view of the above, and an object of the present invention is to provide a brushless motor control device capable of correcting a rotor position detected by a position sensor with high accuracy.

  In order to solve the above-mentioned problem, a brushless motor control device according to claim 1, a rotation sensor that detects a rotational position of the rotor of a brushless motor including a rotor and a stator coil, and a rotation of the rotor, A voltage detector that detects an induced voltage induced in the stator coil to which no drive voltage is applied, frequency domain data obtained by Fourier transform of the induced voltage, and a rotational position detected by the rotation sensor. Based on the voltage command, the phase difference detected by the phase difference detection unit, and the rotational position of the rotor detected by the rotation sensor, the phase difference detection unit that detects the phase difference from the data to be expressed And a control circuit for setting energization timing and controlling the rotation of the rotor.

  According to this brushless motor control device, for example, by obtaining the frequency domain data of the induced voltage by Fourier transform and detecting the phase difference between the frequency domain data and the signal output from the rotation sensor as the position sensor. The position of the rotor detected by the position sensor can be corrected with high accuracy, and the voltage can be applied to the stator coil with accurate energization timing.

  The brushless motor control device according to claim 2 is the brushless motor control device according to claim 1, wherein the phase difference detection unit has an order corresponding to the number of poles of the brushless motor in the data in the frequency domain. The phase difference is detected using frequency data.

  According to this brushless motor control device, the position of the rotor detected by the position sensor is detected with high accuracy by using the frequency data corresponding to the number of poles of the motor from the frequency region of the induced voltage for the detection of the phase difference. Can be corrected.

  A brushless motor control device according to a third aspect of the present invention is the brushless motor control device according to the first or second aspect, wherein the voltage detection unit is configured such that each phase of the stator coil is de-energized and the rotor rotates inertially. The induced voltage is sampled every predetermined sampling period.

  According to this brushless motor control device, the rotor is inertially rotated without energizing each phase of the stator coil, so that the induced voltage can be detected easily and accurately, and the position of the rotor detected by the position sensor is highly accurate. It can be corrected with.

  The brushless motor control device according to claim 4, wherein the control circuit calculates a correction angle of a rotational position of the rotor detected by the rotation sensor based on the phase difference, and the rotation sensor outputs the correction angle based on the correction angle. The generated signal is synchronized with the waveform of the induced voltage.

  According to this brushless motor control device, the position of the rotor can be detected with high accuracy by synchronizing the signal output from the rotation sensor with the waveform of the induced voltage.

  The brushless motor control device according to claim 5 is the brushless motor control device according to claim 4, wherein the phase difference detection unit rotates the rotor by a mechanical angle of 360 degrees based on a signal output from the rotation sensor. When the inertial rotation period to coincide with a specified period that is a predetermined multiple of the predetermined sampling period, sampling of the induced voltage by the voltage detection unit is stopped, and the induced voltage sampled within the specified period until the sampling is stopped is Fourier transformed. The phase difference is detected based on the frequency domain data obtained by conversion and the data representing the rotational position detected by the rotation sensor, and at least one induced voltage is sampled, and the time Detecting the time difference from the time when the edge of the rectangular wave of the signal output by the rotation sensor rises near The control circuit calculates the correction angle of the rotational position of the rotor detected by the rotation sensor based on the phase difference and the time difference.

  According to this brushless motor control device, the position sensor also detects the time difference between the time when the induced voltage is sampled and the time when the edge of the rectangular wave of the signal output from the position sensor rises immediately before or after the sampling. The position of the rotor can be corrected with high accuracy.

  The brushless motor control device according to claim 6 is the brushless motor control device according to claim 5, wherein the formula for calculating the correction angle is the phase difference term and the sum of the time difference and the predetermined sampling period. This term is included.

  According to this brushless motor control device, the position of the rotor detected by the position sensor can be corrected with high accuracy based on the above-described phase difference, time difference, and sampling period.

  The brushless motor control device according to claim 7 is the brushless motor control device according to claim 4, wherein the phase difference detection unit detects one edge from the rectangular wave of the signal output from the rotation sensor. The sampling of the induced voltage by the voltage detection unit is started and the sampling of the signal output from the rotation sensor is started, and at the timing corresponding to the inertial rotation cycle in which the rotor rotates 360 degrees from the start of the sampling. Waveform obtained by stopping sampling of the induced voltage by the voltage detection unit and stopping sampling of the signal output from the rotation sensor when the edge is detected from the rectangular wave, and Fourier transforming the sampled induced voltage And the phase difference between the signal output from the rotation sensor and the waveform obtained by Fourier transform. And, wherein the control circuit calculates the correction angle of the rotational position of the rotor detected by the rotation sensor based on the phase difference.

  According to this brushless motor control device, the position sensor calculates the correction angle from the phase difference between the waveform of the induced voltage obtained by Fourier transform and the waveform of the signal output from the rotation sensor obtained by Fourier transform. The position of the rotor detected in step 1 can be corrected with high accuracy.

  The brushless motor control device according to claim 8 is the brushless motor control device according to any one of claims 5 to 7, wherein the Fourier transform is one of a fast Fourier transform and a discrete Fourier transform.

  According to this brushless motor control apparatus, not only a fast Fourier transform that requires sampling at a predetermined multiple of a specified sampling period, but also a discrete Fourier transform that does not require sampling at a predetermined multiple of a specified sampling period. The correction angle of the rotational position of can be calculated.

It is a figure which shows the outline of the brushless motor control apparatus which concerns on the 1st Embodiment of this invention. It is the block diagram which showed an example of sensor edge angle information correction | amendment of the brushless motor control apparatus which concerns on embodiment of this invention in the case of rotating a motor at high speed. It is the flowchart which showed an example of the sensor edge angle information correction process of the brushless motor control apparatus which concerns on embodiment of this invention. It is the schematic which showed an example of the frequency domain of the induced voltage obtained by FFT in the 1st Embodiment of this invention. In the 1st Embodiment of this invention, it is the schematic which showed an example of the analysis of the phase spectrum by FFT. It is explanatory drawing which showed the meaning of the phase difference shown by P3 + 90 in the 1st Embodiment of this invention. It is an example of the explanatory view which concerns on calculation of the time difference t of the signal detected by the position sensor, and the waveform of an induced voltage in the 1st Embodiment of this invention. (A) shows an example of a rectangular wave signal obtained from a sinusoidal electric signal output from the position sensor, (B) shows an example of a sinusoidal induced voltage signal, and (C) shows a sine wave signal. An example of a rectangular wave signal obtained from a wave-like induced voltage signal is shown. It is a figure which shows the outline of the brushless motor control apparatus which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which wrote together the Hall signal which shows the change of the magnetic field of the sensor magnet converted into the rectangular wave signal by the comparison etc., the sinusoidal Hall signal before being converted by the comparator etc., and the induced voltage. . It is the schematic which showed an example of the analysis of the phase spectrum of a Hall signal. It is the schematic which showed an example of the analysis of the phase spectrum of an induced voltage. FIG. 13 is a diagram showing an outline of a brushless motor control apparatus 10B according to the third embodiment of the present invention.

[First Embodiment]
FIG. 1 is a diagram schematically showing a brushless motor control device 10 according to the first embodiment of the present invention. The motor 52 is a 4-pole 6-slot brushless motor. Moreover, the inverter circuit 40 switches the electric power supplied to the coil of the stator 14 of the motor 52 by FET44A-44F which is a switching element. For example, the FETs 44A and 44D are in a U-phase coil 14U (not shown), the FETs 44B and 44E are in a V-phase coil 14V (not shown), and the FETs 44C and 44F are in a W-phase coil 14W (not shown). Switching of the power to be supplied is performed.

  The drains of the FETs 44A, 44B, and 44C are connected to the positive electrode of a battery 90 that is a power source. The sources of the FETs 44D, 44E, and 44F are grounded through the resistor R6.

  Further, on the substrate of the brushless motor control device 10 of the present embodiment, in addition to the inverter circuit 40 described above, a differential amplifier circuit 54, a position detection unit 56, an AD conversion unit 58, a sensor phase correction unit 60, an angle calculation. The unit 62, the output command unit 64, the drive unit 70, the position sensor 12, and the like are mounted. The position detection unit 56, the AD conversion unit 58, the sensor phase correction unit 60, the angle calculation unit 62, the output command unit 64, and the drive unit 70 may be configured as a single integrated circuit as the microcomputer 30.

  In the present embodiment, the magnetic field of the rotor of the motor 52 or the magnetic field of the sensor magnet provided coaxially with the rotor is detected by the position sensor 12 such as a Hall IC. The position sensor 12 includes a hall element that detects a change in the magnetic field of the sensor magnet as a sinusoidal signal, and the sinusoidal signal detected by the hall element is converted into a rectangular wave signal as shown in FIG. Convert and output. The position detection unit 56 performs zero-cross detection that detects rising edges and falling edges of the rectangular wave output from the position sensor 12. The information on the rising edge and the falling edge detected by the position detection unit 56 is input to the angle calculation unit 62 and the sensor phase correction unit 60 described later as sensor edge angle information.

  The differential amplifier circuit 54 is a device that amplifies the induced voltage generated in the coil 14 </ b> V of the motor 52 and outputs the amplified voltage to the AD converter 58. As shown in FIG. 1, in the differential amplifier circuit 54, the negative input terminal 54N is connected to the source of the FET 44A and the drain of the FET 44D through the resistor R4, and the control voltage Vcc is connected to the negative input terminal 54N and the resistor R1. It has an operational amplifier 54A to which a reference voltage output from a voltage dividing circuit composed of a resistor R2 is input. The + input terminal 54P of the operational amplifier 54A is connected to the source of the FET 44B and the drain of the FET 44E through the resistor R5, and is short-circuited to the output terminal 54O of the operational amplifier 54A through the resistor R3.

  The configuration shown in FIG. 1 detects an induced voltage generated in the V-phase coil of the motor 52. Although not shown in FIG. 1, the brushless motor control apparatus 10 according to the present embodiment differentially amplifies so as to detect each of the induced voltage generated in the U-phase coil and the induced voltage generated in the W-phase. A circuit related to the circuit may be configured.

  The AD conversion unit 58 is a circuit that generates a rectangular wave signal as shown in FIG. 8C by converting the signal output from the differential amplifier circuit 54 into a digital signal at each specified sampling timing. . The signal generated by the AD conversion unit 58 is input to the sensor phase correction unit 60.

  The sensor phase correction unit 60 compares the signal based on the induced voltage input from the AD conversion unit 58 with the signal of the sensor edge angle information input from the position detection unit 56, and based on the above equation (1). The correction angle is calculated and output to the angle calculation unit 62.

  The angle calculation unit 62 corrects and corrects the sensor edge angle information indicating the position of the rotor detected by the position sensor 12 input from the position detection unit 56 based on the correction angle input from the sensor phase correction unit 60. The sensor edge angle information is output to the output command unit 64.

  Based on the voltage command input from the outside and the corrected sensor edge angle information input from the angle calculation unit 62, the output command unit 64 generates a voltage phase and voltage magnitude (pulses) to be generated by the inverter circuit 40. A voltage duty ratio by width modulation (PWM) is determined and output to the drive unit 70.

  The drive unit 70 outputs a PWM signal in accordance with the phase and duty ratio input from the output command unit 64 to the inverter circuit 40, and the inverter circuit 40 switches the six FETs 44A to 44F in accordance with the PWM signal, so that the motor A voltage to be applied to the 52 coils is generated.

  FIG. 2 is a block diagram showing an example of sensor edge angle information correction of the brushless motor control device 10 according to the present embodiment when the motor 52 is rotated at a high speed. In the case illustrated in FIG. 2, a correction angle calculation unit 80 is provided instead of the differential amplifier circuit 54, the AD conversion unit, the sensor phase correction unit 60, and the angle calculation unit 62. The configuration shown in FIG. 2 is used, for example, in a test before product shipment. In this test, the induced voltage generated in the coil of the motor 52 is input to the error detector 80 </ b> A of the correction angle calculation unit 80 instead of the differential amplifier circuit 54. Sensor edge angle information calculated by the position detector 56 based on the signals Hu, Hv, and Hw from the position sensor 12 is also input to the error detector 80A.

  In the error detector 80A, the induced voltage detected when the rotor of the motor 52 is rotated by inertia is sampled and AD converted at every specified sampling period, the phase of the AD converted data is analyzed by Fourier transform, and the sine is obtained. An accurate phase of the induced voltage that changes in a wave shape is extracted, and a correction angle is calculated based on the extracted phase. As an example of the Fourier transform, fast Fourier transform (FFT) is used, but discrete Fourier transform (DFT) may be used.

  Then, the correction angle calculation unit 80 corrects the sensor edge angle information output from the position detection unit 56 with the calculated correction angle and outputs the corrected sensor edge angle information to the output command unit 64. The output command unit 64 sets the voltage phase and voltage duty ratio to be generated by the inverter circuit 40 based on the voltage command input from the outside and the corrected sensor edge angle information input from the correction angle calculation unit 80. Determine and output to the drive unit 70.

  The configuration shown in FIG. 2 may be used in a test before product shipment as described above. However, the differential amplifier circuit 54, the AD conversion unit 58, the sensor phase correction unit 60, the angle calculation unit 62, and the configuration shown in FIG. Instead of the position detection unit 56, a sensor edge angle information correction unit 82 including the correction angle calculation unit 80 and the position detection unit 56 shown in FIG. When the sensor edge angle information correction unit 82 is mounted on the substrate, the position detection of the rotor is strictly performed by performing sensor edge angle information correction processing described later for each operation of the motor 52.

  The sensor edge angle information correction process can be performed either when the motor 52 is started or when the motor 52 is stopped. However, as described later, since the rotor of the motor 52 needs to be rotated by inertia, the motor 52 is corrected. It is reasonable to do so when stopping. The correction angle calculated immediately before the stop is held in the memory, and when the motor 52 is started next, the sensor edge angle information output from the position detecting unit 56 is corrected using the correction angle held in the memory.

  Hereinafter, the operation and effect of the brushless motor control device 10 according to the present embodiment will be described. FIG. 3 is a flowchart showing an example of sensor edge angle information correction processing of the brushless motor control apparatus 10 according to the present embodiment. The process shown in FIG. 3 is started when, for example, when the motor 52 is stopped, energization of the coil of the motor 52 is stopped and the rotor is inertially rotated.

  In step 300, it is determined whether the rotor is in inertial rotation. In the present embodiment, when the position sensor 12 indicates the rotation of the rotor and the PWM signal is not output from the drive unit 70 to the inverter circuit 40, an affirmative determination is made that the rotor is rotating inertially.

  If the determination in step 302 is affirmative, the procedure proceeds to step 302. If the determination in step 302 is negative, the procedure returns to step 310, and it is determined again whether the rotor is rotating inertially.

In step 302, sampling is performed for each predetermined sampling period and AD conversion is performed, and in step 304, it is determined whether or not the inertial rotation period of the rotor coincides with a predetermined period indicated by a predetermined sampling period × 2 ^N. Note that N is a natural number, and as an example, N = 4. Further, the inertial rotation period of the rotor is calculated based on the change in the magnetic field of the rotor detected by the position sensor 12. In FFT, it is necessary to perform sampling at a predetermined multiple of a specified sampling period when data sampling is performed, and thus the specified period is set as described above. However, in the case of DFT, it is not necessary to perform sampling at a predetermined multiple of a prescribed sampling period such as FFT. Therefore, when using DFT, the determination in step 304 is not required. When DFT is used, sufficient data including a range in which the rotor of the motor 52 rotates 360 degrees in mechanical angle may be sampled.

  If the determination in step 304 is affirmative, sampling of the induced voltage is stopped in step 306. If the determination in step 304 is negative, the procedure returns to step 302 and sampling of the induced voltage is continued.

  In step 308, FFT processing is performed on the sampled induced voltage data. In step 310, the correction angle of the sensor edge angle information is calculated based on the result of the FFT processing, and the rotor detected by the position sensor 12 at the calculated correction angle. The correction is made to advance or retard the position of the magnetic pole, and the process ends.

  FIG. 4 is a schematic diagram showing an example of the frequency domain of the induced voltage obtained by FFT. The origin O in FIG. 4 is the timing at which the edge of the rectangular wave of the signal detected by the position sensor 12 such as a Hall IC rises. As shown in FIG. 4, when FFT processing is performed, waveforms having various phases such as cos θ, cos (2θ-P3), cos (3θ-PX) are detected. This is because the motor 52 according to the present embodiment is a four-pole motor. This is because, since a plurality of S poles and N poles exist in one rotor, a waveform of an induced voltage in which a plurality of phases are superimposed is sampled. In motor control, the waveform of the induced voltage is often handled as a sine wave, but in this embodiment, the waveform is expressed as a cosine wave based on the cosine term constituting the real term of the FFT. Yes.

  In this embodiment, the phase spectrum of the induced voltage on which waveforms having different phases are superimposed by FFT processing is analyzed, the phase of the induced voltage when the number of pole pairs is 2, ie, the number of pole pairs is extracted. Based on the phase of the induced voltage of 2, the correction angle of the sensor edge angle information is calculated.

  As described above, the origin O in FIG. 4 is the timing at which the edge of the rectangular wave of the signal detected by the position sensor 12 rises, so PX of cos (θ−PX) is a rectangle based on the signal detected by the position sensor 12. The phase difference from the wave is shown.

  FIG. 5 is a schematic diagram showing an example of phase spectrum analysis by FFT. In FIG. 5, P3 that is a phase difference when the number of pole pairs is 2, that is, the number of pole pairs is 2 is “−5 degrees” as an example.

In this embodiment, as described above, the waveform of the induced voltage is expressed by a cosine wave based on the cosine term constituting the real number term of FFT. However, if the brushless motor control device 10 controls the rotor position detection using the induced voltage as a sine wave, the cosine wave extracted by FFT is converted into a sine wave using the following equation (2). P3 + 90 in the sine term of Equation (2) corresponds to the phase difference between the waveform of the induced voltage and the signal detected by the position sensor 12, as will be described later.
cos (P3) = sin (P3 + 90) (2)

  FIG. 6 is an explanatory diagram showing the meaning of the phase difference indicated by P3 + 90. In FIG. 6, a rectangular wave 92 is an example of a signal detected by the position sensor 12, and a curve 94 is an example of a waveform after the waveform of the induced voltage extracted by FFT is converted into a sine wave.

When the curve 94 that is the waveform of the induced voltage is 0, the rectangular wave 92 should show a rising edge. Therefore, in the case shown in FIG. Thus, there is a delay of P3 + 90. Therefore, the formula (1) for calculating the correction angle is as shown in the following formula (3) in the case of FIG.
Correction angle = (P3 + 90) −720 × t / T (3)

  Next, calculation of the value of the time difference t in the above equation (3) will be described. FIG. 7 is an example of an explanatory diagram relating to the calculation of the time difference t between the signal detected by the position sensor 12 and the waveform of the induced voltage.

As described above, in the present embodiment, sampling is performed at a specified sampling period t2 and AD conversion is performed, and when the inertia rotation period of the rotor coincides with the specified period indicated by the specified sampling period × 2 ^N , Stop sampling. In the present embodiment, as an example, since N = 4, the number of samplings is 16.

  A rectangular wave 92 in FIG. 7 is an example of a signal detected by the position sensor 12, and a curve 96 in FIG. 7 corrects a phase difference (P3 + 90) between the curve 94 in FIG. This is an induced voltage waveform in which the induced voltage becomes 0 when 92 indicates a rising edge. The time T is the inertia rotation period of the rotor. When the motor 52 is a four-pole motor, the time is the time for the rotor to actually rotate 360 degrees (mechanical angle 360 degrees), and the time for the electrical angle to rotate 720 degrees. Become.

In FIG. 7, sampling starts from sample S ₁ and sampling ends at sample S ₁₆ . Samples S _{1 to} S ₁₆ sampled during a predetermined period are subjected to FFT processing as described above. Then, a time 102 sampling the sample S _16, detects a time difference t1 between the immediately before or after, the time 100 the square wave 92 has risen close to its other words time 102 time 102.

The time difference t1 is a time difference related to the calculation of the correction angle, but as shown in FIG. 7, the time T ₀ from the sample S ₁ to the sampling of the sample S ₁₆ is the specified sampling with respect to the time T. The period t2 is shorter.

As described above, in this embodiment, when the inertial rotation period of the rotor coincides with the specified period indicated by the specified sampling period t2 × 2 ^N , sampling of the induced voltage related to the correction angle calculation is completed. In the case of N = 4, the specified period is t2 × 16. Further, since the inertial rotation period of the rotor is time T in FIG. 7, it is necessary that T = t2 × 16.

However, since the time T ₀ is T ₀ = t2 × 15 as shown in FIG. 7, the time obtained by adding the specified sampling period t2 to the time when the sampling is ended from the time when the sampling is started is the specified period. It is. Therefore, the time difference t between the rectangular wave 92 and the curve 96 is a value obtained by adding the specified sampling period t2 to the time difference t1.

From the above, the correction angle calculation formula in the present embodiment is the following formula (4).
Correction angle = (P3 + 90) −720 × (t1 + t2) / T (4)

  In the present embodiment, correction is performed to advance or retard the position of the magnetic pole of the rotor detected by the position sensor 12 using the correction angle calculated by the above equation (4). Alternatively, the rectangular wave generated from the signal output from the position sensor 12 is synchronized with the waveform of the induced voltage by the correction angle calculated by the above formula (4), and the rotor is based on the rectangular wave synchronized with the waveform of the induced voltage. The position may be calculated.

  As described above, in this embodiment, the waveform of the induced voltage is analyzed by FFT, and the correction angle for correcting the position of the rotor detected by the position sensor 12 is calculated based on the analyzed waveform. Since the waveform of the induced voltage can be accurately extracted by FFT, the position of the rotor detected by the position sensor 12 can be corrected with high accuracy even when the motor 52 has a high rotation characteristic.

  Further, in the present embodiment, when the sensor edge angle information correction unit 82 shown in FIG. 2 is connected to the product at the time of product shipment and the processing of FIG. 3 is performed, the differential amplifier circuit 54 shown in FIG. Such a circuit becomes unnecessary, and the configuration of the product can be simplified.

  Further, according to the present embodiment, the error in detecting the position of the rotor due to mounting displacement of the position sensor 12 can be corrected with high accuracy, and the position of the rotor due to mounting misalignment of the circuit board on which the position sensor 12 is mounted on the housing. Detection errors can be corrected with high accuracy.

  Furthermore, according to the present embodiment, it is possible to correct the rotor position detection error due to the assembly deviation between the rotor and the sensor magnet with high accuracy, and to reduce the rotor position detection error due to variations in magnetization of the rotor or the sensor magnet. Can be corrected with high accuracy.

[Second Embodiment]
FIG. 9 is a diagram showing an outline of a brushless motor control apparatus 10A according to the second embodiment of the present invention. In the brushless motor control device 10A according to the present embodiment, the sinusoidal signal output from the position sensor 12 is input not only to the position detection unit 56 but also to the AD conversion unit 58A and detected by the position detection unit 56. Sensor edge angle information, which is information about the rising edge and falling edge, is input only to the angle calculation unit 62 and not to the sensor phase correction unit 60A, so that the brushless motor control according to the first embodiment is performed. Different from the device 10. Further, the position sensor 12A according to the present embodiment has a circuit such as a comparator, and not only a Hall IC that outputs a change in the magnetic field of the sensor magnet as a rectangular wave signal but also a change in the magnetic field of the sensor magnet in a sine wave form. This is different from the brushless motor control apparatus 10 according to the first embodiment in that it includes a hall sensor that outputs in response to this signal. However, since the other configuration is the same as that of the brushless motor control apparatus 10 according to the first embodiment, the other components are denoted by the same reference numerals as those of the first embodiment and detailed description thereof is omitted.

  The AD conversion unit 58A has a circuit such as a comparator, and converts the signal output from the differential amplifier circuit 54 into a digital signal at each specified sampling timing, thereby forming a rectangular wave shape as shown in FIG. In the case where the position sensor 12A is a Hall sensor that outputs a sine wave signal, the sine wave signal is a rectangular wave signal as shown in FIG. The sensor waveform 122 is converted. When the position sensor 12A is a Hall IC that outputs a rectangular wave signal, the signal output by the position sensor 12A is handled as the sensor waveform 122 without being converted.

  The induced voltage waveform 120 and the sensor waveform 122 generated by the AD conversion unit 58A are input to the sensor phase correction unit 60A. The sensor phase correction unit 60A calculates a correction angle 124 based on the induced voltage waveform 120 and the sensor waveform 122 input from the AD conversion unit 58A, and outputs the correction angle 124 to the angle calculation unit 62.

  In the present embodiment, the sensor phase correction unit 60A performs Fourier transform on the induced voltage waveform 120 and the sensor waveform 122. The Fourier transform to be executed is generally FFT (FFT processing) but may be DFT (DFT processing). In the present embodiment, the phase spectrum is analyzed as in the first embodiment, but the phase spectrum is analyzed not only for the induced voltage waveform 120 but also for the sensor waveform 122.

  In the present embodiment, the position sensor 12A or the AD converter 58A or the like has a sine wave signal indicating a change in the magnetic field of the sensor magnet detected by the position sensor 12A while the rotor of the motor 52 is inertially rotated. For example, the signal is converted into a rectangular wave signal, and an edge is detected from the rectangular wave signal. The AD conversion unit 58A uses the detected one edge as a base point, and rotates the rotor of the motor 52 by inertia, and the induced voltage signal output by the differential amplifier circuit 54 and the sensor magnet detected by the position sensor 12A. A signal indicating a change in the magnetic field is sampled at a predetermined sampling period.

  Sampling is performed at a cycle of a mechanical angle cycle (mechanical angle 360 degrees). As in the present embodiment, when the 4-pole rotor, that is, the number of pole pairs is 2, the mechanical angle of 360 degrees corresponds to the electrical angle of 720 degrees. When the AD conversion unit 58A detects an edge corresponding to a cycle of a mechanical angle of 360 degrees (electrical angle of 720 degrees), the AD conversion unit 58A ends sampling at a specified sampling cycle, and an induced voltage signal and sensor obtained by the sampling A signal indicating a change in the magnetic field of the magnet is processed by Fourier transform.

  FIG. 10 shows a Hall signal COMP130 indicating a change in the magnetic field of the sensor magnet converted into a rectangular wave signal by comparison or the like, a sinusoidal Hall signal 132 before being converted by a comparator or the like, an induced voltage 134, It is explanatory drawing which wrote together.

  As shown in FIG. 10, when the edge 136, which is the above-described one edge, is detected, sampling of the Hall signal 132 and the induced voltage 134 is started, which corresponds to a cycle of a mechanical angle of 360 degrees (an electrical angle of 720 degrees). When the edge 138 to be detected is detected, the sampling at the specified sampling period is finished.

  As shown in FIG. 10, there is a phase difference between the induced voltage 134 and the Hall signal 132. In the present embodiment, the sensor phase correction unit 60A calculates the correction angle 124 based on the phase difference between the induced voltage 134 and the Hall signal 132.

  In order to calculate the phase difference between the induced voltage 134 and the Hall signal 132, the AD converter 58A samples the induced voltage 134 detected when the rotor of the motor 52 is inertially rotated at a specified sampling period. After AD conversion, the phase of the AD converted data is analyzed by Fourier transform (FFT or DFT). In addition, the Hall signal 132 detected when the rotor of the motor 52 is inertially rotated is sampled and AD-converted at a predetermined sampling period by the AD converter 58A, and the phase of the AD-converted data is subjected to Fourier transform (FFT). Or DFT).

  Since the motor 52 according to the present embodiment is a four-pole motor, when Fourier transform processing is performed, the induced voltage 134 and the Hall signal 132 are detected as waveforms having various phases as shown in FIG. In this embodiment, each of the induced voltage 134 and the Hall signal 132 is subjected to phase spectrum analysis by Fourier transform.

  FIG. 11 is a schematic diagram illustrating an example of the analysis of the phase spectrum of the Hall signal 132. In FIG. 11, P3 that is the phase difference when the number of pole pairs is 2 is “−5 degrees” as an example.

  FIG. 12 is a schematic diagram illustrating an example of analysis of the phase spectrum of the induced voltage 134. In FIG. 12, P3 ′, which is the phase difference when the number of pole pairs is 2, indicates “−35 degrees” as an example.

From the analysis result of the above phase spectrum, the phase difference between the induced voltage 134 and the Hall signal 132 is expressed by the following equation (5).
Phase difference between induced voltage 134 and Hall signal 132 = (P3) − (P3 ′) (5)

  The phase difference represented by the above equation (5) is the correction angle 124 output from the sensor phase correction unit 124.

  In the present embodiment, correction is performed to advance or retard the position of the magnetic pole of the rotor detected by the position sensor 12A using the correction angle calculated by the above equation (5). Alternatively, the rectangular wave generated from the signal output from the position sensor 12A is synchronized with the waveform of the induced voltage by the correction angle calculated by the above equation (5), and the rotor is based on the rectangular wave synchronized with the waveform of the induced voltage. The position may be calculated.

  As described above, in the present embodiment, the waveform of each of the induced voltage 134 and the Hall signal is analyzed by Fourier transform, and the correction for correcting the position of the rotor detected by the position sensor 12A based on the analyzed waveform. The corner is calculated. Since the waveforms of the induced voltage 134 and the hall signal 132 can be accurately extracted by Fourier transform, the position of the rotor detected by the position sensor 12A can be corrected with high accuracy even when the motor 52 has a high rotation characteristic.

  Further, according to the present embodiment, the error in detecting the position of the rotor due to mounting displacement of the position sensor 12 can be corrected with high accuracy, and the position of the rotor due to mounting misalignment of the circuit board on which the position sensor 12 is mounted on the housing. Detection errors can be corrected with high accuracy.

[Third embodiment]
FIG. 13 is a diagram showing an outline of a brushless motor control apparatus 10B according to the third embodiment of the present invention. The brushless motor control device 10B according to the present embodiment is different from the differential amplifier circuit 54 of the brushless motor control device 10 according to the first embodiment in the configuration of the differential amplifier circuit 154. However, since the other configuration is the same as that of the brushless motor control apparatus 10 according to the first embodiment, the other components are denoted by the same reference numerals as those of the first embodiment and detailed description thereof is omitted.

  The differential amplifier circuit 154 includes an operational amplifier whose positive input terminal 54P is connected to the source of the FET 44A, the drain of the FET 44D, and the coil 14U of the motor 52 through the resistor R4, and short-circuited to the output terminal 54O through the resistor R3. 54B. The negative input terminal 54N of the operational amplifier 54B is connected to the source of the FET 44B, the drain of the FET 44E, and the coil 14V of the motor 52 through the resistor R5. The source of the FET 44C, the drain of the FET 44F, and the coil 14W of the motor 52 are composed of a resistor R1 and a resistor R2, and the control voltage Vcc is divided into bias voltages corresponding to the resistance values of the resistors R1 and R2. An output terminal 54D of the voltage dividing circuit for output is connected via a resistor R7. Further, the output terminal 54D of the voltage dividing circuit is connected to the negative input terminal 54N of the operational amplifier 54B, and is connected between one end of the resistor R3 on the positive input terminal 54P side and one end of the resistor R4 on the positive input terminal 54P side. Has been. Therefore, the bias voltage output from the output terminal 54D of the dividing circuit is applied to each of the coils 14U, 14V, and 14W.

  Inductive voltages generated in the coils 14U, 14V, and 14W are used to detect the rotational position of the rotor of the brushless motor. The differential amplifier circuit 154 amplifies a voltage corresponding to the difference between the induced voltage generated in any of the coils 14U, 14V, and 14W and the bias voltage, and outputs the amplified voltage from the output terminal 54O to the AD converter 58.

  Thereafter, as in the first embodiment, sampling and AD conversion are performed at a specified sampling period, the phase of the AD converted data is analyzed by Fourier transform (FFT or DFT), and the number of pole pairs of the motor 52 is determined. The correct phase of the induced voltage is extracted, and the correction angle is calculated based on the extracted phase.

  As described above, in the present embodiment, the correction angles for correcting the position of the rotor detected by the position sensor 12 can be calculated using the induced voltages generated in the coils 14U, 14V, and 14W, respectively. When the position sensor 12 uses a Hall element, a separate Hall element is generally required for each of the U phase, the V phase, and the W phase, but the Hall element is mounted in each of the U phase, the V phase, and the W phase. There may be a shift in position. In the present embodiment, each of the induced voltages generated in the coils 14U, 14V, and 14W is used to calculate a correction angle for correcting the position of the rotor detected by the position sensor 12, thereby obtaining a U-phase, a V-phase, An error in detecting the position of the rotor caused by a shift in the mounting position of any W-phase Hall element can be corrected with high accuracy.

10, 10A, 10B ... brushless motor control device, 12, 12A ... position sensor, 14 ... stator, 14U, 14V, 14W ... coil, 30 ... microcomputer, 40 ... inverter circuit, 44A, 44B, 44C, 44D, 44E, 44F ... FET, 52 ... motor, 54 ... differential amplifier circuit, 54A, 54B ... op amp, 54D ... output terminal, 54N ...- input terminal, 54O ... output terminal, 54P ... + input terminal, 56 ... position detector, 58, 58A ... AD conversion unit, 60, 60A ... sensor phase correction unit, 62 ... angle calculation unit, 64 ... output command unit, 70 ... drive unit, 80 ... correction angle calculation unit, 80A ... error detector, 82 ... sensor edge angle Information correction unit, 90 ... battery, 92 ... rectangular wave, 94, 96 ... curve, 100, 102 ... time, 110, 112, 114, 116 ... signal, 11 ... Offset error, 120 ... Induced voltage waveform, 122 ... Sensor waveform, 124 ... Correction angle, 124 ... Sensor phase correction unit, 130 ... Hall signal COMP, 132 ... Hall signal, 134 ... Induced voltage, 136,138 ... Edge, 154 ... differential amplifier circuit, Hu, Hv, Hw ... signal, O ... origin, R1, R2, R3, R4 , R5, R6, R7 ... resistors, S _1, S ₁₆ ... sample, T, T ₀ ... time, Vcc ... control voltage, d ... zero cross detection error, t, t1 ... time difference, t2 ... prescribed sampling period

Claims (8)

A rotation sensor for detecting a rotational position of the rotor of a brushless motor having a rotor and a stator coil;
A voltage detection unit for detecting an induced voltage induced in the stator coil to which a driving voltage is not applied in accordance with the rotation of the rotor;
A phase difference detector for detecting a phase difference between data in a frequency domain obtained by Fourier transforming the induced voltage and data representing a rotational position detected by the rotation sensor;
A control circuit that controls the rotation of the rotor by setting the energization timing to the stator coil based on the voltage command, the phase difference detected by the phase difference detector, and the rotational position of the rotor detected by the rotation sensor. When,
Including brushless motor control device.   2. The brushless motor control device according to claim 1, wherein the phase difference detection unit detects the phase difference using frequency data of an order corresponding to the number of poles of the brushless motor among the data in the frequency domain.   3. The brushless motor control device according to claim 1, wherein the voltage detection unit samples the induced voltage at a predetermined sampling period when the rotor is rotating in inertia with each phase of the stator coil being de-energized. 4. .   The control circuit calculates a correction angle of a rotational position of the rotor detected by the rotation sensor based on the phase difference, and synchronizes a signal output from the rotation sensor with the waveform of the induced voltage based on the correction angle. Item 4. The brushless motor control device according to item 3. The phase difference detection unit, based on a signal output from the rotation sensor, when the inertial rotation period in which the rotor rotates 360 degrees at a mechanical angle coincides with a specified period that is a predetermined multiple of the predetermined sampling period, Frequency domain data obtained by stopping the sampling of the induced voltage by the voltage detection unit and Fourier transforming the induced voltage sampled within a specified period until the sampling is stopped, and data representing the rotational position detected by the rotation sensor; And detecting the time difference between the time when at least one induced voltage was sampled and the time when the edge of the rectangular wave of the signal output from the rotation sensor rises near the time. And
The brushless motor control device according to claim 4, wherein the control circuit calculates a correction angle of a rotational position of the rotor detected by the rotation sensor based on the phase difference and the time difference.   The brushless motor control device according to claim 5, wherein the equation for calculating the correction angle includes a term of the phase difference and a term of a sum of the time difference and the predetermined sampling period. The phase difference detection unit starts sampling of an induced voltage by the voltage detection unit and starts sampling of a signal output from the rotation sensor when an edge of 1 is detected from a rectangular wave of a signal output from the rotation sensor. When an edge is detected from the rectangular wave at a timing corresponding to a coasting rotation period in which the rotor rotates 360 degrees in mechanical angle from the start of the sampling, sampling of the induced voltage by the voltage detection unit is stopped. Stops sampling the signal output from the rotation sensor and calculates the phase difference between the waveform obtained by Fourier transforming the sampled induced voltage and the waveform obtained by Fourier transforming the signal output by the rotation sensor And
The brushless motor control device according to claim 4, wherein the control circuit calculates a correction angle of a rotational position of the rotor detected by the rotation sensor based on the phase difference.   The brushless motor control device according to any one of claims 5 to 7, wherein the Fourier transform is one of a fast Fourier transform and a discrete Fourier transform.